of California*

Name of Book and Volume,

Division .......

Range

Shelf.

Received..

BIOLOGY

LIBRARY

G

f • • *

University of California.

THE MEDICAL LIBRARY

Ml-' !

i

V. -I . POTT \\ (1 RA*U I >. .M . 1 > .

Of San Francisco.

PEESENTED BY MBS. AND MISS FOURGEAUD.
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n^PARTMENT of PHYSIOLOGY
DIVERSITY 07 CALIFORNIA

o
* <•

A TREATISE

HUMAN PHYSIOLOGY;

DESIGNED FOR THE USE OF

STUDENTS AXD PRACTITIONERS OF MEDICINE.

BY

JOHN c. p ALTON, JR., M. D.,

PROFESSOR OF PHYSIOL03Y AXD MICROSCOPIC ANATOMY IX THE COLLEGE OF PHYSICIANS AND SURGEONS,

NEW YORK ; MEMBER OF THE NEW YORK ACADEMY OF MEDICINE ; OF THE NEW YORK

PATHOLOGICAL SOCIETY ; OF THE AMERICAN ACADEMY OF ARTS AXD SCIENCES,

BOSTON, MASS. ; AXD OF THE BIOLOGICAL DEPARTMENT OF THE

ACADEMY OF NATURAL SCIENCES OF PHILADELPHIA.

(limb (Ebition, JUbistb anb (Enlargeb.

WITH

TWO HUNDRED AND SEVENTY-THREE ILLUSTRATIONS.

PHILADELPHIA:

BLANCHARD AND LEA.
1864.

BIOLOGY

LIBRARY

G

ENTERED according to the Act of Congress, in the year 1864, by
BLANCHARD AND LEA,

in the Office of the Clerk of the District Court of the United States in and for
the Eastern District of the State of Pennsylvania.

PHILADELPHIA:
COLLINS, PRINTER, 705 JAYNE STREET.

TO MY FATHER,

JOHN C. DALTON, M.D.,

IS

HOMAGE OF HIS LONG AND SUCCESSFUL DEVOTION

TO THE

SCIENCE AND ART OF MEDICINE,

A. 3D in

GRATEFUL RECOLLECTION OF HIS PROFESSIONAL PRECEPTS AND EXAMPLE,

IS RESPECTFULLY AND AFFECTIONATELY

INSCRIBE D.

PREFACE TO THE THIRD EDITION.

Ix the present edition of this work, the general plan and arrange-
ment of the two former ones are retained. The improvements and
additions which have been introduced consist in the incorporation
into the text of certain new facts and discoveries, relating mainly
to details, which have made their appearance within the last three
years. Such are the experiments of the author with regard to the
secretion and properties of the parotid saliva in the human subject,
and the quantitative analysis of this fluid by Mr. Perkins; the
valuable observations of Prof. Austin Flint, Jr., on Stercorine,
Cholesterin, and the effects of permanent biliary fistula, and those
of Prof. Jeffries Wyman on Fissure of Hare-lip in the median
line, from arrest of development. Three new illustrations have
been introduced, one of which (Fig. 183) replaces a previous one.
The author is much indebted to his friend, Dr. Foster Swift, for
aid in carrying the work through the press.

NEW YORK, January, 1864.

(v)

PREFACE TO THE SECOND EDITION.

Ix presenting a new edition of this work, the author desires to
express his sincere acknowledgments to his professional brethren
for the very favorable manner in which it was received at the
time of its first appearance, two years ago. In the present edition,
the author has endeavored to supply, as fully as possible, the
deficiencies which, he is well aware, existed in the former volume.
Some of these deficiencies were evident to his own mind, while
others were indicated by the suggestions of judicious criticism.
These suggestions, accordingly, have been adopted in all cases in
which they appear to be well founded, and not inconsistent with
the general plan of the work. In those instances, on the other
hand, in which the views of the author on physiological questions
seemed to him to be positively sustained by the results of observa-
tion, he has retained these views unchanged in the present edition.
At the same time, he has abstained, as before, from the lengthened
discussion of theoretical points, and has purposely avoided even
the enumeration of new experiments and observations, wherever
they have not materially affected the position of physiological
doctrines; for in a work like the present, it is not the object of
the writer to give a detailed history of physiological science, but
only such prominent and essential points in its development as
will enable the reader fully to comprehend its actual condition at
the present time.

The principal additions and alterations which have thus been
found advisable are: —

First, the introduction of an entire chapter devoted to the con-
sideration of the Special Senses, which were only incidentally treated
of in the former edition.

( vii )

Vlii PREFACE TO THE SECOND EDITION,

Second, the re-arrangement of the chapter on the Cranial Nerves,
and the introduction of some new views and facts in regard to their
physiology.

Third, an account of some new experiments, original with the
author, relating to the function of the Cerebellum, and the conclu-
sions to which they lead.

Fourth, certain considerations respecting the general properties
of Sensation and Motion, as resident in the nervous system, which
are important as an introduction to the more detailed study of
these functions.

Fifth, the introduction of a chapter on Imbibition and Exhalation
and the functions of the Lymphatic System; including the study of
endosmosis and exosmosis, and their mode of action in the animal
frame, the experiments of Dutrochet, Chevreuil, Gosselin, Matteucci,
and others, on this subject, the constitution and circulation of the
lymph and chyle, and, finally, a quantitative estimate of the entire
processes of exudation and reabsorption, as taking place in the
living body.

Additions have also been made, in various parts, to the chapters
on Secretion, Excretion, the Circulation, and the functions of the
Digestive Apparatus. In every instance, these alterations have
been incorporated with the text in such a manner as to avoid, so
far as possible, increasing unnecessarily the size of the book.

Twenty-two new and original illustrations have been introduced
into the present volume, of which number five replace others in
the former edition, which were regarded as imperfect, either in
design or execution. The remaining seventeen are additional.

It is hoped that the above alterations and additions will be found
to be improvements, and that they will enable the work, in its pre-
sent form, to accomplish more fully the object for which it was
designed.

NEW YORK, February, 1861.

PREFACE TO THE FIRST EDITION.

THIS volume is offered to the medical profession of the United
States as a text-book for students, and also as a means of Commu-
nicating, in a condensed form, such new facts and ideas in physio-
logy as have marked the progress of the science within a recent
period. Many of these topics are of great practical importance to
the medical man, as influencing, in various ways, his views on
pathology and therapeutics; and they are all of interest for the
physician who desires to keep pace with the annual advance of his
profession, as indicating the present position and extent of one of
the most progressive of the departments of medicine.

It has been the object of the author, more particularly, to pre-
sent, at the same time with the conclusions which physiologists
have been led to adopt on any particular subject, the experimental
basis upon which those conclusions are founded; and he has en-
deavored, so far as possible, to establish or corroborate them by
original investigation, or by a repetition of the labors of others.
This is more especially the case in that part of the book (Section
I.) devoted to the function of Nutrition ; and as a general thing,
throughout the work, any statement of experimental facts, not
expressly referred to the authority of some other writer, is given
by the author as the result of direct personal observation.

The illustrations for the work have been prepared with special
reference to the subject-matter; and it is hoped that they will be
found of such a character as materially to assist the student in
comprehending the most important and intricate parts of the sub-
ject. It is more particularly in the departments of the Nervous
System and Embryonic Development that simple, clear, and faithful

X PREFACE TO THE FIRST EDITION.

illustrations are indispensable for the proper understanding of the
printed descriptions ; the latter being often necessarily somewhat
intricate, and requiring absolutely the assistance of properly
arranged figures and diagrams. Of the two hundred and fifty-
four illustrations in the present volume, only eleven have been
borrowed from other writers, to whom they will be found duly
credited in the list of woodcuts.

Of the remaining illustrations, prepared expressly for the pre-
sent work, the drawings of anatomical structures, crystals, and
microscopic views generally were all taken from nature. The
diagrams were arranged, for purposes of convenience, in such
a manner as to illustrate known anatomical or physiological ap-
pearances, in the most compact and intelligible form.

Physiological questions which are in an altogether unsettled
state, as well as purely hypothetical topics have been purposely
avoided, as not coming within the plan of this work, nor as calcu-
lated to increase its usefulness.

XEW YORK, January 1, 1859.

CONTENTS.

INTRODUCTION.

PAGE

Definition of Physiology — Its mode of study — Nature of Vital Phenomena —
Division of the subject 49-59

SECTION I.

NUTRITION.
CHAPTER I.

PROXIMATE PRINCIPLES IN GENERAL.

Definition of Proximate Principles — Mode of their extraction — Manner in which
they are associated with each other — Natural variation in their relative
quantities — Three distinct classes of proximate principles . . . 61-68

CHAPTER II.

PROXIMATE PRINCIPLES OF THE FIRST CLASS.

Inorganic substances — Water — Chloride of Sodium — Chloride of Potassium —
Phosphate of Lime — Carbonate of Lime — Carbonate of Soda — Phosphates of
Magnesia, Soda, and Potassa — Inorganic proximate principles not altered in
the body — Their discharge — Nature of their function .... 69-78

CHAPTER III.

PROXIMATE PRINCIPLES OF THE SECOND CLASS.

STARCH — Percentage of starch in different kinds of food — Varieties of this
substance — Properties and reactions of starch — Its conversion into sugar —
SUGAR — Varieties of sugar — Physical and chemical properties — Proportion
in different kinds of food — FATS — Varieties — Properties and reactions of fat
— Its crystallization — Proportion in different kinds of food— Its condition in
the body — Internal production of fat — Origin and destination of proximate
principles of this class ......... 70-94

Xll CONTENTS.

CHAPTER IY.

PROXIMATE PRINCIPLES OF THE THIRD CLASS.

PAGE

General characters of organic substances— Their chemical constitution — Hygro-
scopic properties — Coagulation — Catalysis — Fermentation — Putrefaction —
Fibrin — Albumen — Casein — Globuline — Pepsine — Pancreatine — Mucosine —
Osteine — Cartilagine — Musculine — Hsematine — Melanine — Biliverdine —
Urosacine — Origin and destruction of proximate principles of this class 95-104

CHAPTER V.

OF FOOD.

Importance of inorganic substances as ingredients of food — Of saccharine and
starchy substances — Of fatty matters — Insufficiency of these substances
when used alone — Effects of an exclusive non-nitrogenous diet — Organic
substances also insufficient by themselves — Experiments of Magendie on
exclusive diet of gelatine or fibrin — Food requires to contain all classes of
proximate principles — Composition of various kinds of food — Daily quantity
of food required by man — Digestibility of food — Effect of cooking . 105-114

CHAPTER VI.

DIGESTION.

Nature of digestion — Digestive apparatus of fowl — Of ox — Of man — MASTICA-
TION— Varieties of teeth — Effect of mastication — SALIVA — Its composition —
Daily quantity produced — Its action on starch — Effect of its suppression —
Function of the saliva — GASTRIC JUICE, AND STOMACH DIGESTION — Structure of
gastric mucous membrane — Dr. Beaumont's experiments on St. Martin —
Artificial gastric fistulse — Composition and properties of gastric juice — Its
action on albuminoid substances — Peristaltic action of stomach — Time re-
quired for digestion — Daily quantity of gastric juice— Influences modifying
its secretion — INTESTINAL JUICES, AND THE DIGESTION OF SUGAR AND STARCH —
Follicles of intestine — Properties of intestinal j nice — PANCREATIC JUICE, AND
THE DIGESTION OP FAT — Composition and properties of pancreatic juice — Its
action on oily matters — Successive changes in intestinal digestion — The large
intestine and its contents 115-161

CHAPTER VII.

ABSORPTION.

Closed follicles and vilii of small intestine — Peristaltic motion — Absorption
by bloodvessels and lymphatics — Chyle — Lymph — Absorbent system — Lac-
teals and lymphatics — Absorption of fat — Its accumulation in the blood
during digestion — Its final decomposition and disappearance . . 162-174

CONTENTS. Xlll

CHAPTER VIII.

THE BILE.

PAGE

Physical properties of the bile — Its composition — Biliverdine — Cliolesterin —
Biliary salts — Their mode of extraction — Crystallization — Glyko-chojate of
soda — Tauro-cholate of soda — Biliary salts in different species of animals
and in man — Tests for bile — Variations and functions of bile — Daily quan-
tity— Time of its discharge into intestine — Its disappearance from the ali-
mentary canal — Its reabsorption — Its ultimate decomposition . . 175-199

CHAPTER IX.

FORMATION OF SUGAR IN THE LIVER.

Existence of sugar in liver of all animals — Its percentage— Internal origin of
liver-sugar— Its production after death — Glycogenic matter of the liver — Its
properties and composition — Absorption of liver-sugar by hepatic veins —
Its accumulation in the blood during digestion — Its final decomposition and
disappearance ........ 200-207

CHAPTER X.

THE SPLEEN.

Capsule of Spleen — Variations in size of the organ — Its internal structure —
Malpighian bodies of the spleen — Action of spleen on the blood — Effect
of its extirpation ..... . 208-212

CHAPTER XI.

THE BLOOD.

RED GLOBULES of the blood — Their microscopic characters — Structure and com-
position— Variations in size in different animals — WHITE GLOBULES of the
blood — Independence of the two kinds of blood-globules — PLASMA — Its com-
position— Fibrin — Albumen — Fatty matters — Saline ingredients — Extractive
matters — COAGULATION OF THE BLOOD — Separation of clot and serum — Influ-
ences hastening or retarding coagulation — Coagulation not a commencement
of organization — Formation of buffy coat — Entire quantity of blood in body

213-231

CHAPTER XII.

RESPIRATION.

Respiratory apparatus of aquatic and air-breathing animals— Structure of
lungs in human subjects — Respiratory movements of chest — Of glottis —
Changes in the air during respiration — Changes in the blood — Proportions
of oxygen and carbonic acid, in venous and arterial blood — Solution of gases
by the blood-globules — Origin of carbonic acid in the blood — Its mode of
production — Quantity of carbonic acid exhaled from the body — Variations
according to age, sex, temperature, &c. — Respiration by the skin . 232-252

CONTENTS.

CHAPTER XIII.

ANIMAL HEAT.

PAGE

Standard temperature of animals — How maintained — Production of heat by
Vegetables — Mode of generation of animal heat — Theory of combustion —
Objections to this theory — No oxidation in vegetables during production of
*fceat— Quantities of oxygen and carbonic acid in animals do not correspond
with each other — Production of animal heat a local process — Depends on
the chemical phenomena of nutrition . . . 253-263

CHAPTER XI Y.

THE CIRCULATION.

Circulatory apparatus of fish — Of reptiles — Of mammalians — Course of blood
through the heart — Action of valves — Sounds of heart — Movements — Im-
pulse— Successive pulsations — Arterial system — Movement of blood through
the arteries — Arterial pulse — Arterial pressure — Rapidity of arterial circula-
tion— The veins — Causes of movement of blood in the veins — Rapidity of
venous current — Capillary circulation — Phenomena and causes of capillary
circulation — Rapidity of entire circulation — Local variations in different
parts ......... 264-306

CHAPTER XV.

IMBIBITION AND EXHALATION. — THE LYMPHATIC SYSTEM.

Eudosmosis and exosmosis — Mode of exhibiting them — Conditions which regu-
late their activity — Nature of the membrane — Extent of contact — Constitu-
tion of the liquids — Temperature — Pressure — Nature of endosmosis — Its
conditions in the living body — Its rapidity — Phenomena of endosmosis in
the circulation — The lymphatics — Their origin — Constitution of the lymph
and chyle — Their quantity — Liquids secreted and reabsorbed in twenty-
four hours ........ 307-323

CHAPTER XYI.

SECRETION.

Nature of secretion — Variations in activity — Mucus— Sebaceous matter — Its
varieties — Perspiration — Structure of perspiratory glands — Composition and
quantity of the perspiration — Its use in regulating the animal temperature —
Tears — Milk — Its acidification — Secretion of bile — Anatomical peculiarities

324-340

CONTENTS. XV

CHAPTER XYII.

EXCRETION.

PAGE

Nature of excretion — Excrementitious substances — Effect of their retention —
Urea — Its source — Conversion into carbonate of ammonia — Daily quantity
of urea — Creatine — Creatinine — Urate of soda — Urates of potassa and ammo-
nia— General characters of the urine — Its composition — Variations — Acci-
dental ingredients of the urine — Acid and alkaline fermentations — Final
decomposition of the urine ...... 341-364

SECTION II.
NERVOUS SYSTEM.

CHAPTER I.

GENERAL CHARACTER AND FUNCTIONS OF THE NERVOUS SYSTEM.

Nature of the function performed by nervous system — Two kinds of nervous
tissue — Fibres of white substance — Their minute structure — Division and
inosculation of nerves — Gray substance — Nervous system of radiata — Of
mollusca — Of articulata — Of mammalia and human subject — Structure of
encephalon — Connections of its different parts . . . 365-887

CHAPTER II.

OF NERVOUS IRRITABILITY, AND ITS MODE OF ACTION.

Irritability of muscles — How exhibited — Influences which exhaust and destroy
it — Nervous irritability — How exhibited — Continues after death — Exhausted
by repeated excitement — Influence of direct and inverse electrical currents
— Nervous irritability distinct from muscular irritability — Nature of the
nervous force — Its resemblance to electricity — Differences between the two

388-397

CHAPTER III.

THE SPINAL CORD.

Power of sensation — Power of motion — Distinct seat of sensation and motion
in nervous system — Sensibility and excitability — Distinct seat of sensibility
and excitability in spinal cord — Crossed action of spinal cord — Independent
and associated action of motor and sensitive filaments — Reflex action of
spinal cord — How manifested during disease — Influence in health on
sphincters, voluntary muscles, urinary bladder, &c. . . . 398-416

CONTENTS.

CHAPTER IV.

THE BRAIN.

PAGE

Seat of sensibility and excitability in different parts of the encephalon— Olfac-
tory ganglia — Optic thalami— Corpora striata — Hemispheres — Remarkable
cases of injury of hemispheres — Effect of their removal — Imperfect develop-
ment in idiots — Aztec children — Theory of phrenology — Cerebellum — Effect
of its injury or removal — Comparative development in different classes —
Tubercula quadrigemina — Tuber annulare — Medulla oblongata — Three kinds
of reflex action in nervous system ..... 417-445

CHAPTER V.

THE CRANIAL NERVES.

Olfactory nerves — Optic nerves — Auditory nerves — Classification of cranial
nerves — Motor nerves — Sensitive nerves — Motor oculi communis — Patheti-
cus — Motor externus — Fifth pair — Its sensibility — Effect of division — Influ-
ence on mastication — Influence on the organ of sight — Facial nerve — Effect
of its paralysis — Glosso-pharyngeal nerve — Pneumogastric — Its distribution
— Influence on pharynx and oesophagus — On larynx — On lungs — On stomach
and digestion — Spinal accessory nerve — Hypoglossal . . . 446-477

CHAPTER VI.

THE SPECIAL SENSES.

General and special sensibility — Sense of touch in the skin and mucous mem-
branes— Nature of the special senses — TASTE — Apparatus of this sense — Its
conditions — Its resemblance to ordinary sensation — Injury to the taste in
paralysis of the facial nerve — SMELL — Arrangement of nerves in nasal pas-
sages— Conditions of this sense — Distinction between odors and irritating
vapors — SIGHT — Structure of the eyeball — Special sensibility of the retina —
Action of the lens — Of the iris — Combined action of two eyes — Vivid nature
of the visual impressions — HEARING — Auditory apparatus — Action of mem-
brana tympani — Of chain of bones — Of their muscles — Appreciation of the
direction of sound — Analogies of hearing with ordinary sensation . 478-513

CHAPTER VII.

SYSTEM OP THE GREAT SYMPATHETIC.

Ganglia of the great sympathetic — Distribution of its nerves — Sensibility and
excitability of sympathetic — Sluggish action of this nerve — Influence over
organs of special sense — Elevation of temperature after division of sympa-
thetic— Contraction of pupil following the same operation — Reflex actions
taking place through the great sympathetic .... 514-524

CONTEXTS. xvii

SECTION III.
REPRODUCTION.

CHAPTER I.

ON THE NATURE OF REPRODUCTION, AND THE ORIGIN OF PLANTS AND

ANIMALS.

PAGE

Nature and objects of the function of reproduction — Mode of its accomplish-
ment— By generation from parents — Spontaneous generation — Mistaken in-
stances of this mode of generation — Production of infusoria — Conditions of
their development— Schultze's experiment on generation of infusoria— Pro-
duction of animal and vegetable parasites — Encysted entozoa — Trichina
spiralis — Taenia — Cysticercus — Production of taenia from cysticercus — Of
cysticercus from eggs of taenia — Plants and animals always produced by
generation from parents ...... 525-539

CHAPTER II.

ON SEXUAL GENERATION AND THE MODE OF ITS ACCOMPLISHMENT.

Sexual apparatus of plants — Fecundation of the germ — Its development into
a new plant — Sexual apparatus of animals — Ovaries and testicles — Uni-
sexual and bisexual species— Distinctive characters of the two sexes 540-543

CHAPTER III.

ON THE EGG, AND THE FEMALE ORGANS OF GENERATION.

Size and appearance of the egg — Vitelline membrane — Vitellus — Germinative
vesicle — Germinative spot — Ovaries — Graafiau follicles — Oviducts — Female
generative organs of frog — Ovary and oviduct of fowl — Changes in the egg,
while passing through the oviduct — Complete fowl's egg — Uterus and ova-
ries of the sow — Female generative apparatus of the human subject — Fal-
lopian tubes — Body of the uterus — Cervix of the uterus . . 544-555

CHAPTER IV.

ON THE SPERMATIC FLUID, AND THE MALE ORGANS OF GENERATION.

The spermatozoa— Their varieties in different species — Their movement — For-
mation of spermatozoa in the testicles — Accessory male organs of generation
— Epididymis — Vas deferens — Vesiculse seminales — Prostate — Cowper's
glands — Function of spermatozoa — Physical conditions of fecundation 556-562

2

XViil CONTENTS.

CHAPTER Y.

ON PERIODICAL OVULATION, AND THE FUNCTION OF MENSTRUATION.

PAGE

PERIODICAL OVULATION — Pre-existence of eggs in the ovaries of all animals —
Their increased development at the period of puberty — Their successive
ripening and periodical discharge — Discharge of eggs independently of sexual
intercourse — Rupture of Graafian follicle, and expulsion of the egg — Pheno-
mena of oestruation — MENSTRUATION — Correspondence of menstrual periods
with periods of ovulation in the lower animals — Discharge of egg during
menstrual period — Conditions of its impregnation, after leaving the ovary

563-575

CHAPTER VI.

ON THE CORPUS LUTEUM OF MENSTRUATION AND PREGNANCY.

CORPUS LUTEUM OF MENSTRUATION — Discharge of blood into the ruptured Graafian
follicle — Decolorization of the clot, and hypertrophy of the membrane of the
vesicle — Corpus luteum of menstruation, at the end of three weeks — Yellow
coloration of convoluted wall — Corpus luteum of menstruation at the end
of four weeks — Shrivelling and condensation of its tissues — Its condition at
the end of nine weeks — Its final atrophy and disappearance — CORPUS LUTEUM
OF PREGNANCY — Its continued development after the third week — Appearance
at the end of second month — Of fourth month — At the termination of preg-
nancy— Its atrophy and disappearance after delivery — Distinctive characters
of corpora lutea of menstruation and pregnancy . . . 576-585

CHAPTER VII.

ON THE DEVELOPMENT OF THE IMPREGNATED EGG.

Segmentation of the vitellus — Formation of blastodermic membrane — Two
layers of blastodermic membrane — Thickening of external layer — Formation
of primitive trace — Dorsal plates — Abdominal plates — Closure of dorsal and
abdominal plates on the median line — Formation of intestine — Of mouth
and anus — Of organs of locomotion — Continued development of organs, after
leaving the egg . . . . . . . . 586-595

CHAPTER VIII.

THE UMBILICAL VESICLE.

Separation of vitelline sac into two cavities — Closure of abdominal walls, and
formation of umbilical vesicle in fish — Mode of its disappearance after hatch-
ing— Umbilical vesicle in human embryo — Formation and growth of pedicle
— Disappearance of umbilical vesicle during embryonic life . . 596-598

CONTENTS. XIX

CHAPTER IX.

AMNION AND ALLANTOIS — DEVELOPMENT OF THE CHICK.

PAGE

Necessity for accessory organs in the development of birds and quadrupeds —
Formation of amniotic folds — Their union and adhesion — Growth of allantois
from lower part of intestine — Its vascularity — Allantois in the egg of the
fowl— Respiration of the egg — Absorption of calcareous matter from the
shell — Ossification of skeleton — Fracture of egg-shell — Casting off of amuion
and allantois . . . . . . • 599-607

CHAPTER X.

DEVELOPMENT OF THE EGG IN THE HUMAN SPECIES— FORMATION OF THE

CHORION.

Conversion of allantois into chorion — Subsequent changes of the chorion —
Its villosities — Formation of bloodvessels in villosities — Action of villi of
chorion in providing for nutrition of fretus — Proofs that the chorion is formed
from the allantois — Partial disappearance of villosities of chorion, and
changes in its external surface ...... 608-613

CHAPTER XI.

DEVELOPMENT OF UTERINE MUCOUS MEMBRANE — FORMATION OF THE

DECIDUA.

Structure of uterine mucous membrane — Uterine tubules — Thickening of ute-
rine mucous membrane after impregnation — Decidua vera — Entrance of egg
into uterus — Decidua reflexa — Inclosure of egg by decidua reflexa — Union
of chorion with decidua — Changes in the relative development of different
portions of chorion and decidua ..... 614-620

CHAPTER XII.

THE PLACENTA.

Nourishment of foetus by maternal and fcetal vessels — Arrangement of the
vascular membranes in different species of animals— Membranes of fcetal
pig — Cotyledon of cow's uterus — Development of foetal tufts in human pla-
centa— Development of uterine sinuses — Relation of foetal and maternal
bloodvessels in the placenta — Proofs that the maternal sinuses extend
through the whole thickness of the placenta — Absorption and exhalation
by the placental vessels ...... 621-629

XX CONTENTS.

CHAPTER XIII

DISCHARGE OF THE OVUM, AND INVOLUTION OF THE UTERUS.

PAGE

Enlargement of amniotic cavity — Contact of amnion and chorion — Amniotic
fluid — Movements of foetus — Union of decidua vera and reflexa — Expulsion
of the ovum and discharge of decidual membrane — Separation of the pla-
centa— Formation of new mucous membrane underneath the old decidua —
Fatty degeneration and reconstruction of muscular walls of uterus 630-63 G

CHAPTER XIY.

DEVELOPMENT OF THE EMBRYO — NERVOUS SYSTEM, ORGANS OF SENSE,
SKELETON AND LIMBS.

Formation of spinal cord and cerebro-spinal axis — Three cerebral vesicles —
Hemispheres — Optic thalami — Tubercula quadrigemina — Cerebellum — Me-
dulla oblongata — Eye — Pupillary membrane — Skeleton — Chorda dorsalis —
Bodies of the vertebrae — Laminae and ribs — Spina bifida — Anterior and pos-
terior extremities — Tail — Integument — Hair — Vernix caseosa — Exfoliation
of epidermis . ...... 637-643

CHAPTER XY.

DEVELOPMENT OF THE ALIMENTARY CANAL AND ITS APPENDAGES.

Formation of intestine — Stomach — Duodenum — Convolutions of intestine —
Large and small intestine— Caput coli and appendix vermiformis — Umbi-
lical hernia — Formation of urinary bladder — Urachus — Vesico-rectal septum
— Perineum — Liver — Secretion of bile — Gastric juice — Meconium — Glyco-
genic function of liver — Diabetes of foetus — Pharynx and oesophagus — Dia-
phragm— Diaphragmatic hernia — Heart and pericardium — Ectopia cordis —
Development of the face ...... 644-654

CHAPTER XYI.

DEVELOPMENT OF THE KIDNEYS, WOLFFIAN BODIES, AND INTERNAL ORGANS

OF GENERATION.

Wolffian bodies — Their structure— First appearance of kidneys — Growth of
kidneys, and atrophy of Wolffian bodies — Testicles and ovaries — Descent of
the testicles — Tunica vaginalis testis — Congenital inguinal hernia — Descent
of the ovaries — Development of the uterus .... 655-664

CONTEXTS. XXI

CHAPTER XVII.

DEVELOPMENT OF THE CIRCULATORY APPARATUS.

PA.GK

First, or vitelline circulation — Area vasculosa — Sinus terminalis — Vitelline
circulation of fish — Arrangement of arteries and veins in body of fetus —
Second, or placental circulation — Omphalo-mesenteric arteries and vein —
Circulation of the umbilical vesicle — Of the allantois and placenta — Umbi-
lical arteries and veins — Third, or adult circulation — Portal and pulmonary
systems — Development of the arterial system — Development of the venous
system — Changes in the hepatic circulation — Portal vein — Umbilical vein
— Ductus venosus — Changes in the cardiac circulation — Division of heart
into right and left cavities— Aorta and pulmonary artery — Ductus arteriosus
— Foramen ovale and Eustachian valve — Changes in circulation at the
period of birth ........... 665-686

CHAPTER XVIII.

DEVELOPMENT OF THE BODY AFTER BIRTH.

Condition of fcetus at birth — Gradual establishment of respiration — Inactivity
of the animal functions — Preponderance of reflex actions in the nervous
system — peculiarities in the action of drugs on infant — Difference in relative
size of organs, in infant and adult — Withering and separation of umbilical
cord — Exfoliation of epidermis — First and second sets of teeth — Subsequent
changes in osseous, muscular and tegumentary systems, and general devel-
opment of -the body .......... 687-690

2*

LIST OF ILLUSTRATIONS,

ALL OF WHICH HAVE BEEN PREPARED FROM ORIGINAL DRAWINGS, WITH THE
EXCEPTION OF TEN, CREDITED TO THEIR AUTHORITIES.

FIG. PAGE

1. Fibula tied in a knot, after maceration in a dilute acid . . .75

2. Grains of potato starch ....... 80

3. Starch grains of Bermuda arrowroot . . . . .80

4. Starch grains of wheat flour ...... 81

5. Starch grains of Indian corn . . . . . .81

6. Starch grains from wall of lateral ventricle . . . .82

7. Stearine ......... 87

8. Oleaginous principles of human fat . . . .88

9. Human adipose tissue ....... 90

10. Chyle ......... 90

11. Globules of cow's rnilk ....... 91

12. Cells of costal cartilages . • . . . .91

13. Hepatic cells • ... 0 ... 92

14. Uriniferous tubules of dog ...... 92

15. Muscular fibres of human uterus .... 93

16. Alimentary canal of fowl . . . . . .117

17. Compound stomach of ox . . . From Rymer Jones 118
IS. Human alimentary canal . . . . . . .119

19. Skull of rattlesnake . . . From Achille-Richard 121

20. Skull of polar bear . . . . . . .122

21. Skull of the horse . . . . . . .122

22. Molar tooth of the horse . . . . . . .122

23. Human teeth — upper jaw. . . . . . .123

24. Buccal and glandular epithelium deposited from saliva . . .124

25. Gastric mucous membrane, viewed from above . . . .133

26. Gastric mucous membrane, in vertical section .... 133

27. Mucous membrane of pig's stomach . . . . .134

28. Gastric tubules from pig's stomach, pyloric portion . . . 134

29. Gastric tubules from pig's stomach, cardiac portion . . . 134

30. Confervoid vegetable, growing in gastric juice .... 140

31. Follicles of Lieberkiihn ....... 151

32. Brunner's duodenal glands . ... . . . 152

33. Contents of stomach, during digestion of meat .... 158

34. From duodenum of dog, during digestion of meat . . .158

35. From middle of small intestine ...... 159

( xxiii )

LIST OF ILLUSTRATIONS.

FIG. PAGE

36. From last quarter of small intestine . . • 159

37. One of the closed follicles of Peyer's patches . . .162

38. Glandula agminatse . ...

39. Extremity of intestinal villus . . . 163

40. Panizza's experiment on absorption by bloodvessels

41. Chyle, from commencement of thoracic duct . . . .167

42. Lacteals, thoracic duct, &c. . • • • • .168

43. Lacteals and lymphatics .

44. Intestinal epithelium, in intervals of digestion . . 172

45. Intestinal epithelium, during digestion . ... 172

46. Cholesterin .... ... 177

47. Ox-bile, crystallized . . .178

48. Glyko-cholate of soda from ox-bile ..... 178

49. Glyko-cholate and tauro-cholate of soda, from ox-bile . . 179

50. Dog's bile, crystallized ... . .182

51. Human bile, showing resinous matters . . . 183

52. Crystalline and resinous biliary substances, from dog's intestine . 189

53. Duodenal fistula ..... .190

54. Human blood-globules ....... 214

55. The same, seen out of focus . . . . . .214

56. The same, seen within the focus ...... 215

57. The same, adhering together in rows . . . . .215

58. The same, swollen by addition of water .... 217

59. The same, shrivelled by evaporation ..... 217

60. Blood-globules of frog ....... 220

61. White globules of the blood . - . . . .221

62. Coagulated fibrin ........ 223

63. Coagulated blood ........ 226

64. Coagulated blood, after separation of clot and serum . . . 227

65. Recent coagulum ........ 230

66. Coagulated blood, clot buffed and cupped .... 230

67. Head and gills of menobrauchus ...... 233

68. Lung of frog . . . . . . . . 234

69. Human larynx, trachea, bronchi, and lungs .... 235

70. Single lobule of human lung . . . ... . 235

71. Diagram illustrating the respiratory movements . . . 237

72. Small bronchial tube ....... 239

73. Human larynx, with glottis closed ..... 240

74. The same, with glottis open ...... 240

75. Human larynx — posterior view ...... 241

76. Circulation of fish ....... 265

77. Circulation of reptiles ....... 266

78. Circulation of mammalians ...... 267

79. Human heart, anterior view ...... 268

80. Human heart, posterior view ...... 268

81. Right auricle and ventricle, tricuspid valve open, arterial valves closed 268

82. Right auricle and ventricle, tricuspid valve closed, arterial valves open 269

83. Course of blood through the heart . . . . .270

84. Illustrating production of valvular sounds .... 273

85. Heart of frog, in relaxation • . . . . . . 276

LIST OF ILLUSTRATIONS. XXV

FIG. "^ PAGE

86. Heart of frog, in contraction ...... 276

87. Simple looped fibres ....... 276

88. Bullock's heart, showing superficial muscular fibres . . . 277

89. Left ventricle of bullock's heart, showing deep fibres . . . 277

90. Diagram of circular fibres of the heart .... 278

91. Converging fibres of the apex of the heart .... 278

92. Artery in pulsation ....... 283

93. Curves of the arterial pulsation ..... 285

94. Volkmann's apparatus ....... 289

95. The same ........ 289

96. Vein, with valves open ....... 293

97. Vein, with valves closed ...... 293

98. Small artery, with capillary branches . . . . . 295

99. Capillary network ....... 296

100. Capillary circulation ....... 297

101. Diagram of the circulation ...... 305

102. Follicles of a compound mucous glandule . From Kolliker 327

103. Meibomian glands .... From Ludovic 329

104. Perspiratory gland . . . From Todd and Bowman 330

105. Glandular structure of mamma ..... 333

106. Colostrum corpuscles ....... 334

107. Milk-globules .....'... 335

108. Division of portal vein in liver ..... 338

109. Lobule of liver ....... 339

110. Hepatic cells ........ 340

111. Urea .... From Lehrnami (Funke's Atlas) 343

112. Creatine . . . From Lehmaun (Funke's Atlas) 346

113. Creatinine . . . From Lehmanu (Funke's Atlas) 346

114. Urate of soda ........ 347

115. Uric acid ........ 354

116. Oxa.late of lime ........ 360

117. Phosphate of magnesia and ammonia ..... 362

118. Nervous filaments, from brain ...... 369

119. Nervous filaments from sciatic nerve ..... 370

120. Division of a nerve . . . . . . . 371

121. Inosculation of nerves ....... 372

122. Nerve cells ........ 372

123. Nervous system of starfish ...... 373

124. Nervous system of aplysia ...... 375

125. Nervous system of centipede ...... 376

126. Cerebro-spinal system of man ...... 379

127. Spinal cord ........ 380

128. Brain of alligator ....... 382

129. Brain of rabbit ....... 383

130. Medulla oblongata of human brain ..... 384

131. Diagram of human brain ...... 3S6

132. Experiment showing irritability of muscles .... 389

133. Experiment showing irritability of nerve .... 391

134. Action of direct and inverse currents ..... 394

135. Diagram of spinal cord and nerves ..... 402

XXVI LIST OF ILLUSTRATIONS.

FIG. PAGE

136. Spinal cord in vertical section . . . 409

137. Experiment, showing effect of poisons upon nerves . . 412

138. Pigeon, after removal of the hemispheres . . . 421

139. Aztec children ....... 426

140. Brain in situ ... ... 428

141. Transverse section of brain .... . 429

142. Pigeon, after removal of the cerebellum .... 431

143. Brain of healthy pigeon in profile ..... 433

144. Brain of operated pigeon in profile ..... 433

145. Brain of healthy pigeon, posterior view .... 433

146. Brain of operated pigeon, posterior view . . 433

147. Inferior surface of brain of cod ..... 436

148. Inferior surface of brain of fowl ...... 436

149. Course of optic nerves in man ...... 437

150. Distribution of fifth nerve upon the face ... . . 452

151. Facial nerve ........ 457

152. Pneumogastric nerve ....... 462

153. Diagram of tongue ....... 483

154. Distribution of nerves in the nasal passages .... 489

155. Vertical section of eyeball ...... 493

156. Dispersion of rays of light ...... 495

157. Action of crystalline lens ...... 495

158. Myopia ......... 496

159. Presbyopia ........ 496

160. Vision at short distance . . . . . .497

161. Vision at long distance ....... 497

162. Refraction of lateral rays ...... 500

163. Skull, as seen by left eye ...... 502

164. Skull, as seen by right eye . . . .502

165. Human auditory apparatus ...... 507

166. Great sympathetic . . . „ . . . 515

167. Cat, after division of sympathetic in the neck . . . 522

168. Different kinds of infusoria ...... 530

169. Experiment on spontaneous generation . From Schultze 532

170. Trichina spiralis . . . . . . .535

171. Tsenia ......... 536

172. Cysticercus, retracted . . . . . . .537

173. Cysticercus, unfolded ....... 537

174. Blossom of Convolvulus purpureus . . . . . 540

175. Single articulation of Tsenia crassicollis .... 541

176. Human ovum ........ 544

177. Human ovum, ruptured by pressure ..... 545

178. Female generative organs of frog ..... 547

179. Mature frogs' eggs ....... 548

180. Female generative organs of fowl . . . . .551

181. Fowl's egg ... . .... 552

182. Uterus and ovaries of the sow ...... 553

183. Generative organs of human female ..... 554

184. Spermatozoa ........ 557

185. Graafian follicle . 5b'8

LIST OF ILLUSTRATIONS. XXVU

FIG. PAGE

186. Ovary with Graafian follicle ruptured . . . . .568

187. Graafian follicle, ruptured and filled with blood . . . 577

188. Corpus luteum, three weeks after menstruation . . . 578

189. Corpus luteum, four weeks after menstruation . . . 579

190. Corpus luteum, nine weeks after menstruation . . . 579

191. Corpus luteum of pregnancy, at end of second month . . . 582

192. Corpus luteum of pregnancy, at end of fourth mouth . . . 582

193. Corpus luteum of pregnancy, at term ..... 583

194. Segmentation of the vitellus . . . . . .587

195. Impregnated egg, showing embryonic spot .... 590

196. Impregnated egg, showing two layers of blastodermic membrane . 591

197. Impregnated egg, farther advanced ..... 591

198. Frog's egg, at an early period . . . 592

199. Egg of frog, in process of development ..... 592

200. Egg of frog, farther advanced ...... 592

201. Tadpole, fully developed . . . . . .593

202. Tadpole, changing into frog ...... 594

203. Perfect frog ........ 594

204. Egg of fish ........ 596

205. Young fish, with umbilical vesicle ..... 597

206. Human embryo, with umbilical vesicle .... 597

207. Fecundated egg, showing formation of amniou .... 600

208. Fecundated egg, showing commencement of allantois . . . 601

209. Fecundated egg, with allantois nearly complete . . . 601

210. Fecundated egg, with allantois fully formed .... 602

211. Egg of fowl, showing area vasculosa ..... 603

212. Egg of fowl, showing allantois, amnion, &c. . 604

213. Human ovum, showing formation of chorion .... 608

214. Compound villosity of human chorion .... 610

215. Extremity of villosity of choriou ..... 611

216. Human ovum, at end of third month ..... 612

217. Uterine mucous membrane ...... 615

218. Uterine tubules ........ 615

219. Impregnated uterus, showing formation of decidua . . . 617

220. Impregnated uterus, showing formation of decidua reflexa . . 617

221. Impregnated uterus, with decidua reflexa complete . . . 617

222. Impregnated uterus, showing union of chorion and decidua . . 619

223. Pregnant uterus, showing formation of placenta . . . 620

224. Foetal pig, with membranes ...... 622

225. Cotyledon of cow's uterus . . . . . .622

226. Extremity of foetal tuft, human placenta .... 624

227. Foetal tuft of human placenta injected .... 625

228. Vertical section of placenta . . . . . .626

229. Human ovum, at end of first month ..... 630

230. Human ovum, at end of third month ..... 631

231. Gravid human uterus and contents ..... 632

232. Muscular fibres of unimpregnated uterus .... 635

233. Muscular fibres of human uterus, ten days after parturition . . 635

234. Muscular fibres of human uterus, three weeks after parturition . 636

235. Formation of cerebro-spinal axis ..... 637

XXVlll LIST OF ILLUSTRATIONS.

FIG. PAGE

236. Formation of cerebro-spinal axis ... . 638

237. Fo3tal pig, showing brain and spinal cord .... 638

238. Foetal pig, showing brain and spinal cord .... 639

239. Head of foetal pig . . . . . . .639

240. Brain of adult pig . . . . . .639

241. Formation of alimentary canal ...... 645

242. Foetal pig, showing umbilical hernia ..... 646

243. Head of human embryo, at twenty days . . From Longet 652

244. Head of human embryo, at end of sixth week .... 652

245. Head of human embryo, at end of second month . . . 653

246. Foetal pig, showing Wolffian bodies ' . . . . .655

247. Foetal pig, showing first appearance of kidneys . . . 657

248. Internal organs of generation ...... 657

249. Internal organs of generation ...... 659

250. Formation of tunica vaginalis testis ..... 660

251. Congenital inguinal hernia ...... 661

252. Egg of fowl, showing area vasculosa ..... 666

253. Egg of fish, showing vitelline circulation .... 666

254. Young embryo and its vessels ...... 667

255. Embryo and its vessels, farther advanced .... 668

256. Arterial system, embryonic form ..... 670

257. Arterial system, adult form ...... 670

258. Early condition of venous system ..... 672

259. Venous system, farther advanced ..... 673

260. Continued development of venous system .... 673

261. Adult condition of venous system ..... 674

262. Early form of hepatic circulation ..... 675

263. Hepatic circulation farther advanced ..... 678

264. Hepatic circulation, during latter part of foetal life . . . 676

265. Adult form of hepatic circulation ..... 677

266. Foetal heart ........ 678

267. Foetal heart ........ 678

268. Foetal heart ........ 678

269. Foetal heart ........ 679

270. Heart of infant ......".. 679

271. Heart of human foetus, showing Eustachian valve . . . 681

272. Circulation through the foetal heart ..... 632

273. Adult circulation through the heart . 685

HUMAN PHYSIOLOGY.

INTRODUCTION.

I. PHYSIOLOGY is the study of the phenomena presented by
organized bodies, animal and vegetable.

These phenomena are different from those presented by inorganic
substances. They require, for their production, the existence of
peculiarly formed animal and vegetable organisms, as well as the
presence of various external conditions, such as warmth, light, air,
moisture, &c.

They are accordingly more complicated than the phenomena of
the inorganic world, and require for their study, not only a pre-
vious acquaintance with the laws of chemistry and physics, but, in
addition, a careful examination of other characters which are pecu-
liar to them.

These peculiar phenomena, by which we so readily distinguish
living organisms from inanimate substances, are called Vital pheno-
mena, or the phenomena of Life. Physiology consequently includes
the study of all these phenomena, in whatever order or species of
organized body they may originate.

We find, however^ upon examination, that there are certain
general characters by which the vital phenomena of vegetables
resemble each other, and by which they are distinguished from the
vital phenomena of animals. Thus, vegetables absorb carbonic
acid, and exhale oxygen ; animals absorb oxygen, and exhale car-
bonic acid. Yegetables nourish themselves by the absorption of
unorganized liquids and gases, as water, ammonia, saline solutions,
&c. ; animals require for their support animal or vegetable sub-
stances as food, such as meat, fruits, milk, &c. Physiologv, then,
4 (49)

50 INTRODUCTION.

is naturally divided into two parts, viz., Vegetable Physiology, and
Animal Physiology.

Again, the different groups and species of animals, while they
resemble each other in their general characters, are distinguished
by certain minor differences, both of structure and function, which
require a special study. Thus, the physiology of fishes is not
exactly the same with that of reptiles, nor the physiology of birds
with that of quadrupeds. Among the warm-blooded quadrupeds,
the carnivora absorb more oxygen, in proportion to the carbonic
acid exhaled, than the herbivora. Among the herbivorous quad-
rupeds, the process of digestion is comparatively simple in the
horse, while it is complicated in the ox; and other ruminating ani-
mals. There is, therefore, a special physiology for every distinct
species of animal.

HUMAN PHYSIOLOGY treats of the vital phenomena of the human
species. It is more practically important than the physiology of
the lower animals, owing to its connection with human pathology
and therapeutics. But it cannot be made the exclusive subject of
our study ; for the special physiology of the human body cannot
be properly understood without a previous acquaintance with the
vital phenomena common to all animals, and to all vegetables;
beside which, there are many physiological questions that require
for their solution experiments and observations, which can only be
made upon the lower animals.

While the following treatise, therefore, has for its principal sub-
ject the study of Human Physiology, this will be illustrated, when-
ever it may be required, by what we know in regard to the vital
phenomena of vegetables and of the lower animals.

II. Since Physiology is the study of the active phenomena of
living bodies, it requires a previous acquaintance with their struc-
ture, and with the substances of which they are composed ; that is,
with their anatomy.

Anatomy, again, requires a previous acquaintance with inorganic
substances ; since some of these inorganic substances enter into the
composition of the body. Chloride of sodium, for example, water,
and phosphate of lime, are component parts of the animal frame,
and therefore require to be studied as such by the anatomist.
Now these inorganic substances, when placed under the requisite
external conditions, present certain active phenomena, which are
characteristic of them, and by which they may be recognized.

INTRODUCTION". 51

Thus lime, dissolved in water, if brought into contact with car-
bonic acid, alters its condition, and takes part in the formation of
an insoluble substance, carbonate of lime, which is thrown down
as a deposit. A knowledge of such chemical reactions as these is
necessary to the anatomist, since it is by them that he is enabled to
recognize the inorganic substances, forming a part of the animal
body.

It is important to observe, however, that a knowledge of these
reactions is necessary to the anatomist only in order to enable him
to judge of the presence or absence of the inorganic substances to
which they belong. It is the object of the anatomist to make him-
self acquainted with every constituent part of the body. Those
parts, therefore, which cannot be recognized by their form and
texture, he distinguishes by their chemical reactions. But after-
ward, he has no occasion to decompose them further, or to make
them enter into new combinations ; for he "only wishes to know
these substances as they exist in the body, and not as they may exist
under other conditions.

The unorganized substances which exist in the body as compo-
nent parts ^of its structure, such as chloride of sodium, water, phos-
phate of lime, &c., are called the proximate principles of the body.
Mingled together in certain proportions, they make up the animal
fluids, and associated also in a solid form, they constitute the tissues
and organs, and in this way make up the entire frame.

Anatomy makes us acquainted with all these component parts of
the body, both solid and fluid. It teaches us the structure of the
body in a state of rest ; that is, just as it would be after life had
suddenly ceased, and before putrefaction had begun. On the other
hand, Physiology is a description of the body in a state of activity,
It shows us its movements, its growth, its reproduction, and the
chemical changes which go on. in its interior; and in order to com-
prehend these, we must know, beforehand, its entire mechanical,
textural, and chemical structure.

It is evident, therefore, that the description of i\Q proximate prin-
ciples, or the chemical substances entering into the constitution of
the body, is, strictly speaking, a part of Anatomy. But there are
many reasons why this study is more conveniently pursued in con-
nection with Physiology ; for some of the proximate principles are
derived directly, as we shall hereafter show, from the external world,
and some are formed from the elements of the food in the process
of digestion ; while most of them undergo certain changes in the

52 INTRODUCTION".

interior of the body, which result in the formation of new sub-
stances ; all these active phenomena belonging necessarily to the
domain of Physiology.

The description of the proximate principles of animals and vege-
tables will therefore be introduced into the following pages.

The description of the minute structures of the body, or Micro-
scopic Anatomy, is also so closely connected with some parts of Phy-
siology as to make it convenient to speak of them together ; and
this will accordingly be done, whenever the nature of the subject
may make it desirable.

III. The study of Physiology, like that of all the other natural
sciences, is a study of phenomena, and of phenomena alone. The
essential nature of the vital processes, and their ultimate causes,
are questions which are beyond the reach of the physiologist, and
cannot be determined by the means of investigation which are at
his disposal.

Consequently, all efforts to solve them will only serve to mislead
the investigator, and to distract his attention from the real subject
of examination. Much time has been lost, for example, in discuss-
ing the probable reason why menstruation returns, in the human
female, at the end of every four weeks. But the observation of
nature, which is our only means of scientific investigation, cannot
throw any light on this point, but only shows us the fact that men-
struation does really occur at the above periods, together with the
phenomena which accompany it, and the conditions under which it
is hastened or retarded, and increased or diminished, in intensity,
duration, &c. If we employ ourselves, consequently, in the discus-
sion of the reason above mentioned, we shall only become involved
in a network of hypothetical surmises, which can never lead to any
definite result. Our time, therefore, will be much more profitably
devoted to the study of the above phenomena, which can be learned
from nature, and which constitute afterward, a permanent acquisi-
tion.

The physiologist, accordingly, confines himself strictly to the
study of the vital phenomena, their characters, their frequency,
their regularity or irregularity, and the conditions under which
they originate.

When he has discovered that a certain phenomenon always takes
place in the presence of certain conditions, he has established what
is called a general principle, or a LAW of Physiology.

INTRODUCTION. 53

As, for example, when he has ascertained that sensation and
motion occupy distinct situations in every part of the nervous
system.

This " Law," however, it must be remembered, is not a discovery
by itself, nor does it give him any new information, but is simply
the expression, in convenient and comprehensive language, of the
facts with which he was already previously acquainted. It is very
dangerous, therefore, to make these laws or general principles the
subjects of our study instead of the vital phenomena, or to suppose
that they have any value, except as the expression of previously
ascertained facts. Such a misconception would lead to bad prac-
tical results. For if we were to observe a phenomenon in discord-
ance with a " law" or " principle," we might be led to neglect or
misinterpret the phenomenon, in order to preserve the law. But
this would be manifestly incorrect. For the law is not superior to
the phenomenon, but, on the contrary, depends upon it, and derives
its whole authority from it. Such mistakes, however, have been
repeatedly made in Physiology, and have frequently retarded its
advance.

IY. There is only one means by which Physiology can be
studied : that is, the observation of nature. Its phenomena cannot
be reasoned out by themselves, nor inferred, by logical sequence,
form any original principles, nor from any other set of phenomena
whatever.

In Mathematics and Philosophy, on the other hand, certain truths
are taken for granted, or perceived by intuition, and the remainder
afterward derived from them by a process of reasoning. But in
Physiology, as in all the other natural sciences, there is no such
starting point, and it is impossible to judge of the character of a
phenomenon until after it has been observed. Thus, the only way
to learn what action is exerted by nitric acid upon carbonate of
soda is to put the two substances together, and observe the changes
which take place ; for there is nothing in the general characters of
these two substances which could guide us in anticipating the result.

Neither can we infer the truths of Physiology from those of
Anatomy, nor the truths of one part of Physiology from those of
another part ; but all must be ascertained directly and separately
by observation.

For, although one department of natural science is almost always
a necessary preliminary to the study of another, yet the facts of

54 INTRODUCTION.

the latter can never be in the least degree inferred from those of the
former, but must be studied ly themselves.

Thus Chemistry is essential to Anatomy, because certain sub-
stances, as we have already shown, belonging to Chemistry, such
as chloride of sodium, occur as constituents of the animal body.
Chemistry teaches us the composition, reactions, mode of crystal-
lization, solubility, &c., of chloride of sodium ; and if we did not
know these, we could not extract it, or recognize it when extracted
from the body. But, however well we might know the chemistry
of this substance, we could never, on that account, infer its presence
in the body or otherwise, nor in what quantities nor in what situa-
tions it would present itself. These facts must be ascertained for
themselves, by direct investigation, as a part of anatomy proper.

So, again, the structure of the body in a state of rest, or its
anatomy, is to be first understood ; but its active phenomena or its
physiology must then be ascertained by direct observation and
experiment. The most intimate knowledge of the minute struc-
ture of the muscular and nervous fibres could not teach us any-
thing of their physiology. It is only by experiment that we
ascertain one of them to be contractile, the other sensitive.

Many of the phenomena of life are chemical in their character,
and it is requisite, therefore, that the physiologist know the ordi-
nary chemical properties of the substances composing the animal
frame. But no amount of previous chemical knowledge will
enable him to foretell the reactions of any chemical substance in
the interior of the body; because the peculiar conditions under
which it is there placed modify these reactions, as an elevation or
depression of temperature, or other external circumstance, might
modify them outside the body.

We must not, therefore, attempt to deduce the chemical phe-
nomena of physiology from any previously established facts, since
these are no safe guide ; but must study them by themselves, and
depend for our knowledge of them upon direct observation alone.

Y. By the term Vital phenomena, we mean those phenomena
which are manifested in the living body, and which are character-
istic of its functions.

Some of these phenomena are physical or mechanical in their
character; as, for example, the play of the articulating surfaces
upon each other, the balancing of the spinal column with its ap-
pendages, the action of the elastic ligaments. Nevertheless, these

INTRODUCTION. 55

phenomena, though strictly physical in character, are often entirely
peculiar and different from those seen elsewhere, because the me-
chanism of their production is peculiar in its details. Thus the
human voice and its modulations are produced in the larynx, in
accordance with the general physical laws of sound; but the
arrangement of the elastic and movable vocal chords, and their
relations with the columns of air above and below, the moist and
flexible mucous membrane, and the contractile muscles outside, are
of such a special character that the entire apparatus, as well as the
sounds produced by it, is peculiar ; and its action cannot be properly
compared with that of any other known musical instrument.

In the same manner, the movements of the heart are so compli-
cated and remarkable that they cannot be comprehended, even by
one who is acquainted with the anatomy of the organ, without a
direct examination. This is not because there is anything essen-
tially obscure or mysterious in their nature,, for they are purely
mechanical in character ; but because their conditions are so pecu-
liar, owing to the tortuous course of the muscular fibres, their
arrangement in interlacing layers, their attachments and relations,
that their combined action produces an effect altogether peculiar,
and one which is not similar to anything outside the living body.

A very large and important class of the vital phenomena are
those of a chemical character. It is one of the characteristics of
living bodies that a succession of chemical actions, combinations
and decompositions, is constantly going on in their interior. It is
one of the necessary conditions of the existence of every animal
and every vegetable, that it should constantly absorb various sub-
stances from without, which undergo different chemical alterations
in its interior, and are finally discharged from it under other forms.
If these changes be prevented from taking place, life is immediately
extinguished. Thus animals constantly absorb, on the one hand,
water, oxygen, salts, albumen, oil, sugar, &c., and give up, on the
other hand, to the surrounding media, carbonic acid, water, ammonia,
urea, and the like ; while between these two extreme points, of ab-
sorption and exhalation, there take place a multitude of different
transformations which are essential to the continuance of life.

Some of these chemical actions are the same with those which
are seen outside the body ; but most of them are entirely peculiar,
and do not take place, and cannot be made to take place, anywhere
else. This, again, is not because there is anything particularly
mysterious or extraordinary in their nature, but because the con-

56 INTRODUCTION.

ditions necessary for their accomplishment exist in the body, and
do not exist elsewhere. All chemical phenomena are liable to be
modified by surrounding conditions. Many reactions, for example,
which will take place at a high temperature, will not take place at
a low temperature, and vice versa. Some will take place in the light,
but not in the dark ; others will take place in the dark, but not in
the light. If a hot concentrated solution of sulphate of soda be
allowed to cool in contact with the atmosphere, it crystallizes;
covered with a film of oil, it remains fluid. Because a chemical
reaction, therefore, takes place under one set of conditions, we can-
not be at all sure that it will also take place under others, which
are different.

The chemical conditions of the living body are exceedingly com-
plicated. In the animal solids and fluids there are many substances
mingled together in varying quantities, which modify or interfere
with each other's reactions. New substances are constantly entering
by absorption, and old ones leaving by exhalation ; while the circu-
lating fluids are constantly passing from one part of the body to
another, and coming in contact with different organs of different
texture and composition. All these conditions are peculiar, and so
modify the chemical actions taking place in the body, that they are
unlike those met with anywhere else.

If starch and iodine be mingled together in a watery solution,
they unite with each other, and strike a deep opaque blue color ;
but if they be mingled in the blood, no such reaction takes place,
because it is prevented by the presence of certain organic substances
which interfere with it.

If dead animal matter be exposed to warmth, air, and moisture,
it putrefies ; but if introduced into the living stomach, even after
putrefaction has commenced, this process is arrested, because the
fluids of the stomach cause the animal substance to undergo a
peculiar transformation (digestion), after which the bloodvessels
immediately remove it by absorption. There are also certain sub-
stances which make their appearance in the living body, both of
animals and vegetables, and which cannot be formed elsewhere ;
such as fibrin, albumen, casein, pneumic acid, the biliary salts, mor-
phine, &c. These substances cannot be manufactured artificially,
simply because the necessary conditions cannot be imitated. They
require for their production the presence of a living organism.

The chemical phenomena of the living body are, therefore, not
different in their nature from any other chemical phenomena ; but

INTRODUCTION. 57

they are different in their conditions and in their results, and are
consequently peculiar and characteristic.

Another set of vital phenomena are those which are manifested
in the processes of reproduction and development. They are again
entirely distinct from any phenomena which are exhibited by
matter not endowed with life. An inorganic substance, even when
it has a definite form, as, for example, a crystal of fluor spar, has
no particular relation to any similar form which has preceded, or
any other which is to follow it. On the other hand, every animal
and every vegetable owes its origin to preceding animals or vege-
tables of the same kind ; and the manner in which this production
takes place, and the different forms through which the new body
successively passes in the course of its development, constitute the
phenomena of reproduction. These phenomena are mostly depend-
ent on the chemical processes of nutrition and growth, which take
place in a particular direction and in a particular manner ; but their
results, viz., the production of a connected series of different forms,
constitute a separate class of phenomena, which cannot be explained
in any manner by the preceding, and require, therefore, to be studied
by themselves.

Another set of vital phenomena are those which belong to the
nervous system. These, like the processes of reproduction and
development, depend on the chemical changes of nutrition and
growth. That is to say, if the nutritive processes did not go on in
a healthy manner, and maintain the nervous system in a healthy
condition, the peculiar phenomena which are characteristic of it
could not take place. The nutritive processes are necessary condi-
tions of the nervous phenomena. But there is no other connection
between them ; and the nervous phenomena themselves are distinct
from all others, both in their nature and in the mode in which they
are to be studied.

A troublesome confusion might arise if we were to neglect the
distinction that really exists between these different sets of phe-
nomena, and confound them together under the expectation of
thereby simplifying our studies. Since this can only be done by
overlooking real points of difference, its effect will merely be to
introduce erroneous ideas and suggest unfounded similarities, and
will therefore inevitably retard our progress instead of advancing it.

It has been sometimes maintained, for example, that all the vital
phenomena, those of the nervous system included, are to be reduced
to the chemical changes of nutrition, and that these again are to be

58 INTRODUCTION.

regarded as not at all different in any respect from the ordinary
chemical changes taking place outside the body. This; however,
is not only erroneous in theory, but conduces also to a vicious
mode of study. For it draws away our attention from the phe-
nomena themselves and their real characteristics, and leads us to
deduce one set of phenomena from what we know of another ; a
method which we have already shown to be unsafe and pernicious.
It has also been asserted that the phenomena of the nervous
system are identical with those of electricity ; for no other reason
than that there exist between them certain general resemblances.
But when we examine the phenomena in detail, we find that, beside
these general resemblances, there are many essential points of dis-
similarity, which must be suppressed and kept out of sight in order
to sustain the idea of the assumed identity. This assumption is
consequently a forced and unnatural one, and the simplicity which
it was intended to introduce into our physiological theories is
imaginary and deceptive, and is attained only by sacrificing a part
of those scientific truths, which are alone the real object of our
study. We should avoid, therefore, making any such unfounded
comparisons ; for the theoretical simplicity which results from them
does not compensate for the loss of essential scientific details.

VI. The study of Physiology is naturally divided into three dis-
tinct Sections : —

The first of these includes everything which relates to the NUTRI-
TION of the body in its widest sense. It comprises the history of
the proximate principles, their source, the manner of their produc-
tion, the proportions in which they exist in different kinds of food
and drink, the processes of digestion and absorption, and the con-
stitution of the circulating fluids ; then the physical phenomena of
the circulation and the forces by which it is accomplished ; the
changes which the blood undergoes in different parts of the body ;
all the phenomena, both physical and chemical, of respiration ; those
of secretion and excretion, and the character and destination of the
secreted and excreted fluids. All these processes have reference to
a common object, viz., the preservation of the internal structure and
healthy organization of the individual. With certain modifications,
they take place in vegetables as well as in animals, and are conse-
quently known by the name of the vegetative functions.

The Second Section, in the natural order of study, is devoted to
the phenomena of the NERVOUS SYSTEM. These phenomena are

INTRODUCTION. 59

not exhibited by vegetables, but belong exclusively to animal or-
ganizations. They bring the animal body into relation with the
external world, and preserve it from external dangers, by means of
sensation, movement, consciousness, and volition. They are more
particularly distinguished by the name of the animal functions.

Lastly comes the study of the entire process of EEPBODUCTION.
Its phenomena, again, with certain modifications, are met with in
both animals and vegetables ; and might, therefore, with some pro-
priety, be included under the head of vegetative functions. But
their distinguishing peculiarity is, that they have for their object
the production of new organisms, which take the place of the old
and remain after they have disappeared. These phenomena do
not, therefore, relate to the preservation of the individual, but to
that of the species; and any study which concerns the species
comes properly after we have finished everything relating to the
individual.

SECTION I.
NUTRITION.

CHAPTER I.

PROXIMATE PRINCIPLES IN GENERAL.

THE study of NUTRITION begins naturally with that of the proxi-
mate, principles, or the substances entering into the composition of
the different parts of the body, and the different kinds of food. In
examining the body, the anatomist finds that it is composed, first,
of various parts, which are easily recognized by the eye, and which
occupy distinct situations. In the case of the human body, for
example, a division is easily made of the entire frame into the
head, neck, trunk, and extremities. Each of these regions, again,
is found, on examination, to contain several distinct parts, or
" organs," which require to be separated from each other by dissec-
tion, and which are distinguished by their form, color, texture, and
consistency. In a single limb, for example, every bone and every
muscle constitutes a distinct organ. In the trunk, we have the
heart, the lungs, the liver, spleen, kidneys, spinal cord, &c., each of
which is also a distinct organ. When a number of organs, differing
in size and form, but similar in texture, are found scattered through-
out the entire frame, or a large portion of it, they form a connected
set or order of parts, which is called a " system." Thus, all the
muscles taken together constitute the muscular system ; all the
bones, the osseous system ; all the arteries, the arterial system.
Several entirely different organs may also be connected with each
other, so that their associated actions tend to accomplish a single
object, and they then form an "apparatus." Thus the heart, arte-
ries, capillaries, and veins, together, form the circulatory apparatus ;
the stomach, liver, pancreas, intestine, &c., the digestive apparatus.
Every organ, asrain, on microscopic examination, is seen to be made

( 61 )

62 PROXIMATE PRINCIPLES IN GENERAL.

up of minute bodies, of definite size and figure, which are so small
as to be invisible to the naked eye, and which, after separation
from each other, cannot be further subdivided without destroying
their organization. They are, therefore, called "anatomical ele-
ments." Thus, in the liver, they are hepatic cells, capillary blood-
vessels, the fibres of Glisson's capsule, and the ultimate filaments
of the hepatic nerves. Lastly, two or more kinds of anatomical
elements, interwoven with each other in a particular manner, form
a "tissue." Adipose vesicles, with capillaries and nerve tubes,
form adipose tissue. White fibres and elastic fibres, with capillaries
and nerve tubes, form areolar tissue. Thus the solid parts of the
entire body are made up of anatomical elements, tissues, organs,
systems, and apparatuses. Every organized frame, and even every
apparatus, every organ, and every tissue, is made up of different
parts, variously interwoven and connected with each other, and it
is this character which constitutes its organization.

But beside the above solid forms, there are also certain fluids,
which are constantly present in various parts of the body, and which,
from their peculiar constitution, are termed " animal fluids." These
fluids are just as much an essential part of the body as the solids.
The blood and the lymph, for example, the pericardial and synovial
fluids, the saliva, which always exists more or less abundantly in
the ducts of the parotid gland, the bile in the biliary ducts and the
gall-bladder : all these go to make up the entire body, and are quite
as necessary to its structure as the muscles or the nerves. Now, if
these fluids be examined, they are found to be made up of many
different substances, which are mingled together in certain propor-
tions; these proportions being constantly maintained at or about
the same standard by the natural processes of nutrition. Such a
fluid is termed an organizing fluid. It is organized by virtue of the
numerous ingredients which enter into its composition, and the
regular proportions in which these ingredients are maintained.
Thus in the plasma of the blood, we have albumen, fibrin, water,
chlorides, carbonates, phosphates, &c. In the urine, we find water,
urea, urate of soda, creatine, creatinine, coloring matter, salts, &c.
These substances, which are mingled together so as to make up, in
each instance, by their intimate union, a homogeneous liquid, are
called the PROXIMATE PRINCIPLES of the animal fluid.

In the solids, furthermore, even in those parts which are appa-
rently homogeneous, there is the same mixture of different ingre-
dients. In the hard substance of bone, for example, there is, first

PROXIMATE PRINCIPLES IN GENERAL. 63

water, which may be expelled by evaporation ; second, phosphate
and carbonate of lime, which may be extracted by the proper sol-
vents ; third, a peculiar animal matter, with which these calcareous
salts are in union ; and fourth, various other saline substances, in
special proportions. In the muscular tissue, there is chloride of
potassium, lactic acid, water, salts, albumen, and an animal matter
termed musculine. The difference in consistency between the solids
and fluids does not, therefore, indicate any radical difference in their
constitution. Both are equally made up of proximate principles,
mingled together in, various proportions.

It is important to understand, however, exactly what are proxi-
mate principles, and what are not such ; for since these principles
are extracted from the animal solids and fluids, and separated from
each other by the help of certain chemical manipulations, such as
evaporation, solution, crystallization, and the like, it might be sup-
posed that every substance which could be extracted from an organ-
ized solid or fluid, by chemical means, should be considered as a
proximate principle. That, however, is not the case. A proximate
principle is properly denned to be any substance, whether simple or
compound, chemically speaking, which exists, under its own form, in the
animal solid or fluid, and which can be extracted by means which do
not alter or destroy its chemical properties. Phosphate of lime, for
example, is a proximate principle of bone, but phosphoric acid is
not so, since it does not exist as such in the bony tissue, but is
produced only by the decomposition of the calcareous salt ; still
less phosphorus, which is obtained only bv the decomposition of
the phosphoric acid.

Proximate principles may, in fact, be said to exist in all solids or
fluids of mixed composition, and may be extracted from them by
the same means as in the case of the animal tissues or secretions.
Thus, in a watery solution of sugar, we have two proximate prin-
ciples, viz : first, the water, and second, the sugar. The water may
be separated by evaporation and condensation, after which the
sugar remains behind, in a crystalline form. These two substances
have, therefore, been simply separated from each other by the pro-
cess of evaporation. They have not been decomposed, nor their
chemical properties altered. On the other hand, the oxygen and
hydrogen of the water were not proximate principles of the original
solution, and did not exist in it under their own forms, but only in
a state of combination ; forming, in this condition, a fluid substance
(water), endowed with sensible properties entirely different from

64: PROXIMATE PRINCIPLES IN GENERAL.

theirs. If we wish to ascertain, accordingly, the nature and proper-
ties of a saccharine solution, it will afford us but little satisfaction to
extract its ultimate chemical elements ; for its nature and properties
depend not so much on the presence in it of the ultimate elements,
oxygen, hydrogen, and carbon, as on the particular forms of com-
bination, viz., water and sugar, under which they are present.

It is very essential, therefore, that in extracting the proximate
principles from the animal body, only such means should be adopted
as will isolate the substances already existing in the tissues and
fluids, without decomposing them, or altering their nature. A
neglect of this rule has been productive of much injury in the pur-
suit of organic chemistry ; for chemists, in subjecting the animal
tissues to the action of acids and alkalies, of prolonged boiling, or
of too intense heat, have often obtained, at the end of the analysis,
many substances which were erroneously described as proximate
principles, while they were only the remains of an altered and dis-
organized material. Thus, the fibrous tissues, if boiled steadily for
thirty -six hours, dissolve, for the most part, at the end of that time,
in the boiling water ; and on cooling the whole solution solidifies
into a homogeneous, jelly-like substance, which has received the
name of gelatine. But this gelatine does not really exist in the body
as a proximate principle, since the fibrous tissue which produces it
is not at first soluble, even in boiling water, and its ingredients
become altered and converted into a gelatinous matter only by pro-
longed ebullition. So, again, an animal substance containing ace-
tates or lactates of soda or lime will, upon incineration in the open
air, yield carbonates of the same bases, the organic acid having been
destroyed, and replaced by carbonic acid ; or sulphur and phospho-
rus, in the animal tissue, may be converted by the same means into
sulphuric and phosphoric acids, which, decomposing the alkaline
carbonates, become sulphates and phosphates. In either case, the
analysis of the tissues, so conducted, will be a deceptive one, and
useless for all anatomical and physiological purposes, because its
real ingredients have been decomposed, and replaced by others, in
the process of manipulation.

It is in this way that different chemists, operating upon the same
animal solid or fluid, by following different plans of analysis, have
obtained different results ; enumerating as ingredients of the body
many artificially formed substances, which are not, in reality,
proximate principles, thereby introducing much confusion into
physiological, chemist^.

PROXIMATE PRINCIPLES IN GENERAL. 65

It is to be kept constantly in view, in the examination of an
animal tissue or fluid, that the object of the operation is simply the
separation of its ingredients from each other, and not their decomposi-
tion or ultimate analysis. Only the simplest forms of chemical
manipulation should, therefore, be employed. The substance to
be examined should first be subjected to evaporation, in order to
extract and estimate its water. This evaporation must be conducted
at a heat not above 212° F., since a higher temperature would de-
stroy or alter some of the animal ingredients. Then, from the
dried residue, chloride of sodium, alkaline sulphates, carbonates,
and phosphates may be extracted with water. Coloring matters
may be separated by alcohol. Oils may be dissolved out by ether,
&c. &c. When a chemical decomposition is unavoidable, it must
be kept in sight and afterward corrected. Thus the glyko-cholate
of soda of the bile is separated from certain other ingredients by
precipitating it with acetate of lead, forming glyko-cholate of lead ;
but this is afterward decomposed, in its turn, by carbonate of soda,
reproducing the original glyko-cholate of soda. Sometimes it is
impossible to extract a proximate principle in an entirely unaltered
form. Thus the fibrin of the blood can be separated only by allow-
ing it to coagulate ; and once coagulated, it is permanently altered,
and can no longer present all its original characters of fluidity, &c.,
as it existed beforehand in the blood. In such instances as this,
we can only make allowance for an unavoidable difficulty, and be
careful that the substance suffers no further alteration. By bearing
in mind the above considerations, we may form a tolerably correct
estimate of the nature and quantity of all of the proximate princi-
ples existing in the substance under examination.

The manner in which the proximate principles are associated
together, so as to form the animal tissues, is deserving of notice.
In every animal solid and fluid, there is a considerable number of
proximate principles, which are present in certain proportions, and
which are so united with each other that the mixture presents a
homogeneous appearance. But this union is of a complicated cha-
racter ; and the presence of each ingredient depends, to a certain
extent, upon that of the others. Some of them, such as the alkaline
carbonates and phosphates, are in solution directly in the water.
Some, which are insoluble in water, are held in solution by the
presence of other soluble substances. Thus, phosphate of lime is
held in solution in the urine by the bi-phosphate of soda. In the
blood, it is dissolved by the albumen, which is itself fluid by union
5

66 PROXIMATE PRINCIPLES IN GENERAL.

with the water. The same substance may be fluid in one part of
the body, and solid in another part. Thus in the blood and secre-
tions the water is fluid, and holds in solution other substances, both
animal and mineral, while in the bones and cartilages it is solid —
not crystallized, as in the case of ice or of saline substances which
contain water of crystallization, but amorphous and solid, by the
fact of its intimate union with the animal and saline ingredients,
which are abundant in quantity, and which are themselves present
in the solid form. Again, the phosphate of lime in the blood is
fluid by solution in the albumen ; but in the bones it forms a solid
substance with the animal matter of the osseous tissue; and yet
the union of the two is as intimate and homogeneous in the bones
as in the blood. A proximate principle, therefore, never exists
alone in any part of the body, but is always intimately associated
with a number of others, by a kind of homogeneous mixture or
solution.

Every animal tissue and fluid contains a number of proximate
principles which are present, as we have already mentioned, in
certain characteristic proportions. Thus, water is present in very
large quantity in the perspiration and the saliva, but in very small
quantity in the bones and teeth. Chloride of sodium is compara-
tively abundant in the blood and deficient in the muscles. On the
other hand, chloride of potassium is more abundant in the muscles,
less so in the blood. But these proportions, it is important to ob-
serve, are nowhere absolute or invariable. There is a great differ-
ence, in this respect, between the chemical composition of an inor-
ganic substance and the anatomical constitution of an animal fluid.
The former is always constant and definite; the latter is always
subject to certain variations. Thus, water is always composed of
exactly the same relative quantities of oxygen and hydrogen ; and
if these proportions be altered in the least, it thereby ceases to be
water, and is converted into some other substance. But in the
urine, the proportions of water, urea, urate of soda, phosphates,
&c., vary within certain limits in different individuals, and even in
the same individual, from one hour to another. This variation,
which is almost constantly taking place, within the limits of health,
is characteristic of all the animal solids and fluids ; for they are
composed of different ingredients which are supplied by absorption
or formed in the interior, and which are constantly given up again,
under the same or different forms, to the surrounding media by the
unceasing activity of the vital processes. Every variation, then,

PROXIMATE PRINCIPLES IN GENERAL. 67

in the general condition of the body, as a whole, is accompanied by
a corresponding variation, more or less pronounced, in the consti-
tution of its different parts. This constitution is consequently of
a very different character from the chemical constitution of an
oxide or a salt. Whenever, therefore, we meet with the quanti-
tative analysis of an animal fluid, in which the relative quantity
of its different ingredients is represented in numbers, we must
understand that such an analysis is always approximative, and not
absolute.

The proximate principles are naturally divided into three differ-
ent classes.

The first of these classes comprises all the proximate principles
which are purely INORGANIC in their nature. These principles are
derived mostly from the exterior. They are found everywhere, in
unorganized as well as in organized bodies ; and they present them-
selves under the same forms and with the same properties in the
interior of the animal frame as elsewhere. They are crystallizable,
and have a definite chemical composition. They comprise such
substances as water, chloride of sodium, carbonate and phosphate
of lime, &c.

The second class of proximate principles is known as CRYSTAL-
LIZABLE SUBSTANCES OF ORGANIC ORIGIN. This is the name given
to them by Kobin and Yerdeil,1 whose classification of the proxi-
mate principles is the best which has yet been offered. They are
crystallizable, as their name indicates, and have a definite chemical
composition. They are said to be of " organic origin," because they
first make their appearance in the interior of organized bodies, and
are not found in external nature as the ingredients of inorganic
substances. Such are the different kinds of sugar, oil, and starch.

The third class comprises a very extensive and important order
of proximate principles, which go by the name of the ORGANIC
SUBSTANCES proper. They are sometimes known as " albuminoid"
substances or " protein compounds." The name organic substances
is given to them in consequence of the striking difference which
exists between them and all the other ingredients of the body. The
substances of the second class differ from those of the first by their

1 Chiuiie Anatomique et Physiologique. Paris, 1853.

68 PROXIMATE PRINCIPLES IN GENERAL.

exclusively organic origin, but they resemble the latter in their crys-
tallizability and their definite chemical composition ; in consequence
of which their chemical investigation may be pursued in nearly
the same manner, and their chemical changes expressed in nearly
the same terms. But the proximate principles of the third class
are in every respect peculiar. They have an exclusively organic
origin ; not being found except as ingredients of living or recently
dead animals or vegetables. They have not a definite chemical
composition, and are consequently not crystallizable ; and the forms
which they present, and the chemical changes which they undergo
in the body, are such as cannot be expressed by ordinary chemical
phraseology. This class includes such substances as albumen,
fibrin, casein, &c.

PROXIMATE PRINCIPLES OF THE FIRST CLASS. 69

CHAPTER II.

PKOXIMATE PRINCIPLES OF THE FIRST CLASS.

THE proximate principles of the first class, or those of an inor-
ganic nature, are very numerous. Their most prominent characters
have already been stated. They are all crystallizable, and have a
definite chemical composition. They are met with extensively in
the inorganic world, and form a large part of the crust of the earth.
They occur abundantly in the different kinds of food and drink ;
and are necessary ingredients of the food, since they are necessary
ingredients of the animal frame. Some of them are found universally
in all parts of the body, others are met with only in particular
regions ; but there are hardly any which are not present at the
same time in more than one animal solid or fluid. The following
are the most prominent of them, arranged in the order of their
respective importance.

1. WATER. — Water is universally present in all the tissues and
fluids of the body. It is abundant in the blood and secretions,
where its presence is indispensable in order to give them the fluidity
which is necessary to the performance of their functions; for it
is by the blood and secretions that new substances are introduced
into the body, and old ingredients discharged. And it is a neces-
sary condition both of the introduction and discharge of substances
naturally solid, that they assume, for the time being, a fluid form ;
water is therefore an essential ingredient of the fluids, for it holds
their solid materials in solution, and enables them to pass and repass
through the animal frame.

But water is an ingredient also of the solids. For if we take a
muscle or a cartilage, and expose it to a gentle heat in dry air, it
loses water by evaporation, diminishes in size and weight, and be-
comes dense and stiff. Even the bones and teeth lose water by
evaporation in this way, though in smaller quantity. In all these
solid and semi-solid tissues, the water which they contain is useful

70 PROXIMATE PRINCIPLES OF THE FIRST CLASS.

by giving them the special consistency which is characteristic of
them, and which would be lost without it. Thus a tendon, in its
natural condition, is white, glistening, and opaque ; and though very
strong, perfectly flexible. If its water be expelled by evaporation
it becomes yellowish in color, shrivelled, semi-transparent, inflexi-
ble,,and totally unfit for performing its mechanical functions. The
same thing is true of the skin, muscles, cartilages, &c.

The following is a list, compiled by Eobin and Verdeil from
various observers, showing the proportion of water per thousand
parts, in different solids and fluids : —

QUANTITY OF WATER IN 1,000 PARTS IN

Epidermis ... 37 Bile 880

Teeth . . . .100 Milk . . . .887

Bones .... 130 Pancreatic juice . . 900

Cartilage . . . .550 Urine . . . .936

Muscles . . . .750 Lymph . . . .960

Ligaments . . . 768 Gastric juice . . . 975

Brain .... 789 Perspiration . . . 986

Blood . . . .795 Saliva . . . .995
Synovial fluid . . . 805

According to the best calculations, water constitutes, in the
human subject, between two-thirds and three-quarters of the entire
weight of the body.

The water which thus forms a part of the animal frame is derived
from without. It is taken in the different kinds of drink, and also
forms an abundant ingredient in the various articles of food. For
no articles of food are taken in an absolutely dry state, but all
contain a larger or smaller quantity of water, which may readily
be expelled by evaporation. The quantity of water, therefore,
which is daily taken into the system, cannot be ascertained in any
case by simply measuring the quantity of drink, but its proportion
in the solid food, taken at the same time, must also be determined
by experiment, and this ascertained quantity added to that which
is taken in with the fluids. By measuring the quantity of fluid
taken with the drink, and calculating in addition the proportion
existing in the solid food, we have found that, for a healthy adult
man, the ordinary quantity of water introduced per day, is a little
over 4 \ pounds.

After forming part of the animal solids and fluids, and taking
part in the various physical and chemical processes of the body, the
water is again discharged; for its presence in the body, like that
of all the other proximate principles, is not permanent, but only

CHLORIDE OF SODIUM. 71

temporary. After being taken in with the food and drink, it is
associated with other principles in the fluids and solids, passing
from the intestine to the blood, and from the blood to the tissues
and secretions. It afterward makes its exit from the body, from
which it is discharged by four different passages, viz., in a liquid
form with the urine and the feces, and in a gaseous form with the
breath and the perspiration. Of all the water which is expelled in
this way, about 48 per cent, is discharged with the urine and feces,1
and about 52 per cent, by the lungs and skin. The researches of
Lavoisier and Seguin, Yalentin, and others, show that from a pound
and a half to two pounds is discharged daily by the skin, a little
over one pound by exhalation from the lungs, and a little over two
pounds by the urine. Both the absolute and relative amount dis-
charged, both in a liquid and gaseous form, varies according to
circumstances. There is particularly a compensating action in this
respect between the kidneys and the skin, so that when the cutane-
ous perspiration is very abundant the urine is less so, and vice versa.
The quantity of water exhaled from the lungs varies also with the
state of the pulmonary circulation, and with the temperature and
dryness of the atmosphere. The water is not discharged at any
time in a state of purity, but is mingled in the urine and feces with
saline substances which it holds in solution, and in the cutaneous
and pulmonary exhalations with animal vapors and odoriferous
substances of various kinds. In the perspiration it is also mingled
with saline substances, which it leaves behind on evaporation.

2. CHLORIDE OF SODIUM. — This substance is found, like water,
throughout the different tissues and fluids of the body. The only
exception to this is perhaps the enamel of the teeth, where it has
not yet been discovered. Its presence is important in the body, as
regulating the phenomena of endosmosis and exosmosis in different
parts of the frame. For we know that a solution of common salt
passes through animal membranes much less readily than pure
water ; and tissues which have been desiccated will absorb pure
water more abundantly than a saline solution. It must not be sup-
posed, however, that the presence or absence of chloride of sodium,
or its varying quantity in the animal fluids, is the only condition
which regulates their transudation through the animal membranes.
The manner in which endosmosis and exosmosis take place in the

1 Op. cit., vol. ii. pp. 143 and 145.

72 PROXIMATE PRINCIPLES OF THE FIRST CLASS.

animal frame depends upon the relative quantity of all the ingre-
dients of the fluids, as well as on the constitution of the solids
themselves; and the chloride of sodium, as one ingredient among
many, influences these phenomena to a great extent, though it does
not regulate them exclusively.

It exerts also an important influence on the solution of various
other ingredients, with which it is associated. Thus, in the blood
it increases the solubility of the albumen, and perhaps also of the
earthy phosphates. The blood-globules, again, which become dis-
integrated and dissolved in a solution of pure albumen, are main-
tained in a state of integrity by the presence of a small quantity of
chloride of sodium.

It exists in the following proportions in several of the solids and
fluids :' —

QUANTITY OF CHLORIDE OF SODIUM IN 1,000 PARTS IN THE

Muscles .... 2 Bile .... 3.5

Bones . " . . . 2.5 Blood .... 4.5

Milk .... 1 Mucus .... 6

Saliva . , . . . 1.5 Aqueous humor . . 11

Urine .... 3 Vitreous humor . . 14

In the blood it is rather more abundant than all the other saline
ingredients taken together.

Since chloride of sodium is so universally present in all parts of
the body, it is an important ingredient also of the food. It occurs,
of course, in all animal food, in the quantities in which it naturally
exists in the corresponding tissues; and in vegetable food also,
though in smaller amount. Its proportion in muscular flesh,
however, is much less than in the blood and other fluids. Conse-
quently, it is not supplied in sufficient quantity as an ingredient of
animal and vegetable food, but is taken also by itself as a condi-
ment. There is no other substance so universally used by all races
and conditions of men, as an addition to the food, as chloride of
sodium. This custom does not simply depend on a fancy for grati-
fying the palate, but is based upon an instinctive desire for a sub-
stance which is necessary to the proper constitution of the tissues
and fluids. Even the herbivorous animals are greedy of it, and if
freely supplied with it, are kept in a much better condition than
when deprived of its use.

The importance of chloride of sodium in this respect has been
well demonstrated by Boussingault, in his experiments on the

1 Robin and Verdeil.

CHLORIDE OF SODIUM. 73

fattening of animals. These observations were made upon six
bullocks, selected, as nearly as possible, of the same age and vigor,
and subjected to comparative experiment. They were all supplied
with an abundance of nutritious food ; but three of them (lot No.
1) received also a little over 500 grains of salt each per day. The
remaining three (lot No. 2) received no salt, but in other respects
were treated like the first. The result of these experiments is given
by Boussingault as follows : — l

" Though salt administered with the food has but little effect in
increasing the size of the animal, it appears to exert a favorable
influence upon his qualities and general aspect. Until the end of
March (the experiment began in October) the two lots experimented
on did not present any marked difference in their appearance ; but
in the course of the following April, this difference became quite
manifest, even to an unpractised eye. The lot No. 2 had then been
without salt for six mouths. In the animals of both lots the skin
had a fine and substantial texture, easily stretched and separated
from the ribs ; but the hair, which was tarnished and disordered in
the bullocks of the second lot, was smooth and glistening in those
of the first. As the experiment went on, these characters became
more marked ; and at the beginning of October the animals of lot
No. 2, after going without salt for an entire year, presented a rough
and tangled hide, with patches here and there where the skin was
entirely uncovered. The bullocks of lot No. 1 retained, on the
contrary, the ordinary aspect of stall-fed animals. Their vivacity
and their frequent attempts at mounting contrasted strongly with
the dull and unexcitable aspect presented by the others. No doubt,
the first lot would have commanded a higher price in the market
than the second."

Chloride of sodium acts also in a favorable manner by exciting
the digestive fluids, and assisting in this way the solution of the
food. For food which is tasteless, however nutritious it may be in
other respects, is taken with reluctance and digested with difficulty ;
while the attractive flavor which is developed by cooking, and by
the addition of salt and other condiments in proper proportion,
excites the secretion of the saliva and gastric juice, and facilitates
consequently the whole process of digestion. The chloride of
sodium is then taken up by absorption from the intestine, and is
deposited in various quantities in different parts of the body.

1 Chimie Agricole, Paris, 1854, p. 271.

74 PROXIMATE PRINCIPLES OF THE FIRST CLASS.

It is discharged with the urine, mucus, cutaneous perspiration,
&c., in solution in the water of these fluids. According to the esti-
mates of M. Barral.1 a small quantity of chloride of sodium dis-
appears in the body; since he finds by accurate comparison that all
the salt introduced with the food is not to be found in the excreted
fluids, but that about one-fifth of it remains unaccounted for. This
portion is supposed to undergo a double decomposition in the blood
with phosphate of potassa, forming chloride of potassium and phos-
phate of soda. By far the greater part of the chloride of sodium,
however, escapes under its own form with the secretions.

3. CHLORIDE OF POTASSIUM. — This substance is found in the
muscles, the blood, the milk, the urine, and various other fluids
and tissues of the body. It is not so universally present as chlo-
ride of sodium, and not so important as a proximate principle.
In some parts of the body it is more abundant than the latter salt,
in others less so. Thus, in the blood there is more chloride of
sodium than chloride of potasssium, but in the muscles there is more
chloride of potassium than chloride of sodium. This substance is
always in a fluid form, by its ready solubility in water, and is easily
separated by lixiviation. It is introduced mostly with the food, but
is probably formed partly in the interior of the body from chloride
of sodium by double decomposition, as already mentioned. It is
discharged with the mucus, the saliva, and the urine.

4. PHOSPHATE OF LIME. — This is perhaps the most important
of the mineral ingredients of the body next to chloride of sodium.
It is met with universally, in every tissue and every fluid. Its
quantity, however, varies very much in different parts, as will be
seen by the following list : — -

QUANTITY OF PHOSPHATE OF LIME IN 1,000 PARTS IN THE
Enamel of the teeth . . 885 Muscles . . . .2.5

Dentine . . . .643 Blood . . . .0.3

Bones .... 550 Gastric juice . . .0.4

Cartilages ... 40

It occurs also under different physical conditions. In the bones,
teeth, and cartilages it is solid, and gives to these tissues the resist-
ance and solidity which are characteristic of them. The calcareous
salt is not, however, in these instances, simply deposited mechani-
cally in the substance of the bone or cartilage as a granular powder,

1 In Robin and Verdeil, op. cit., vol. ii. 193.

PHOSPHATE OF LIME.

75

Fig. 1.

but is intimately united with the animal matter of the tissues, like
a coloring matter in colored glass, so as to present a more or less
homogeneous appearance. It can, however, be readily dissolved
out by maceration in dilute muriatic acid, leaving behind the
animal substance, which still retains the original form of the bone
or cartilage. It is not, therefore, united with the animal matter so
as to lose its identity and form a new chemical substance, as where
an acid combines with an alkali to form a salt, but in the same
manner as salt unites with water in a saline solution, both sub-
stances retaining their original character and composition, but so
intimately associated that they cannot be separated by mechanical
means.

In the blood, phosphate of lime is in a liquid form, notwithstand-
ing its insolubility in water and in alkaline fluids, being held in
solution by the albuminous matters of the circulating fluid. In the
urine, it is retained in solution by the bi-phosphate of soda.

In all the solid tissues it is useful by giving to them their proper
consistence and solidity. For example, in the ena-
mel of the teeth, the hardest tissue of the body, it
predominates very much over the animal matter,
and is present in greater abundance there than in
any other part of the frame. In the dentine, a
softer tissue, it is in somewhat smaller quantity,
and in the bones smaller still ; though in the bones
it continues to form more than one-half the entire
mass of the osseous substance. The importance of
phosphate of lime, in communicating to bones their
natural stiffness and consistency, may be readily
shown by the alteration which they suffer from its
removal. If a long bone be macerated in dilute
muriatic acid, the earthy salt, as already mentioned,
is entirely dissolved out, after which the bone loses
its rigidity, and may be bent or twisted in any di-
rection without breaking. (Fig. 1.)

Whenever the nutrition of the bone during life
is interfered with from any pathological cause, so
that its phosphate of lirne becomes deficient in
amount, a softening of the osseous tissue is the
consequence, by which the bones yield to external
pressure, and become more or less distorted. (Osteo-malakia.)

After forming, for a time, a part of the tissues and fluids, the

FIBULA TIED iir
A K^OT, after ma-
ceration in a dilate
acid. (From a speci-
men in the museum
of the Coll. of Physi-
cians and Surgeons.)

76 PROXIMATE PRINCIPLES OF THE FIRST CLASS.

phosphate of lime is discharged from the body by the urine, the
perspiration, mucus, &c. Much the larger portion is discharged by
the urine. A small quantity also occurs in the feces, but this is pro-
bably only the superfluous residue of what is taken in with the food.

5. CARBONATE OF LIME. — Carbonate of lime is to be found in
the bones, and sometimes in the urine. The concretions of the
internal ear are almost entirely formed of it. It very probably
occurs also in the blood, teeth, cartilages, and sebaceous matter;
but its presence here is not quite certain, since it may have been
produced from the lactate, or other organic combination, by the
process of incineration. In the bones, it is in much smaller quan-
tity than the phosphate. Its solubility in the blood and the urine
is accounted for by the presence of free carbonic acid, and also of
chloride of potassium, both of which substances exert a solvent
action on carbonate of lime.

6. CARBONATE OF SODA. — This substance exists in the bones,
blood, saliva, lymph, and urine. As it is readily soluble in water,
it naturally assumes the liquid form in the animal fluids. It is
important principally as giving to the blood its alkalescent reaction,
by which the solution of the albumen is facilitated, and various
other chemico-physiological processes in the blood accomplished.
The alkalescence of the blood is, in fact, necessary to life ; for it is
found that, in the living animal, if a mineral acid be gradually
injected into the blood, so dilute as not to coagulate the albumen,
death takes place before its alkaline reaction has been completely
neutralized.1

The carbonate of soda of the blood is partly introduced as such
with the food ; but the greater part of it is formed within the body
by the decomposition of other salts, introduced with certain fruits
and vegetables. These fruits and vegetables, such as apples, cher-
ries, grapes, potatoes, &c., contain malates, tartrates, and citrates
of soda and potassa. Now, it has been often noticed that, after
the use of acescent fruits and vegetables containing the above salts,
the urine becomes alkaline in reaction from the presence of the
alkaline carbonates. Lehmann2 found, by experiments upon his
own person, that, within thirteen minutes after taking half an ounce

1 Cl. Bernard. Lectures on the Blood ; reported by W. F. Atlee, M. D. Phila-
delphia, 1854, p. 31.

2 Physiological Chemistry. Philadelphia ed., vol. i. p. 97.

PHOSPHATES OF MAGNESIA, SODA, AND POTASSA. 77

of lactate of soda, the urine had an alkaline reaction. He also ob-
served that, if a solution of lactate of soda were injected into the
jugular vein of a dog, the urine became alkaline at the end of five,
or, at the latest, of twelve minutes. The conversion of these salts
into carbonates takes place, therefore, not in the intestine but in the
blood. The same observer1 found that, in many persons living on
a mixed diet, the urine became alkaline in two or three hours after
swallowing ten grains of acetate of soda. These salts, therefore,
on being introduced into the animal body, are decomposed. Their
organic acid is destroyed and replaced by carbonic acid ; and they
are then discharged under the form of carbonates of soda and potassa.

7. CARBONATE OF POTASSA. — This substance occurs in very
nearly the same situations as the last. In the blood, however, it is
in smaller quantity. It is mostly produced, as above stated, by
the decomposition of the malate, tartrate, and citrate, in the same
manner as the carbonate of soda. Its function is also the same as
that of the soda salt, and it is discharged in the same manner from
the body.

8. PHOSPHATES OF MAGNESIA, SODA, AND POTASSA. — All these
substances exist universally in all the solids and fluids of the body,
but in very small quantity. The phosphates of soda and potassa
are easily dissolved in the animal fluids, owing to their ready solu-
bility in water. The phosphate of magnesia is held in solution in
the blood by the alkaline chlorides and phosphates ; in the urine,
by the acid phosphate of soda.

A peculiar relation exists between the alkaline phosphates and
carbonates in different classes of animals. For while the fluids of
carnivorous animals contain a preponderance of the phosphates,
those of the herbivora contain a preponderance of the carbonates :
a peculiarity readily understood when we recollect that muscular
flesh and the animal tissues generally are comparatively abundant
in phosphates ; while vegetable substances abound in salts of the
organic acids, which give rise, as already described, by their decom-
position in the blood, to the alkaline carbonates.

The proximate principles included in the above list resemble
each other not only in their inorganic origin, their crystallizability,

1 Physiological Chemistry, vol. ii. p. 130.

78 PROXIMATE PRINCIPLES OF THE FIRST CLASS.

and their definite chemical composition, but also in the part which
they take in the constitution of the animal frame. They are
distinguished in this respect, first by being derived entirely from
without. There are a few exceptions to this rule ; as, for example,
in the case of the alkaline carbonates, which partly originate in
the body from the decomposition of malates, tartrates, &c. These,
however, are only exceptions ; and in general, the proximate prin-
ciples belonging to the first class are introduced with the food,
and taken up by the animal tissues in precisely the same form
under which they occur in external nature. The carbonate of lime
in the bones, the chloride of sodium in the blood and tissues, are
the same substances which are met with in the calcareous rocks,
and in solution in sea water. They do not suffer any chemical
alteration in becoming constituent parts of the animal frame.

They are equally exempt, as a general rule, from any alteration
while they remain in the body, and during their passage through
it. The exceptions to this rule are very few ; as, for example, where
a small part of the chloride of sodium suffers double decomposition
with phosphate of potassa, giving rise to chloride of potassium and
phosphate of soda ; or where the phosphate of soda itself gives up
a part of its base to an organic acid (uric), and is converted in this
way into a bi-phosphate of soda.

Nearly the whole of these substances, finally, are taken up un-
changed from the tissues, and discharged unchanged with the excre-
tions. Thus we find the phosphate of lime and the chloride of so-
dium, which were taken in with the food, discharged again under
the same form in the urine. They do not, therefore, for the most
part, participate directly in the chemical changes going on in the
body ; but only serve by their presence to enable those changes to
be accomplished in the other ingredients of the animal frame, which
are necessary to the process of nutrition.

PROXIMATE PRINCIPLES OF THE SECOND CLASS. 79

CHAPTER III.

PROXIMATE PRINCIPLES OF THE SECOND CLASS.

THE proximate principles belonging to the second class are
divided into three principal groups, viz : starch, sugar, and oil.
They are distinguished, in the first place, by their organic origin.
Unlike the principles of the first class, they do not exist in
external nature, but are only found as ingredients of organized
bodies. They exist both in animals and in vegetables, though in
somewhat different proportions. All the substances belonging to
this class have a definite chemical composition ; and are further
distinguished by the fact that they are composed of oxygen,
hydrogen, and carbon alone, without nitrogen, whence they are
sometimes called the " non-nitrogenous" substances.

1. STARCH (C12H,0010). — The first of these substances seems to
form an exception to the general rule in a very important particu-
lar, viz., that it is not crystallizable. Still, since it so closely
resembles the rest in all its general properties, and since it is easily
convertible into sugar, which is itself crystallizable, it is naturally
included in the second class of proximate principles. Though not
crystallizable, furthermore, it still assumes a distinct form, by
which it differs from substances that are altogether amorphous.

Starch occurs in some part or other of almost all the flowering
plants. It is very abundant in corn, wheat, rye, oats, and rice, in
the parenchyma of the potato, in peas and beans, and in most
vegetable substances used as food. It constitutes almost entirely
the different preparations known as sago, tapioca, arrowroot, &c.,
which are nothing more than varieties of starch, extracted from
different species of plants.

The following is a list showing the percentage of starch occurring
in different kinds of food : — '

1 Pereira on Food and Diet, New York, 1843, p. 39.

80

PKOX1MATE PRINCIPLES OF THE SECOND CLASS.

QUANTITY OF STARCH IN 100 PARTS IN
Rice . . . .85.07 Wheat flour

Maize . . . .80.92 Iceland moss

Barley meal . . . 67.18 Kidney bean ,

Rye meal . . .61.07 Peas

Oat meal 59.00 Potato .

56.50
44.60
35.94
32.45
15.70

Fig. 2.

GRAINS OF POTATO STARCH.

When purified from foreign substances, starch is a white, light
powder, which gives rise to a peculiar crackling sensation when

rubbed between the fingers.
It is not amorphous, as we
have already stated, but is
composed of solid granules,
which, while they have a
general resemblance to each
other, differ somewhat in va-
rious particulars. The starch
grains of the potato (Fig. 2)
vary considerably in size.
The smallest have a diameter
of Ttfi™ tne largest 7JT of
an inch. They are irregu-
larly pear-shaped in form,
and are marked by concen-
tric laminae, as if the matter
of which they are composed had been deposited in successive layers.
At one point on the surface of every starch grain, there is a minute

pore or depression, called the
hilus, around which the cir-
cular markings are arranged
in a concentric form.

The starch granules of
arrowroot (Fig. 3) are gene-
rally smaller and more uni-
form in size, than those of

the potato. They vary from
2injT> to 5^ of an inch in
diameter. They are elongated
and cylindrical in form, and
the concentric markings are
less distinct than in the pre-
ceding variety. The hilus

Fig. 3.

STARCH GRAINS OF BERMUDA ARROWROOT.

STARCH.

81

STARCH GRAINS OF WHEAT FLOUR.

has here sometimes the form of a circular pore, and sometimes that
of a transverse fissure or slit.

The grains of wheat starch (Fig. -i) are still smaller than those
of arrowroot. They vary

from ^0^ to 7£ff of an inch FlS- 4-

in diameter. They are
nearly circular in form, with
a round or transverse hilus,
but without any distinct
appearance of lamination;
Many of them are flattened
or compressed laterally, so
that they present a broad
surface in one position, and
a narrow edge when viewed
in the opposite direction.

The starch grains of In-
dian corn (Fig. 5) are of
nearly the same size with

those of wheat flour. They are somewhat more irregular and
angular in shape ; and are often marked with crossed or radiating
lines, as if from partial fracture.

Starch is also an ingre- Fig- 5-

dient of the animal body.
It was first observed by
Purkinje, and afterward by
Kolliker,1 that certain bodies
are to be found in the interior
of the brain, about the late-
ral ventricles, in the fornix,
septum lucidum and other
parts, which present a cer-
tain resemblance to starch
grains, and which have there-
fore been called "corpora
amylacea." Subsequently
Virchow8 corroborated the
above observations, and ascertained the corpora amylacea to b(

STARCH GRAINS OF IXDIAX CORS.

1 Handbuch der fJnweLelelire, Leipzig, 1852, p. 311.

2 In American Journal Med. Sui., April, 1854, p. 466.

82

PROXIMATE PRINCIPLES OF THE SECOND CLASS.

STARCH GRAINS FROM WALT, OP LATERAL
VENTRICLES; from a woman aged 35.

really substances of a starchy nature ; since they exhibit the usual
chemical reactions of vegetable starch.

The starch granules of the human brain (Fig. 6) are transparent

and colorless, like those from
plants. They refract the light
strongly, and vary in size
from 4^0(7 to TTV^ of an
inch. Their average is ygViy
of an inch. They are some-
times rounded or oval, and
sometimes angular in shape.
They resemble considerably
in appearance the starch,
granules of Indian corn. The

\ © ^ / largest of them present a

very faint concentric lamina-
tion, but the greater number
are destitute of any such
appearance. They have
nearly always a distinct hilus, which is sometimes circular and
sometimes slit-shaped. They are also often marked with delicate
radiating lines and shadows. On the addition of iodine, they become
colored, first purple, afterward of a deep blue. They are less firm
in consistency than vegetable starch grains, and can be more readily
disintegrated by pressing or rubbing them upon the glass.

Starch, derived from all these different sources, has, so far as
known, the same chemical composition, and may be recognized by
the same tests. It is insoluble in cold water, but in boiling water
its granules first swell, become gelatinous and opaline, then fuse
with eachxDther, and finally liquefy altogether, provided a sufficient
quantity of water be present. After that, they cannot be made to
resume their original form, but on cooling and drying merely solidify
into a homogeneous mass or paste, more or less consistent, accord-
ing to the quantity of water which remains in union with it. The
starch is then said to be amorphous or " hydrated." By this process
it is not essentially altered in its chemical properties, but only in
its physical condition. Whether in granules, or in solution, or in
an amorphous and hydrated state, it strikes a deep blue color on
the addition of free iodine.

Starch may be converted into sugar by three different methods.
First, by boiling with a dilute acid. If starch be boiled with dilute

SUGAR. 83

nitric, sulphuric, or muriatic acid during thirty-six hours, it first
changes its opalescent appearance, and becomes colorless and trans-
parent ; losing at the same time its power of striking a blue color
with iodine. After a time, it begins to acquire a sweet taste, and
is finally altogether converted into a peculiar species of sugar.

Secondly, by contact with certain animal and vegetable sub-
stances. Thus, boiled starch mixed with human saliva and kept
at the temperature of 100° F., is converted in a few minutes into
sugar.

Thirdly, by the processes of nutrition and digestion in animals
and vegetables. A large part of the starch stored up in seeds and
other vegetable tissues is, at some period or other of the growth of
the plant, converted into sugar by the molecular changes going on
in the vegetable fabric. It is in this way, so far as we know, that
all the sugar derived from vegetable sources has its origin. /

Starch, as a proximate principle, is more especially important as
entering largely into the composition of many kinds of vegetable
food. With these it is introduced into the alimentary canal, and
there, during the process of digestion, is converted into sugar.
Consequently, it does not appear in the blood, nor in any of the
secreted fluids.

2. SUGAR. — This group of proximate principles includes a con-
siderable number of substances, which differ in certain minor
details, while they resemble each other in the following particulars :
They are readily soluble in water, and crystallize more or less
perfectly on evaporation ; they have a distinct sweet taste ; and
finally, by the process of fermentation, they are converted into
alcohol and carbonic acid.

These substances are derived from both animal and vegetable
sources. Those varieties of sugar which are most familiar to us
are the following six, three of which are of vegetable and three of
animal origin.

c Cane sugar, f Milk sugar,

Vegetal J Grape sugar> Animal 1 Liver sugar?

suSars- 1 Sugar of starch. suSars' I Sugar of honey.

The cane and grape sugars are held in solution in the juices of
the plants from which they derive their name. Sugar of starch, or
glucose, is produced by boiling starch for a long time with a dilute
acid. Liver sugar and sugar of milk are produced in the
tissues of the liver and the mammary gland, and the sugar of

84 PROXIMATE PRINCIPLES OF THE SECOND CLASS.

honey is prepared in some way by the bee from materials of vege-
table origin.

These varieties differ but little in their ultimate chemical compo-
sition. The following formulae have been established for three of
them.

Cane sugar = C24H22022

..Milk sugar . . . ' . . . = C24H24021
Glucose = C24H28O23

Cane sugar is sweeter than most of the other varieties, and more
soluble in water. Some sugars, such as liver sugar and sugar of
honey, crystallize only with great difficulty ; but this is probably
owing to their being mingled witn other substances, from which it
is difficult to separate them completely. If they could be obtained
in a state of purity, they would doubtless crystallize as perfectly as
Vane sugar. The different sugars vary also in the readiness with
which they undergo fermentation. Some of them, as grape sugar
and liver sugar, enter into fermentation very promptly ; others,
such as milk and cane sugar, with considerable difficulty.

The above are not to be regarded as the only varieties of sugar
existing in nature. On the contrary, it is probable that nearly
every different species of .animal and vegetable produces a distinct
kind of sugar, differing slightly from the rest in its degree of sweet-
ness, its solubility, its crystallization, its aptitude for fermentation,
and perhaps in its elementary composition. Nevertheless, there is
so close a resemblance between them that they are all properly
regarded as belonging to a single group.

The test most commonly employed for detecting the presence of
sugar is that known as Trommels test. It depends upon the fact
that the saccharine substances have the power of reducing the
persalts of copper when heated with them in an alkaline solution.
The test is applied in the following manner : A very small quantity
of sulphate of copper in solution should be added to the suspected
liquid, and the mixture then rendered distinctly alkaline by the
addition of caustic potassa. The whole solution then takes a deep
blue color. On boiling the mixture, if sugar be present, the in-
soluble suboxide of copper is thrown down as an opaque red,
yellow, or orange-colored deposit; otherwise no change of color
takes place.

This test requires some precautions in its application. In the
first place, it is not applicable to all varieties of sugar. Cane
sugar, for example, when pure, has no power of reducing the salts

SUGAR. 85

of copper, even when present in large quantity. Maple sugar, also,
which resembles cane sugar in some other respects, reduces the
copper, in Trommer's test, but slowly and imperfectly. Beet-root
sugar, according to Bernard, presents the same peculiarity. If
these sugars, however, be boiled for two or three minutes with a
trace of sulphuric acid, they become converted into glucose, and
acquire the power of reducing the salts of copper. Milk sugar,
liver sugar, and sugar of honey, as well as grape sugar and glucose,
all act promptly and perfectly with Trommer's test in their natural
condition.

Secondly, care must be taken to add to the suspected liquid only
a small quantity of sulphate of copper, just sufficient to give to the
whole a distinct blue tinge, after the addition of the alkali. If a
larger quantity of the copper salt be used, the sugar in solution
may not be sufficient to reduce the whole of it ; and that which
remains as a blue sulphate will mask the yellow color of the sub-
oxide thrown down as a deposit. By a little care, however, in
managing the test, this source of error may be readily avoided.

Thirdly, there are some albuminous substances which have the
power of interfering with Trommer's test, and prevent the reduc-
tion of the copper even when sugar is present. Certain animal
matters, to be more particularly described hereafter, which are
liable to be held in solution in the gastric juice, have this effect.
This source of error may be avoided, and the substances in ques-
tion eliminated when present, by treating the suspected fluid with
animal charcoal, or by evaporating and extracting it with alcohol
before the application of the test.

A less convenient but somewhat more certain test for sugar is
that of fermentation. The saccharine fluid is mixed with a little
yeast, and kept at a temperature of 70° to 100° F. until the fer-
menting process is completed. By this process, as already men-
tioned, the sugar is converted into alcohol and carbonic acid. The
gas, which is given off in minute bubbles during fermentation,
should be collected and examined. The remaining fluid is purified
by distillation and also subjected to examination. If the gas be
found to be carbonic acid, and the remaining fluid contain alcohol,
there can be no doubt that sugar was present at the commencement
of the operation.

The following list shows the percentage of sugar in various
articles of food.1

1 Pereira, op. cit., p. 5o.

86 PROXIMATE PRINCIPLES OF THE SECOND CLASS.

QUANTITY OF SUGAR IN 100 PARTS IN

Figs .... 62.50 Wheat flour. . 4.20 to 8.48

Cherries . . . 18.12 Rye meal . .3.28

Peaches . . . 16.48 Indian meal . 1.45

Tamarinds . . . 12.50 Peas . . . 2.00

Pears .... 11.52 Cow's milk . . 4.77

Beets .... 9.00 Ass's milk . . 6.08

Sweet almonds . . 6.00 Human milk . 6.50

Barley meal . . . 5.21

Besides the sugar, therefore, which is taken into the alimentary
canal in a pure form, a large quantity is also introduced as an in-
gredient of the sweet-flavored fruits and vegetables. All the
starchy substances of the food are also converted into sugar in the
process of digestion. Two of the varieties of sugar, at least,
originate in the interior of the body, viz., sugar of milk and liver
sugar. The former exists in a solid form in the substance of the
mammary gland, from which it passes in solution into the milk.
The liver sugar is found in the substance of the liver, and almost
always also in the blood of the hepatic veins. The sugar which is
introduced with the food, as well as that which is formed in the
liver, disappears by decomposition in the animal fluids, and does
not appear in any of the excretions.

3. FATS. — These substances, like the sugars, are derived from
both animal and vegetable sources. There are three principal
varieties of them, which may be considered as representing the
class, viz : —

Oleine = C94 H87 015

Margarine = C76 H75 012

Stearine = C,42H14101T

The principal difference between the oleaginous and saccharine
substances, so far as regards their ultimate chemical composition,
is that in the sugars the oxygen and hydrogen always exist together
in the proportion to form water ; while in the fats the proportions of
carbon and hydrogen are nearly the same, but that of oxygen is
considerably less. The fats are all fluid at a high temperature, but
assume the solid form on cooling. Stearine, which is the most
solid of the three, liquefies only at 143° F. ; margarine at 118° F. ;
while oleine remains fluid considerably below 100° F., and even
very near the freezing point of water. The fats are all insoluble
in water, but readily soluble in ether. By prolonged boiling in
water with a caustic alkali, they are decomposed, and as the result of
the decomposition there are formed two new bodies ; first, glycerine,

FATS.

87

which is a neutral fluid substance, and secondly, a fatty acid, viz:
oleic, rnargaric, or stearic acid, corresponding to the kind of fat
which has been used in the experiment. The glycerine remains in
a free state, while the fatty acid unites with the alkali employed,
forming an oleate, margarate, or stearate. This combination is
termed a soap, and the process by which it is formed is called
1 sapontjication. This process, however, is not a simple decomposition
of the fatty body, since it can only take place in the presence of
water ; several equivalents of which unite with the elements of the
fatty body, and enter into the composition of the glycerine, &c., so
that the fatty acid and the glycerine together weigh more than the
original fatty substance which was decomposed. It is not proper,
therefore, to regard an oleaginous body as formed by the union of a
fatty acid with glycerine. It is formed, on the contrary, in all pro-
bability, by the direct combination of its ultimate chemical elements.
The different kinds of oil, fat, lard, suet, &c., contain the three
oleaginous matters mentioned above, mingled together in different
proportions. The more solid fats contain a larger quantity of
stearine and margarine ; the less consistent varieties, a larger pro-
portion of oleine. Xeither of the oleaginous matters, stearine,
margarine, or oleine, ever occur separately; but in every fatty sub-
stance they are mingled together, so that the more fluid of them hold
in solution the more solid.

Generally speaking, in the Flg* 7*

living body, these mixtures
are fluid, or nearly so; for
though both stearine and
margarine are solid, when
pure, at the ordinary tem-
perature of the body, they
are held in solution, during
life, by the oleine with which
they are associated. After
death, however, as the body
cools, the stearine and mar-
garine sometimes separate
from the mixture in a crys-
talline form, since the oleine
can no longer hold in solu-
tion so large a quantity of them as it had dissolved at a higher
temperature.

STEARISE c ystallized from a Warm Solution in
Oleine.

Fig. 8.

88 PKOXIMATE PRINCIPLES OF THE SECOND CLASS.

These substances crystallize in very slender needles, which are
sometimes straight, but more often somewhat curved or wavy in
their outline. (Fig. 7.)

They are always deposited in a more or less radiated form ; and
have sometimes a very elegant, branched, or arborescent arrange-
ment.

When in a fluid state, the fatty substances present themselves

under the form of drops or
globules, which vary indefi-
nitely in size, but which
may be readily recognized
by their optical properties.
They are circular in shape,
and have a faint amber color,
distinct in the larger globules,
less so in. the smaller. They
have a sharp, well defined
outline (Fig. 8) ; and as they
refract the light strongly,
and act therefore as double
convex lenses, they present
a brilliant centre, surrounded

OLEAGINOUS PRINCIPLES £F HUMAN FAT. , , , , „.

Stearine and Margarine crystallized ; Oleiiie fluid. DJ a QarK border.

marks will generally be
sufficient to distinguish them under the microscope.

The following list shows the percentage of oily matter present in
various kinds of animal and vegetable food.1

QUANTITY OF FAT ix 100 PARTS IN

Filberts .
Walnuts
Cocoa-nuts
Olives .
Linseed
Indian Corn
Yolk of eggs

60.00
50.00
47.00
32.00
22.00
9.00
28.00

Ordinary meat
Liver of the ox
Cow's milk
Human milk
Asses' milk .
Goats' milk .

14.30
3.89
3.13
3.55
0.11
3.32

The oleaginous matters present a striking peculiarity as to the
form under which they exist in the animal body; a peculiarity
which distinguishes them from all the other proximate principles.
The rest of the proximate principles are all intimately associated
together by molecular union, so as to form either clear solutions or

1 Pereira, op. cit., p. 81.

FATS. 89

homogeneous solids. Thus, the sugars of the blood are in solution
in water, in company with the albumen, the phosphate of lime,
chloride of sodium, and the like ; all of them equally distributed
throughout the entire mass of the fluid. In the bones and car-
tilages, the animal matters and the calcareous salts are in similarly
intimate union with each other ; and in every other part of the
body the animal and inorganic ingredients are united in the same
way. But it is different with the fats. For, while the three prin-
cipal varieties of oleaginous matter are always united with each
other, they are not united with any of the other kinds of proximate
principles ; that is, with water, saline substances, sugars, or albu-
minous matters. Almost the only exception to this is in the nerv-
ous tissue; in which, according to Robin and Yerdeil, the oily
matters seem to be united with an albuminoid substance. Another
exception is, perhaps, in the bile ; since some of the biliary salts
have the power of dissolving a certain quantity of fat. Every-
where else, instead of forming a homogeneous solid or fluid with
the other proximate principles, the oleaginous matters are found
in distinct masses or globules, which are suspended in serous fluids,
interposed in the interstices between the anatomical elements, in-
cluded in the interior of cells, or deposited in the substance of
fibres or membranes. Even in the vegetable tissues, the oil is
always deposited in this manner in distinct drops or granules.

Owing to this fact, the oils can be easily extracted from the
organized tissues by the employment of simply mechanical pro-
cesses. The tissues, animal or vegetable, are merely cut into small
pieces and subjected to pressure, by which the oil is forced out
from the parts in which it was entangled, and separated, without
any further manipulation, in a state of purity. A moderately
elevated temperature facilitates the operation by increasing the
fluidity of the oleaginous matter; but no other chemical agency is
required for its separation. Under the microscope, also, the oil-
drops and granules can be readily perceived and distinguished
from the remaining parts of the tissue, and can, moreover, be
easily recognized by the dissolving action of ether, which acts
upon them, as a general rule, without attacking the other proxi-
mate principles.

Oils are found, in the animal body, most abundantly in the
adipose tissue. Here they are contained in the interior of. the
adipose vesicles, the cavities of which they entirely fill, in a state

90

PROXIMATE PRINCIPLES OF THE SECOND CLASS.

Fig. 9.

HUMAN ADIPOSK TISSUE.

of health. These vesicles are transparent, and have a somewhat
angular form, owing to their mutual compression. (Fig. 9.) They

vary in diameter, in the hu-
man subject, from 5^ to .j^
of an inch, and are composed
of a thin, structureless ani-
mal membrane, forming a
closed sac, in the interior of
which the oily matter is con-
tained. There is here, accord-
ingly, no union whatever of
the oil with the other proxi-
mate principles, but only a
mechanical inclusion of it in
the interior of the vesicles.
Sometimes, when emaciation
is going on, the oil partially

_.c J

disappears from the cavity of
the adipose vesicle, and its place is taken by a watery serum ; but
the serous and oily fluids always remain distinct, and occupy differ-
ent parts of the cavity of the vesicle.

In the chyle, the oleaginous matter is in a state of emulsion or
suspension in the form of minute particles in a serous fluid. Its

subdivision is here more com-

Fi8- 10- plete, and its molecules more

minute, than anywhere else
in the body. It presents the
appearance of a fine granular
dust, which has been known
by the name of the " molecu-
lar base of the chyle." A
few of these granules are to
be seen which measure J-GVVV
of an inch in diameter ; but
they are generally much less
than this, and the greater part
are so small that they cannot
be accurately measured. (Fig.
10.) For the same reason
they do not present the bril-
liant centre and dark border of the larger oil-globules; but appear

0 H T i, E , from
from tjie Dog.

commencement of Thoracic Duct,

PATS.

91

Fig. 11.

by transmitted light only as minute dark granules. The white
color and opacity of the chyle, as of all other fatty emulsions,
depend upon this molecular condition of the oily ingredients. The
albumen, salts, &c., which are in intimate union with each other,
and in solution in the water, would alone make a colorless and
transparent fluid ; but the oily matters, suspended in distinct par-
ticles, which have a different refractive power from the serous fluid,
interfere with its transparency
and give it the white color and
opaque appearance which are
characteristic of emulsions.
The oleaginous nature of these
particles is readily shown by
their solubility in ether.

In the milk, the oily matter
occurs in larger masses than
in the chyle. In cow's milk
(Fig. 11), these oil-drops, or
"milk-globules," are not quite
fluid, but have a pasty con-
sistency, owing to the large
quantity of margarine which
they contain, in proportion to
the oleine. When forcibly amalgamated with each other and
collected into a mass by prolonged beating or churning, they con-
stitute butter. In cow's milk,
the globules vary somewhat
in size, but their average
diameter is 4 oW °f an inch.
They are simply suspended
in the serous fluid of the
milk, and are not covered
with any albuminous mem-
brane.

In the cells of the laryn-
geal, tracheal, and costal car-
tilages (Fig. 12), there is
always more or less fat de-
posited in the form of rounded
globules, somewhat similar to

n , .,, CKI.T.S op COSTAL CARTILAGRS, containing Oil-

those Of the milk. Globules. Human.

GLOBULES OF Cow's MII.K.

Fig. 12.

92

PROXIMATE PRINCIPLES OF THE SECOND CLASS.

Fig. 13.

In the glandular cells of the liver, oil occurs constantly, in a
state of health. It is here deposited in the substance of the cell

(Fig.13), generally in smaller
globules than the preceding.
In some cases of disease, it
accumulates in excessive
quantity, and produces the
state known as fatty degene-
ration of the liver. This is
consequently only an ex-
aggerated condition of that
which normally exists in
health.

" In the carnivorous animals
oil exists in considerable
quantity in the convoluted
portion of the uriniferous

HEPATIC CELLS. Human. . T . .

tubules. (Fig. 14.) It is here

in the form of granules and rounded drops, which sometimes appear

to fill nearly the whole calibre of the tubules.

It is found also in the secreting cells of the sebaceous and other

glandules, deposited in the
same manner as in those of
the liver, but in smaller
quantity. It exists, beside,
in large proportion, in a
granular form, in the secre-
tion of the sebaceous gland-
ules.

It occurs abundantly in
the marrow of the bones,
both under the form of free
oil-globules and inclosed in
the vesicles of adipose tissue.
It is found in considerable
quantity in the substance of
the yellow wall of the corpus
luteum, and is the immediate

cause of the peculiar color of this body.

It occurs also in the form of granules and oil-drops in the

muscular fibres of the uterus (Fig. 15), in which it begins to be

14>

UaiNiFERors Ti;nui.E8 OF DOG, from Cortical
Portion of Kidney.

FATS.

93

Fig. 15.

HU»A» UTERUS, three

deposited soon after delivery, and where it continues to be present
during the whole period of the resorption or involution of this organ.

In all these instances, the oleaginous matters remain distinct in
form and situation from 'the
other ingredients of the ani-
mal frame, and are only me-
chanically entangled among
its fibres and cells, or im-
bedded separately in their
interior.

A large part of the fat
which is found in the body
may be accounted for by that
which is taken in with the
food, since oily matter occurs
in both animal and vegetable
substances. Fat is, however,
formed in the body, independ-

ently Of What is" introduced M<""7''A»

J weeks after parturition.

with the food. This im-

portant fact has been definitely ascertained by the experiments of
MM. Dumas and Milne-Edwards on bees,1 M. Persoz on geese,7 and
finally by those of M. Boussingault on geese, ducks, and pigs.3 The
observers first ascertained the quantity of fat existing in the whole
body at the commencement of the experiment. The animals were
then subjected to a definite nutritious regimen, in which the
quantity of fatty matter was duly ascertained by analysis. The
experiments lasted for a period varying, in different instances, from
thirty -one days to eight months; after which the animals were
killed and all their tissues examined. The result of these investi-
gations showed that considerably more fat had been accumulated
by the animal during the course of the experiment than could be
accounted for by that which existed in the food ; and placed it
beyond a doubt that oleaginous substances may be, and actually
are, formed in the interior of the animal body by the decomposition
or metamorphosis of other proximate principles.

It is not known from what proximate principles the fat is pro-
duced, when it originates in this way in the interior of the body.
Particular kinds of food certainly favor its production and accu-

1 Annales de China, et de Phys., 3d series, vol. xiv. p. 400.
3 Clnrnie Agricole, Paris, It- 54.

2 Ibid., p. 408.

94 PROXIMATE PRINCIPLES OF THE SECOND CLASS.

mulation to a considerable degree. It is well known, for instance,
that in sugar-growing countries, as in Louisiana and the West
Indies, during the few weeks occupied in gathering the cane and
extracting the sugar, all the negroes employed on the plantations,
and even the horses and cattle, that are allowed to feed freely on
the saccharine juices, grow remarkably fat ; and that they again lose
their superabundant flesh when the season is past. Even in these
instances, however, it is not certain whether the saccharine substances
are directly converted into fat, or whether they are first assimilated
and only afterward supply the materials for its production. The
abundant accumulation of fat in certain regions of the body, and its
absence in others ; and more particularly its constant occurrence in
certain situations to which it could not be transported by the blood,
as for example the interior of the cells of the costal cartilages, the
substance of the muscular fibres of the uterus after parturition, &c.,
make it probable that under ordinary conditions the oily matter is
formed by decomposition of the tissues upon the very spot where
it subsequently makes its appearance.

In the female during lactation a large part of the oily matter
introduced with the food, or formed in the body, is discharged with
the milk, and goes to the support of the infant. But in the female
in the intervals of lactation, and in the male at all times, the oily
matters almost entirely disappear by decomposition in the interior
of the body; since the small quantity which is discharged with the
sebaceous matter by the skin bears only an insignificant proportion
to that which is introduced daily with the food.

The most important characteristic, in a physiological point of
view, of the proximate principles of the second class, relates to their
origin and their final destination. Not only are they all of a purely
organic origin, making their appearance first in the interior of vege-
tables ; but the sugars and the oils are formed also, to a certain ex-
tent, in the bodies of animals ; continuing to make their appearance
when no similar substances, or only an insufficient quantity of them,
have been taken with the food. Furthermore, when introduced
with the food, or formed in the body and deposited in the tissues,
these substances do not reappear in the secretions. They, therefore,
for the most part disappear by decomposition in the interior of the
body. They pass through a series of changes by which their es-
sential characters are destroyed ; and they are finally replaced in
the circulation by other substances, which are discharged with the
excreted fluids.

PROXIMATE PRINCIPLES OF THE THIRD CLASS. 95

CHAPTER IV.

PROXIMATE PRINCIPLES OF THE THIRD CLASS.

THE substances belonging to this class are very important, and
form by far the greater part of the entire mass of the body. They
are derived both from animal and vegetable sources. They have
been known by the name of the "protein compounds" and the
" albuminoid substances." The name organic substances was given
to them by Kubin and Yerdeil, by whom their distinguishing pro-
perties were first accurately described. They have not only an
organic origin, in common with the proximate principles of the
second class, but their chemical constitution, their physical struc-
ture and characters, and the changes which they undergo, are all so
different from those met with in any other class, that the term " or-
ganic substances" proper appears particularly appropriate to them.

Their first peculiarity is that they are not crystallizable. They
always, when pure, assume an amorphous condition, which is some-
times solid (organic substance of the bones), sometimes fluid (albu-
men of the blood), and sometimes semi-solid in consistency, midway
between the solid and fluid condition (organic substance of the
muscular fibre).

Their chemical constitution differs from that of bodies of the
second class, first in the fact that they all contain the four chemical
elements, oxygen, hydrogen, carbon, and nitrogen; while the
starches, sugars, and oils are destitute of the last named ingredient.
The organic matters have therefore been sometimes known by the
name of the " nitrogenous substances," while the sugars, starch, and
oils have been called " non-nitrogenous." Some of the organic mat-
ters, viz., albumen, fibrin, and casein, contain sulphur also, as an in-
gredient ; and others, viz., the coloring matters, contain iron. The
remainder consist of oxygen, hydrogen, carbon, and nitrogen alone.

The most important peculiarity, however, of the organic sub-
stances, relating to their chemical composition, is that it is not
definite. That is to say, they do not always contain precisely the
same proportions of oxygen, hydrogen, carbon, and nitrogen ; but

96 PROXIMATE PRINCIPLES OF THE THIRD CLASS.

the relative quantities of these elements vary within certain limits,
in different individuals and at different times, without modifying, in
any essential degree, the peculiar properties of the animal matters
which they constitute. This fact is altogether a special one, and
characteristic of organic substances. No substance having a definite
chemical composition, like phosphate of lime, starch, or olein, can
suffer the slightest change in its ultimate constitution without being,
by that fact alone, totally altered in its essential properties. If
phosphate of lime, for example, were to lose one or two equivalents
of oxygen, an entire destruction of the salt would necessarily result,
and it would cease to be phosphate of lime. For its properties as a
salt depend entirely upon its ultimate chemical constitution ; and if
the latter be changed in any way, the former are necessarily lost.

But the properties which distinguish the organic substances, and
which make them important as ingredients of the body, do not
depend immediately upon their ultimate chemical constitution, and
are of a peculiar character ; being such as are only manifested in
the interior of the living organism. Albumen, therefore, though
it may contain a few equivalents more or less of oxygen or nitrogen,
does not on that account cease to be albumen, so long as it retains
its fluidity and its aptitude for undergoing the processes of absorp-
tion and transformation, which characterize it as an ingredient of
the living body.

It is for this reason that considerable discrepancy has existed at
various times among chemists as to the real ultimate composition
of these substances, different experimenters often obtaining differ-
ent analytical results. This is not owing to any inaccuracy in the
analyses, but to the fact that the organic substance itself really has
a different ultimate constitution at different times. The most ap-
proved formula are those which have been established by Liebig
for the following substances : —

Fibrin = C29JI228N40092S2

Albumen = C2;6HI69N27068S2

Casein = C,88H228N36090S2

v Owing to the above mentioned variations, however, the same
degree of importance does not attach to the quantitative ultimate
analysis of an organic matter, as to that of other substances.

This absence of a definite chemical constitution in the organic sub-
stances is undoubtedly connected with their incapacity for crystalli-
zation. It is also connected with another almost equally peculiar
fact, viz., that although the organic substances unite with acids and

ORGANIC SUBSTANCES. 97

with alkalies, they do not play the part of an acid towards the base,
or of a base towards the acid ; for the acid or alkaline reaction of
the substance employed is not neutralized, but remains as strong
after the combination as before. Futhermore, the union does not
take place, so far as can be ascertained, in any definite proportions.
The organic substances have, in fact, no combining equivalent ; and
their molecular reactions and the changes which they undergo in
the body cannot therefore be expressed by the ordinary chemical
phrases which are adapted to inorganic substances. Their true
characters, as proximate principles, are accordingly to be sought
for in other properties than those which depend upon their exact
ultimate composition.

One of these characters is that they are hygroscopic. As met with
in different parts of the body, they present different degrees of con-
sistency ; some being nearly solid, others more or less fluid. But on
being subjected to evaporation they all lose water, and are reduced
to a perfectly solid form. If after this desiccation they be exposed
to the contact of moisture, they again absorb water, swell, and
regain their original mass and consistency. This phenomenon is
quite different from that of capillary attraction, by which some in-
organic substances become moistened when exposed to the contact
of water ; for in the latter case the water is simply entangled me-
chanically in the meshes and pores of the inorganic body, while that
which is absorbed by the organic matter is actually united with its
substance, and diffused equally throughout its entire mass. Every
organic matter is naturally united in this way with a certain quantity
of water, some more and some less. Thus the albumen of the blood
is in union with so much water that it has the fluid form, while the
organic substance of cartilage contains less and is of a firmer con-
sistency. The quantity of water contained in each organic sub-
stance may be diminished by artificial desiccation, or by a deficient
supply ; but neither of them can be made to take up more than a
certain amount. Thus if the albumen of the blood and the organic
substance of cartilage be both reduced by evaporation to a similar
degree of dryness and then placed in water, the albumen will absorb
so much as again to become fluid, but the cartilaginous substance
only so much as to regain its usual nearly solid consistency. Even
where the organic substance, therefore, as in the case of albumen,
becomes fluid under these circumstances, it is not exactly a solution
of it in water, but only a reabsorption by it of that quantity of fluid
with which it is naturally associated.
7

98 PROXIMATE PRINCIPLES OF THE THIRD CLASS.

Another peculiar phenomenon characteristic of organic substances
is their coagulation. Those which are naturally fluid suddenly as-
sume, under certain conditions, a solid or semi-solid consistency.
They are then said to be coagulated ; and after coagulation they
cannot be made to resume their original condition. Thus fibrin
coagulates on being withdrawn from the bloodvessels, albumen on
being subjected to the temperature of boiling water, casein on being
placed in contact with an acid. When an organic substance thus
coagulates, the change which takes place is a peculiar one, and has
no resemblance to the precipitation of a solid substance from a
watery solution. On the contrary, the organic substance merely
assumes a special condition ; and in passing into the solid form it
retains all the water with which it was previously united. Albumen,
for example, after coagulation, retains the same quantity of water in
union with it, which it held before. After coagulation, accordingly,
this water may be driven off by evaporation, in the same manner
as previously ; and on being again exposed to moisture, the organic
matter will again absorb the same quantity, though it will not re-
sume the fluid form.

By coagulation, an organic substance is permanently altered ; and
though it may be afterwards dissolved by certain chemical re-agents,
as, for example, the caustic alkalies, it is not thereby restored to its
original condition, but only suffers a still further alteration.

In many instances we are obliged to resort to coagulation in
order to separate an organic substance from the other proximate
principles with which it is associated. This is the case, for example,
with the fibrin of the blood, which is obtained in the form of floe-
culi, by beating freshly-drawn blood with a bundle of rods. But
when separated in this way, it is already in an unnatural condition,
and no longer represents exactly the original fluid fibrin, as it ex-
isted in the circulating blood. Nevertheless, this is the only mode
in which it can be examined, as there are no means of bringing it
back to its previous condition.

Another important property of the organic substances is that
they readily excite, in other proximate principles and in each other,
those peculiar indirect chemical changes which are termed catalyses
or catalytic trarisformations. That is to say, they produce the changes
referred to, not directly, by combining with the substance which
suffers alteration, or with any of its ingredients ; but simply by their
presence which induces the chemical change in an indirect manner.
Thus, the organic substances of the intestinal fluids induce a cata-

OKGANIC SUBSTANCES. 99

lytic action by which starch is converted into sugar. The albumen
of the blood, by contact with the organic substance of the muscular
fibre, is transformed into a substance similar to it. The entire
process of nutrition, so far as the organic matters are concerned,
consists of such catalytic transformations. Many crystallizable
substances, which when pure remain unaltered in the air, become
changed if mingled with organic substances, even in small quantity.
Thus the casein of milk, after being exposed for a short time to a
warm atmosphere, becomes a catalytic body, and converts the sugar
of the milk into lactic acid. In this change there is no loss nor
addition of any chemical element, since lactic acid has precisely the
same ultimate composition with sugar of milk. It is simply a
transformation induced by the presence of the casein. Oily matters,
which are entirely unalterable when pure, readily become rancid at
warm temperatures, if mingled with an organic impurity.

Fourthly, The organic substances, when beginning to undergo
decay, induce in certain other substances the phenomena of fer-
mentation. Thus, the mucus of the urinary bladder, after a short
exposure to the atmosphere, causes the urea of the urine to be con-
verted into carbonate of ammonia, with the development of gaseous
bubbles. The organic matters of grape juice, under similar circum-
stances, give rise to fermentation of the sugar, by which it is con-
verted into alcohol and carbonic acid.

Fifthly, The organic substances are the only ones capable of
undergoing the process of putrefaction. This process is a compli-
cated one, and is characterized by a gradual liquefaction of the ani-
mal substance, by many mutual decompositions of the saline matters
which are associated with it, and by the development of peculiarly
fetid and unwholesome gases, among which are carbonic acid,
nitrogen, sulphuretted, phosphoretted, and carburetted hydrogen,
and ammoniacal vapors. Putrefaction takes place constantly after
death, if the organic tissue be exposed to a moist atmosphere at a
moderately warm temperature. It is much hastened by the presence
of other organic substances, in which decomposition has already
commenced.

The organic substances are readily distinguished, by the above
general characters, from all other kinds of proximate principles.
They are quite numerous ; nearly every animal fluid and tissue
containing at least one which is peculiar to itself. They have not
as yet been all accurately described. The following list, however,
comprises the most important of them, and those with which we are

100 PROXIMATE PRINCIPLES OF THE THIRD CLASS.

at present most thoroughly acquainted. The first seven are fluid,
or nearly so, and either colorless or of a faint yellowish tinge.

1. FIBRIN. — Fibrin is found in the blood ; where it exists, in the
human subject, in the proportion of two to three parts per thousand.
It is fluid, and mingled intimately with the other ingredients of the
blood. It occurs also, but in much smaller quantity, in the ly_rnph.
It is distinguished by what is called its " spontaneous" coagulation ;
that is, it coagulates on being withdrawn from the vessels, or on the
occurrence of any stoppage to tho circulation. It is rather more
abundant in the blood of some of the lower animals than in that of
th human subject. In general, it is found in larger quantity in
the blood of the herbivora than in that of the carnivora.

2. ALBUMEN. — Albumen occurs in the blood, the lymph, the
fluid of the pericardium, and in that of the serous cavities gene-
rally. It is also present in the fluid which may be extracted by
pressure from the muscular tissue. In the blood it occurs in the
proportion of about seventy -five parts per thousand. The white of
egg, which usually goes by the same name, is not identical with the
albumen of the blood, though it resembles it in some respects ; it is
properly a secretion from the mucous membrane of the fowl's ovi-
duct, and should be considered as a distinct organic substance.
Albumen coagulates on being raised to the temperature of 160° F.;
and the coagulum, like that of all the other proximate principles, is
soluble in caustic potassa. It coagulates also by contact with alco-
hol, the mineral acids, ferrocyanide of potassium in an acidulated
solution, tannin, and the metallic salts. The alcoholic coagulum, if
separated from the alcohol by washing, does not redissolve in water.
A very small quantity of albumen has been sometimes found in the
saliva.

3. CASEIN. — This substance exists in milk, in the proportion of
about forty parts per thousand. Ic coagulates by contact with all
the acids, mineral and organic ; but is not affected by a boiling
temperature. It is coagulated also by the juices of the stomach.
It is important as an article of food, being the principal organic
ingredient in all the preparations of milk. In a coagulated form,
it constitutes the different varieties of cheese, which are more or
less highly flavored with various oily matters remaining entangled
in the coagulated casein.

GLOBULINE. — MUCOSINE. 101

What is called vegetable casein or " legumine," is different from
the casein of milk, aud constitutes the organic substance present in
various kinds of peas and beans.

4. GLOBULIXE. — This is the organic substance forming the prin-
cipal mass of the red globules of the blood. It is nearly fluid in
its natural condition, and readily dissolves in water. It does not
dissolve, however, in the serum of the blood ; and the globules,
therefore, retain their natural form and consistency, unless the
serum be diluted with an excess of water. Globuline resembles
albumen in coagulating at the temperature of boiling water. It is
said to differ from it, however, in not being coagulated by contact
with alcohol.

5. PEPSINE. — This substance occurs as an ingredient in the gas-
tric juice. It is not the same substance which Schwann extracted
by maceration from the mucous membrane of the stomach, and
which is regarded by Eobin, Bernard, &c., as only an artificial pro-
duct of the alteration of the gastric tissues. There seems no good
reason, furthermore, why we should not designate by this name the
organic substance which really exists in the gastric juice. It occurs
in this fluid in very small quantity, not over fifteen parts per
thousand. It is coagulable by heat, and also by contact with alco-
hol. But if the alcoholic coagulum be well washed, it is again
soluble in a watery acidulated fluid.

6. PAXCREATIXE. — This is the organic substance of the pancreatic
juice, where it occurs in great abundance. It coagulates by heat,
and by contact with sulphate of magnesia in excess. In its natural
condition it is fluid, but has a considerable degree of viscidity. .

7. MUSCOSLSE is the organic substance which is found in the dif-
ferent varieties of mucus, and which imparts to them their viscidity
and other physical characters. Some of these mucous secretions
are so mixed with other fluids, that their consistency is more or less
diminished ; others, which remain pure, like that secreted by the
mucous follicles of the cervix uteri, have nearly a semi-solid con-
sistency. But little is known with regard to their other specific
characters.

The next three organic substances are solid or semi-solid in con-
sistency.

102 PROXIMATE PRINCIPLES OF THE THIRD CLASS.

8. OSTEDSTE is the organic substance of the bones, in which it is
associated with a large proportion of phosphate of lime. It exists,
in those bones which have been examined, in the proportion of
about two hundred parts per thousand. It is this substance which
by long boiling of the bones is transformed into gelatine or glue.
In its natural condition, however, it is insoluble in water, even at
the boiling temperature, and becomes soluble only after it has been
permanently altered by ebullition.

9. CARTILAGINE. — This forms the organic ingredient of cartilage.
Like that of the bones, it is altered by long boiling, and is converted
into a peculiar kind of gelatine termed "chondrine." Chondrine
differs from the gelatine of bones principally in being precipitated
by acids and certain metallic salts which have no effect on the latter.
Cartilagine, in its natural condition, is very solid, and is closely
united with the calcareous salts.

10. MUSCULINE. — This substance forms the principal mass of the
muscular fibre. It is semi-solid, and insoluble in water, but soluble
in dilute muriatic acid, from which it may be again precipitated by
neutralizing with an alkali. It closely resembles albumen in its
chemical composition, and like it, contains, according to Scherer,
two equivalents of sulphur.

The four remaining organic substances form a somewhat peculiar
group. They are the coloring matters of the body. They exist
always in small quantity, compared with the other ingredients, but
communicate to the tissues and fluids a very distinct coloration.
They all contain iron as one of their ultimate elements.

11. H^MATINE is the coloring matter of the red globules of the
blood. It is nearly fluid like the globuline, and is united with it
in a kind of mutual solution, lit is much less abundant than the
globuline, and exists in the proportion of about one part of haema-
tine to seventeen parts of globuline. The following is the formula
for its composition which is adopted by Lehmann : —

Hsematine = C44H22N306Fe.

When the blood-globules from any cause become disintegrated, the
haematine is readily imbibed after death by the walls of the blood-
vessels and the neighboring parts, staining them of a deep red
color. This coloration has sometimes been mistaken for an evidence

MELANINE. — URO3ACINE. 103

of arteritis ; but is really a simple effect of post-mortem imbibition,
as above stated.

12. MELANINE. — This is the blackish-brown coloring matter
which is found in the choroid coat of the eye, the iris, the hair, and
more or less abundantly in the epidermis. So far as can be ascer-
tained, the coloring matter is the same in all these situations. It is
very abundant in the black and brown races, less so in the yellow
and white, but is present to a certain extent in all. Even where
the tinges produced are entirely different, as, for example, in brown
and blue eyes, the coloring matter appears to be the same in cha-
racter, and to vary only in its quantity and the mode of its arrange-
ment; for the tinge of an animal tissue does not depend on its
local pigment only, but also on the muscular fibres, fibres of areolar
tissue, capillary bloodvessels, &c. All these ingredients of the
tissue are partially transparent, and by their mutual interlacement
and superposition modify more or less the effect of the pigment
which is deposited below or among them.

Melanine is insoluble in water and the dilute acids, but dissolves
slowly in caustic potassa. Its ultimate composition resembles that
of hasmatine, but the proportion of iron is smaller.

13. BILIVERDIXE is the coloring matter of the bile. It is yellow
by transmitted light, greenish by reflected light. On exposure to
the air in its natural fluid condition, it absorbs oxygen and assumes
a bright grass-green color. The same effect is produced by treating
it with nitric acid or other oxidizing substances. It occurs in very
small quantity in the bile, from which it may be extracted by pre-
cipitating it with milk of lime (Robin), from which it is afterward
separated by dissolving out the lime with muriatic acid. Obtained
in this form, however, it is insoluble in water, having been coagu-
lated by contact with the calcareous matter ; and is not, therefore,
precisely in its original condition.

14. UROSACIXE is the yellowish -red coloring matter of the urine.
It consists of the same ultimate elements as the other coloring mat-
ters, but occurs in the urine in such minute quantity, that the
relative proportion of its elements has never been determined. It
readily adheres to insoluble matters when they are precipitated from
the urine, and is consequently found almost always, to a greater or
less extent, as an ingredient in urinary calculi formed of the urates

104 PKOXIMATE PKINCIPLES OF THE THIRD CLASS.

or of uric acid. When the urates are thrown down also in the form
of a powder, as a urinary deposit, they are usually colored more or
less deeply, according to the quantity of urosacine which is preci-
pitated with them.

The organic substances which exist in the body require for their
production an abundant supply of similar substances in the food.
All highly nutritious articles of diet, therefore, contain more or less
of these substances. Still, though nitrogenous matters must be
abundantly supplied, under some form, from without, yet the par-
ticular kinds of organic substances, characteristic of the tissues, are
formed in the body by a transformation of those which are intro-
duced with the food. The, organic matters derived from vegetables,
though similar in their general characters to those existing in the
animal body, are yet specifically different. The gluten of wheat,
the legumine of peas and beans, are not the same with animal albu-
men and fibrin. The only organic substances taken with animal
food, as a general rule, are the albumen of eggs, the casein of milk,
and the musculine of flesh; and even these, in the food of the
human species, are so altered and coagulated by the process of
cooking, as to lose their specific characters before being introduced
into the alimentary canal. They are still further changed by the
process of digestion, and are absorbed under another form into the
blood. But from their subsequent metamorphoses there are formed,
in the different parts of the body, osteine, cartilagine, haematine,
globuline, and all the other varieties of organic matter that cha-
racterize the different tissues. These varieties, therefore, originate
as such in the animal economy by the catalytic changes which the
ingredients of the blood undergo in nutrition.

Only a very small quantity of organic matter is discharged
with the excretions. The coloring matters of the bile and urine,
and the mucus of the urinary bladder, are almost the only ones
that find an exit from the body in this way. There is a minute
quantity of organic matter exhaled in a volatile form with the
breath, and a little also, in all probability, from the cutaneous sur-
face. But the entire quantity so discharged bears but a very small
proportion to that which is daily introduced with the food. The
organic substances, therefore, are decomposed in the interior of the
body. They are transformed by the process of destructive assimi-
lation, and their elements are finally eliminated and discharged
under other forms of combination.

OF FOOD. 105

CHAPTER V.

OF FOOD.

the term " food" are included all those substances, solid
and liquid, which are necessary to sustain the process of nutrition.
The first act of this process is the absorption from without of all
those materials which enter into the composition of the living frame,
or of others which may be converted into them in the interior of
the body.

The proximate principles of the first class, or the "inorganic
substances," require to be supplied in sufficient quantity to keep up
the natural proportion in which they exist in the various solids and
fluids. As we have found it to be characteristic of these substances,
except in a few instances, that they suffer no alteration in the in-
terior of the body, but, on the contrary, are absorbed, deposited in
its tissue, and pass out of it afterward unchanged, nearly every one
of them requires to be present under its own proper form, and in
sufficient quantity in the food. The alkaline carbonates, which
are formed, as we have seen, by a decomposition of the malates,
citrates and tartrates, constitute almost the only exception to this
rule.

Since water enters so largely into the composition of nearly every
part of the body, it is equally important as an ingredient of the
food. In the case of the human subject, it is probably the most
important substance to be supplied with constancy and regularity,
and the system suffers more rapidly when entirely deprived of
fluids, than when the supply of solid food only is withdrawn. A
man may pass eight or ten hours, for example, without solid food,
and suffer little or no inconvenience ; but if deprived of water for
the same length of time, he becomes rapidly exhausted, and feels
the deficiency in a very marked degree. Magendie found, in his
experiments on dogs subjected to inanition,1 that if the animals

1 Comptes Rendus, vol. xiii. p. 256,

106 OF FOOD.

were supplied with water alone they lived six, eight, and even ten
days longer than if they were deprived at the same time of both
solid and liquid food. Chloride of sodium, also, is usually added
to the food in considerable quantity, and requires to be supplied
with tolerable regularity ; but the remaining inorganic materials,
such as calcareous salts, the alkaline phosphates, &c., occur natu-
rally in sufficient quantity in most of the articles which are used as
food.

The proximate principles of the second class, so far as they con-
stitute ingredients of the food, are naturally divided into two
groups : 1st, the sugar, and 2d, the oily matters. Since starch is
always converted into sugar in the process of digestion, it may be
included, as an alimentary substance, in. the same group with the
sugars. There is a natural desire in the human species for both
saccharine and oleaginous food. In the purely carnivorous animals,
however, though no starch or sugar be taken, yet the body is main-
tained in a healthy condition. It has been supposed, therefore, that
saccharine matters could not be absolutely necessary as food ; the
more so since it has been found, by the experiments of Cl. Bernard,
that, in carnivorous animals kept exclusively on a diet of flesh,
sugar is still formed in the liver, as well as in the mammary gland.
The above conclusion, however, which has been drawn from these
facts, does not apply practically to the human species. The car-
nivorous animals have no desire for vegetable food, while in the
human species there is a natural craving for it, which is almost
universal. It may be dispensed with for a few days, but not with
impunity for any great length of time. The experiment has often
enough been tried, in the treatment of diabetes, of confining the
patient to a strictly animal diet. It has been invariably found that,
if this regimen be continued for some weeks, the desire for vegetable
food on the part of the patient becomes so imperative that the plan
of treatment is unavoidably abandoned.

A similar question has also arisen with regard to the oleaginous
matters. Are these substances indispensable as ingredients of the
food, or may they be replaced by other proximate principles, such
as starch or sugar ? It has already been seen, from the experiments
of Boussingault and others, that a certain amount of fat is produced
in the body over and above that which is taken with the food ; and
it appears also that a regimen abounding in saccharine substances
is favorable to the production of fat. It is altogether probable,
therefore, that the materials for the production of fat may be

OF FOOD. 107

derived, under these circumstances, either directly or indirectly
from saccharine matters. But saccharine matters alone are not
entirely sufficient. M. Huber1 thought he had demonstrated that
bees fed on pure sugar would produce enough wax to show that
the sugar could supply all that was necessary to the formation of
the fatty matter of the wax. Dumas and Milne-Edwards, however,
in repeating Huber's experiments,2 found that this was not the case.
Bees, fed on pure sugar, soon cease to work, and sometimes perish
in considerable numbers; but if fed with honey, which contains
some waxy and other matters beside the sugar, they thrive upon
it ; and produce, in a given time, a much larger quantity of fat
than was contained in the whole supply of food.

The same thing was established by Boussingault with regard to
starchy matters. He found that in fattening pigs, though the
quantity of fat accumulated by the animal considerably exceeded
that contained in the food, yet fat must enter to some extent into
the composition of the food in order to maintain the animals in a
good condition ; for pigs, fed on boiled potatoes alone (an article
abounding in starch but nearly destitute of oily matter), fattened
slowly and with great difficulty ; while those fed on potatoes mixed
with a greasy fluid fattened readily, and accumulated, as mentioned
above, much more fat than was contained in the food.

The apparent discrepancy between these facts may be easily ex-
plained, when we recollect that, in order that the animal may become
fattened, it is necessary that he be supplied not only with the
materials of the fat itself, but also with everything else which is
necessary to maintain the body in a healthy condition. Oleaginous
matter is one of these necessary substances. The fats which are
taken in with the food are not destined to be simply transported
into the body and deposited there unchanged. On the contrary,
they are altered and used up in the processes of digestion and
nutrition ; while the fats which appear in the body as constituents
of the tissues are, in great part, of new formation, and are produced
from materials derived, perhaps, from a variety of different sources.

It is certain, then, that either one or the other of these two
groups of substances, saccharine or oleaginous, must enter into the
composition of the food; and furthermore, that, though the oily
matters may sometimes be produced in the body from the sugars,

1 Natural History of Bees, Edinburgh, 1821, p. 330.

2 Annales de Chini. et de Phys., 3d series, vol. xiv. p. 400.

108 OF FOOD.

it, is also necessary for the perfect nutrition of the body that fat be
supplied, under its own form, with the food. For the human
species, also, it is natural to have them both associated in the
aliment' .ry materials. They occur together in most vegetable sub-
stances, and there is a natural desire for them both, as elements of
the food.

They are not, however, when alone, or even associated with each
other, sufficient for the nutrition of the animal body. Magendie
found that dogs, fed exclusively on starch or sugar, perished after a
short time with symptoms of profound disturbance of the nutritive
functions. An exclusive diet of butter or lard had a similar effect.
The animal became exceedingly debilitated, though without much
emaciation; and after death, all the internal organs and tissues
were found infiltrated with oil. Boussingault1 performed a similar
experiment, with a like result, upon a duck, which was kept upon
an exclusive regimen of butter. " The duck received 1350 to 1500
grains of butter every day. At the end of three weeks it died of
inanition. The butter oozed from every part of its body. The
feathers looked as though they had been steeped in melted butter,
and the body exhaled an unwholesome odor like that of butyric
acid."

Lehmann was also led to the same result by some experiments
which he performed upon himself for the purpose of ascertaining
the effect produced on the urine by different kinds of food.2
This observer confined himself first to a purely animal diet for
three weeks, and afterwards to a purely vegetable one for sixteen
days, without suffering any marked inconvenience. He then put
himself upon a regimen consisting entirely of non-nitrogenous sub-
stances, starch, sugar, gum, and oil, but was only able to continue
this diet for two, or at most for three days, owing to the marked
disturbance of the general health which rapidly supervened. The
unpleasant symptoms, however, immediately disappeared on his
return to an ordinary mixed diet. The same fact has been esta-
blished more recently by Prof. Wm. A. Hammond,3 in a series of
experiments which he performed upon himself. He was enabled
to live for ten days on a diet composed exclusively of boiled starch
and water. After the third day, however, the general health began

1 Chimie Agricole, p. 166.

2 Journal fur praktische Chemie, vol. xxvii. p. 257.

3 Experimental Researches, &c., being the Prize Essay of the American Medical
Association for 1857.

OF FOOD. 109

to deteriorate, and became very much disturbed before the termi-
nation of the experiment. The prominent symptoms were debility,
headache, pyrosis, and palpitation of the heart. After the starchy
diet was abandoned, it required some days to restore the health to
its usual condition.

The proximate principles of the third class, or the organic sub-
stances proper, enter so largely into the constitution of the animal
tissues and fluids, that their importance, as elements of the food, is
easily understood. No food can be long nutritious, unless a certain
proportion of these substances be present in it. Since they are so
abundant as ingredients of the body, their loss or absence from the
food is felt more speedily and promptly than that of any other sub-
stance except water. They have, therefore, sometimes received the
name of "nutritious substances," in contradistinction to those of
the second class, which contain no nitrogen, and which have been
found by the experiments of Magendie and others to be insufficient
for the support of life. The organic substances, however, when
taken alone, are no more capable of supporting life indefinitely than
the others. It was found in the experiments of the French " Gela-
tine Commission"1 that animals fed on pure fibrin and albumen, as
well as those fed on gelatine, become, after a short time, much en-
feebled, refuse the food which is offered to them, or take it with
reluctance, and finally die of inanition. This result has been
explained by supposing that these substances, when taken alone,
excite after a time such disgust in the animal that they are either
no longer taken, or if taken are not digested. But this disgust
itself is simply an indication that the substances used are insufficient
and finally useless as articles of food, and that the system demands
instinctively other materials for its nourishment.

The instinctive desire of animals for certain substances is the
surest indication that they are in reality required for the nutritive
process ; and on the other hand, the indifference or repugnance
manifested for injurious or useless substances, is an equal evidence
of their unfitness as articles of food. This repugnance is well de-
scribed by Magendie, in the report of the commission above alluded
to, while detailing the result of his investigations on the nutritive
qualities of gelatine. "The result," he says, "of these first trials
was that pure gelatine was not to the taste of the dogs experimented
on. Some of them suffered the pangs of hunger with the gelatine

1 Cotnptes Rendus, 1841, vol. xiii. p. 2 7.

110 OF FOOD.

within their reach, and would not touch it ; others tasted of it, but
would not eat ; others still devoured a certain quantity of it once
or twice, and then obstinately refused to make any further use of it."

In one instance, however, Magendie succeeded in inducing a dog
to 'take a considerable quantity of pure fibrin daily throughout the
whole course of the experiment; but notwithstanding this, the
animal became emaciated like the others, and died at last with the
same symptoms of inanition.

The alimentary substances of the second class, however, viz., the
sugars and the oils, have been sometimes thought less important
than the albuminous matters, because they do not enter so largely
or so permanently into the composition of the solid tissues. The
saccharine matters, when taken as food, cannot be traced farther
than the blood. They undergo already, in the circulating fluid,
some change by which their essential character is lost, and they
cannot be any longer recognized. The appearance of sugar in the
mammary gland and the milk is only exceptional, and does not
occur at all in the male subject. The fats are, it is true, very gene-
rally distributed throughout the body, but it is only in the brain
and nervous matter that they exist intimately united with the re-
maining ingredients of the tissues. Elsewhere, as already mention ed,
they are deposited in distinct drops and granules, and so long as
they remain in this condition must of course be inactive, so far as
regards any chemical nutritive process. In this condition they
seem to be held in reserve, ready to be absorbed by the blood,
whenever they may be required for the purposes of nutrition. On
being reabsorbed, however, as soon as they again enter the blood
or unite intimately with the substance of the tissues, they at once
change their condition and lose their former chemical constitution
and properties.

It is for these reasons that the albuminoid matters have been
sometimes considered as the only "nutritious" substances, because
they alone constitute under their own form a great part of the
ingredients of the tissues, while the sugars and the oils rapidly dis-
appear by decomposition. It has even been assumed that the pro-
cess by which the sugar and the oils disappear is one of direct
combustion or oxidation, and that they are destined solely to be
consumed in this way, not to enter at all into the composition of
the tissues but only to maintain the heat of the body by an inces-
sant process of combustion in the blood. They have been therefore
termed the " combustible" or " heat-producing" elements, while the

OF FOOD. Ill

albuminoid substances were known as the nutritious or " plastic"
elements.

This distinction, however, has no real foundation. In the first
place, it is not at all certain that the sugars and the oils which dis-
appear in the body are destroyed by combustion. This is merely
an inference which has been made without any direct proof. All
we know positively in regard to the matter is that these substances
soon become so altered in the blood that they can no longer be
recognized by their ordinary chemical properties ; but we are still
ignorant of the exact nature of the transformations which they
undergo. Furthermore, the difference between the sugars and the
oils on the one hand, and the albuminoid substances on the other,
so far as regards their decomposition and disappearance in the
body, is only a difference in time. The albuminoid substances
become transformed more slowly, the sugars and the oils more
rapidly. Even if it should be ascertained hereafter that the sugars
and the oils really do not unite at all with the solid tissues, but are
entirely decomposed in the blood, this would not make them any
less important as alimentary substances, since the blood is as
essential a part of the body as the solid tissues, and its nutrition
must be provided for equally with theirs.

It is evident, therefore, that no single proximate principle, nor
even any one class of them alone, can be sufficient for the nutrition
of the body; but that the food, to be nourishing, must contain
substances belonging to all the different groups of proximate prin-
ciples. The albuminoid substances are first in importance because
they constitute the largest part of the entire mass of the body ; and
exhaustion therefore follows more rapidly when they are withheld
than when the animal is deprived of other kinds of alimentary
matter. But starchy and oleaginous substances are also requisite ;
and the body feels the want of them sooner or later, though it may
be plentifully supplied with albumen and fibrin. Finally, the in-
organic saline matters, though in smaller quantity, are also neces-
sary to the continuous maintenance of life. In order that the
animal tissues and fluids remain in a healthy condition and take
their proper part in the functions of life, they must be supplied
with all the ingredients necessary to their constitution ; and a man
may be starved to death at last by depriving him of chloride of
sodium or phosphate of lime just as surely, though not so rapidly,
as if he were deprived of albumen or oil.

In the different kinds of food, accordingly, which have been

112 OF FOOD.

adopted by the universal and instinctive choice of man, the three
different classes of proximate principles are all more or less abund-
antly represented. In all of them there exists naturally a certain
proportion of saline substances ; and water and chloride of sodium
are generally taken with them in addition. In milk, the first food
supplied to the infant, we have casein which is an albuminoid sub-
stance, butter which represents the oily matters, and sugar of milk
belonging to the saccharine group, together with water and saline
matters, in the following proportions : — 1

COMPOSITION OF Cow's MILK.

Water 87.02

Casein 4.48

Butter 3.13

Sugar of milk 4.77

Soda

Chlorides of potassium and sodium ....
Phosphates of soda and potassa .....

Phosphate of lime

" magnesia

Alkaline carbonates .
Iron, &c.

0.60

100.00

In wheat flour, gluten is the albuminoid matter, sugar and starch
the non -nitrogenous principles.

COMPOSITION OF WHEAT FLOUR.

Gluten .... 10.2 Gum . . . .2.8

Starch . . . . 72.8 Water .... 10.0

Sugar .... 4.2

100.0

The other cereal grains mostly contain oil in addition to the
above.

COMPOSITION OF DRIED OATMEAL.

Starch 59.00

Bitter matter and sugar 8.25

Gray albuminous matter . . . . . . . .4.30

Fatty oil 2.00

Gum 2.50

Husk, mixture, and loss 23.95

100.00

Eggs contain albumen and salts in the white, with the addition
of oily matter in the yolk.

1 The accompanying analyses of various kinds of food are taken from Pereira
on Food and Diet, New York, 1843.

OF FOOD. 113

COMPOSITION OP EGGS.
White of Egg.

Water .... 80.00

Albumen and mucus . 15.28 .....

Yellow oil

Salts .... 4.72

100.00 1UO.OO

In ordinary flesh or butcher's meat, we have the albuminoid
matter of the muscular fibre and the fat of the adipose tissue.

COMPOSITION OF ORDINARY BOTCHER'S MEAT.

I Water . . . .63.418
Meat devoid of fat . 85.7 \ Solid Inatter . . . 22.282

Fat, cellular tissue, &c 14.300

100.000

From what has been said above, it will easily be seen that the
nutritious character of any substance, or its value as an article of
food, does not depend simply upon its containing either one of the
alimentary substances mentioned above in large quantity ; but upon
its containing them mingled together in such proportion as is
requisite for the healthy nutrition of the body. What these pro-
portions are cannot be determined from simple chemical analysis,
nor from any other data than those derived from direct observation
and experiment.

The total quantity of food required by man has been variously
estimated. It will necessarily vary, indeed, not only with the con-
stitution and habits of the individual, but also with the quality of
the food employed ; since some articles, such as corn and meat, con-
tain very much more alimentary material in the same bulk than
fresh fruits or vegetables. Any estimate, therefore, of the total
quantity should state also the kind of food used ; otherwise it will
be altogether without value. From experiments performed while
living on an exclusive diet of bread, fresh meat, and butter, with
coffee and water for drink, we have found that the entire quantity
of food required during twenty-four hours by a man in full health,
and taking free exercise in the open air, is as follows : —

Meat . . . . .16 ounces or 1.00 Ib. Avoirdupois.

Bread 19 " " 1.19 "

Butter or fat . . . . 3.} " " 0.22 " "

Water 52 fluid oz. " 3.3^ - "

That is to say, rather less than two and a half pounds of solid food,
and rather over three pints of liquid food.

114 OF FOOD.

Another necessary consideration, in estimating the value of any
substance as an article of food, is its digestibility. A vegetable or
animal tissue may contain an abundance of albuminoid or starchy
matter, but may be at the same time of such an unyielding consist-
ency as to be insoluble in the digestive fluids, and therefore useless
as an article of food. Bones and .cartilages, and the fibres of yellow
elastic tissue, are indigestible, and therefore not nutritious. The
same remark may be made with regard to the substances contained
in woody fibre, and the hard coverings and kernels of various fruits.
Everything, accordingly, which softens or disintegrates a hard ali-
mentary substance renders it more digestible, and so far increases
its value as .an article of food.

The preparation of food by cooking has a twofold object : first,
to soften or disintegrate it, and second, to give it an attractive
flavor. Many vegetable substances are so hard as to be entirely
indigestible in a raw state. Eipe peas and beans, the different kinds
of grain, and many roots and fruits, require to be softened by boil-
ing, or some other culinary process, before they are ready for use.
With them, the principal change produced by cooking is an altera-
tion in consistency. With most kinds of animal food, however, the
effect is somewhat different. In the case of muscular flesh, for ex-
ample, the muscular fibres themselves are almost always more or
less hardened by boiling or roasting; but, at the same time, the
fibrous tissue by which they are held together is gelatinized and
softened, so that the muscular fibres are more easily separated from
each other, and more readily attacked by the digestive fluids. But
beside this, the organic substances contained in meat, which are all
of them very insipid in the raw state, acquire by the action of heat
in cooking, a peculiar and agreeable flavor. This flavor excites
the appetite and stimulates the flow of the digestive fluids, and
renders, in this way, the entire process of digestion more easy and
expeditious.

The changes which the food undergoes in the interior of the body
may be included under three different heads : first, digestion, or the
preparation of the food in the alimentary canal ; second, assimilation,
by which the elements of the food are converted into the animal
tissues ; and third, excretion, by which they are again decomposed,
and finally discharged from the body.

DIGESTION. 115

CHAPTEK VI.

DIGESTION.

DIGESTION is that process by which the food is reduced to a form
in which it can be absorbed from the intestinal canal, and taken up
by the bloodvessels. This process does not occur in vegetables.
For vegetables are dependent for their nutrition, mostly, if not
entirely, upon a supply of inorganic substances, as water, saline
matters, carbonic acid, and ammonia. These materials constitute
the food upon which plants subsist, and are converted in their inte-
rior into other substances, by the nutritive process. These mate-
rials, furthermore, are constantly supplied to the vegetable under
such a form as to be readily absorbed. Carbonic acid and ammonia
exist in a gaseous form in the atmosphere, and are also to be found
in solution, together with the requisite saline matters, in the water
with which the soil is penetrated. All these substances, therefore,
are at once ready for absorption, and do not require any preliminary
modification. But with animals and man the case is different.
They cannot subsist upon these inorganic substances alone, but
require for their support materials which have already been organ-
ized, and which have previously constituted a part of animal or
vegetable bodies. Their food is almost invariably solid or semi-solid
at the time when it is taken, and insoluble in water. Meat, bread,
fruits, vegetables, &c., are all taken into the stomach in a solid and
insoluble condition ; and even those substances which are naturally
fluid, such as milk, albumen, white of egg. are almost always, in
the human species, coagulated and solidified by the process of cook-
ing, before being taken into the stomach.

In animals, accordingly, the food requires to undergo a process
of digestion, or liquefaction, before it can be absorbed. In all cases,
the general characters of this process are the same. It consists
essentially in the food being received into a canal, running through
the body from mouth to anus, called the "alimentary canal," in
which it comes in contact with certain digestive fluids, which act

116 DIGESTION.

upon it in such a way as to liquefy and dissolve it. These fluids
are secreted by the mucous membrane of the alimentary canal, and
by certain glandular organs situated in its neighborhood. Since the
food always consists, as we have already seen, of a mixture of vari-
ous substances, having different physical and chemical properties,
the several digestive fluids are also different from each other ; each
one of them exerting a peculiar action, which is more or less con-
fined to particular species of food. As the food passes through the
intestine from above downward, those parts of it which become
liquefied are successively removed by absorption, and taken up by
the vessels ; while the remaining portions, consisting of the indi-
gestible matter, together with the refuse of the intestinal secretions,
gradually acquire a firmer consistency owing to the absorption of
the fluids, and are finally discharged from the intestine under the
form of feces.

In different species of animals, however, the difference in their
habits, in the constitution of their tissues, and in the character of
their food, is accompanied with a corresponding variation in the
anatomy of the digestive apparatus, and the character of the secreted
fluids. As a general rule, the digestive apparatus of herbivorous
animals is more complex than that of the carnivora ; since, in vege-
table substances, the nutritious matters are often present in a very
solid and unmanageable form, as, for example, in raw starch and
the cereal grains, and are nearly always entangled among vegetable
cells and fibres of an indigestible character. In those instances
where the food consists mostly of herbage, as grass, leaves, &c., the
digestible matters bear only a small proportion to the entire quan-
tity ; and a large mass of food must therefore be taken, in order
that the requisite amount of nutritious material may be extracted
from it. In such cases, accordingly, the alimentarjr canal is large
and long ; and is divided into many compartments, in which
different processes of disintegration, transformation, and solution
are carried on.

In the common fowl, for instance (Fig. 16), the food, which con-
sists mostly of grains, and frequently of insects with hard, coria- .
ceous integument, first passes down the oesophagus (a) into a
diverticulum or pouch (b) termed the crop. Here it remains for
a time mingled with a watery secretion in which the grains are
macerated and softened. The food is then carried farther down
until it reaches a second dilatation (c), the proventriculus, or
secreting stomach. The mucous membrane here is thick and

DIGESTION.

117

glandular, and is provided with numerous se-
creting follicles or crypts. From them an
acid fluid is poured out, by which the food is
subjected to further changes. It next passes
into the gizzard (d), or triturating stomach, a
cavity inclosed by thick muscular walls, and
lined with a remarkably tough and horny
epithelium. Here it is subjected to the crush-
ing and grinding action of the muscular pa-
rietes, assisted by grains of sand and gravel,
which the animal instinctively swallows with
the food, by which it is so triturated and dis-
integrated, that it is reduced to a uniform pulp,
upon which the digestive fluids can effectually
operate. The mass then passes into the intes-
tine (e), where it meets with the intestinal
juices, which complete the process of solution ;
and from the intestinal cavity it is finally ab-
sorbed in a liquid form, by the vessels of the
mucous membrane.

In the ox, again, the sheep, the camel, the
deer, and all ruminating animals, there are
four distinct stomachs through which the
food passes in succession; each lined with
mucous membrane of a different structure,
and adapted to perform a different part in
the digestive process. (Fig. 17.) When first
swallowed, the food is received into the ru-
men, or paunch (b), a large sac, itself par-
tially divided by incomplete partitions, and
lined by a mucous membrane thickly set
with long prominences or villi. Here it ac-
cumulates while the animal is feeding, and is
retained and macerated in its own fluids. When the animal has
finished browsing, and the process of rumination commences, the
food is regurgitated into the mouth by an inverted action of the
muscular walls of the paunch and oesophagus, and slowly masticated.
It then descends again along the oesophagus ; but instead of enter-
ing the first stomach, as before, it is turned off' by a muscular valve
into the second stomach, or reticulum (c), which is distinguished
by the intersecting folds of its mucous membrane, which give it

ALIMENTARY CASAL OF
FOWL. — «. (Esophagus. b.
Crop. c. Proventriculus, or
secreting stomach, d. Gizzard,
or triturating stomach, e. In-
testine. /. Two long csecal
tubes which open into the in-
testine a short distance above
its termination.

118

DIGESTION".

Fig. 17.

COMPOTND STOMACH OF Ox.—
gus 6. Rumen, or first stomach, c. Reticulum, or
second, d. Omasus, or third, e Abomasus, or
fourth. /. Duodenum. (From Rymer Jones.)

a lioney-combed or reticulated appearance. Here the food, already

triturated in the mouth, and
mixed with the saliva, is further
macerated in the fluids swal-
lowed by the animal, which al-
ways accumulate in considerable
quantity in the reticulum. The
next cavity is the omasus, or
" psalterium" (d\ in which the
mucous membrane is arranged
in longitudinal folds, alternately
broad and narrow, lying parallel
with each other like the leaves
of a book, so that the extent of
mucous surface, brought in con-
tact with the food, is very much

(Esopha- t ««

increased. The exit from this
cavity leads directly into the
abomasus, or " rennet" (e), which
is the true digestive stomach, in which the mucous membrane is
softer, thicker, and more glandular than elsewhere, and in which
an acid and highly solvent fluid is secreted. Then follows the in-
testinal canal with its various divisions and variations.

In the carnivora, on the other hand, the alimentary canal is
shorter and narrower than in the preceding, and presents fewer
complexities. The food, upon which these animals subsist, is softer
than that of the herbivora, and less encumbered with indigestible
matter ; so that the process of its solution requires a less extensive
apparatus.

In the human species, the food is naturally of a mixed cha-
racter, containing both animal and vegetable substances. But the
digestive apparatus in man resembles almost exactly that of the
carnivora. For the vegetable matters which we take as food are,
in the first place, artificially separated, to a great extent, from indi-
gestible impurities; and secondly, they are so softened by the
process of cooking as to become nearly or quite as easily digestible
as animal substances.

In the human species, however, the process of digestion, though
simpler than in the herbivora, is still complicated. The alimentary
canal is here, also, divided into different compartments or cavities,
which communicate with each other by narrow orifices. At its

DIGESTION.

119

Fig. 18.

\

commencement (Fig. 18), we find the cavity of the mouth, which is
guarded at its posterior extremity by the muscular valve of the
isthmus of the fauces.
Through the pharynx and
oesophagus (a), it commu-
nicates with the second
compartment, or the sto-
mach (b), a flask-shaped
dilatation, which is guarded
at the cardiac and pyloric
orifices by circular bands
of muscular fibres. Then
comes the small intestine (e),
different parts of which,
owing to the varying struc-
ture of their mucous mem-
branes, have received the
different names of duode-
num, jejunum, and ileum.
In the duodenum we have
the orifices of the biliary
and pancreatic ducts (/, g).
Finally, we have the large
intestine (h, i,j, k), separated
from the smaller by the
ileo-csecal valve, and ter-
minating, at its lower ex-
tremity, by the anus, at
which is situated a double
sphincter, for the purpose
of guarding its orifice.
Everywhere the alimentary
canal is composed of a
mucous membrane and a

mUSCular COat, with a layer RCMAS ALIMEXTARY CANAL. — n. (Esophagus.

of submucous areolar tissue IJ^. Bu^T plST L, '' ^

between the tWO. The mUS- cendiug colon, t. Transverse colon, j. Descending
, . , colon. A-. Rectum.

cular coat is everywhere

composed of a double layer of longitudinal and transverse fibres,
by the alternate contraction and relaxation of which the food is
carried through the canal from above downward. The mucous

120 DIGESTION".

membrane presents, also, a different structure, and has different
properties in different parts. In the mouth and oesophagus, it is
smooth, with a hard, whitish, and tessellated epithelium. This kind
of epithelium terminates abruptly at the cardiac orifice of the
stomach. The mucous membrane of the gastric cavity is soft and
glandular, covered with a transparent, columnar epithelium, and
thrown into minute folds or projections on its free surface, which
are sometimes reticulated with each other. In the small intestine,
we find large transverse folds of mucous membrane, the valvulse
conniventes, the minute villosities which cover its surface, and the
peculiar glandular structures which it contains. Finally, in the
large intestine, the mucous membrane is again different. It is here
smooth and shining, free from villosities, and provided with a dif-
ferent glandular apparatus.

Furthermore, the digestive secretions, also, vary in these different
regions. In its passage from above downward, the food meets
with no less than five different digestive fluids. First it meets with
the saliva in the cavity of the mouth ; second, with the gastric juice,
in the stomach ; third, with the bile ; fourth, with the pancreatic
fluid; and fifth, with the intestinal juice. It is the most important
characteristic of the process of digestion, as established by modern
researches, that different elements of the food are digested in different
parts of the alimentary canal by the agency of different digestive fluids.
By their action, the various ingredients of the alimentary mass are
successively reduced to a fluid condition, and are taken up by the
vessels of the intestinal mucous membrane.

The action which is exerted upon the food by the digestive
fluids is not that of a simple chemical solution. It is a transforma-
tion, by which the ingredients of the food are altered in character
at the same time that they undergo the process of liquefaction.
The active agent in producing this change is in every instance an
organic matter, which enters as an ingredient into the digestive
fluid ; and which, by coming in contact with the food, exerts upon
it a catalytic action, and transforms its ingredients into other sub-
stances. It is these newly formed substances which are finally
absorbed by the vessels, and mingled with the general current of
the circulation.

In our study of the process of digestion, the different digestive
fluids will be examined separately, and their action on the aliment-
ary substances in the different regions of the digestive apparatus
successively investigated.

MASTICATION. 121

MASTICATION. — In the first division of the alimentary canal, viz.,
the mouth, the food undergoes simultaneously two different opera-
tions, viz., mastication and insalivation. Mastication consists in
the cutting and trituration of the food by the teeth, by the action
of which it is reduced to a state of minute subdivision. This pro-
cess is entirely a mechanical one. It is necessary, in order to pre-
pare the food for the subsequent action of the digestive fluids. As
this action is chemical in its nature, it will be exerted more promptly
and efficiently if the food be finely divided than if it be brought in
contact with the digestive fluids in a solid mass. This is always
the case when a solid body is subjected to the chemical action of a
solvent fluid; since, by being broken up into minute particles, it
offers a larger surface to the contact of the fluid, and is more readily
attacked and dissolved or decomposed by it.

In the structure of the teeth, and their physiological action, there
are certain marked differences, corresponding with the habits of the
animal, and the kind of food upon which it subsists. In fish and
serpents, in which the food is swallowed entire, and in which the
process of digestion, accordingly, is comparatively slow, the teeth
are simply organs of prehension. They have generally the form
of sharp, curved spines, with their points set backward (Fig. 19),
and arranged in a double or triple row

•••**•' • TfifT 1 Q

about the edges of the jaws, and sometimes
covering the mucous surfaces of the mouth,
tongue, and palate. They serve merely to
retain the prey, and prevent its escape,
after it has been seized by the animal. In

the CarmVOrOUS quadrupeds, as those Of SKTLL OP RATTLESNAKE.
. , , , . , , - . ., (After Achille-Richard.)

the dog and cat kind, and other similar

families, there are three different kinds of teeth adapted to different
mechanical purposes. (Fig. 20.) First, the incisors, twelve in num-
ber, situated at the anterior part of the jaw, six in the superior,
and six in the inferior maxilla, of flattened form, and placed with
their thin edges running from side to side. The incisors, as their
name indicates, are adapted for dividing the food by a cutting
motion, like that of a pair of shears. Behind them come the canine
teeth, or tusks, one on each side of the upper and under jaw.
These are long, curved, conical, and pointed; and are used as
weapons of offence, and for laying hold of and retaining the prey.
Lastly, the molars, eight or more in number on each side, are
larger and broader than the incisors, and provided with serrated

122

DIGESTION.

Fig. 20.

edges, each presenting several sharp points, arranged generally in
a direction parallel with the line of the jaw. In these animals,

mastication is very imperfect, since
the food is not ground up, but only
pierced and mangled by the action
of the teeth before being swallowed
into the stomach. In the herbi-
vora, on the other hand, the inci-
sors are present only in the lower
jaw in the ruminating animals,
though in the horse they are found
in both the upper and lower max-
illa. (Fig. 21.) They are used merely
for cutting off the bundles of grass
or herbage, on which the animal feeds. The canines are either
absent or slightly developed, and the real process of mastication is

Fig. 21.

SKULL OF POLAR BEAR. Anterior
Tiew ; showing incisors and cauines.

Fig. 22.

SKTLL or THK HORSE.

performed altogether by the molars. These are large and thick
(Fig. 22), and present a broad, flat surface, diversified by variously
folded and projecting ridges of enamel, with shal-
low grooves, intervening between them. By the
lateral rubbing motion of the roughened surfaces
against each other, the food is effectually commi-
nuted and reduced to a pulpy mass.

In the human subject, the teeth combine the
characters of those of the carnivora and the herbi-
TOOTH OF Vora. (Fig. 23.) The incisors (a), four in number

THE HORSE. Grind- _V •-.-••-*

ing surface in each jaw, have, as in other instances, a cutting

SALIVA.

123

Fig. 23.

HUMAN TEETH — UPPER JAW. — a. Incisors. 6. Canines,
c. Anterior molars, d. Posterior molars.

edge running from side to side. The canines (b), which are situated
immediately behind the former, are much less prominent and
pointed than in the car-
nivora, and differ less
in form from the inci-
sors on the one hand,
and the first molars on
the other. The molars,
again (c, d), are thick
and strong, and have
comparatively flat sur-
faces, like those of the
herbivora; but instead
of presenting curvili-
near ridges, are covered
with more or less coni-
cal eminences, like those
of the carnivora. In the
human subject, therefore, the teeth are evidently adapted for a mixed
diet, consisting of both animal and vegetable food. Mastication is
here as perfect as it is in the herbivora, though less prolonged and
laborious ; for the vegetable substances used by man, as already
remarked, are previously separated to a great extent from their
impurities, and softened by cooking ; so that they do not require,
for their mastication, so extensive and powerful a triturating ap-
paratus. Finally, animal substances are more completely masti-
cated in the human subject than they are in the carnivora, and
their digestion is accordingly completed with greater rapidity.

We can easily estimate, from the facts above stated, the great
importance, to the digestive process, of a thorough preliminary
mastication. If the food be hastily swallowed in undivided masses,
it must remain a long time undissolved in the stomach, where it
will become a source of irritation and disturbance ; but if reduced
beforehand, by mastication, to a state of minute subdivision, it is
readily attacked by the digestive fluids, and becomes speedily and
completely liquefied.

SALIVA. — At the same time that the food is masticated, it is mixed
in the cavity of the mouth with the first of the digestive fluids, viz.,
the saliva. Human saliva, as it is obtained directly from the buc-
cal cavity, is a colorless, slightly viscid and alkaline fluid, with a

124

DIGESTION.

Fig. 24.

specific gravity of 1005. When first discharged, it is frothy and
opaline, holding in suspension minute, whitish flocculi. On being
allowed to stand for some hours in a cylindrical glass vessel, an
opaque, whitish deposit collects at the bottom, while the supernatant
fluid becomes clear. The deposit, when examined by the micro-
scope (Fig. 24), is seen to
consist of abundant epithe-
lium scales from the internal
surface of the mouth, de-
tached by mechanical irrita-
tion, minute, roundish, gra-
nular, nucleated cells, appa-
rently epithelium from the
mucous follicles, a certain
amount of granular matter,
and a few oil-globules. The
supernatant fluid has a faint
bluish tinge, and becomes
slightly opalescent by boil-

BCCCAL AND GLANDULAR EPITHELIUM, with ™g, and by the addition of
Granular Matter and Oil-globules; deposited as sedi- nitric acid. Alcohol in 6X-
roent from human saliva. n ...

cess causes the precipitation

of abundant whitish flocculi. According to Bidder and Schmidt,1
the composition of saliva is as follows : —

COMPOSITION OF SALIVA.

Water

Organic matter .........

Sulpho-cyanide of potassium

Phosphates of soda, lime, and magnesia .....

Chlorides of sodium and potassium . .

Mixture of epithelium

1000.00

The organic substance present in the saliva has been occasionally
known by the name of pty aline. It is coagulable by alcohol, but
not by a boiling temperature. A very little albumen is also pre-
sent, mingled with the ptyaline, and produces the opalescence
which appears in the saliva when raised to a boiling temperature.
The sulpho-cyanogen may be detected by a solution of chloride of
iron, which produces the characteristic red color of sulpho-cyanide

1 Verdauungsssefte und Stoffwechsel. Leipzig, 1852.

SALIVA. | 125

of iron. The alkaline reaction of the saliva varies in intensity
during the day, but is nearly always sufficiently distinct.

The saliva is not a simple secretion, but a mixture of four dis-
tinct fluids, which differ from each other in the source from which
they are derived, and in their physical and chemical properties.
These secretions are, in the human subject, first, that of the parotid
gland ; second, that of the submaxillary ; third, that of the sub-
lingual ; and fourth, that of the mucous follicles of the mouth.
These different fluids have been comparatively studied, in the
lower animals, by Bernard, Frerichs, and Bidder and Schmidt.
The parotid saliva is obtained in a state of purity from the dog by
exposing the duct of Steno where it crosses the masseter muscle,
and introducing into it, through an artificial opening, a fine silver
canula. The parotid saliva then runs directly from its external
orifice, without being mixed with that of the other salivary glands.
It is clear, limpid, and watery, without the slightest viscidity, and
has a faintly alkaline reaction. The submaxillary saliva is ob-
tained in a similar manner, by inserting a canula into Wharton's
duct. It differs from the parotid secretion, so far as its physical
properties are concerned, chiefly in possessing a well-marked vis-
cidity. It is alkaline in reaction. The sublingual saliva is also
alkaline, colorless, and transparent and possesses a greater degree
of viscidity than that from the submaxillary. The mucous secre-
tion of the follicles of the mouth, which forms properly a part of
the saliva, is obtained by placing a ligature simultaneously on
Wharton's and Steno's ducts, and on that of the sublingual gland,
so as to shut out from the mouth all the glandular salivary secre-
tions, and then collecting the fluid secreted by the buccal mucous
membrane. This fluid is very scanty, and much more viscid than
either of the other secretions ; so much so, that it cannot be poured
out in drops when received in a glass vessel, but adheres strongly
to the surface of the glass.

We have obtained the parotid saliva of the human subject in a
state of purity by introducing directly into the orifice of Steno's
duct a silver canula ^5 to 2V of an inch in diameter. The other
extremity of the canula projects from the mouth, between the lips,
and the saliva is collected as it runs from the open orifice. This
method gives results much more valuable than observations made
on salivary fistulas and the like, since the secretion is obtained
under perfectly healthy conditions, and unmixed with other animal
fluids.

126 DIGESTION.

The result of many different observations, conducted in this way,
is that the human parotid saliva, like that of the dog, is colorless,
watery, and distinctly alkaline in reaction. It differs from the mixed
saliva of the mouth, in being perfectly clear, without any turbidity
or opalescence. Its flow is scanty while the cheeks and jaws remain
at rest ; but as soon as the movements of mastication are excited by
the introduction of food, it runs in much greater abundance. We
have collected, in this way, from the parotid duct of one side only,
in a healthy man, 480 grains of saliva in the course of twenty
minutes ; and in seven successive observations, made on different
days, comprising in all three hours and nine minutes, we have
collected a little over 3000 grains.

The parotid saliva obtained in this way has been analyzed by
Mr. Maurice Perkins, Assistant to the Professor of Chemistry in
the College of Physicians and Surgeons, with the following result : —

COMPOSITION OF HUMAN PAROTID SALIVA.

Water *. 983.300

Organic matter precipitable by alcohol ..... 7.352

Substance destructible by heat, but not precipitated by alcohol
or acids ...........

Sulpho-cyanide of sodium. .......

Phosphate of liuie .

Chloride of potassium ........

Chloride of sodium and carbonate of soda ....

1000.00

Mr. Perkins found, in accordance with our own observations,
that the fresh parotid saliva, when treated with perchloride of iron,
showed no evidences of sulpho-cyanogen ; but after the organic mat-
ters had been precipitated by alcohol, the filtered fluid was found
to contain an appreciable quantity of the sulpho-cyanide.

The organic matter in the parotid saliva is in rather large quan-
tity as compared with the mineral ingredients. It is precipitable by
alcohol, by a boiling temperature, by ^nitric acid, and by sulphate
of soda in excess, but not by an acidulated solution of ferrocyanide
of potassium. It bears some resemblance, accordingly, to albumen,
but yet is not precisely identical with that substance.

The parotid saliva also differs from the mixed saliva of the mouth
in containing some substance which masks the reaction of sulpho-
cyanogen. For if the parotid saliva and that from the mouth be
drawn from the same person within the same hour, the addition of
perchloride of iron will produce a distinct red color in the latter, while
no such change takes place in the former. And yet the parotid

SALIVA. 127

saliva contains sulpho-cyanogen, which may be detected, as we have
already seen, after the organic matters have been precipitated by
alcohol.

A very curious fact has been observed by M. Colin, Professor of
Anatomy and Physiology at the Veterinary School of Alfort,1 viz.,
that in the horse and ass, as well as in the cow and other ruminat-
ing animals, the parotid glands of the two opposite sides, during
mastication, are never in active secretion at the same time ; but
that they alternate with each other, one remaining quiescent while
the other is active, and vice versa. In these animals mastication is
said to be unilateral, that is, when the animal commences feeding
or ruminating, the food is triturated, for fifteen minutes or more, by
the molars of one side only. It is then changed to the opposite
side ; and for the next fifteen minutes mastication is performed by
the molars of that side only. It is then changed back again, and
so on alternately, so that the direction of the lateral movements of
the jaw may be reversed many times during the course of a meal.
By establishing a salivary fistula simultaneously on each side, it is
found that the flow of saliva corresponds with the direction of the
masticatory movement. \Yhen the animal masticates on the right
side, it is the right parotid which secretes actively, while but little
saliva is supplied by the left ; when mastication is on the left side,
the left parotid pours out an abundance of fluid, while the right is
nearly inactive.

We have observed a similar alternation in the flow of parotid
saliva in the human subject, when the mastication is changed from
side to side. In ah experiment of this kind, the tube being inserted
into the parotid duct of the left side, the quantity of saliva dis-
charged during twenty minutes, while mastication was performed
mainly on the opposite side of the mouth, was 127.5 grains ; while
the quantity during the same period, mastication being on the same
side of the mouth, was 374.4 grains — being nearly three times as
much in the latter case as in the former.

Owing to the variations in the rapidity of its secretion, and also
to the fact that it is not so readily excited by artificial means as
by the presence of food, it becomes somewhat difficult to estimate
the total quantity of saliva secreted daily. The first attempt to do so
was made by Mitscherlich,2 who collected from two to three ounces
in twenty-four hours from an accidental salivary fistula of Steno's

1 Traite de Physiologie Comparee, Paris, 1854, p. 468.
1 Simon's Chemistry of Mail. Phila. ed., 1846, p. 295.

128 DIGESTION.

duct in the human subject ; from which it was supposed that the
total amount secreted by all the glands was from ten to twelve
ounces daily. As this man was a hospital patient, however, and
suffering from constitutional debility, the above calculation cannot
be regarded as an accurate one, and accordingly Bidder and Schmidt1
make a higher estimate. One of these observers, in experimenting
upon himself, collected from the mouth in one hour, without using
any artificial stimulus to the secretion, 1500 grains of saliva; and
calculates, therefore, the amount secreted daily, making an allow-
S ance of seven hours for sleep, as not far from 25,000 grains, or
about three and a half pounds avoirdupois.

On repeating this experiment, however, we have not been able to
collect from the mouth, without artificial stimulus, more than 556
grains of saliva per hour. This quantity, however, may be greatly
increased by the introduction into the mouth of any smooth un-
irritating substance, as glass beads or the like; and during the
mastication of food, the saliva is poured out in very much greater
abundance. The very sight and odor of nutritious food, when the
appetite is excited, will stimulate to a remarkable degree the flow
of saliva ; and, as it is often expressed, " bring the water into the
mouth." Any estimate, therefore, of the total quantity of saliva,
based on the amount secreted in the intervals of mastication, would
be a very imperfect one. We may make a tolerably accurate
calculation, however, by ascertaining how much is really secreted
during a meal, over and above that which is produced at other times.
We have found, for example, by experiments performed for this
purpose, that wheaten bread gains during complete mastication 55
per cent, of its weight of saliva ; and that fresh cooked meat gains,
under the same circumstances, 48 per cent, of its weight. We have
already seen that the daily allowance of these two substances, for a
man in full health, is 19 ounces of bread, and 16 ounces of meat.
The quantity of saliva, then, required for the mastication of these
two substances, is, for the bread 4,572 grains, and for the meat 3,360
grains. If we now calculate the quantity secreted between meals
as continuing for 22 hours at 556 grains per hour, we have : —

Saliva required for mastication of bread = 4572 grains.
" " « " " meat = 3360 "

secreted in intervals of meals = 1 2232 "

Total quantity in twenty-four hours = 20164 grains ;

or rather less than 3 pounds avoirdupois.

1 Op. cit., p. 14.

SALIVA. 129

The most important question, connected with this subject, relates
to the function of the saliva in the digestive process. A very remark-
able property of this fluid is that which was discovered by Leuchs
in German}^, viz., that it possesses the power of converting boiled
starch into sugar, if mixed with it in equal proportions, and kept
for a short time at the temperature of 100° F. This phenomenon
is one of catalysis, in which the starch is transformed into sugar by
simple contact with the organic substance contained in the saliva.
This organic substance, according to the experiments of Mialhe,1
may even be precipitated by alcohol, and kept in a dry state for an
indefinite length of time without losing the power of converting
starch into sugar, when again brought in contact with it in a state
of solution.

This action of ordinary human saliva on boiled starch takes place
sometimes with great rapidifv. Traces of glucose may occasionally
be detected in the mixture in one minute after the two substances
have been brought in contact ; and we have even found that starch
paste, introduced into the cavity of the mouth, if already at the
temperature of 100° F., will yield traces of sugar at the end of half
a minute. The rapidity however, with which this action is mani-
fested, varies very much, as was formerly noticed by Lehmann, at
different times ; owing, in all probability, to the varying constitution
of the saliva itself. It is often impossible, for example, to find any
evidences of sugar, in the mixture of starch and saliva, under five,
ten, or fifteen minutes ; and it is frequently a longer time than this
before the whole of the starch is completely transformed. Even
when the conversion of the starch commences very promptly, it is
often a long time before it is finished. If a thin starch paste, for
example, which contains no traces of sugar, be taken into the mouth
and thoroughly mixed with the buccal secretions, it will often, as
already mentioned, begin to show the reaction of sugar in the course
of half a minute ; but some of the starchy matter still remains, and

will continue to manifest its characteristic reaction with iodine, for

•

fifteen or twenty minutes, or even half an hour.

It was supposed, when this property of converting starch into
sugar was first discovered in the saliva, that it constituted the true
physiological action of this secretion, and that the function of the
saliva was, in reality, the digestion and liquefaction of starchy
substances. It was very soon noticed, however, by the French

1 Chimie appliquee a la Phvsiologie et & la Therapeutique, Paris, 1856, p. 43.

9

130 DIGESTION.

observers, that this property of the saliva was rather an accidental
than an essential one; and that, although starchy substances are
really converted into sugar, if mixed with saliva in a test-tube,
yet they are not affected by it to the same degree in the natural
process of digestion. We have already mentioned the extremely
variable activity of the saliva, in this respect, at different times ;
and it must be recollected, also, that in digestion the food is not
retained in the cavity of the mouth, but passes at once, after mas-
tication, into the stomach. Several German observers, as Frerichs,
Jacubowitsch, Bidder and Schmidt, maintained at first that the
saccharine conversion of starch, after being commenced in the
mouth, might be, and actually was, completed in the stomach. "We
have convinced ourselves, however, by frequent experiments, that
this is not the case. If a dog, with a gastric fistula, be fed with a
mixture of meat and boiled starch, and portions of the fluid con-
tents of the stomach withdrawn afterward through the fistula,
the starch is easily recognizable by its reaction with iodine for ten,
fifteen, and twenty minutes afterward. In forty-five minutes it is
diminished in quantity, and in one hour has usually altogether dis-
appeared ; but no sugar is to be detected at any time. Sometimes
the starch disappears more rapidly than this ; but at no time, accord-
ing to our observations, is there any indication of the presence of
sugar in the gastric fluids. Bidder and Schmidt have also concluded,
from subsequent investigations,1 that the first experiments performed
under their direction by Jacubowitsch were erroneous ; and it is
now acknowledged by them, as well as by the French observers,
'that sugar cannot be detected in the stomach, after the introduction
of starch in any form or by any method. In the ordinary process
of digestion, in fact, starchy matters do not remain long enough in
the mouth to be altered by the saliva, but pass at once into the sto-
mach. Here they meet with the gastric fluids, which become min-
gled with them, and prevent the change which would otherwise be
effected b}r the saliva. We have found that the gastric juice will
interfere, in this manner, with the action of the saliva in the test-
tube, as well as in the stomach. If two mixtures be made, one of
starch and saliva, the other of starch, saliva, and gastric juice, and
both kept for fifteen minutes at the temperature of 100° F., in the
first mixture the starch will be promptly converted into sugar, while
in the second no such change will take place. The above action,

1 Op cit., p. 26.

SALIVA. 131

therefore, of saliva on starch, though a curious and interesting pro-
perty, has no significance as to its physiological function, since it
does not take place in the natural digestive process. We shall see
hereafter that there are other means provided for the digestion of
starchy matters, altogether independent of the action of the saliva.

The true function of the saliva is altogether a physical one. Its
action is simply to moisten the food and facilitate its mastication,
as well as to lubricate the triturated mass, and assist its passage
down the oesophagus. Food which is hard and dry, like crusts,
crackers, &c., cannot be masticated and swallowed with readiness,
unless moistened by some fluid. If the saliva, therefore, be prevented
from entering the cavity of the mouth, its loss does not interfere
directly with the chemical changes of the food in digestion, but only
with its mechanical preparation. This is the result of direct experi-
ments performed by various observers. Bidder and Schmidt,1 after
tying Steno's duct, together with the common duct of the sub-
maxillary and sublingual glands on both sides in the dog, found
that the immediate effect of such an operation was " a remarkable
diminution of the fluids which exude upon the surfaces of the mouth ;
so that these surfaces retained their natural moisture only so long
as the mouth was closed, and readily became dry on exposure to
contact with the air. Accordingly, deglutition became evidently
difficult and laborious, not only for dry food, like bread, but even
for that of a tolerably moist consistency, like fresh meat. The
animals also became very thirsty, and were constantly ready to
drink."

Bernard3 also found that the only marked effect of cutting off
the flow of saliva from the mouth was a difficulty in the mechani-
cal processes of mastication and deglutition. He first administered
to a horse one pound of oats, in order to ascertain the rapidity with
which mastication would naturally be accomplished. The above
quantity of grain was thoroughly masticated and swallowed at the
end of nine minutes. An opening had been previously made in
the oesophagus at the lower part of the neck, so that none of the
food reached the stomach ; but each mouthful, as it passed down the
oesophagus, was received at the cesophageal opening and examined
by the experimenter. The parotid duct on each side of the face
was then divided, and another pound of oats given to the animal.
Mastication and deglutition were both found to be immediately

1 Op. cit., p. 3.

2 Lemons de Physiologic Experimentale, Paris, 1856, p. 146.

132 DIGESTION.

retarded. The alimentary masses passed down the oesophagus at
longer intervals, and their interior was no longer moist and pasty,
as before, but dry and brittle. Finally, at the end of twenty-five
minutes, the animal had succeeded in masticating and swallowing
only about three-quarters of the quantity which he had previously
disposed of in nine minutes.

It appears also, from the experiments of Magendie, Bernard, and
Lassaigne, on horses and cows, that the quantity of saliva absorbed
by the food during mastication is in direct proportion to its hard-
ness and dryness, but has no particular relation to its chemical
qualities. These experiments were performed as follows : The oeso-
phagus was opened at the lower part of the neck, and a ligature
placed upon it, between the wound and the stomach. The animal
was then supplied with a previously weighed quantity of food, and
this, as it passed out by the cesophageal opening, was received into
appropriate vessels and again weighed. The difference in weight,
before and after swallowing, indicated the quantity of saliva absorbed
by the food. The following table gives the results of some of Las-
saigne's experiments,1 performed upon a horse : — •

KIND OF FOOD EMPLOYED. QUANTITY OF SALIVA ABSORBED.

For 100 parts of hay there were absorbed 400 parts saliva.

" barley meal " 186 "

" oats " 113 "

" green stalks and leaves- " 49 "

It is evident from the above facts, that the quantity of saliva
produced has not so much to do with the chemical character of the
food as with its physical condition. When the food is dry and
hard, and requires much mastication, the saliva is secreted in
abundance ; when it is soft and moist, a smaller quantity of the
secretion is poured out ; and finally, when the food is taken in a
fluid form, as soup or milk, or reduced to powder and moistened
artificially with a very large quantity of water, it is not mixed at
all with the saliva, but passes at once into the cavity of the stomach.
The abundant and watery fluid of the parotid gland is most useful
in assisting mastication ; while the glairy and mucous secretion of
the submaxillary gland and the muciparous follicles serve to lubri-
cate the exterior of the triturated mass, and facilitate its passage
through the oesophagus.

By the combined operation of the two processes which the food
undergoes in the cavity of the mouth, its preliminary preparation

1 Comptes Rendus, vol. xxi. p. 362.

GASTRIC JUICE, AN$ STOMACH DIGESTION". 133

is accomplished. It is triturated and disintegrated by the teeth,
and, at the same time, by the movements of the jaws, tongue, and
cheeks, it is intimately mixed with the salivary fluids, until the
whole is reduced to a soft, pasty mass, of the same consistency
throughout. It is then carried backward by the semi-involuntary
movements of the tongue into the pharynx, and conducted by the
muscular contractions of the oesophagus into the stomach.

GASTRIC JUICE, AND STOMACH DIGESTION. — The mucous mem-
brane of the stomach is distinguished by its great vascularity
and the abundant glandular apparatus with which it is provided.
Its entire thickness is occupied by certain glandular organs, the
gastric tubules or follicles, which are so closely set as to leave
almost no space between them except what is required for the
capillary bloodvessels. The free surface of the gastric mucous
membrane is not smooth, but is raised in minute ridges and pro-
jecting eminences. In the cardiac portion (Fig. 25), these ridges
are reticulated with each other, so as to include between them
polygonal interspaces, each of which is encircled by a capillary
network. In the pyloric portion (Fig. 26), the eminences are more

Fig. 25.

Fig. 26.

Fig. 25. Free surface of GASTRIC Mucous MEMBRA XK, viewed from above ; from Pig's Sto-
mach, Cardiac portion. Magnified 70 diameters.

Fig. 26. Free surface of GASTRIC Mucous MEMBRANE, viewed in vertical section; from
Pig's Stomach, Pyloric portion. Magnified 420 diameters.

or less pointed and conical in form, and generally flattened from
side to side. They contain each a capillary bloodvessel, which re-

134

DIGESTION.

Fig. 27.

turns upon itself in a loop at the extremity of the projection, and
communicates freely with adjacent vessels. The gastric follicles are

very different in different
parts of the stomach. In the
pyloric portion (Fig. 27), they
are nearly straight, simple
tubules, ?J.tf of an inch in
diameter, easily separated
from each other, lined with
glandular epithelium, and ter-
minating in blind extremities
at the under surface of the
mucous membrane. They are
sometimes slightly branched,
or provided with one or two
rounded diverticula, a short
distance above their termina-
tion. They open on the free
surface of the mucous mem-
brane, in the interspaces be-
tween the projecting folds or villi. Among these tubular glandules
there is also found, in the gastric mucous membrane, another kind
of glandular organ, consisting of closed follicles, similar to the soli-

Fig. 28.

M U C 0 17 3 M E M B K A N K O F P I G ' S S T O M A C H , from

Pyloric portion; vertical section; showing gastric
tubules, and, at a, a closed follicle. Magnified 70
diameters.

Fig. 28. GASTRIC TUBULES FROM PIG'S STOMACH, Pyloric portion, showing their Caecal
Extremities. At a, the torn extremity of a tubule, showing its cavity.

Fig. 29. GASTRIC TUB ULES FROM PIG'S STOMACH; Cardiac portion. At a, a large tubule
dividing into two small ones. b. Portion of a tubule, seen endwise, c. Its central cavity.

GASTRIC JUICE, AND STOMACH DIGESTION. 135

tary glands of the small intestine. These follicles, which are not very
numerous, are seated in the lower part of the mucous membrane,
and enveloped by the caecal extremities of the tubules. (Fig. 27, a.)

In the cardiac portion of the stomach, the tubules are very wide
in the superficial part of the mucous membrane, and lined with
large, distinctly marked cylinder epithelium cells. (Fig. 29.) In the
deeper parts of the membrane they become branched and conside-
rably reduced in size. From the point where the branching takes
place to their termination below, they are lined with small glandular
epithelium cells, and closely bound together by intervening areolar
tissue, so as to present somewhat the appearance of compound
glandules.

The bloodvessels which come up from the submucous layer of
areolar tissue form a close plexus around all these glandules, and
provide the mucous membrane with an abundant supply of blood,
for the purposes both of secretion and absorption.

That part of digestion which takes place in the stomach has
always been regarded as nearly, if not quite, the most important
part of the whole process. The first observers who made any
approximation to a correct idea of gastric digestion were Keaumur
and Spallanzani, who showed by various methods that the reduction
and liquefaction of the food in the stomach could riot be owing to
mere contact with the gastric mucous membrane, or to compression
by the muscular walls of the organ ; but that it must be attributed
to a digestive fluid secreted by the mucous membrane, which pene-
trates the food and reduces it to a fluid form. They regarded this
process as a simple chemical solution, and considered the gastric
juice as a universal solvent for all alimentary substances. They
succeeded even in obtaining some of this gastric juice, mingled
probably with many impurities, by causing the animals upon which
they experimented to swallow sponges attached to the ends of
cords, by which they were afterward withdrawn, the fluids which
they had absorbed being then expressed and examined.

The first decisive experiments on this point, however, were those
performed by Dr. Beaumont, of the U. S. Army, on the person of
Alexis St. Martin, a Canadian boatman, who had a permanent gas-
tric fistula, the result of an accidental gunshot wound. The musket,
which was loaded with buckshot at the time of the accident, was
discharged, at the distance of a few feet* from St. Martin's body, in
such a manner as to tear away the integument at the lower part of
the left chest, open the pleural cavity, and penetrate, through the

136 DIGESTION.

lateral portion of the diaphragm, into the great pouch of the stomach.
After the integument and the pleural and peritoneal surfaces had
united and cicatrized, there remained a permanent opening, of about
four-fifths of an inch in diameter, leading into the left extremity of
the stomach, which was usually closed by a circular valve of pro-
truding mucous membrane. This valve could be readily depressed
at any time, so as to open the fistula and allow the contents of the
stomach to be extracted for examination.

Dr. Beaumont experimented upon this person at various intervals
from the year 1825 to 1832.1 He established during the course of
his examinations the following important facts : First, that the ac-
tive agent in digestion is an acid fluid, secreted by the walls of the
stomach ; secondly, that this fluid is poured out by the glandular
walls of the organ only during digestion, and under the stimulus of
the food ; and finally, that it will exert its solvent action upon the
food outside the body as well as in the stomach, if kept in glass
phials upon a sand bath at the temperature of 100° F. He made
also a variety of other interesting investigations as to the effect
of various kinds of stimulus on the secretion of the stomach, the
rapidity with which the process of digestion takes place, the com-
parative digestibility of various kinds of food, &c. &c.

Since Dr. Beaumont's time it has been ascertained that similar
gastric fistulas may be produced at will on some of the lower animals
by a simple operation; and the gastric juice has in this way been
obtained, usually from the dog, by Blondlot, Schwann, Bernard,
Lehmann and others. The simplest and most expeditious mode
of doing the operation is the best. An incision should be made
through the abdominal parietes in the median line, over the great
curvature of the stomach. The anterior wall of the organ is then
to be seized with a pair of hooked forceps, drawn out at the external
wound, and opened with the point of a bistoury. A short silver
canula, one-half to three-quarters of an inch in diameter, armed at
each extremity with a narrow projecting rim or flange, is then in-
serted into the wound in the stomach, the edges of which are fast-
ened round the tube with a ligature in order, to prevent the escape
of the gastric fluids into the peritoneal cavity. The stomach is then
returned to its place in the abdomen, and the canula allowed to re-
main with its external flange resting upon the edges of the wound
in the abdominal integuments, which are to be drawn together by

1 Experiments and Observations upon the Gastric Juice. Boston, 1834.

GASTRIC JUICE, AND STOMACH DIGESTION. 137

sutures. The animal may be kept perfectly quiet, during the ope-
ration, by the administration of ether or chloroform. In a few-
days the ligatures come away, the wounded peritoneal surfaces are
united with each other, and the canula is retained in a permanent
gastric fistula ; being prevented by its flaring extremities both from
falling out of the abdomen and from being accidentally pushed into
the stomach. It is closed externally by a cork, which may be with-
drawn at pleasure, and the contents of the stomach withdrawn for
examination.

Experiments conducted in this manner confirm, in the main, the
results obtained by Dr. Beaumont. Observations of this kind are
in some respects, indeed, more satisfactory when made upon the
lower animals, than upon the human subject ; since animals are
entirely under the control of the experimenter, and all sources of
deception or mistake are avoided, while the investigation is, at the
same time, greatly facilitated by the simple character of their food.

The gastric juice, like the saliva, is secreted in considerable
quantity only under the stimulus of recently ingested food. Dr/
Beaumont states that_it is entirely absent during the intervals of^
digestion ; and that the stomach at that time contains no acid fluid,
but only a little neutral or alkaline mucus. He was able to obtain
a sufficient quantity of gastric juice for examination, by gently irri-
tating the mucous membrane with a gum-elastic catheter, or the end
of a glass rod, and by collecting the secretion as it ran in drops
from the fistula. On the introduction of food, he found that the
mucous membrane became turgid and reddened, a clear acid fluid
collected everywhere in drops underneath the layer of mucus lin-
ing the walls of the stomach, and was soon poured out abundantly
into its cavity. We have found, however, that the rule laid down
by Dr. Beaumont in this respect, though correct in the main, is not
invariable. The truth is, the irritability of the gastric mucous
membrane, and the readiness with which the flow of gastric juice
may be excited, varies considerably in different animals ; even in
those belonging to the same species. In experimenting with gastric
fistula? on different dogs, for example, we have found in one instance,
like Dr. Beaumont, that the gastric juice was always entirely absent
in the intervals of digestion ; the mucous membrane then present-
ing invariably either a neutral or slightly alkaline reaction. In
this animal, which was a perfectly healthy one, the secretion could
not be excited by any artificial means, such as glass rods, metallic
catheters, and the like; but only by the natural stimulus of ingested

138 DIGESTION.

food. We have even seen tough and indigestible pieces of tendon,
introduced through the fistula, expelled again in a few minutes, one
after the other, without exciting the flow of a single drop of acid
fluid ; while pieces of fresh meat, introduced in the same way, pro-
duced at once an abundant supply. In other instances, on the con-
trary, the introduction of metallic catheters, &c., into the empty
stomach has produced a scanty flow of gastric juice; and in experi-
menting upon dogs that have been kept without food during various
periods of time and then killed by section of the medulla oblongata,
we have usually, though not always, found the gastric mucous mem-
brane to present a distinctly acid reaction, even after an abstinence
of six, seven, or eight days. There is at no time, however, under
these circumstances, any considerable amount of fluid present in
the stomach ; but only just sufficient to moisten the gastric mucous
membrane, and give it an acid reaction.

The gastric juice, which is obtained by irritating the stomach
with a metallic catheter, is clear, perfectly colorless, and acid in
reaction. A sufficient quantity of it cannot be obtained by this
method for any extended experiments ; and for that purpose, the
animal should be fed, after a fast of twenty-four hours, with fresh
lean meat, a little hardened by short boiling, in order to coagulate
the fluids of the muscular tissue, and prevent their mixing with the
gastric secretion. No effect is usually apparent within the first five
minutes after the introduction of the food. At the end of that time
the gastric juice begins to flow ; at first slowly, and in drops. It is
then perfectly colorless, but very soon acquires a slight amber
tinge. It then begins to flow more freely, usually in drops, but
often running for a few seconds in a continuous stream. In this
way from sij to siiss may be collected in the course of fifteen
minutes. Afterward it becomes somewhat turbid with the debris
of the food, which has begun to be disintegrated ; but from this it
may be readily separated by filtration. After three hours, it con-
tinues to run freely, but has become very much thickened, and
even grumous in consistency, from the abundant admixture of
alimentary debris. In six hours after the commencement of diges-
tion it runs less freely, and in eight hours has become very scanty,
though it continues to preserve the same physical appearances as
before. It ceases to flow altogether in from nine to twelve hours,
according to the quantity of food taken.

For purposes of examination, the fluid drawn during the first
fifteen minutes after feeding should be collected, and separated by

GASTRIC JUICE, AND STOMACH DIGESTION. 139

filtration from accidental impurities. Obtained in this way, the
gastric juice is a clear, watery fluid, without any appreciable vis-
cidity, very distinctly acid to test paper, of a faint amber color,
and with a specific gravity of 1010. It becomes opalescent on
boiling, owing to the coagulation of its organic ingredients. The
following is the composition of the gastric juice of the dog, based
on a comparison of various analyses by Lehmann, and Bidder and
Schmidt : —

COMPOSITION OF GASTRIC JUICE.

Water 975.00

Organic matter ......... 15.00

Lactic acid 4.78

/

Chloride of sodium ........ 1 70

" " potassium 1.08

" " calcium 0.20

" ammonium ........ 0.65

Phosphate of lime 1.48

" " magnesia 0.06

" " iron 0.05

1000.00

In place of lactic acid, Bidder and Schmidt found, in most of their
analyses, hydrochloric acid. Lehmann admits that a small quantity
of hydrochloric acid is sometimes present, but regards lactic acid
as much the most abundant and important of the two. Eobin and
Yerdeil also regard the acid reaction of the gastric juice as due to
lactic acid ; and, finally, Bernard has shown,1 by a series of well
contrived experiments, that the free acid of the dog's gastric juice
is undoubtedly the lactic ; and that the hydrochloric acid obtained
by distillation is really produced by a decomposition of the chlo-
rides, which enter into the composition of the fresh juice.

The free acid is an extremely important ingredient of the gastric
secretion, and is, in fact, essential to its physiological properties ;
for the gastric juice will not exert its solvent action upon the food,
after it has been neutralized by the addition of an alkali or an
alkaline carbonate.

The most important ingredient of the gastric juice, beside the
free acid, is its organic matter or " ferment," which is sometimes
known under the name of pepsine. This name, "pepsine," was
originally given by Schwann to a substance which he obtained
from the mucous membrane of the pig's stomach, by macerating it
in distilled water until a putrid odor began to be developed. The

1 Leqoiis de Physiologic Experimentale, Paris, 1856, p. 396.

uo

DIGESTION.

substance in question was precipitated from the watery infusion by
the addition of alcohol, and dried ; and if dissolved afterward in
acidulated water, it was found to exert a solvent action on boiled
white of egg. This substance, however, did not represent precisely
the natural ingredient of the gastric secretion, and was probably a
mixture of various matters, some of them the products of com-
mencing decomposition of the mucous membrane itself. The name
pepsine, if it be used at all, should be applied to the organic matter
which naturally occurs in solution in the gastric juice. It is alto-
gether unessential, in this respect, from what source it may be
originally derived. It has been regarded by Bernard and others,
on somewhat insufficient grounds, as a product of the alteration of
the mucus of the stomach. But whatever be its source, since it is
always present in the secretion of the stomach, and takes an active
part in the performance of its function, it can be regarded in no
other light than as a real anatomical ingredient of the gastric juice,
and as essential to its constitution.

Pepsine is precipitated from its solution in the gastric juice by
absolute alcohol, and by various metallic salts, but is not affected

by ferrocyanide of potassium.

FiS- 30. It is precipitated also, and

coagulated, by a boiling tem-
perature; and the gastric
juice, accordingly, after being
boiled, becomes turbid, and
loses altogether its power of
dissolving alimentary sub-
stances. Gastric juice is also
affected in a remarkable
manner by being mingled
with bile. We have found
that four to six drops of dog's
bile precipitate completely
with 3j of gastric juice from
the same animal ; so that the
whole of the biliary coloring
matter is thrown down as a

deposit, and the filtered fluid is found to have lost entirely its
digestive power, though it retains an acid reaction.

A very singular property of the gastric juice is its inaptitude for
putrefaction. It may be kept for an indefinite length of time in a

CONFERVOID VEGETABLE, growing in the Gas-
tric Juice of the Dog. The fibres have an average
diameter of 1-7000 of an inch.

GASTRIC JUICE, AND STOMACH DIGESTION". 141

common glass-stoppered bottle without developing any putrescent
odor. A light deposit generally collects at the bottom, and a con-
fervoid vegetable growth or "mould" often shows itself in the fluid
after it has been kept for one or two weeks. This growth has the
form of white, globular masses, each of which is composed of deli-
cate radiating branched filaments (Fig. 30) ; each filament consisting
of a row of elongated cells, like other vegetable growths of a similar
nature. These growths, however, are not accompanied by any
putrefactive changes, and the gastric juice retains its acid reaction
and its digestive properties for many months.

By experimenting artificially with gastric juice on various ali-
mentary substances, such as meat, boiled white of egg, &c., it is
found, as Dr, Beaumont formerly observed, to exert a solvent action
on these substances outside the body, as well as in the cavity of the
stomach. This action is most energetic at the temperature of 100°
F. It gradually diminishes in intensity below that point, and ceases
altogether near 32°. If the temperature be elevated above 100°
the action also becomes enfeebled, and is entirely suspended about
160°, or the temperature of coagulating albumen. Contrary to
what was supposed, however, by Dr. Beaumont, and his predeces-
sors, the gastric juice is not a universal solvent for all alimentary
substances, but, on the contrary, affects only a single class of the
proximate principles, viz., the albuminoid or organic substances.
Neither starch nor oil, when digested in it at the temperature of
the body, suffers the slightest chemical alteration. Fatty matters
are simply melted by the heat, and starchy substances are only
hydrated and gelatinized to a certain extent by the combined influ-
ence of the warmth and moisture. Solid and semi-solid albuminoid
matters, however, are at once attacked and liquefied by the diges-
tive fluid. Pieces of coagulated white of egg suspended in it, in a
test-tube, are gradually softened on their exterior, and their edges
become pale and rounded. They grow thin and transparent;
and their substance finally melts away, leaving a light scanty de-
posit, which collects at the bottom of the test-tube. While the
disintegrating process is going on, it may almost always be noticed
that minute, opaque spots show themselves in the substance of the
liquefying albumen, indicating that certain parts of it are less easily
attacked than the rest; and the deposit which remains at the bot-
tom is probably also composed of some ingredient, not soluble in
the gastric juice. If pieces of fresh meat be treated in the same
manner, the areolar tissue entering into its composition is first

142 DIGESTION.

dissolved, so that the muscular bundles become more distinct, and
separate from each other. They gradually fall apart, and a little
brownish deposit is at last all that remains at the bottom of the
tube. If the hard adipose tissue of beef or mutton be subjected
to the same process, the walls of the fat vesicles and the inter-
vening areolar tissue, together with the capillary bloodvessels, &c.,
are dissolved ; while the oily matters are set free from their en-
velops, and collect in a white, opaque layer on the surface. In
cheese, the casein is dissolved, and the oil which it contains set
free. In bread the gluten is digested, and the starch left un-
changed. In milk, the casein is first coagulated by contact with
the acid gastric fluids, and afterward slowly liquefied, like other
albuminoid substances.

The time required for the complete liquefaction of these sub-
stances varies with the quantity of matter present, and with its state
of cohesion. The process is hastened by occasionally shaking up
the mixture, so as to separate the parts already disintegrated, and
bring the gastric fluid into contact with fresh portions of the diges-
tible substance.

The liquefying process which the food undergoes in the gastric
juice is not a simple solution. It is a catalytic transformation,
produced in the albuminoid substances by contact with the organic
matter of the digestive fluid. This organic matter acts in a similar
manner to that of the catalytic bodies, or "ferments," generally.
Its peculiarity is that, for its active operation, it requires to be dis-
solved in an acidulated fluid. In common with other ferments, it
requires also a moderate degree of warmth ; its action being checked,
both by a very low, and a very high temperature. By its opera-
tion the albuminoid matters of the food, whatever may have been
their original character, are all, without distinction, converted into
a new substance, viz., albuminose. This substance has the general
characters belonging to the class of organic matters. It is uncrys-
tallizable, and contains nitrogen as an ultimate element. It is pre-
cipitated, like albumen, by an excess of alcohol, and by the metallic
salts ; but unlike albumen, is not affected by nitric acid or a boil-
ing temperature. It is freely soluble in water, and after it is once
produced by the digestive process, remains in a fluid condition,
and is ready to be absorbed by the vessels. In this way, casein,
fibrin, musculine, gluten, &c., are all reduced to the condition of
albuminose. By experimenting as above, with a mixture of food
and gastric juice in test-tubes, we have found that the casein of

GASTRIC JUICE, AND STOMACH DIGESTION. 143

cheese is entirely converted into albuminose, and dissolved under
that form. A very considerable portion of raw white of egg, how-
ever, dissolves in the gastric juice directly as albumen, and retains
its property of coagulating by heat. Soft-boiled white of egg and
raw meat are principally converted into albuminose ; but at the
same time, a small portion of albumen is also taken up unchanged.

The above process is a true liquefaction of the albuminoid sub-
stances, and not a simple disintegration. If fresh meat be cut into
small pieces, and artificially digested in gastric juice in test-tubes,
at 100° F., and the process assisted by occasional gentle agitation,
the fluid continues to take up more and more of the digestible
material for from eight to ten hours. At the end of that time if it
be separated and filtered, the filtered fluid has a distinct, brownish
color, and is saturated with dissolved animal matter. Its specific
gravity is found to have increased from 1010 to 1020 ; and on the
addition of alcohol it becomes turbid, with a very abundant whitish
precipitate (albuminose). There is also a peculiar odor developed
during this process, which resembles that produced in the malting
of barley.

Albuminose, in solution in gastric juice, has several peculiar
properties. One of the most remarkable of these is that it inter-
feres with the operation of Trommer's test for grape sugar (see
page 84). We first observed and described this peculiarity in
1854, ' but could not determine, at that time, upon what particular
ingredient of the gastric juice it depended. A short time subse-
quently it was also noticed by M. Longet, in Paris, who published
his observations in the Gazette Hebdomadaire for February 9th,
1S55.J He attributed the reaction not to the gastric juice itself,
but to the albuminose held in solution by it. "We have since found
this explanation to be correct. Gastric juice obtained from the
empty stomach of the fasting animal, by irritation with a metallic
catheter, which is clear and perfectly colorless, does not interfere
in any way with Trommer's test ; but if it be macerated fur some
hours in a test-tube with finely chopped meat, at a temperature of
100°, it will then be found to have acquired the property in a
marked degree. The reaction therefore depends undoubtedly upon
the presence of albuminose in solution. As the gastric juice, drawn
from the dog's stomach half an hour or more after the introduction

1 American Journ. Med. Sci., Oct. 1854, p. 319.

2 Nouvelles recherches relatives a 1'action du sue gastrique sur les substances
albuminoides.— Gaz. Hebd. 9 F'vrier, 1855, p. 103.

144 DIGESTION.

of food, already contains some albuminose in solution, it presents
the same reaction. If such gastric juice be mixed with a small
quantity of glucose, and Trommer's test applied, no peculiarity is
observed on first dropping in the sulphate of copper ; but on adding
afterward the solution of potassa, the mixture takes a rich purple hue,
instead of the clear blue tinge which is presented under ordinary
circumstances. On boiling, the color changes to claret, cherry red,
and finally to a light yellow; but no oxide of copper is deposited, and
the fluid remains clear. If the albuminose be present only in small
quantity, an incomplete reduction of the copper takes place, so that
the mixture becomes opaline and cloudy, but still without any well
marked deposit. This interference will take place when sugar is
present in very large proportion. We have found that in a mix-
ture of honey and gastric juice in equal volumes, no reduction of
copper takes place on the application of Trommer's test. It is
remarkable, however, that if such a mixture be previously diluted
with an equal quantity of water, the interference does not take
place, and the copper is deposited as usual.

Usually this peculiar reaction, now that we are acquainted with
its existence, will not practically prevent the detection of sugar,
when present ; since the presence of the sugar is distinctly indi-
cated by the change of color, as above mentioned, from purple to
yellow, though the copper may not be thrown down as a precipi-
tate. All possibility of error, furthermore, may be avoided by
adopting the following precautions. The purple color, already men-
tioned, will, in the first place, serve to indicate the presence of the
albuminoid ingredient in the suspected fluid. The mixture should
then be evaporated to dryness, and extracted with alcohol, in order
to eliminate the "animal matters. After that, a watery solution of
the sugar contained in the alcoholic extract will react as usual with
Trommer's test, and reduce the oxide of copper without difficulty.

Another remarkable property of gastric juice containing albu-
minose, which is not, however, peculiar to it, but common to many
other animal fluids, is that of interfering with the mutual reaction
of starch and iodine. If 3j of such gastric juice be mixed with 3j
of iodine water, and boiled starch be subsequently added, no blue
color is produced ; though if a larger quantity of iodine water be
added, or if the tincture be used instead of the aqueous solution,
the superabundant iodine then combines with the starch, and pro-
duces the ordinary blue color. This property, like that described
above, is not possessed by pure, colorless, gastric juice, taken from

GASTRIC JUICE, AND STOMACH DIGESTION. 145

the empty stomach, but is acquired by it on being digested with
albuminoid substances.

Another important action which takes place in the stomach,
beside the secretion of the gastric juice, is the peristaltic movement
of the organ. This movement is accomplished by the alternate
contraction and relaxation of the longitudinal and circular fibres
of its muscular coat. The motion is minutely described by Dr.
Beaumont, who examined it, both by watching the movements of
the food through the gastric fistula, and also by introducing into
the stomach the bulb and stem of a thermometer. According to
his observations, when the food first passes into the stomach, and
the secretion of the gastric juice commences, the muscular coat,
which was before quiescent, is excited and begins to contract act-
ively. The contraction takes place in such a manner that the food,
after entering the cardiac orifice of the stomach, is first carried to
the left, into the great pouch of the organ, thence downward and
along the great curvature to the pyloric portion. At a short distance
from the pylorus, Dr. B. often found a circular constriction of the
gastric parietes, by which the bulb of the thermometer was gently
grasped and drawn toward the pylorus, at the same time giving a
twisting motion to the stem of the instrument, by which it was
rotated in his fingers. In a moment or two, however, this constric-
tion was relaxed, and the bulb of the thermometer again released,
and carried together with the food along the small curvature of
the organ to its cardiac extremity. This circuit was repeated so
long as any food remained in the stomach ; but, as the liquefied
portions were successively removed toward the end of digestion, it
became less active, and at last ceased altogether when the stomach
had become completely empty, and the organ returned to its ordi-
nary quiescent condition.

It is easy to observe the muscular action of the stomach during
digestion in the dog, by the assistance of a gastric fistula, artificially
established. If a metallic catheter be introduced through the fistula
when the stomach is empty, it must usually be held carefully in
place, or it will fall out by its own weight. But immediatelv upon
the introduction of food, it can be felt that the catheter is grasped
and retained with some force, by the contraction of the muscular
coat. A twisting or rotatory motion of its extremity may also be
frequently observed, similar to that described by Dr. Beaumont.
This peristaltic action of the stomach, however, is a gentle one,
and not at all active or violent in character. We have never seen,
10

146 DIGESTION.

in opening the abdomen, any such energetic or extensive contrac-
tions of the stomach, even when full of food, as may be easily
excited in the small intestine by the mere contact of the atmosphere,
or by pinching them with the blades of a forceps. This action of
the stomach, nevertheless, though quite gentle, is sufficient to pro-
duce a constant churning movement of the masticated food, by
which it is carried back and forward to every part of the stomach,
and rapidly incorporated with the gastric juice which is at the
same time poured out by the mucous membrane ; so that the
digestive fluid is made to penetrate equally every part of the ali»
mentary mass, and the digestion of all its albuminous ingredients
goes on simultaneously. This gentle and continuous movement of
the stomach is one which cannot be successfully imitated in experi-
ments on artificial digestion with gastric juice in test-tubes ; and
consequently the process, under these circumstances, is never so
rapid or so complete as when it takes place in the interior of the
stomach.

The length of time which is required for digestion varies in
different species of animals. In the carnivora, a moderate meal of
fresh uncooked meat requires from nine to twelve hours for its
complete solution and disappearance from the stomach. According
to Dr. Beaumont, the average time required for digestion in the
human subject is considerably less ; varying from one hour to five
hours -and a half, according to the kind of food employed. This
is probably owing to the more complete mastication of the food
which takes place in man, than in the carnivorous animals. By
examining the contents of the stomach at various intervals after
feeding, Dr. Beaumont made out a list, showing the comparative
digestibility of different articles of food, of which the following are
the most important : —

Time required for digestion, according to Dr. Beaumont : —

KIND OF FOOD. HOURS. MINUTES.

Pig's feet 1 00

Tripe 1 00

Trout (broiled) 1 30

Venison steak 1 35

Milk 2 00

Roasted turkey 2 30

" beef 3 00

" mutton 3 15

Veal (broiled) 4 00

Salt beef (boiled) 4 15

Roasted pork ........ 5 15

GASTRIC JUICE, AND STOMACH DIGESTION. 147

The comparative digestibility of different substances varies more
or less in different individuals according to temperament ; but the
above list undoubtedly gives a correct average estimate of the time
required for stomach digestion under ordinary conditions.

A very interesting question is that which relates to the total
quantity of gastric juice secreted daily. Whenever direct experi-
ments have been performed with a view of ascertaining this point,
their results have given a considerably larger quantity than was
anticipated. Bidder and Schmidt found that, in a dog weighing
34 pounds, they were able to obtain by separate experiments, con-
suming in all 12 hours, one pound and three-quarters of gastric
juice. The total quantity, therefore, for 24 hours, in the same ani-
mal, would be 3J pounds; and, by applying the same calculation to
a man of medium size, the authors estimate the total daily quantity
in the human subject as but little less than 14 pounds (av.). This
estimate is probably not an exaggerated one. In order to deter-
mine the question, however, if possible, in a different way, we
adopted the following plan of experiment with the gastric juice of
the dog. It was first ascertained, by direct experiment, that the
fresh lean meat of the bullock's heart loses, by complete desiccation,
78 per cent, of its weight. 300 grains of such meat, cut into small
pieces, were then digested for ten hours, in |iss of gastric juice at
100° F.; the mixture being thoroughly agitated as often as every
hour, in order to insure the digestion of as large a quantity of meat
as possible. The meat remaining undissolved was then collected
on a previously weighed filter, and evaporated to dryness. The
dry residue weighed 55 grains. This represented, allowing for the
loss by evaporation, 250 grains of the meat, in its natural moist
condition ; 50 grains of meat were then dissolved by 3iss of gastric
juice, or 33J grains per ounce.

From these data we can form some idea of the large quantity of
gastric juice secreted in the dog during the process of digestion.
One pound of meat is only a moderate meal for a medium-sized
animal ; and yet, to dissolve this quantity, no less than thirteen pints
of gastric juice will be necessary. This quantity, or any approxi-
mation to it, would be altogether incredible if we did not recollect
that the gastric juice, as soon as it has dissolved its quota of food,
is immediately reabsorbed, and again enters the circulation, together
with the alimentary substances which it holds in solution. The
secretion and reabsorption of the gastric juice then go on simulta-
neously; and the fluids which the blood loses by one process are

148 DIGESTION.

incessantly restored to it by the other. A very large quantity,
therefore, of the secretion may be poured out during the digestion
of a meal, at an expense to the blood, at any one time, of only two
or three ounces of fluid. The simplest investigation shows that
the gastric juice does not accumulate in the stomach in any con-
siderable quantity during digestion ; but that it is gradually
secreted so long as any food remains undissolved, each portion, as
it is digested, being disposed of by reabsorption, together with its
solvent fluid. There is accordingly, during digestion, a constant
circulation of the digestive fluids from the bloodvessels to the ali-
mentary canal, and from the alimentary canal back again to the
bloodvessels.

That this circulation really takes place is proved by the fol-
lowing facts: First, if a dog be killed some hours after feeding,
there is never more than a very small quantity of fluid found in
the stomach, just sufficient to smear over and penetrate the half
digested pieces of meat ; and, secondly, in the living animal gastric
juice, drawn from the fistula five or six hours after digestion has
been going on, contains little or no more organic matter in solution
than that extracted fifteen to thirty minutes after the introduction
of food. It has evidently been freshly secreted ; and, in order to
obtain gastric juice saturated with alimentary matter, it must be
artificially digested with food in test-tubes, where this constant ab-
sorption and renovation cannot take place.

An unnecessary difficulty has sometimes been felt in understand-
ing how it is that the gastric juice, which digests so readily all albu-
minous substances, should not destroy the walls of the stomach
itself, which are composed of similar materials. This, in fact, was
brought forward at an early day, as an insuperable objection to the
-doctrine of Eeaumur and Spallanzani, that digestion was a process
of chemical solution performed by a digestive fluid. It was said
to be impossible that a fluid capable of dissolving animal matters
should be secreted by the walls of the stomach without attacking
them also, and thus destroying the organ by which it was itself
produced. Since that time, various complicated hypotheses have
been framed, in order to reconcile these apparently contradictory
facts. The true explanation, however, as we believe, lies in this—
that the process of digestion is not a simple solution, but a catalytic
transformation of the alimentary substances, produced by contact
with the pepsine of the gastric juice. We know that all the or-
ganic substances in the living tissues are constantly undergoing, in

GASTRIC JUICE, AND STOMACH DIGESTION. 149

the process of nutrition, a series of catalytic changes, which are
characteristic of the vital operations, and which are determined by
the organized materials with which they are in contact, and by all
the other conditions present in the living organism. These changes,
therefore, of nutrition, secretion, &c., necessarily exclude for the
time all other catalyses, and take precedence of them. In the same
way, any dead organic matter, exposed to warmth, air, and moist-
ure, putrefies ; but if immersed in gastric juice, at the same
temperature, the putrefactive changes are stopped or altogether
prevented, because the catalytic actions, excited by the gastric
juice, take precedence of those, which constitute putrefaction. For
a similar reason the organic ingredient of the gastric juice, which
acts readily on dead animal matter, has no effect on the living
tissues of the stomach, because they are already subject to other
catalytic influences, which exclude those of digestion, as well as
those of putrefaction. As soon as life departs, however, and the
peculiar actions taking place in the living tissues come to an end
with the stoppage of the circulation, the walls of the stomach are
really attacked by the gastric juice remaining in its cavity, and
are more or less completely digested and liquefied. In the human
subject, it is rare to make an examination of the body twenty-four
or thirty-six hours after death, without finding the mucous mem-
brane of the great pouch of the stomach more or less softened and
disintegrated from this cause. Sometimes the mucous membrane
is altogether destroyed, and the submucous cellular layer exposed ;
and occasionally, when death has taken place suddenly during
active digestion, while the stomach contained an abundance of
gastric juice, all the coats of the organ have been found destroyed,
and a perforation produced leading into the peritoneal cavity.
These post-mortem changes show that, after death, the gastric juice
really dissolves the coats of the stomach without difficulty. But
during life, the chemical changes of nutrition, which are going on
in their tissues, protect them from its influence, and effectually
preserve their integrity.

The secretion of the gastric juice is much influenced by nervous
conditions. It was noticed by Dr. Beaumont, in his experiments
upon St. Martin, that irritation of the temper, and other moral
causes, would frequently diminish or altogether suspend the supply
of the gastric fluids. Any febrile action in the system or any
unusual fatigue, was liable to exert a similar effect. Every one is
aware how readily any mental disturbance, such as anxiety, anger,

150 DIGESTION.

or vexation, will take away the appetite and interfere with diges-
tion. Any nervous impression of this kind, occurring at the com-
mencement of digestion, seems moreover to produce some change
which has a lasting effect upon the process; for it is very often
noticed that when any annoyance, hurry, or anxiety occurs soon
after the food has been taken, though it may last only for a few
moments, the digestive process is not only liable to be suspended
for the time, but to be permanently disturbed during the entire
day. In order that digestion, therefore, may go on properly in the
stomach, food must be taken only when the appetite demands it ;
it should also be thoroughly masticated at the outset ; and, finally,
both mind and body, particularly during the commencement of the
process, should be free from any unusual or disagreeable excite-
ment.

INTESTINAL JUICES, AND THE DIGESTION OF SUGAR AND STARCH.
— From the stomach, those portions of the food which have not
already suffered digestion pass into the third division of the ali-
mentary canal, viz., the small intestine. As already mentioned, it
is only the albuminous matters which are digested in the stomach.
Cane sugar, it is true, is slowly converted by the gastric juice, out-
side the body, into glucose. We have found that ten grains of
cane sugar, dissolved in 3ss of gastric juice, give traces of glucose
at the end of two hours ; and in three hours, the quantity of this
substance is considerable. It cannot be shown, however, that the
gastric juice exerts this effect on sugar during ordinary digestion.
If pure sugar cane be given to a dog with a gastric fistula, while
digestion of meat is going on, it disappears in from two to three
hours, without any glucose being detected in the fluids withdrawn
from the stomach. It is, therefore, either directly absorbed under
the form of cane sugar, or passes, little by little, into the duodenum,
where the intestinal fluids at once convert it into glucose.

It is equally certain that starchy matters are not digested in the
stomach, but pass unchanged into the small intestine. Here they
meet with the mixed intestinal fluids, which act at once upon the
starch, and convert it rapidly into sugar. The intestinal fluids,
taken from the duodenum of a recently killed dog, exert this
transforming action upon starch with the greatest promptitude, if
mixed with it in a test-tube, and kept at the temperature of 100° F.
Starch is converted into sugar by this means much more rapidly
and certainly than by the saliva ; and experiment shows that the

INTESTINAL JUICES, DIGESTION OF SUGAR, ETC. 151

intestinal fluids are the active agents in its digestion during life.
If a dog be fed with a mixture of meat and boiled starch, and killed
a short time after the meal, the stomach is found to contain starch
but no sugar ; while in the small intestine there is an abundance of
sugar, and but little or no starch. If some observers have failed
to detect sugar in the intestine after feeding the animal with
starch, it is because they have delayed the examination until too
late. For it is remarkable how rapidly starchy substances, if pre-
viously disintegrated by boiling, are disposed of in the digestive
process. If a dog, for example, be fed as above with boiled starch
and meat, while some of the meat remains in the stomach for
eight, nine, or ten hours, the starch begins immediately to pass into
the intestine, where it is at once converted into sugar, and then as
rapidly absorbed. The whole of the starch may be converted into
sugar, and completely absorbed, in an hour's time. We have even
found, at the end of three-quarters of an hour, after a tolerably
full meal of boiled starch and meat, that all trace of both starch
and sugar had disappeared from both stomach and intestine. The
rapidity with which this passage of the starch into the duodenum
takes place varies, to some

extent, in different animals, Flg< 31*

according to the general ac-
tivity of the digestive appa-
ratus ; but it is always a
comparatively rapid process,
when the starch is already
liquefied and is administered
in a pure form. There can
be no doubt that the natural
place for the digestion of
starchy matters is the small
intestine, and that it is ac-
complished by the action of
the intestinal juices.

Our knowledge is not very
complete with regard to the
exact nature of the fluids by which this digestion of the starch is
accomplished. The juices taken from the duodenum are generally
a mixture of three different secretions, viz., the bile, the pancreatic
fluid, and the intestinal juice proper. Of these, the bile may be
left out of the question ; since it does not, when in a pure state,

FOLLICLES OF LIEBKRKCHN, f.om Small
testine of dog.

la-

152

DIGESTION.

Fie. 32.

exert any digestive action on starch. The pancreatic juice, on the
other hand, has the property of converting starch into sugar ; but
it is not known whether this fluid be always present in the duode-
num. The true intestinal juice is the product of two sets of glan-
dular organs, seated in the substance of or beneath the mucous
membrane, viz., the follicles of Lieberkiihn and the glands of Brun-
ner. The first of these, or Lieberkiihii's follicles (Fig. 31), are the
most numerous. They are simple, nearly straight tubules, lined
with a continuation of the intestinal epithelium, and somewhat
similar in their appearance to the follicles of the pyloric portion of
the stomach. They occupy the whole thickness of the mucous
membrane, and are found in great numbers throughout the entire
length of the small and large intestine.

The glands of Brunner (Fig. 32), or the duodenal glandube, as
they are sometimes called, are confined to the upper part of the duo-
denum, where they exist as a
closely set layer, in the deeper
portion of the mucous mem-
brane, extending downward a
short distance from the pylo-
rus. They are composed of
a great number of rounded
follicles, clustered round a
central excretory duct. Each
follicle consists of a delicate
membranous wall, lined with
glandular epithelium, and
covered on its surface with
small, distinctly marked nu-
clei. The follicles collected
around each duct are bound
together by a thin layer of

areolar tissue, and covered with a plexus of capillary bloodvessels.
The intestinal juice, which is the secreted product of the above
glandular organs, has been less successfully studied than the other
digestive fluids, owing to the difficulty of obtaining it in a pure
state. The method usually adopted has been to make an opening
in the abdomen of the living animal, take out a loop of intestine,
empty it by gentle pressure, and then to shut off a portion of it
from the rest of the intestinal cavity by a couple of ligatures,
situated six or eight inches apart ; after which the loop is returned

Portion of one of BKUN NEK'S
GLANDS, from Human Intestine.

DUODENAL

FANCKEATIC JUICE, AND THE DIGESTION OF FAT. 153

into the abdomen, and the external wound closed by sutures.
After six or eight hours the animal is killed, and the fluid, which
has collected in the isolated portion of intestine, taken out and
examined. The above was the method adopted by Frerichs. Bid-
der and Schmidt, in order to obtain pure intestinal juice, first tied
the biliary and pancreatic ducts, so that both the bile and the pan-,
creatic juice should be shut out from the intestine, and then estab-
lished an intestinal fistula below, from which they extracted the
fluids which accumulated in the cavity of the gut. From the great
abundance of the follicles of Lieberkuhn, we should expect to find
the intestinal juice secreted in large quantity. It appears, however,
in point of fact, to be quite scanty, as the quantity collected in the
above manner by experimenters has rarely been sufficient for a
thorough examination of its properties. It seems to resemble very
closely, in its physical characters, the secretion of the mucous folli-
cles of the mouth. It is colorless and glassy in appearance, viscid
and mucous in consistency, and has a distinct alkaline reaction.
It has the property when pure, as well as when mixed with other
secretions, of rapidly converting starch into sugar, at the tempera-
ture of the living body.

PANCREATIC JUICE. AXD THE DIGESTION OF FAT. — The only re-
maining ingredients of the food that require digestion are the _oily
matters. These are not affected, as we have already stated, by con-
tact with the gastric juice ; and examination shows, furthermore,
that they are not digested in the stomach. So long as they remain
in the cavity of this organ they are unchanged in their essential
properties. They are merely melted by the warmth of the stomach,
and set free by the solution of the vesicles, fibres, or capillary tubes
in which they are contained, or among which they are entangled ;
and are still readily discernible by the eye, floating in larger or
smaller drops on the surface of the semi-fluid alimentary mass.
Very soon, however, after its entrance into the intestine, the oily
portion of the food loses its characteristic appearance, and is con-
verted into a white, opaque emulsion, which is gradually absorbed.
This emulsion is termed the chyle, and is always found in the small
intestine during the digestion of fat, entangled among the yalvulse
conniventes, and adhering to the surface of the villi. The digestion
of the oil, however, and its conversion into chyle, does not take
place at once upon its entrance into the duodenum, but only after
it has passed the orifices of the pancreatic and biliary ducts. Since

154: DIGESTION.

these ducts almost invariably open into the intestine at or near the
same point, it was for a long time difficult to decide by which of
the two secretions the digestion of the oil was accomplished. M.
Bernard, however, first threw some light on this question by ex-
perimenting on some of the lower animals, in which the two ducts
open separately. In the rabbit, for example, the biliary duct opens
as usual just below the pylorus, while the pancreatic duct com-
municates with the intestine some eight or ten inches lower down.
Bernard fed these animals with substances containing oil, or in-
jected melted butter into the stomach ; and, on killing them after-
ward, found that there was no chyle in the intestine between the
opening of the biliary and pancreatic ducts, but that it was abun-
dant immediately below the orifice of the latter. Above this point,
also, he found the lacteals empty or transparent, while below it
they were full of white and opaque chyle. The result of these ex-
periments, which have since been confirmed by Prof. Samuel Jack-
son, of Philadelphia/ led to the conclusion that the pancreatic fluid
is the active agent in the digestion of oily substances ; and an ex-
amination of the properties of this secretion, when obtained in a
pure state from the living animal, fully confirms the above opinion.
In order to obtain pancreatic juice from the dog, the animal
must be etherized soon after digestion has commenced, an incision
made in the upper part of the abdomen, a little to the right of the
median line, and a loop of the duodenum, together with the lower
extremity of the pancreas which lies adjacent to it, drawn out at
the external wound. The pancreatic duct is then to be exposed
and opened, and a small silver canula inserted into it and secured
by a ligature. The whole is then returned into the abdomen and
the wound closed by sutures, leaving only the end of the canula
projecting from it. In the dog there are two pancreatic ducts,
situated from half an inch to an inch apart. The lower one of
these, which is usually the larger of the two, is the one best adapted
for the insertion of the canula. After the effects of etherization
have passed off, and the digestive process has recommenced, the
pancreatic juice begins to run from the orifice of the canula, at first
very slowly and in drops. Sometimes the drops follow each other
with rapidity for a few moments, and then an interval occurs during
which the secretion seems entirely suspended. After a time it re-
commences, and continues to exhibit similar fluctuations during

1 American Journ Mud. Sci., Oct. 1S54.

PANCREATIC JUICE, AND THE DIGESTION OF FAT. 155

the whole course of the experiment. Its flow, however, is at all
times scanty, compared with that of the gastric juice; and we have
never been able to collect more than a little over two fluidounces
and a half during a period of three hours, in a dog weighing not
more than forty-five pounds. This is equivalent to about 36i
grains per hour ; but as the pancreatic juice in the dog is secreted
with freedom only during digestion, and as this process is in opera-
tion not more than twelve hours out of the twenty-four, the entire
amount of the secretion for the whole day, in the dog, may be esti-
mated at 4,368 grains. This result, applied to a man weighing 1-iO
pounds, would give, as the total daily quantity of the pancreatic
juice, about 13,101 grains, or 1^872 pounds avoirdupois.

Pancreatic juice obtained by the above process is a clear, color-
less, somewhat viscid fluid, with a distinct alkaline reaction. Its
composition, according to the analysis of Bidder and Schmidt, is as
follows : —

COMPOSITION OF PAXCREATIC JUICE.

Water 900.76

Organic matter (paiK-reatiiu-) . . . . . . . 90.38

Chloride of sodium ......... 7.36

Free soda 0.32

Phosphate of sorla 0.45

Sulphate of soda ......... 0.10

Sulphate of potassa ......... 0.02

{Lime 0 54

Magnesia . . . . . . 0.05

Oxide of iron 0.02

1000.00

The most important ingredient of the pancreatic juice is its
organic matter, or pancreatim. It will be seen that this is much
more abundant in proportion to the other ingredients of the secre-
tion than the organic matter of any other digestive fluid. It is
coagulable by heat ; and the pancreatic juice often solidifies com-
pletely on boiling, like white of egg, so that not a drop of fluid re-
mains after its coagulation. It is precipitated, furthermore, by
nitric acid and by alcohol, and also by sulphate of magnesia in
excess. By this last property, it may be distinguished from albu-
men, which is not affected by contact with sulphate of magnesia.

Fresh pancreatic juice, brought into contact with oily matters at
the temperature of the body, exerts upon them, as was first noticed
by Bernard, a very peculiar effect. It disintegrates them, and re-
duces them to a state of complete emulsion, so that the mixture is
at once converted into a white, opaque, creamy-looking fluid. This

156 DIGESTION.

effect is instantaneous and permanent, and only requires that the
two substances be well mixed by gentle agitation. It is singular
that some of the German observers should deny that the pancreatic
juice possesses the property of emulsioning fat, to a greater extent
than the bile and some other digestive fluids ; and should state that
although, when shaken up with oil, outside the body, it reduces
the oily particles to a state of extreme minuteness, the emulsion
is not permanent, and the oily particles "soon separate again on
the surface."1 We have frequently repeated this experiment with
different specimens of pancreatic juice obtained from the dog, and
have never failed to see that the emulsion produced by it is by
far more prompt and complete than that which takes place with
saliva, gastric juice, or bile. The effect produced by these fluids is
in fact altogether insignificant, in comparison with the prompt and
energetic action exerted by the pancreatic juice. The emulsion
produced with the latter secretion may be kept, furthermore, for at
least twenty-four hours, according to our observations, without any
appreciable separation of the oily particles, or a return to their
original condition.

The pancreatic juice, therefore, is peculiar in its action on oily
substances, and reduces them at once to the condition of an emul-
sion. The oil, in this process, does not suffer any chemical.ujyLera-
tion. It is not decomposed or saponified, to any appreciable extent.
It is simply emulsioned ; that is; it is broken up into a state of minute
subdivision, and retained in suspension, by contact with the organic
matter of the pancreatic juice. That its chemical condition is not
altered is shown by the fact that it is still soluble in ether, which
will withdraw the greater part of the fat from a mixture of oil and
pancreatic juice, as well as from the chyle in the interior of the
intestine. In a state of emulsion, the fat, furthermore, is capable
of being absorbed, and its digestion may be then said to be accom-
plished.

We find, then, that the digestion of the food is not a simple
operation, but is made up of several different processes, which
commence successively in different portions of the alimentary
canal. In the first place, the food is subjected in the mouth to the
physical operations of mastication arid insalivation. Reduced to a
soft pulp and mixed abundantly with the saliva, it passes, secondly,
into the stomach. Here it excites the secretion of the gastric juice,

1 Lehmann's Physiological Chemistry. Philada. ed., vol. i. p. 507.

PHENOMENA OF INTESTINAL DIGESTION. 157

bv the influence of which its chemical transformation and solution
are commenced. If the meal consist wholly or partially of mus-
cular flesh, the first effect of the gastric juice is to dissolve the
intervening cellular substance, by which the tissue is disintegrated
and the muscular fibres separated from each other. Afterward
the muscular fibres themselves become swollen and softened by
the imbibition of the gastric fluid, and are finally disintegrated
and liquefied. In the small intestine, the pancreatic and intestinal
juices convert the starchy ingredients of the food into sugar, and
break up the fatty matters into a fine emulsion, by which they are
converted into chyle.

Although the separate actions of these digestive fluids, however,
commence at different points of the alimentary canal, they after-
ward go on simultaneously in the small intestine ; and the changes
which take place here, and which constitute the process of intestinal
digestion, form at the same time one of the most complicated, and
one of the most important parts of the whole digestive function.

The phenomena of intestinal digestion may be studied, in the
dog, by killing the animal at various periods after feeding, and
examining the contents of the intestine. We have also succeeded,
by establishing in the same animal an artificial intestinal fistula,
in gaining still more satisfactory information on this point. The
fistula may be established, for this purpose, by an operation precisely
similar to that already described as employed for the production of
a permanent fistula in the stomach. The silver tube having been
introduced into the lower part of the duodenum, the wound is
allowed to heal, and the intestinal secretions may then be with-
drawn at will, and subjected to examination at different periods
during digestion.

By examining in this way, from time to time, the intestinal
fluids, it at once becomes manifest that the action of the gastric
juice, in the digestion of albuminoid substances, is not confined to
the stomach, but continues after the food has passed into the intes-
tine. About half an hour after the ingestion of a meal, the gastric
juice begins to pass into the duodenum, where it may be recognized
by its strongly-marked acidity, and by its peculiar action, already
described, in interfering with Trommer's test for grape sugar. It
has accordingly already dissolved some of the ingredients of the
food while still in the stomach, and contains a certain quantity of
albuminose in solution. It soon afterward, as it continues to pass
into the duodenum, becomes mingled with the debris of muscular

158

DIGESTION.

Fig. 33.

CONTENTS OP STOMACH DURING DIGESTION
OF MEAT, from the Dog.— a. Fat Vesicle, filled with
opaque, solid, granular fat. &, 5. Bits of partially
disintegrated muscular fibre, c. Oil globules.

Fig. 34.

fibres, fat vesicles, and oil drops; substances which are easily
recognizable under the microscope, and which produce a grayish

turbidity in the fluid drawn
from the fistula. This turbid
admixture grows constantly
thicker from the second to
the tenth or twelfth hour;
after which the intestinal
fluids become less abundant,
and finally disappear almost
entirely, as the process of di-
gestion comes to an end.

The passage of disintegrated
muscular tissue into the intes-
tine may also be shown, as
already mentioned, by killing
the animal and examining
the contents of the alimentary
canal. During the digestion
of muscular flesh and adipose
tissue, the stomach contains
masses of softened meat,
smeared over with gastric
juice, and also a moderate
quantity of grayish, grumous
fluid, with an acid reaction.
This fluid contains muscular
fibres, isolated from each
other, and more or less dis-
integrated, by the action of
the gastric juice. (Fig. 33.)
The fat vesicles are but little
or not at all altered in the
FROM DUODENUM OP DOG, DURING DIGES- stomach, and there are only

TION OF MEAT.-«. Fat Vesicle, with its contents & few frQQ ^j fflot,ules to fce

diminishing. The vesicle is beginning to shrivel and

the fat breaking up. b, b. Disintegrated muscular SQQH floating in the mixed

fluids, contained in the cavity

of the organ. In the duodenum the muscular fibres are further
disintegrated. (Fig. 34.) They become very much broken up, pale
and transparent, but can still be recognized by the granular mark-
ings and striations which are characteristic of them. The fat vesi-

PHENOMENA OF INTESTINAL DIGESTION.

159

Fig. 35.

cles also begin to become altered in the duodenum. The solid
granular fat of beef, and similar kinds of meat, becomes liquefied
and emulsioned ; and appears
under the form of free oil
drops and fatty molecules;
while the fat vesicle itself is
partially emptied, and becomes
more or less collapsed and
shrivelled. In the middle
and lower parts of the intes-
tine (Figs. 35 and 86) these
changes continue. The mus-
cular fibres become constantly
more and more disintegrated,
and a large quantity of granu-
lar debris is produced, which
is at last also dissolved. The

„ , -IT FROM MIDDLE OP SMALL INTESTINE — a, a.

tat also progressively dlSap- Fat vesicles, nearly emptied of their contents.

Fig. 36.

pears, and the vesicles may
be seen in the lower part of
the intestine, entirely collapsed
and empty.

In this way the digestion of
the different ingredients of
the food goes on in a continu-
ous manner, from the stomach
throughout the entire length
of the small intestine. At the
same time, it results in the
production of three different
substances, viz : 1st. Albumi-
nose, produced by the action
of the gastric juice on the
albuminoid matters ; 2d. An
oily emulsion, produced by the action of the pancreatic juice on
fat ; and, 3d. Sugar, produced from the transformation of starch
by the mixed intestinal fluids. These substances are then ready
to be taken up into the circulation ; and as the mingled ingredients
of the intestinal contents pass successively downward, through the
duodenum, jejunum, and ileum, the products of digestion, together
with the digestive secretions themselves, are gradually absorbed,

FROM LAST QUARTER OF SMALL IXTESTIITE.

a, a. Fat vesicles, quite empty and shrivelled.

160 DIGESTION.

one after another, by the vessels of the mucous membrane, and
carried away by the current of the circulation.

THE LARGE INTESTINE AND ITS CONTENTS. — Throughout the
small intestine, as we have just seen, the secretions are intended
exclusively or mainly to act upon the food, to liquefy or disinte-
grate it, and to prepare it for absorption. But below the situation
of the ileo-csecal valve, and throughout the large intestine, the con-
tents of the alimentary canal exhibit a different appearance, and
are distinct in their color, odor, and consistency. This portion of
the intestinal contents, or the feces, are not composed, for the most
part, of the undigested remains of the food, but consist principally
of animal substances discharged into the intestine by excretion.
These substances have not all been fully investigated ; for although
they are undoubtedly of great importance in regard to the preser-
vation of health, yet the peculiar manner in which they are dis-
charged by the mucous membrane and united with each other in
the feces has interfered, to a great extent, with a thorough investi-
gation of their physiological characters. Those which have been
most fully examined are the following : —

Excretine. — This was discovered and described by Dr. W. Mar-
cet,1 as the most characteristic ingredient in the contents of the
large intestine. It is a slightly alkaline, crystallizable substance,
insoluble in water, but soluble in ether and hot alcohol. It crys-
tallizes in radiated groups of four-sided prismatic needles. It fuses
at 204° K, and burns at a higher temperature. It is non-nitrogenv
ous, and consists of carbon, hydrogen, oxygen, and sulphur, in the
following proportions : —

C78 H73 °2 S<

It is thought to be present mostly in a free state, but partly in union
with certain organic acids, as a saline compound.

Stercorine. — This substance was found to be an ingredient of the
human feces by Prof. A. Flint, Jr.2 It is soluble in ether and
boiling alcohol, and, like excretine, crystallizes in the form of
radiating needles, but fuses at a much lower temperature. It is
regarded by its discoverer as produced, by transformation, from
cholesterine, one of the ingredients of the bile.

Beside these substances, the feces contain a certain amount of

1 American Journal of the Medical Sciences, January, 1855, and January, 1858.

2 Ibid., October, 1862.

THE LARGE INTESTINE AND ITS CONTEXTS. 161

fat, fatty acids, and the remnants of undigested food. Vegetable
cells and fibres may be detected, and some debris of the disin-
tegrated muscular fibres may almost always be found after a meal
composed of animal and vegetable substances. But little absorp-
tion, accordingly, takes place in the large intestine. Its office is
mainly confined to the separation and discharge of certain excre-
mentitious substances.

11

162

ABSORPTION.

Fie. 37.

CHAPTER VII.

ABSORPTION.

BESIDE the glands of B runner and the follicles of Lieberkiihn,
already described, there are, in the inner part of the walls of the

intestine, certain glandular-
looking bodies which are
termed "glandulso solitaries,"
and " glandulaa agminatae."
The glandulae solitariae are
globular or ovoid bodies,
about one-thirtieth of an inch
in diameter, situated partly
in and partly beneath the in-
testinal mucous membrane.
Each glandule (Fig. 37) is
formed of an investing cap-
sule, closed on all sides, and
containing in its interior a
soft pulpy mass, which con-
sists of minute cellular bodies,
imbedded in a homogeneous
substance. The inclosed mass
is penetrated by capillary
bloodvessels, which pass in
through the investing cap-
sule, inosculate freely with
each other, and return upon
themselves in loops near the
centre of the glandular body.
There is no external opening
or duct; in fact, the contents
of the vesicle, being pulpy
and vascular, as already de-
scribed, are not to be regarded

as a secretion, but as consti-
tuting a kind of solid gland-

OXK OF THE CLOSED FOLLICLES OF I

PATCHES, from Small Inte.stiue of Piy. 1
i>Q diameter-.

Fiar. 38.

GLANDULE A a M i x A T M , f
. i'i,g. Magnified 20 d:am 'ters.

>m Small Intestine

ABSORPTION.

163

Fig. 39.

tissue. The glandulse agminatae (Fig. 38), or " Fever's patches," as
they are sometimes called, consist of aggregations of similar globular
or ovoid bodies, found most abundantly toward the lower extremity
of the small intestine. Both the solitary and agminated glandules
are evidently connected with the lacteals and the system of the
mesenteric glands, which latter organs they resemble very much in
their minute structure. They are probably to be regarded as the
first row of mesenteric glands, situated in the walls of the intestinal
canal.

Another set of organs, intimately connected with the process of
absorption, are the villi of the small intestine. These are conical
vascular eminences of the mucous membrane, thickly set over the
whole internal surface of the small intestine. In thejipper.partiQji,of
the intestine, they are flattened and triangular in form, resembling
somewhat the conical projections of the pyloric portion of the sto-
mach. In the lower part they are long and filiform, and often
slightly enlarged, or club-shaped at their free extremity (Fig. 39),
and frequently attaining the length of
one thirty-fifth of an inch. They are
covered externally with a layer of
columnar epithelium, similar to that
which lines the rest of the intestinal
mucous membrane, and contain in their
interior two sets of vessels. The most
superficial of these are the capillary
bloodvessels, which are supplied in each
villus by a twig of the mesenteric
artery, and which form, by their fre-
quent inosculation, an exceedingly close
and abundant network, almost imme-
diately beneath the epithelial layer.
They unite at the base of the villus,
and form a minute vein, which is one
of the commencing rootlets of the por-
tal vein. In the central part of the vil-
lus, and lying nearly in its axis, there
is another vessel, with thinner and more

transparent walls, which is the commencement of a lacteal. The
precise manner in which the lacteal originates in the extremity of
the villus is not known. It commences near the apex, either by a
blind extremity, or by an irregular plexus, passes, in a straight or

EXTREMITY OF I > r E s T i >• A i,
VILLCS, from the Doir.— «. Layer of
epithelium. 6. Bloodvessel, c Lacteal
vessel.

ABSORPTION.

somewhat wavy line, toward the base of the villus, and then be-
comes continuous with a small twig of the mesenteric lacteals.

The villi are the active agents in the process of absorption. By
their projecting form, and their great abundance, they increase enor-
mously the extent of surface over which the digested fluids come
in contact with the intestinal mucous membrane, and increase, also,
to a corresponding degree, the energy with which absorption takes
place. They hang out into the nutritious, semi-fluid mass contained
in the intestinal cavity, as the roots of a tree penetrate the soil ; and
they imbibe the liquefied portions of the food, with a rapidity which
is in direct proportion to their extent of surface, and the activity of
their circulation.

The process of absorption is also hastened by the peristaltic
movements of the intestine. The muscular layer here, as in other
parts of the alimentary canal, is double, consisting of both circular
and longitudinal fibres. The action of these fibres may be readily
seen by pinching the exposed intestine with the blades of a forceps.
A contraction then takes place at the spot irritated, by which the
intestine is reduced in diameter, its cavity obliterated, and its con-
tents forced onward into the succeeding portion of the alimentary
canal. The local contraction then propagates itself to the neighbor-
ing parts, while the portion originally contracted becomes relaxed ;
so that a slow, continuous, creeping motion of the intestine is pro-
duced, by successive waves of contraction and relaxation, which
follow each other from above downward. At the same time, the
longitudinal fibres have a similar alternating action, drawing the
narrowed portions of intestine up and down, as they successively
enter into contraction, or become relaxed in the intervals. The effect
of the whole is to produce a peculiar, writhing, worm-like, or
"vermicular" motion, among the different coils of intestine. During
life, the vermicular or peristaltic motion of the intestine is excited
by the presence of food undergoing digestion. By its action, the
substances which pass from the stomach into the intestine are
steadily carried from above downward, so as to traverse the entire
length of the small intestine, and to come in contact successively
with the whole extent of its mucous membrane. During this pas-
sage, the absorption of the digested food is constantly going on.
Its liquefied portions are taken up by the villi of the mucous mem-
brane, and successively disappear ; so that, at the termination of the
small intestine, there remains only the undigestible portion of the
food, together with the refuse of the intestinal secretions. These

ABSORPTION". 105

pass through the ileo-caecal orifice into the large intestine, and there
become reduced to the condition of feces.

The absorption of the digested fluids is accomplished both by
the bloodvessels and the lacteals. It was formerly supposed that
the lacteals were the only agents in this process ; but it has now
been long known that this opinion was erroneous, and that the
bloodvessels take at least an equal part in absorption, and are in
some respects the most active and important agents of the two.
Abundant experiments have demonstrated not only that soluble
substances introduced into the intestine may be soon afterward
detected in the blood of the portal vein, but that absorption takes
place more rapidly and abundantly by the bloodvessels than by
the lacteals. The most decisive of these experiments were those
performed by Panizza on the abdominal circulation.1 This ob-
server opened the abdomen of a horse, and drew out a fold of the
small intestine, eight or nine inches in length (Fig. 40, a, a), which

Fig. 40.

c

PAMZZA'S EXPERIMENT. — 'in. Intestine, b. Point of lipatnre of inesenteric vein. c. Opening
in intestiue for introduction of poison, d. Opening in mesenteric vein behind tlie ligature.

he included between two ligatures. A ligature was then placed (at
b) upon the mesenteric vein receiving the blood from this portion
of intestine; and, in order that the circulation might not be inter
rupted, an opening was made (at d) in the vein behind the ligature,
so that the blood brought by the mesenteric artery, after circulating

1 In Matteucci's Lectures on the Physical Phenomena of Living Beings, Pereira's
edition, p. 83.

166 ABSORPTION.

in the intestinal capillaries, passed out at the opening, and was
collected in a vessel for examination. Hydrocyanic acid was then
introduced into the intestine by an opening at c, and almost imme-
diately afterward its presence was detected in the venous blood
flowing from the orifice at d. The animal, however, was not poi-
soned, since the acid was prevented from gaining an entrance into
the general circulation by the ligature at b.

Panizza afterward varied this experiment in the following man-
ner : Instead of tying the mesenteric vein, he simply compressed it.
Then, hydrocyanic acid being introduced into the intestine, as above,
no effect was produced on the animal, so long as compression was
maintained upon the vein. But as soon as the blood was allowed
to pass again through the vessels, symptoms of general poisoning
at once became manifest. Lastly, in a third experiment, the same
observer removed all the nerves and lacteal vessels supplying the
intestinal fold, leaving the bloodvessels alone untouched. Hydro-
cyanic acid now being introduced into the intestine, found an
entrance at once into the general circulation, and the animal was
immediately poisoned. The bloodvessels, therefore, are not only
capable of absorbing fluids from the intestine, but may even take
them up more rapidly and abundantly than the lacteals.

These two sets of vessels, however, do not absorb all the aliment-
ary matters indiscriminately. It is one of the most important of
the facts which have been established by modern researches on
digestion that the different substances, produced by the operation of
the digestive fluids on the food, pass into the circulation by different
routes. The fatty matters are taken up by the lacteals under the form
of chyle, while the saccharine and albuminous matters pass by ab-
sorption into the portal vein. Accordingly, after the digestion of a
meal containing starchy and animal matters mixed, alburninose and
sugar are both found in the blood of the portal vein, while they can-
not be detected, in any large quantity, in the contents of the lacteals.
These substances, however, do not mingle at once with the general
mass of the circulation, but owing to the anatomical distribution of
the portal vein, pass first through the capillary circulation of the
liver. Soon after being introduced into the blood and coming in
contact with its organic ingredients, they become altered and con-
verted, by catalytic transformation, into other substances. The
albuminose passes into the condition of ordinary albumen, and
probably also partly into that of fibrin ; while the sugar rapidly
becomes decomposed, and loses its characteristic properties; so

ABSORPTION.

167

Fig. 41.

that, on arriving at the entrance of the general circulation, both
these newly absorbed ingredients have become already assimilated
to those which previously existed in the blood.

The chyle in the intestine consists, as we have already mentioned,
of oily matters which have not been chemically altered, but simply
reduced to a state of emulsion. In chyle drawn from the lacteals
or the thoracic duct (Fig. -Al), it still presents itself in the same
condition and retains all the
chemical properties of oil.
Examined by the microscope,
it is seen to exist under the
form of fine granules and
molecules, which present the
ordinary appearances of oil
in a state of minute subdivi-
sion. The chyle, therefore,
does not represent the entire
product of the digestive pro-
cess, but contains only the
fatty substances, suspended
by emulsion in a serous fluid.

During the time that intes-
tinal absorption is going on,

n , . Drcr, from the D^n — The molecules vary iu size

alter a meal containing fatty from i-io.oootu of au iuch downward,
ingredients, the lacteals may

be seen as white, opaque vessels, distended with milky chyle, pass-
ing through the mesentery, and converging from its intestinal bor-
der toward the receptaculum chyli, near the spinal column. During
their course, they pass through several successive rows of mesenteric
glands, which also become turgid with chyle, while the process of
digestion is going on. The lacteals then conduct the chyle to the
receptaculum chyli, whence it passes upward through the thoracic
duct, and is finally discharged, at the termination of this canal, into
the left subclavian vein. (Fig. 42.) It is then mingled with the
returning current of venous blood, and passes into the right cavities
of the heart.

The lacteals, however, are not a special system of vessels by them-
selves, but are simply a part of the great system of " absorbent" or
" lymphatic" vessels, which are to be found everywhere in the integu-
ments of the head, the parietes of the trunk, the upper and lower
extremities, and in the muscular tissues and mucous membranes

CHYLE FROM COMXKKCEMKXT < • >' T H <> R A c i o.

168

ABSORPTION".

throughout the body. The walls of these vessels are thinner and
more transparent than those of the arteries and veins, and they are
consequently less easily detected by ordinary dissection. They

originate in the tissues of the
above-mentioned parts by an
irregular plexus. They pass
from the extremities toward
the trunk, converging and
uniting with each other like the
veins, their principal branches
taking usually the same di-
rection with the nerves and
bloodvessels, and passing, at
various points in their course,
through certain glandular bo-
dies, the " lymphatic" or "ab-
sorbent" glands. The lym-
phatic glands, among which
are included the mesenteries
glands, consist of an external
layer of fibrous tissue and a
contained pulp or parenchy-
ma. The investing layer of
fibrous tissue sends off thin
septa or laminae from its in-
ternal surface, which pene-
trate the substance of the gland
in every direction and unite
with each other at various
points. In this way theyihrjn

an interlacing laminated framework, which divides the substance
of the gland into numerous rounded spaces or alveoli. These alveoli
are not completely isolated, but communicate with each other by
narrow openings, where the intervening septa are incomplete. These
cavities are filled with a soft, reddish pulp, which is penetrated,
according to Kolliker, like the solitary and agminated glands of the
intestine, by a fine network of capillary bloodvessels. The solitary
and agminated glands of the intestine are, therefore, closely analo-
gous in their structure to the lymphatics. The former are to be
regarded as simple, the latter as compound vascular glands.

The arrangement of the lymphatic vessels in the interior of the

" --a-

LACTEAI.S, THORACIC DUCT, &c.— a. Intes-
tine, b. Vena cava inferior. c, c. Right and left
subclavian veins, d. Point of opening of thoracic
duct into left subclavian.

ABSORPTION. 169

glands is not precisely understood. Each lymphatic vessel, as it
enters the gland, breaks up into a number of minute ramifications,
the vasa afferentia • and other similar twigs, forming the vctsa effer-
entia, pass off in the opposite direction, from the farther side of the
gland ; but the exact mode of communication between the two has
not been definitely ascertained. The fluids, however, arriving by
the vasa afferentia, must pass in some way through the tissue of
the gland, before they are carried away again by the vasa efferentia.
From the lower extremities the lymphatic vessels enter the abdomen
at the groin and converge toward the receptaculum chyli, into
which their fluid is discharged, and afterward conveyed, by the
thoracic duct, to the left subclavian vein.

The fluid which these vessels contain is called the lymph. It is
a colorless or slightly yellowish transparent fluid, which is absorbed
by the lymphatic vessels from the tissues in which they originate.
So far as regards its composition, it is known to contain, beside
water and saline matters, a small quantity of fibrin and albumen.
Its ingredients are evidently derived from the metamorphosis of
the tissues, and are returned to the centre of the circulation in
order to be eliminated by excretion, or in order to undergo some
new transforming or renovating process. We are ignorant, how-
ever, with regard to the precise nature of their character and
destination.

The lacteals are simply that portion of the absorbents which
originate in the mucous membrane of the small intestine. During
the intervals of digestion, these vessels contain a colorless and
transparent lymph, entirely similar to that which is found in other
parts of the absorbent system. After a meal containing only
starchy or albuminoid substances, there is no apparent change in
the character of their contents. But after a meal containing fatty
matters, these substances are taken up by the absorbents of the
intestine, which then become filled with the white chylous emul-
sion, and assume the appearance of lacteals. (Fig. 43.) It is for
this reason that lacteal vessels do not show themselves upon the
stomach nor upon the first few inches of the duodenum ; because
oleaginous matters, as we have seen, are not digested in the stomach,
but only after they have entered the intestine and passed the orifice
of the pancreatic duct.

The presence of chyle in the lacteals is, therefore, not a con-
stant, but only a periodical phenomenon. The fatty substances
constituting the chyle begin to be absorbed during the process of

170 ABSORPTION.

digestion, as soon as they have been disintegrated and emulsioned
by the action of the intestinal fluids. As digestion proceeds, they
accumulate in larger quantity, and gradually fill the whole lacteal

L A R T K A L 4 A X D LYMPHATICS.

system and the thoracic duct. As they are discharged into the
subclavian vein, and mingled with the blood, they can still be dis-
tinguished in the circulating fluid, as a mixture of oily molecules
and granules, between the orifice of the thoracic duct and the right
side of the heart. While passing through the pulmonary circula-
tion, however, they disappear. Precisely what becomes of them,
or what particular chemical changes they undergo, is not certainly

ABSORPTION. 171

known. They are, at all events, so altered in the blood, while
passing through the lungs, that they lose the form of a fatty emul-
sion, and are no longer to be recognized by the usual tests for
oleaginous substances.

The absorption of fat from the intestine is not, however, exclu-
sively performed by the lacteals. Some of it is also taken up,
under the same form, by the bloodvessels. It has been ascertained
by the experiments of Bernard1 that the blood of the mesenteric
veins, in the carnivorous animals, contains, during intestinal diges-
tion, a considerable amount of fatty matter in a state of minute
subdivision. Other observers, also (Lehmann, Schultz, Simon), have
found the blood of the portal vein to be considerably richer in fat
than that of other veins, particularly while intestinal digestion is
going on with activity. In birds, reptiles, and fish, furthermore,
according to Bernard, the intestinal lymphatics are never filled
with opaque chyle, but only with a transparent lymph ; so that these
animals may be said to be destitute of lacteals, and in them the fatty
substances, like other alimentary materials, are taken up altogether
by the bloodvessels. In quadrupeds, on the other hand, and in
the human subject, the absorption of fat is accomplished both by
the bloodvessels and the lacteals. A certain portion is taken up
by the former, while the superabundance of the fatty emulsion is
absorbed by the latter.

A difficulty has long been experienced in accounting for the ab-
sorption of fat from the intestine, owing to its being considered as a
non-endosmotic substance ; that is, as incapable, in its free or undis-
solved condition, of penetrating and passing through an animal
membrane by endosmosis. It is stated, indeed, that if a fine oily
emulsion be placed on one side of an animal membrane in an endos-
mometer, and pure water on the other, the water will readily pene-
trate the substance of the membrane, while the oily particles cannot
be made to pass, even under a high pressure. Though this be true,
however, for pure water, it is not true for slightly alkaline fluids,
like the serum of the blood and the lymph. This has been de-
monstrated by the experiments of Matteucci, in which he made
an emulsion with an alkaline fluid containing 43 parts per thou-
sand of caustic potassa. Such a solution has no perceptible alkaline
taste, and its action on reddened litmus paper is about equal to
that of the lymph and chyle. If this emulsion were placed in an

1 Leqons de Physiologie Experimentale. Paris, 1?5<3, p. 325.

172

ABSORPTION.

Fig. 44.

INTESTINAL EPITHELIUM; from the Dog, while
fasting.

endosmometer, together with a watery alkaline solution of similar
strength, it was found that the oily particles penetrated through the

animal membrane without
much difficulty, and mingled
with the fluid on the opposite
side. Although, therefore,
we cannot explain the exact
mechanism of absorption in
the case of fat, still we know
that it is not in opposition to
the ordinary phenomena of
endosmosis ; for endosmosis
will take place with a fatty
emulsion, provided the fluids
used in the experiment be
slightly alkaline in reaction.
It is, accordingly, by a pro-
cess of endosmosis, or imbi-
bition, that the villi take up

the digested fatty substances. There are no open orifices or canals,
into which the oil penetrates ; but it passes directly into and through

the substance of the villi.
The epithelial cells covering
the external surface of the
villus are the first active
agents in this absorption. In
the intervals of digestion (Fig.
44) these cells are but slightly
granular and nearly trans-
parent in appearance. But if
examined during the diges-
tion and absorption of fat
(Fig. 45), their substance is
seen to be crowded with oily
particles, which they have
taken up from the intestinal

from the Dog, during , , ,. rpn

cavity by absorption. Ihe
oily matter then passes on-
ward, penetrating deeper and deeper into the substance of the villus,
until it is at last received by the capillary vessels and lacteals in its
centre.

INTESTINAL EPITHELIUM
the digestion of fat.

ABSORPTION. 173

The fatty substances taken up by the portal vein, like those ab-
sorbed by the lacteals, do not at once enter the general circulation,
but pass first through the capillary system of the liver. Thence
they are carried, with the blood of the hepatic vein, to the right
side of the heart, and subsequently through the capillary system of
the lungs. During this passage they become altered in character,
as above described, and lose for the most part the distinguishing
characteristics of oily matter, before they have passed beyond the
pulmonary circulation.

But as digestion proceeds, an increasing quantity of fatty matter
finds its way, by these two passages, into the blood ; and a time at
last arrives when the whole of the fat so introduced is not destroyed
during its passage through the lungs. Its absorption taking place
at this time more rapidly than its decomposition, it begins to ap-
pear, -in moderate quantity, in the blood of the general circulation ;
and, lastly, when the intestinal absorption is at its point of greatest
activity, it is found in considerable abundance throughout the
entire vascular system. At this period, some hours after the inges-
tion of food rich in oleaginous matters, the blood of the general
circulation everywhere contains a superabundance of fat, derived
from the digestive process: If blood be then drawn from the veins
or arteries in any part of the body, it will present the peculiar
appearance known as that of " chylous" or " milky" blood. After
the separation of the clot, the serum presents a turbid appearance ;
and the fatty substances, which it contains, rise to the top after a
few hours, and cover its surface with a partially opaque and creamy-
looking pellicle. This appearance has been occasionally observed
in the human subject, particularly in bleeding for apoplectic attacks
occurring after a full meal, and has been mistaken, in some instances,
for a morbid phenomenon. It is, however, a perfectly natural one,
and depends simply on the rapid absorption, at certain periods of
digestion, of oleaginous substances from the intestine. It can be
produced at will, at any time, in the dog, by feeding him with fat
meat, and drawing blood, seven or eight hours afterward, from the
carotid artery or the jugular vein.

This state of things continues for a varying length of time, ac-
cording to the amount of oleaginous matters contained in the food.
When digestion is terminated, and the fat ceases to be introduced
in unusual quantity into the circulation, its transformation and
decomposition continuing to take place in the blood, it disappears
gradually from the veins, arteries, and capillaries of the general

174 ABSORPTION.

system ; and, finally, when the whole of the fat has been disposed
of by the nutritive processes, the serum again becomes transparent,
and the blood returns to its ordinary condition.

In this manner the nutritive elements of the food, prepared for
absorption by the digestive process, are taken up into the circulation
under the different forms of albuminose, sugar, and chyle, and accu-
mulate as such, at certain times, in the blood. But these conditions
are only temporary, or transitional. The nutritive materials soon
pass, by catalytic transformation, into other forms, and become
assimilated to the pre-existing elements of the circulating fluid.
Thus they accomplish finally the whole object of digestion ; which
is to replenish the blood by a supply of new materials from without.
There are, however, two other intermediate processes, taking place
partly in the liver and partly in the intestine, at about the same
time, and having for their object the final preparation and perfec-
tion of the circulating fluid. These two processes require to be
studied, before we can pass on to the particular description of the
blood itself. They are : 1st, the secretion and reabsorption of the
bile ; and 2d, the production of sugar in the liver, and its subse-
quent decomposition in the blood.

THE BILE. 175

CHAPTER VIII.

THE BILE.

THE bile is more easily obtained in a state of purity than any
other of the secretions which find their way into the intestinal
canal, owing to the existence of a gall-bladder in which it accu-
mulates, and from which it may be readily obtained without anv
other admixture than the mucus of the gall-bladder itself. Not-
withstanding this, its study has proved an unusually difficult one.
This difficulty has resulted from the peculiar nature of the biliary
ingredients, and the readiness with which they become altered by
chemical manipulation ; and it is, accordingly, only quite recently
that we have arrived at a correct idea of its real constitution.

The bile, as it comes from the gall-bladder, is a somewhat viscid
and glutinous fluid, varying in color and specific gravity according
to the species of animal from which it is obtained. Human bile is
of a dark golden brown color, ox bile of a greenish yellow, pig'.s
bile of a nearly clear yellow, and dog's bile of a deep brown. We
have found the specific gravity of human bile to be 1018, that of
ox bile 1024, that of pig's bile 1030 to 1036. The reaction of the
bile with test-paper cannot easily be determined ; since it has only
a bleaching or decolorizing effect on litmus, and does not turn it
either blue or red. It is probably either neutral or very slightly
alkaline. A very characteristic physical property of the bile is
that of frothing up into a soap-like foam when shaken in a test-
tube, or when air is forcibly blown into it through a small glass
tube or blowpipe. The bubbles of foam, thus produced, remain
for a long time without breaking, and adhere closely to each other
and to the sides of the glass vessel.

The following is an analysis of the bile of the ox, based on the
calculations of Berzelius, Frerichs, and Lehmann : —

176 THE BILE.

COMPOSITION OF Ox BILE.

Water 888.00

Glyko-cholate of soua I 90 00

Tauro-cholate " " I

Biliverdine 1

Fats I 1342

Oleates, margarates, and stearates of soda and potassa

Cholesterin .......... J

Chloride of sodium 1

Phosphate of soda ........

" " lime }> 15.24

" " magnesia

Carbonates of soda and potassa ...... J

Mucus of the gall-bladder 1.34

1000.00

BILIVERDINE. — Of the above mentioned ingredients, biliverdine
is peculiar to the bile, and therefore important, though not pre-
sent in large quantity. This is the coloring matter of the bile.
It is, like the other coloring matters, an uncrystallizable organic
substance, containing nitrogen, and yielding to ultimate analysis a
small quantity of iron. It exists in such small quantity in the bile
that its exact proportion has never been determined. It is formed,
so far as can be ascertained, in the substance of the liver, and does
not pre-exist in the blood. It may, however, be reabsorbed in
cases of biliary obstruction, when it circulates with the blood and
stains nearly all the tissues and fluids of the body, of a peculiar
lemon yellow color. This is the symptom which is characteristic
of jaundice.

CHOLESTERIN (C25H220). — This is a crystallizable substance which
resembles the fats in many respects ; since it is destitute of nitrogen,
readily inflammable, soluble in alcohol and ether, and entirely in-
soluble in water. It is not saponifiable, however, by the action of
the alkalies, and is distinguished on this account from the ordinary
fatty substances. It occurs, in a crystalline form, mixed with color-
ing matter, as an abundant ingredient in most biliary calculi ; and
is found also in different regions of the body, forming a part of
various morbid deposits. We have met with it in the fluid of
hydrocele, and in the interior of many encysted tumors. The
crystals of cholesterin (Fig. 46) have the form of very thin, color-
less, transparent, rhomboidal plates, portions of which are often
cut out by lines of cleavage parallel to the sides of the crystal.
They frequently occur deposited in layers, in which the outlines of

THE BILE.

177

Fig. 46.

the subjacent crystals show very distinctly through the substance
of those which are placed above. • Cholesterin is not formed in the
liver, but originates in the
substance of the brain and
nervous tissue, from which
it may be extracted in large
quantity by the action of
alcohol. It has also been
found, by Dr. "W. Marcet,1 to
exist, in considerable abund-
ance, in the tissue of the
spleen. From all these tis-
sues it is absorbed by the
blood, then conveyed to the
liver, and discharged with
the bile.

CHOI. ESTER ix, from an Enrysted Tumor.

This fact has been fully
confirmed by the researches

of Prof. A. Flint, Jr.,7 who has found that there is nearly one-quarter
part more cholesterin in the blood of the jugular vein, returning
from the brain, than in that of the carotid artery, before its passage
through that organ ; and that, on the other hand, the blood of the
hepatic artery, as well as that of the portal vein, loses cholesterin
in passing through the liver, so that but a small quantity can be
found in the blood of the hepatic vein.

The cholesterin, however, after being poured into the intestine
with the bile, is decomposed or transformed into some other sub-
stance, since it is not discharged with the feces.3 Its decomposition
is probably effected by the contact of the intestinal fluids.

BILIARY SALTS. — By far the most important and characteristic
ingredients of this secretion are the two saline substances mentioned
above as the glylto-cholate and tauro-cholate of soda. These sub-
stances were first discovered by Strecker, in 1848, in the bile of the
ox. They are both freely soluble in water and in alcohol, but in-
soluble in ether. One of them, the tauro-cholate, has the property,

1 In American Journ. Med. Sci., January, 155?.

2 American Journ. Med. Sci., October, 1SG2.

3 Prof. A. Flint, Jr., in Am. Journ. Med. Sci., Oct. 1862.

12

178

THE BILE.

when itself in solution in water, of dissolving a certain quantity of
fat; and it is probably owing to-tliis circumstance that some free
fat is present in the bile. The two biliary substances are obtained
from ox bile in the following manner : —

The bile is first evaporated to dryness by the water-bath. The
dry residue is then pulverized and treated with absolute alcohol, in
the proportion of at least 3j of alcohol to every five grains of dry
residue. The filtered alcoholic solution has a clear yellowish color.
It contains, beside the glyko-cholate and tauro-cholate of soda, the
coloring matter and more or less of the fats originally present in
the bile. On the addition of a small quantity of ether, a dense,
whitish precipitate is formed, which disappears again on agitating
and thoroughly mixing the fluids. On the repeated addition of
ether, the precipitate again falls down, and when the ether has been
added in considerable excess, six to twelve times the volume of the
alcoholic solution, the precipitate remains permanent, and the whole
mixture is filled with a dense, whitish, opaque deposit, consisting
of the glyko-cholate and tauro-cholate of soda, thrown down under
the form of heavy flakes and granules, part of which subside to

Fig. 47.

Fig. 43.

OX-BILE, extracted with absolute
alcohol and precipitated with ether.

GT.YKO-CHOLATE op SODA FROM OX-BTLE,
after two days' crystallization. At the lower part of
the figure the crystals are melting into drops, from the
evaporation of the ether and absorption of moisture.

the bottom of the test-tube, while part remain for a time in suspen-
sion. Gradually these flakes and granules unite with each other
and fuse together into clear, brownish-yellow, oily, or resinous-

THE BILE.

179

looking drops. At the bottom of the test-tube, after two or three
hours, there is usually collected a nearly homogeneous layer of
this deposit, while the remainder continues to adhere to the sides
of the glass in small, circular, transparent drops. The deposit is
semi-fluid in consistency, and sticky, like Canada balsam or half-
melted resin ; and it is on this account that the ingredients compos-
ing it have been called the " resinous matters" of the bile. They
have, however, no real chemical relation with true resinous bodies,
since they both contain nitrogen, and differ from resins also in
other important particulars.

At the end of twelve to twenty-four hours, the glyko-cholate of
soda begins to crystallize. The crystals radiate from various points
in the resinous deposit, and shoot upward into the supernatant
fluid, in white, silky bundles. (Fig. 47.) If some of these crystals
be removed and examined by the microscope, they are found to be
of a very delicate acicular form, running to a finely pointed
extremity, and radiating, as already mentioned, from a central
point. (Fig. 48.) As the ether evaporates, the crystals absorb
moisture from the air, and melt up rapidly into clear resinous
drops ; so that it is difficult to keep them under the microscope
long enough for a correct

drawing and measurement. Flg' 49*

The crystallization in the
test-tube goes on after the
first day, and the crystals in-
crease in quantity for three
or four, or even five or six
days, until the whole of the
glyko cholate of soda present
has assumed the solid form.
The tauro-cholate, however,
is uncrystallizable, and re-
mains in an amorphous con-
dition. If a portion of the
deposit be now removed and
examined by the microscope,
it is seen that the crystals of
glyko-cholate of soda have
increased considerably in thickness (Fig. 49), so that their trans-
verse diameter may be readily estimated. The uncrystallizable
tauro-cholate appears under the form of circular drops, varying

GLYKO-CHOLATE AND TACRO-CHOLATE OF
SODA, FROM OX-BILE, after six days' crystalliza-
tion' The g1yk°-cholate is crystallized ; the tauro-
cholate is in fluid drops.

180 THE BILE.

considerably in size, clear, transparent, strongly refractive, and
bounded by a dark, well-defined outline. These drops are not to be
distinguished, by any of their optical properties, from oil- globules, as
they usually appear under the microscope. They have the same
refractive power, the same dark outline and bright centre, and the
same degree of consistency. They would consequently be liable at
all times to be mistaken for oil-globules, were it not for the complete
dissimilarity of their chemical properties.

Both the glyko-cholate and tauro-cholate of soda are very freely
soluble in water. If the mixture of alcohol and ether be poured
off and distilled water added, the deposit dissolves rapidly and
completely, with a more or less distinct yellowish color, according
to the proportion of coloring matter originally present in the bile.
The two biliary substances present in the watery solution may be
separated from each other by the following means. On the addi-
tion of acetate of lead, the glyko-cholate of soda is decomposed,
and precipitates as a glyko-cholate of lead. The precipitate, sepa-
rated by nitration from the remaining fluid, is then decomposed in
turn by carbonate of soda, and the original glyko-cholate of soda
reproduced. The filtered fluid which remains, and which contains
the tauro-cholate of soda, is then treated with subacetate of lead,
which precipitates a tauro-cholate of lead. This is separated by
filtration, washed, and decomposed again by carbonate of soda, as
in the former case.

The two biliary substances in ox bile may, therefore, be dis-
tinguished by their reactions with the salts of lead. Both are
precipitable by the subacetate; but the glyko-cholate of soda is
precipitable .also by the acetate, while the tauro-cholate is not so.
If subacetate of lead, therefore, be added to the mixed watery solu-
tion of the two substances, and the whole filtered, the subsequent
addition of acetate of lead to the filtered fluid will produce no pre-
cipitate, because both the biliary matters have been entirely thrown
down with the deposit ; but if the acetate of lead be first added, it
will precipitate the glyko-cholate alone, and the tauro-cholate may
afterward be thrown down separately by the subacetate.
- These two substances, examined separately, have been found to
possess the following properties : —

G-lyko-cholateof soda(N&0,G52TI42~NOu) crystallizes, when precipi-
tated by ether from its alcoholic solution, in radiating bundles of
fine white silky needles, as above described. It is composed of
soda, united with a peculiar acid of organic origin, viz., glyko-cholic

THE BILE. 181

«CK/t(G52H42NOll,HO). This acid is crystallizable and contains nitro-
gen, as shown by the above formula, which is that given by Leh-
mann. If boiled for a long time with a dilute solution of potassa,
glyko-cholic acid is decomposed with the production of two new
substances; the first a non-nitrogenous acid body, ckolic add
(C48H3gO9,HO) ; the second a nitrogenous neutral body, glycine
(C4H5NO4). Hence the name- glyko-cholic acid, given to the
original substance, as if it were a combination of cholic acid with
glycine. In reality, however, these two substances do not exist
originally in the glyko-cholic acid, but are rather new combinations
of its elements, produced by long boiling, in contact with potassa
and water. They are not, therefore, to be regarded as, in any way,
natural ingredients of the bile, and do not throw any light on the
real constitution of glyko-cholic acid.

Tauro-cholate of soda (NaO,C52H45NS2014) is also a very abundant
ingredient of the bile. It is said by Eobin and Yerdeil1 that it is
not crystallizable, owing probably to its not having been separated
as yet in a perfectly pure condition. Lehmann states, on the con-
trary, that it may crystallize,2 when kept for a long time in contact
with ether. We have not been able to obtain this substance, how-
ever, in a crystalline form. Its acid constituent, tauro-cholic acid,
is a nitrogenous body, like glyko-cholic acid, but differs from the
latter by containing in addition two equivalents of sulphur. By
long boiling in a dilute solution of potassa, it is decomposed with
the production of two other substances ; the first of them the same
acid body mentioned above as derived from the glyko-cholic, viz.,
cholic acid; and the second a new nitrogenous neutral body, viz.,
taurine (C4H7NS3Ofl). The same remark holds good with regard to
these two bodies, that we have already made in respect to the sup-
posed constituents of glyko-cholic acid. Neither cholic acid nor
taurine can be properly regarded as really ingredients of tauro-
cholic acid, but only as artificial products resulting from its altera-
tion and decomposition.

The glyko-cholates and tauro-cholates are formed, so far as we
know, exclusively in the liver ; since they have not been found in
the blood, nor in any other part of the body, in healthy animals :
nor even, in the experiments of Kunde, Moleschott, and Lehmann
on frogs,3 after the entire extirpation of the liver, and consequent

t ' Chimie Anatoraique et Physiologique, vol. ii. p. 473.

2 Physiological Chemistry, Phil, ed., vol. i. p. 209.

3 Lehmann's Physiological Chemistry, Phil, ed., vol. i. p. 476.

182

THE BILE.

\

Fig. 50.

suppression of the bile. These substances are, therefore, produced
in the glandular cells of the liver, by transformation of some other
of their ingredients. They are then exuded in a soluble form, as
part of the bile, and finally discharged by the excretory hepatic
ducts.

The two substances described above as the tauro-cholate and
glyko-cholate of soda exist, properly speaking, only in the bile of
the ox, where they were first discovered by Strecker. In examin-
ing the biliary secretions of different species of animals, Strecker
found so great a resemblance between them, that he was disposed
to regard their ingredients as essentially the same. Having estab-
lished the existence in ox-bile of two peculiar substances, one
crystallizable and non-sulphurous (glyko-cholate), the other uncrys-
tallizable and sulphurous (tauro-cholate), he was led to consider
the bile in all species of animals as containing the same substances,
and as differing only in the relative quantity in which the two
were present. The only exception to this was
supposed to be pig's bile, in which Strecker found
a peculiar organic acid, the "hyo-cholic" or
" hyo-cholinic" acid, in combination with soda as
a base.

The above conclusion of his, however, was not
entirely correct. It is true that the bile of all
animals, so far as examined, contains peculiar
substances, which resemble each other in being
freely soluble in water, soluble in absolute alco-
hol, and insoluble in ether ; and in giving also a
peculiar reaction with Pettenkofer's test, to be
described presently. But, at the same time, these
substances present certain minor differences in
different animals, which show them not to be
identical.

In dog's bile, for example, there are, as in ox-
bile, two substances precipitable by ether from
their alcoholic solution; one crystallizable, the
other not so. But the former of these substances
crystallizes much more readily than the glyko-
cholate of soda from ox-bile. Dog's bile will not unfrequently begin
to crystallize freely in five to six hours after precipitation by ether
(Fig. 50) ; while in ox-bile it is usually twelve, and often twenty-
four or even forty-eight hours before crystallization is fully estab-

Doo'sBiLE, extract-
ed with absolute alcoh ol
and precipitated with
ether.

THE BILE.

183

51.

lislied. But it is more particularly in their reaction with the salts
of lead that the difference between these substances becomes mani-
fest. For while the crystallizable substance of ox-bile is precipi-
tated by acetate of lead, that of dog's bile is not affected by it. If
dog's bile be evaporated to dryness, extracted with absolute alcohol,
the alcoholic solution precipitated by ether, and the ether precipitate
then dissolved in water, the addition of acetate of lead to the watery
solution produces not the slighest turbidity. If subacetate of lead
be then added in excess, a copious precipitate falls, composed of both
the crystallizable and uncrystallizable substances. If the lead pre-
cipitate be then separated by nitration, washed, and decomposed,
as above described, by carbonate of soda, the watery solution will
contain the re-formed soda salts of the bile. The watery solution
in a v then be evaporated to dryness, extracted with absolute alcohol,
and the alcoholic solution precipitated by ether ; when the ether
precipitate crystallizes partially after a time as in fresh bile. Both
the biliary matters of dog's bile are therefore
precipitable by subacetate of lead, but neither of
them by the acetate. Instead of calling them,
consequently, glyko-cholate and tauro cholate of
soda, we shall speak of them simply as the " crys-
talline'1 and " resinous" biliary substances.

In cat's bile, the biliary substances act very
much as in dog's bile. The ether precipitate of
the alcoholic solution contains here also a crys-
talline and a resinous substance ; both of which
are precipitable from their watery solution by
subacetate of lead, but neither of them by the
acetate.

In pig's bile, on the other hand, there is no
crystallizable substance, but the ether precipitate
is altogether resinous in appearance. Notwith-
standing this, its watery solution precipitates
abundantly by both the acetate and subacetate of
lead.

In human bile, again, there is no crystallizable
-substance. We have found that the dried bile,
extracted with absolute alcohol, makes a clear, brandy-red solution,
which precipitates abundantly with ether in excess ; but the ether
precipitate, if allowed to stand, shows no sign of crystallization, even
at the end of three weeks. (Fig. 51.) If the resinous precipitate

HUMAN BILB, ex-
tracted -with absolute
alcohol and precipitated
by ether.

184 THE BILE.

be separated by decantation and dissolved in water, it precipitates,
as in the case of pig's bile, by both , the acetate and subacetate of
lead. This might, perhaps, be attributed to the presence of two
different substances, as in ox-bile, one precipitated by the acetate,
the other by the subacetate of lead. Such, however, is not the case.
For if the watery solution be precipitated by the acetate of lead
and then filtered, the filtered fluid gives no precipitate afterward
by the subacetate ; and if first precipitated by the subacetate it
gives no precipitate after filtration by the acetate. The entire
biliary ingredients, therefore, of human bile are precipitated by
both or either of ttfe salts of lead.

Different kinds of bile vary also 'in other respects; as, for ex-
ample, their specific gravity, the depth and tinge of their color, the
quantity of fat which they contain, &c. &c. We have already
mentioned the variations in color and specific gravity. The alco-
holic solution of dried ox-bile, furthermore, does not precipitate at
all on the addition of water ; while that of human bile, of pig's
bile, and of dog's bile precipitate abundantly with distilled water,
owing to the quantity of fat which they hold in solution. These
variations, however, are of secondary importance compared with
those which we have already mentioned, and which show that the
crystalline and resinous substances in different kinds of bile, though
resembling each other in very many respects, are yet in reality far
from being identical.

TESTS FOK BILE. — In investigating the physiology of any animal
fluid it is, of course, of the first importance to have a convenient
and reliable test by which its presence may be detected. For a
long time the only test employed in the case of bile, was that which
depended on a change of color produced by oxidizing substances. If
the bile, for example, or a mixture containing bile, be exposed in
an open glass vessel for a few hours, the upper layers of the fluid,
which are in contact with the atmosphere, gradually assume a
greenish tinge, which becomes deeper with the length of time which
elapses, and the quantity of bile existing in the fluid. Nitric acid,
added to a mixture of bile and shaken up, produces a dense preci-
pitate which takes a bright grass-green hue. Tincture of iodine
produces the same change of color, when added in small quantity ;
and probably there are various other substances which would have
the same effect. It is by this test that the bile has so often been
recognized in the urine, serous effusions, the solid tissues, &c., in

TESTS FOR BILE. 185

cases of jaundice. But it is very insufficient for anything like
accurate investigation, since the appearances are produced simply
by the action of an oxidizing agent on the coloring matter of the
bile. A green color produced by nitric acid does not, therefore,
indicate the presence of the biliary substances proper, but only of
the biliverdine. On the other hand, if the coloring matter be ab-
sent, the biliary substances themselves cannot be detected by it.
For if the biliary substances of dog's bile be precipitated by ether
from an alcoholic solution, dissolved in water and decolorized by
animal charcoal, the colorless watery solution will then give no
green color on the addition of nitric acid or tincture of iodine,
though it may precipitate abundantly by subacetate of lead, and
give the other reactions of the crystalline and resinous biliary
matters in a perfectly distinct manner.

Pettenkofer's Test. — This is undoubtedly the best test yet pro-
posed for the detection of the biliary substances. It consists in
mixing with a watery solution of the bile, or of the biliary sub-
stances, a little cane sugar, and then adding sulphuric acid to the
mixture until a red, lake, or purple color is produced. /A solution
may be made of cane sugar, in the proportion of one part of sugar to
four parts of water, and kept for use. y One drop of this solution is
mixed with the suspected fluid, and the sulphuric acid then imme-
diately added. On first dropping in the sulphuric acid, a whitish
precipitate falls, which is abundant in the case of ox-bile, less so in
that of the dog. This precipitate reclissolves in a slight excess of
sulphuric acid, which should then continue to be added until the
mixture assumes a somewhat syrupy consistency and an opalescent
look, owing to the development of minute bubbles of air. A red
color then begins to show itself at the bottom of the test-tube, and
afterward spreads through the mixture, until the whole fluid is of
a clear, bright, cherryjred. This color gradually changes to a lake,
and finally to a deep, rich, opaque purple. If three or four vol-
umes of water be then added to the mixture, a copious precipitate
falls down, and the color is destroyed.

Various circumstances modify, to some extent, the rapidity and
distinctness with which the above changes are produced. If the
biliary substances be present in large quantity, and nearly pure,
the red color shows itself at once after adding an equal volume of
sulphuric acid, and almost immediately passes into a strong purple.
If they be scanty, on the other hand, the red color may not show
itself for seven or eight minutes, nor the purple under twenty

186 THE BILE.

or twenty-five minutes. If foreign matters, again, not of a biliary
nature, be also present, they are apt to be acted on by the sulphuric
acid, and, by becoming discolored, interfere with the clearness and
\ brilliancy of the tinges produced. On this account it is indispen-
sable, in delicate examinations, to evaporate the suspected fluicLto
dryness, extract the dry residue with absolute alcohol, precipitate
the alcoholic solution with ether, and dissolve the ether-precipitate
in water before applying the test. In this manner, all^ foreign sub-
stances which might do harm will be eliminated, and the test will
succeed without difficulty.

It must not be forgotten, furthermore, that the sugar itself is
liable to be acted on and discolored by sulphuric acid when added
in excess, and may therefore by itself give rise to confusion. A little
care and practice, however, will enable the experimenter to avoid
all chance of deception from this source. When sulphuric acid is
mixed with a watery solution containing cane sugar, after it has
been added in considerable excess, a yellowish color begins to show
itself, owing to the commencing decomposition of the sugar. This
color gradually deepens until it has become a dark, dingy, muddy
brown ; but there is never at any time any clear red or purple
color,, unless biliary matters be present. If the bile be present in
but small quantity, the colors produced by it may be modified and
obscured by the dingy yellow and brown of the sugar ; but even
this difficulty may be avoided by paying attention to the following
precautions. In the first place, only very little sugar should be
added, to the suspected fluid. In the second place, the sulphuric
acid should be added very gradually, and the mixture closely
watched to detect the first changes of color. If bile be present, the
red color peculiar to it is always produced before the yellowish
tinge which indicates the decomposition of the sugar. When the
biliary matters, therefore, are present in small quantity, the addi-
tion of sulphuric acid should be stopped at that point, and the
colors, though faint, will then remain clear, and give unmistakable
evidence of the presence of bile.

The red color alone is not sufficient as an indication of bile. It
is in fact only the commencement of the change 'which indicates the
> biliary matters. If these matters be present, the color passes, as
we have already mentioned, first into a lake, then into a purple ;
and it is this lake and purple color alone which can be regarded as
really characteristic of the biliary reaction.

It is important to observe that Pettenkofer's reaction is produced

TESTS FOB BILE. 187

by the presence of either or both of the biliary substances proper ;
and is not at all dependent on the coloring matter of the bile. For
if the two biliary substances, crystalline and resinous, be extracted
by the process above described, and, after being dissolved in water,
decolorized with animal charcoal, the watery solution will still give
Pettenkofer's reaction perfectly, though no coloring matter be pre-
sent, and though no green tinge can be produced by the addition
of nitric acid or tincture of iodine. If the two biliary substances
be then separated from each other, and tested in distinct solutions,
each solution will give the same reaction promptly and completely.

Various objections have been urged against this test. It has
been stated to be uncertain and variable in its action. Eobin and
Verdeil1 say that its reactions " do not belong exclusively to the
bile, and may therefore give rise to mistakes." Some fatty sub-
stances and volatile oils (oleine, oleic acid, oil of turpentine, oil of
caraway) have been stated to produce similar red and violet colors,
when treated with sugar and sulphuric acid. These objections,
however, have not much, if any, practical weight. The test no
doubt requires some care and practice in its application, as we have
already pointed out ; but this is the case also, to a greater or less
extent, with nearly all chemical tests, and particularly with those
for substances of organic origin. No other substance is, in point
of fact, liable to be met with in the intestinal fluids or the blood,
which would simulate the reactions of the biliary matters. We
have found that the fatty matters of the chyle, taken from the tho-
racic duct, do not give any coloration which would be mistaken for
that of the bile. When the volatile oils (caraway and turpentine)
are acted on by sulphuric acid, a red color is produced which after-
ward becomes brown and blackish, and a peculiar, tarry, empyreu-
matic odor is developed at the same time ; but we do not get the
lake and purple colors spoken of above. Finally, if the precaution
be observed — first of extracting the suspected matters with absolute
alcohol, then precipitating with ether and dissolving the precipitate
in water, no ambiguity could result from the presence of any of the
above substances.

Pettenkofer's test, then, if used with care, is extremely useful,
and may lead to many valuable results. Indeed, no other test than
this can be at all relied on to determine the presence or absence of
the biliary substances proper.

1 Op. cit., vol. ii. p. 468.

188 THE BILE.

VARIATIONS AND FUNCTIONS OF BILE. — With regard to the
entire quantity of bile secreted daily, we have had no very positive
knowledge, until the experiments of Bidder and Schmidt, published
in 1852.1 These experiments were performed on cats, dogs, sheep,
and rabbits, in the following manner. The abdomen was opened,
and a ligature placed upon the ductus communis choledochus, so
as to prevent the bile finding its way into the intestine. An open-
ing was then made in the fundus of the gall-bladder, by which
the bile was discharged externally. The bile, so discharged, was
received into previously weighed vessels, and its quantity accurately
determined. Each observation usually occupied about two hours,
during which period the temporary fluctuations occasionally observ-
able in the quantity of bile discharged were mutually corrected, so
far as the entire result was concerned. The animal was then killed,
weighed, and carefully examined, in order to make sure that the
biliary duct had been securely tied, and that no inflammatory alter-
ation had taken place in the abdominal organs. The observations
were made at very different periods after the last meal, so as to
determine the influence exerted by the digestive process upon the
rapidity of the secretion. The average quantity of bile for twenty-
four hours was then calculated from a comparison of the above
results ; and the quantity of its solid ingredients was also ascer-
tained in each instance by evaporating a portion of the bile in the
water bath, and weighing the dry residue.

Bidder and Schmidt found in this way that the daily quantity
of bile varied considerably in different species of animals. It was
very much greater in the herbivorous animals used for experiment
than in the carnivora. The results obtained by these observers
are as follows : —

For every pound weight of the entire body there is secreted
during twenty -four hours

FRESH BILE. DRY RESIDUE.

In the cat 102 grains. 5. 712 grains.

"dog 140 " 6.916 "

" sheep . . . . . . 178 " 9.408 "

" rabbit . . ... . . 958 " 17.290 "

Since, in the human subject, the digestive processes and the
nutritive actions generally resemble those of the carnivora, rather
than those of the herbivora, it is probable that the daily quantity
of 'bile in man is very similar to that in the carnivorous animals.

1 Verdaungssaefte und Stoffwechsel. Leipzig, 1852.

VARIATIONS AND FUNCTIONS OF BILE.

189

If we apply to the human subject the average results obtained by /
Bidder and Schmidt from the cat and dog, we find that, in an adult
man, weighing 1-iO pounds, the daily quantity of the bile will be
certainly not less than 16,9-iO grains, or very nearly 2J pounds
avoirdupois.

Ills a matter of great importance, in regard to the bile, as well
as the other intestinal fluids, to ascertain whether it be a constant
secretion, like the urine and perspiration, or whether it be intermit-
tent, like the gastric j uice, and discharged only during the digestive
process. In order to determine this point, we have performed the
following series of experiments on dogs. The animals were kept
confined, and killed at various periods after feeding, sometimes by
the inoculation of woorara, sometimes by hydrocyanic acid, but
most frequently by section of the medulla oblongata. The con-
tents of the intestine were then collected and examined. In all
instances, the bile was also taken from the gall-bladder, and treated
in the same way, for purposes of comparison. The intestinal con-
tents always presented some peculiarities of appearance when treated
with alcohol and ether, owing probably to the presence of other
substances than the bile ; but they always gave evidence of the
presence of biliary matters

as well. The biliary sub- Fis- 52-

stances could almost always
be recognized by the mi-
croscope in the ether preci-
pitate of the alcoholic solu-
tion ; the resinous substance,
under the form of rounded,
oily-looking drops (Fig. 52),
and the other, under the
form of crystalline groups,
generally presenting the
appearance of double bun-
dles of slender, radiating,
slightly curved or wavy,
needle - shaped crystals.
These substances, dissolved
in water, gave a purple

color with sugar and sulphuric acid. These experiments were
tried after the animals had been kept for one, two, three, five, six,
seven, eight, and twelve days without food. The result showed that,

CRYSTALLINE ANP RESINOUS BILIARY SUB-
STANCES; from Small Intestine of Dog, after two days'
fasting.

190

THE BILE.

Fig. 53.

in all these instances, bile was present in the small intestine. It is,
therefore, plainly not an intermittent secretion, nor one which is
concerned exclusively in the digestive process ; but its secretion is
constant, and it continues to be discharged into the intestine for
many days after the animal has been deprived of food.

The next point of importance to be examined relates to the time
after feeding at which the bile passes into the intestine in the greatest
abundance. Bidder and Schmidt have already investigated this
point in the following manner. They operated, as above described,
by tying the common bile-duct, and then opening the fundus of the
gall-bladder, so as to produce a biliary fistula, by which the whole
of the bile was drawn off. By doing this operation, and collecting
and weighing the fluid discharged at different periods, they came

to the conclusion that the flow
of bile begins to increase within
two and a half hours after the
introduction of food into the
stomach, but that it does not
reach its maximum of activity
till the end of twelve or fifteen
hours. Other observers, how-
ever, have obtained different
results. Arnold,1 for example,
found the quantity to be largest
soon after meals, decreasing
again after the fourth hour.
Kolliker and Miiller,2 again,
found it largest between the
sixth and eighth hours. Bidder
and Schmidt's experiments, in-
deed, strictly speaking, show
FISTULA.— a. stomach, ft. DUO- only the time at which the bile

denum. c, c, c. Pancreas ; its two ducts are seen ig mQst actively seCreted by the
opening into the duodenum, one near the orifice

of the biliary duct, d, the other a short distance liver, but not when it is actually

, Silver tube passing th,ou^u,e digcharged into the intestine.

Our own experiments, bear-
ing on this point, were performed on dogs, by making a permanent
duodenal fistula, on the same plan that gastric fistulas have so often

lower down.

abdominal wnllsand opening into the d

In Am. Journ. Med. Sci., April, 1856.

2 Ibid., April, 1857.

VARIATIONS AND FUNCTIONS OF BILE. 191

been established for the examination of the gastric juice. (Fig. 53.)
An incision was made through the abdominal walls, a short distance
to the right of the median line, the floating portion of the duodenum
drawn up toward the external wound, opened by a longitudinal in-
cision, and a silver tube, armed at each end with a narrow projecting
collar or flange, inserted into it by one extremity, five and a half
inches below the pylorus, and two and a half inches below the
orifice of the lower pancreatic duct. The other extremity of the
tube was left projecting from the external opening in the abdominal
parietes, the parts secured by sutures, and the wound allowed to
heal. After cicatrization was complete, and the animal had entirely
recovered his healthy condition and appetite, the intestinal fluids
were drawn off at various intervals after feeding, and their contents
examined. This operation, which is rather more difficult than that
of making a permanent gastric fistula, is nevertheless exceedingly
useful when it succeeds, since it enables us to study, not only the
time and rate of the biliary discharge, but also, as mentioned in a
previous chapter (Chap. VI.), many other extremely interesting
matters connected with intestinal digestion.

In order to ascertain the absolute quantity of bile discharged
into the intestine, and its variations during digestion, the duodenal
fluids were drawn off, for fifteen minutes at a time, at various
periods after feeding, collected, weighed, and examined separately,
as follows : each separate quantity was evaporated to dryness, its
dry residue extracted with absolute alcohol, the alcoholic solution
precipitated with ether, and the ether-precipitate, regarded as repre-
senting the amount of biliary matters present, dried, weighed, and
then treated with Pettenkofer's test, in order to determine, as nearly
as possible, their degree of purity or admixture. The result of
these experiments is given in the following table. At the eigh-
teenth hour so small a quantity of fluid was obtained that the
amount of its biliary ingredients was not ascertained. It reacted
perfectly, however, with Pettenkofer's test, showing that bile was
really present.

192

THE BILE.

Time after
feeding.

Quantity of fluid
in 15 minutes.

Dry residue
of same.

Quantity of
biliary matters.

Proportion of
biliary matters
to dry residue.

Immediately

640 grains

33 grains

10 grains

.3J

1 hour

1,990

105 "

4

.03

3 hours

780

60 "

4

.07

6 "

750

73 "

31

.05

9 "

860

78 "

4}

.06

12 "

325

23 "

3|

.16

15 •'

347 '

18 "

4

.22

18 "

—

—

—

—

21 «

384 "

11 "

1

.09

24 "

163 "

9.V "

31

.34

25 «

151 "

5" "

3

.60

From this it appears that the bile passes into the intestine in by
far the largest quantity immediately after feeding, and within the
first hour. After that time its discharge remains pretty constant ;
not varying much from four grains of solid biliary matters every
fifteen minutes, or sixteen grains per hour. The animal used for
the above observations weighed thirty-six and a half pounds.

The next point to be ascertained with regard to this question is
the following, viz : What becomes of the bile in its passage through
the intestine ? Our experiments, performed with a view of settling
this point, were tried on dogs. The animals were fed with fresh
meat, and then killed at various intervals after the meals, the abdo-
men opened, ligatures placed upon the intestine at various points,
and the contents of its upper, middle, and lower portions collected
and examined separately. The results thus obtained show that,
under ordinary circumstances, the bile, which is quite abundant in
the duodenum and upper part of the small intestine, diminishes in
quantity from above downward, and is not to be found in the large
intestine. The entire quantity of the intestinal contents also dimi-
nishes, and their consistency increases, as we approach the ileo-
ca3cal valve ; and at the same time their color changes from a light
yellow to a dark bronze or blackish-green, which is always strongly
pronounced in the last quarter of the small intestine.

The contents of the small and large intestine were furthermore
evaporated to dryness, extracted with absolute alcohol, and the
alcoholic solutions precipitated with ether ; the quantity of ether-
precipitate being regarded as representing approximately that of
the biliary substances proper. The result showed that the quantity
of this ether-precipitate is, both positively and relatively, very much
less in the large intestine than in the small. Its proportion to the
entire solid contents is only one-fifth or one-sixth as great in the

VARIATIONS AND FUNCTIONS OF BILE. 193

large intestine as it is in the small. But even this inconsiderable
quantity, found in contents of the large intestine, does not con-
sist of biliary matters ; for the watery solutions being treated with
sugar and sulphuric acid, those from both the upper and lower
portions of the small intestine always gave Pettenkofer's reaction
promptly and perfectly in less than a minute and a half; while in
that from the large intestine no red or purple color was produced,
even at the end of three hours.

The small intestine consequently contains, at all times, substances
giving all the reactions of the biliary ingredients; while in the
contents of the large intestine no such substances can be recognized
by Pettenkofer's test.

The biliary matters, therefore, disappear in their passage through
the intestine.

In endeavoring to ascertain what is the precise function of the bile
in the intestine, our first object must be to determine what part, if(
any, it takes in the digestive process. As the liver is situated, like
the salivary glands and the pancreas, in the immediate vicinity of
the alimentary canal, and like them, discharges its secretion into
the cavity of the intestine, it seems at first natural to regard the
bile as one of the digestive fluids. We have previously shown,
however, that the digestion of all the different elements of the food
is provided fcr by other secretions ; and furthermore, if we examine
experimentally the digestive power of bile on alimentary substances,
we obtain only a negative result. Bile exerts no special action upon
either albuminoid, starchy, or oleaginous matters, when mixed with
them in test-tubes and kept at the temperature of 100° F. It has
therefore, apparently, no direct influence in the digestion of these
substances.

It is a very remarkable fact, in this connection, that the bile pre-
cipitates by contact with the gastric juice. If four drops of dog's bile
be added to 3j of gastric juice from the same animal, a copious
yellowish- white precipitate falls down, which contains the whole of
the coloring matter of the bile which has been added ; and if the
mixture be then filtered, the filtered fluid passes through quite
colorless. The gastric juice, however, still retains its acid reaction.
This precipitation depends upon the presence of the biliary sub-
stances proper, viz., the glyko-cholate and tauro-cholate of soda, and
lQt upon that of the incidental ingredients of the bile. For if the
bile be evaporated to dryness and the biliary substances extracted
13

194 THE BILE.

by alcohol and precipitated by ether, as above described, their
watery solution will precipitate with gastric juice, in the same
manner as fresh bile would do.

Although the biliary matters, however, precipitate by contact
with fresh gastric juice, they do not do so with gastric juice which holds
albuminose in solution. We have invariably found that if the gas-
tric juice be digested for several hours at the temperature of 100°
F., with boiled white of egg, the filtered fluid, which contains an
abundance of albuminose, will no longer give the slightest precipi-
tate on the addition of bile, or of a watery solution of the biliary
substances, even in very large amount. The gastric juice and the
bile, therefore, are not finally antagonistic to each other in the
digestive process, though at first they produce a precipitate on
being mingled together.

It appears, however, from the experiments detailed above, that
the secretion of the bile and its discharge into the intestine are not
confined to the periods of digestion, but take place constantly, and
continue even after the animal has been kept for many days with-
out food. These facts would lead us to regard the bile as simply
an excrementitious fluid ; containing only ingredients resulting from
the waste and disintegration of the animal tissues, and not intended
to perform any particular function, digestive or otherwise, but
merely to be eliminated from the blood, and discharged from the
system. The same view is more or less supported, also, by the
following facts, viz : —

1st. The bile is produced, unlike all the other animal secretions,
from venous blood ; that is, the blood of the portal vein, which has
already become contaminated by circulation through the abdominal
organs, and may be supposed to contain disorganized and effete in-
gredients; and

2d. Its complete suppression produces, in the human subject,
symptoms of poisoning of the nervous system, analogous to those
which follow the suppression of the urine, or the stoppage of respi-
ration, and the patient dies, usually in a comatose condition, at the
end of ten or twelve days.

The above circumstances, taken together, would combine to
make it appear that the bile is simply an excrementitious fluid, not
necessary or useful as a secretion, but only destined, like the urine,
to be eliminated and discharged. Nevertheless, experiment has
shown that such is not the case ; and that, in point of fact, it is
necessary for the life of the animal, not only that the bile be secreted

VARIATIONS AND FUNCTIONS OF BILE. 195

and discharged, but furthermore that it be discharged into the
intestine, and pass through the tract of the alimentary canal. The
most satisfactory experiments of this kind are those of Bidder and
Schmidt,1 in which they tied the common biliary duct in dogs, and
then established a permanent fistula in the fundus of the gall-bladder,
through which the bile was allowed to flow by a free external orifice.
In this manner the bile was effectually excluded from the intestine,
but at the same time was freely and wholly discharged from the
body, by the artificial fistula. If the bile therefore were simply an
excremeutitious fluid, its deleterious ingredients being all eliminated
as usual, the animals would not suffer any serious injury from this
operation. If, on the contrary, they were found to suffer or die in
consequence of it, it would show that the bile has really some
important function to perform in the intestinal canal, and is not
simply excrementitious in its nature.

The result showed that the effects of such an experiment were
fatal to the animal. Four dogs only survived the immediate effects
of the operation, and were afterward frequently used for purposes
of experiment. One of them was an animal from which the spleen
had been previously removed, and whose appetite, as usual after
this operation, was morbidly ravenous; his system, accordingly,
being placed under such unnatural conditions as to make him an
unfit subject for further experiment. In the second animal that
survived, the communication of the biliary duct with the intestine
became re-established after eighteen days, and the experiment con-
sequently had no result. In. the remaining two animals, however,
everything was successful. The fistula in the gall-bladder became
permanently established ; and the bile-duct, as was proved subse-
quently by post-mortem examination, remained completely closed,
so that no bile found its way into the intestine. Both these ani-
mals died ; one of them at the end of twenty-seven days, the other
at the end of thirty-six days. In both, the symptoms were nearly
the same, viz., constant and progressive emaciation, which proceeded
to such a degree that nearly every trace of fat disappeared from the
body. The loss of flesh amounted, in one case, to more than two-
fifths, and in the other to nearly one-half the entire weight of the
animal. There was also a falling off of the hair, and an unusually
disagreeable, putrescent odor in the feces and in the breath. Not-
withstanding this, the appetite remained good. Digestion was not

1 Op. cit., p. 103.

196 THE BILE.

essentially interfered with, and none of the food was discharged
with the feces ; but there was much rumbling and gurgling in the
intestines, and abundant discharge of flatus, more strongly marked
in one instance than in the other. There was no pain ; and death
took place, at last, without any violent symptoms, but by a simple
and gradual failure of the vital powers.

A similar experiment has been successfully performed by Prof.
A. Flint, Jr.1 In this instance the animal lived for thirty-eight
days after the operation, and died finally of inanition ; the symp-
toms agreeing in every important particular, with those reported
by Bidder and Schmidt.

How is it, then, that although the bile be not an active -agent in
digestion, its presence in the alimentary canal is still essential to
life ? AVhat office does it perform there, and how is it finally dis-
posed of?

We have already shown that the bile disappears in its passage
through the intestine. This disappearance may be explained in
two different ways. First, the biliary matters may be actually re-
absorbed from the intestine, and taken up by the bloodvessels ; or
secondly, they may be sjo_ altered and decomposed by the intestinal
fluids as to lose the power of giving Pettenkofer's reaction with
sugar and sulphuric acid, and so pass off with the feces in an
insoluble form. Bidder and Schmidt2 have finally determined this
point in a satisfactory manner ; and have demonstrated that the
biliary substances are actually reabsorbed, by showing that the
quantity of sulphur present in the feces is far inferior to that
contained in the biliary ingredients as they are discharged into the
intestine.

These observers collected and analyzed all the feces passed, dur-
ing five days, by a healthy dog, weighing 17.7 pounds. The entire
fecal mass during this period weighed 1508.15 grains,

Containing / Water 874.20 grains.

I Solid residue .... 633.95 "

1508.15

1 American Journ. Med. Sci., October, 1862.

2 Op. cit., p. 217.

VARIATIONS AND FUNCTIONS OF BILE. 197

The solid residue was composed as follows : —

Neutral fat, soluble in ether . . 43.710 grains.

Fat, with traces of biliary matter . 77.035 "

Alcohol extract with biliary matter 58.900 containing 1.085 grs. of sulphur.

Substances not of a biliary nature

extracted by muriatic acid and

hot alcohol . . . . 148.800 containing 1.302 grs. of sulphur.

2.387

Fatty acids with oxide of iron . 98 425
Residue consisting of hair, sand, &c., 207.080

633.950

Now, as it has already been shown that the dog secretes, during
24 hours, 6.916 grains of solid biliary matter for every pound weight
of the whole body, the entire quantity of biliary matter secreted
in five days by the above animal, weighing 17.7 pounds, must have
been 612.5 grains, or nearly as much as the whole weight of the
dried feces. But furthermore, the natural proportion of sulphur
in dog's bile (derived from the uncrystallizable biliary matter), is six
per cent, of the dry residue. The 612.5 grains of dry bile, secreted
during five days, contained, therefore, 36.75 grains of sulphur.
But the entire quantity of sulphur, existing in any form in the
feces, was 5.952 grains; and of this only 2.387 grains were derived
from substances which could have been the products of biliary
matters — the remainder being derived from the hairs which are
always contained in abundance in the feces of the dog. That is,
not more than one-fifteenth part of the sulphur, originally present
in the bile, could be detected in the feces. As this is a simple
chemical element, not decomposable by any known means, it must,
accordingly, have been reabsorbed from the intestine.

We have endeavored to complete the evidence thus furnished by
Bidder and Schmidt, and to demonstrate directly the reabsorption
of the biliary matters, by searching for them in the ingredients of
the portal blood. We have examined, for this purpose, the portal
blood of dogs, killed at various periods after feeding. The animals
were killed by section of the medulla oblongata, a ligature imme-
diately placed on the portal vein, while the circulation was still
active, and the requisite quantity of blood collected by opening
the vein. The blood was sometimes immediately evaporated to
dryness by the water bath. Sometimes it was coagulated by boil-
ing in a porcelain capsule, over a spirit lamp, with water and an
excess of sulphate of soda, and the filtered watery solution after-
ward examined. But most frequently the blood, after being col-

198 THE BILE.

lected from the vein, was coagulated by the gradual addition of
three times its volume of alcohol at ninety-five per cent., stirring
the mixture constantly, so as to make the coagulation gradual and
uniform. It was then filtered, the moist mass remaining on the filter
subjected to strong pressure in a linen bag, by a porcelain press,
and the fluid thus obtained added to that previously filtered. The
entire spirituous solution was then evaporated to dryness, the dry
residue extracted with absolute alcohol, and the alcoholic solution
treated as usual, with ether, &c., to discover the presence of biliary
matters. In every instance blood was taken at the same time from
the jugular vein, or the abdominal vena cava, and treated in the
same way for purposes of comparison.

We have examined the blood, in this way, one, four, six, nine,
eleven and a half, twelve, and twenty hours after feeding. As the
result of these examinations, we have found that in the venous
blood, both of the portal vein and of the general circulation, there
exists a substance soluble in water and absolute alcohol, and pre-
cipitable by ether from its alcoholic solution. This substance is
often considerably more abundant in the portal blood than in that
taken from the general venous system. It adheres closely to the
sides of the glass after precipitation, so that it is always difficult,
and often impossible, to obtain enough of it, mixed with ether, for
microscopic examination. It dissolves, also, like the biliary sub-
stances, with great readiness in water ; but in no instance have we
ever been able to obtain from it such a satisfactory reaction with
Pettenkofer's test, as would indicate the presence of bile. This is
not because the reaction is masked, as might be suspected, by some
of the other ingredients of the blood ; for if at the same time, two
drops of bile be added to half an ounce of blood taken from the
abdominal vena cava, and the two specimens treated alike, the ether-
precipitate may be considered more abundant in the case of the
portal blood ; and yet that from the blood of the vena cava, dis-
solved in water, will give Pettenkofer's reaction for bile perfectly,
while that of the portal blood will give no such reaction.

Notwithstanding, then, the irresistible evidence afforded by the
experiments of Bidder and Schmidt, that the biliary matters are
really taken up by the portal blood, we have failed to recognize
them there by Pettenkofer's test. They must accordingly undergo
certain alterations in the intestine, previously to their absorption,
so that they no longer give the ordinary reaction of the biliary sub-
stances. We cannot say, at present, precisely what these alterations

VARIATIONS AND FUNCTIONS OF BILE. 199

are ; but they are evidently transformations of a catalytic nature,
produced by the contact of the bile with the intestinal juices.

The bile, therefore, is a secretion which has not_jfit accomplished
its function when it is discharged from the liver and poured into the
intestine. On the contrary, during its passage through the intestine
it is still in the interior of the body, in contact with glandular sur-
faces, and mingled with various organic substances, the ingredients
of the intestinal fluids, which act upon it as catalytic bodies, and
produce in it new transformations. This may account for the fact
stated above, that the bile, though a constant and uninterrupted
secretion, is nevertheless poured into the intestine in the greatest
abundance immediately after a hearty meal. This is not because it
is to take any direct part in the digestion of the food ; but because
the intestinal fluids, being themselves present at that time in the
greatest abundance, can then act upon and decompose the greatest
quantity of bile. At all events, the biliary ingredients, after being
altered and transformed in the intestine, as they might be in the
interior of a glandular organ, re-enter the blood under some new
form, and are oarried away by the circulation, to complete their
function in some other part of the body.

200 FORMATION OF SUGAR IN THE LIVER.

CHAPTER IX.

FORMATION OF SUGAR IN THE LITER.

BESIDE the secretion of bile, the liver performs also another
exceedingly important function, viz., the production of sugar by a
metamorphosis of some of its organic ingredients.

Under ordinary circumstances a considerable quantity of sac-
charine matter is introduced with the food, or produced from
starchy substances, by the digestive process, in the intestinal canal.
In man and the herbivorous animals, accordingly, an abundant
supply of sugar is derived from these sources; and, as we have
already shown, the sugar thus introduced is necessary for the proper
support of the vital functions. For though the saccharine matter
absorbed from the intestine is destroyed by decomposition soon
after entering the circulation, yet the chemical changes by which
its decomposition is effected are themselves necessary for the proper
constitution of the blood, and the healthy nutrition of the tissues.
Experiment shows,' however, that the system does not depend, for
its supply of sugar, entirely upon external sources : but that sac-
charine matter is also produced independently, in the tissue of the
liver, whatever may be the nature of the food upon- which the
animal subsists.

This important function was first discovered by M. Claude Ber-
nard1 in 1848, and described by him under the name of the glyco-
genic function of the liver.

It has long been known that sugar may be abundantly secreted,
under some circumstances, when no vegetable matters have been
taken with the food. The milk, for example, of all animals, car-
nivorous as well as herbivorous, contains a notable proportion of
sugar ; and the quantity thus secreted, during lactation, is in some
instances very great. In the human subject, also, when suffering
from diabetes, the amount of saccharine matter discharged with the

1 Nouvelle Fonction du Foie. Paris, 1853.

FORMATION OF SUGAR IN THE LIVER. 201

urine has often appeared to be altogether out of proportion to that
which could be accounted for by the vegetable substances taken as
food. The experiments of Bernard, the most important of which
we have repeatedly confirmed, in common with other investigators,
show that in these instances most of the sugar has an internal
origin, and that it first makes its appearance in the tissue of the
liver.

If a carnivorous animal, as, for example, a dog or a cat, be fed
for several days exclusively upon meat, and then killed, the liver
alone of all the internal organs is found to contain sugar among its
other ingredients. For this purpose, a portion of the organ should
be cut into small pieces, reduced to a pulp by grinding in a mortar
with a little water, and the mixture coagulated by boiling with an
excess of sulphate of soda, in order to precipitate the albuminous
and coloring matters. The filtered fluid will then reduce the oxide
of copper, with great readiness, on the application of Trommer's
test. A decoction of the same tissue, mixed with a little yeast, will
also give rise to fermentation, producing alcohol and carbonic acid,
as is usual with saccharine solutions. On the contrary, the tissues
of the spleen, the kidneys, the lungs, the muscles, &c., treated in
the same way, give no indication of sugar, and do not reduce the
salts of copper. Every other organ in the body may be entirely
destitute of sugar, but the liver always contains it in considerable
quantity, provided the animal be healthy. Even the blood of the
portal vein, examined by a similar process, contains no saccharine
element, and yet the tissue of the organ supplied by it shows an
abundance of saccharine ingredients.

It is remarkable for how long a time the liver will continue to
exhibit the presence of sugar, after all external supplies of this
substance have been cut off. Bernard kept two dogs under his own
observation, one for a period of three, the other of eight months,1
during which period they were confined strictly to ji diet of animal
food (boiled calves' heads and tripe), and then killed. Upon exa-
mination, the liver was found, in each instance, to contain a propor-
tion of sugar fully equal to that present in the organ under ordinary
circumstances.

The sugar, therefore, which is found in the liver after death, is a
normal ingredient of the hepatic tissue. It is not formed in other
parts of the body, nor absorbed from the intestinal canal, but takes

1 Nouvelle Fonction du Foie, p. 50.

202 FORMATION OF SUGAR IN THE LIVER.

its origin in the liver itself; it is produced, as a new formation, by
a secreting process in the tissue of the organ.

The presence of sugar in the liver is common to all species of
animals, so far as is yet known. Bernard found it invariably in
monkeys, dogs, cats, rabbits, the horse, the ox, the goat, the sheep,
in birds, in reptiles, and in most kinds of fish. It was only in two
species of fish, viz., the eel and the ray (Mursena anguilla and Kaia
batis), that he sometimes failed to discover it ; but the failure in
these instances was apparently owing to the commencing putres-
cence of the tissue, by which the sugar had probably been destroyed.
In the fresh liver of the human subject, examined after death from
accidental violence, sugar was found to be present in the proportion
of 1.10 to 2.14 per cent, of the entire weight of the organ.

The following list shows the average percentage of sugar present
in the healthy liver of man and different species of animals, accord-
ing to the examinations of Bernard : —

PERCENTAGE OF SUGAR IN THE LIVER.

In man .... 1.68 In ox . . . 2.30

" monkey . . .2.15 " horse . . .4.08

" dog . . . . 1.69 " goat .... 3.89

" cat . . . . 1.94 " birds . . . 1.49

" rabbit ... 1.94 " reptiles . . . 1.04

" sheep . . . 2.00 " fish . . . .1.45

With regard to the nature and properties of the liver sugar, it
resembles very closely glucose, or the sugar of starch, the sugar of
honey, and the sugar of milk, though it is not absolutely identical
with either one of them. Its solution reduces, as we have seen, the
salts of copper in Trommer's test, and becomes colored brown when
boiled with caustic potassa. It ferments very readily, also, when
mixed with yeast and kept at the temperature of 70° to 100° F.
It is distinguished from all the other sugars, according to Bernard,1
by the readiness with which it becomes decomposed in the blood —
since cane sugar and beet root sugar, if injected into the circulation
of a living animal, pass through the system without sensible decom-
position, and are discharged unchanged with the urine ; sugar of
milk and glucose, if injected in moderate quantity, are decomposed
in the blood, but if introduced in greater abundance make their
appearance also in the urine; wMe_aJ&oliLtiQn of liver sugar, though
injected in much larger quantity than either of the others, may dis-

1 Lemons de Physiologie Experimentale. Paris, 1855, p. 213.

FORMATION OF SUGAR IN THE LIVER. 203

appear altogether in the circulation, without passing off by the
kidneys.

This substance is therefore a sugar of animal origin, similar in
its properties to other varieties of saccharine matter, derived from
different sources.

The sugar of the liver is not produced in the blood by a direct
decomposition of the elements of the circulating fluid in the vessels
of the organ, but takes its origin in the solid substance of the hepatic
tissue, as a natural ingredient of its organic texture. The blood
which may be pressed out from a liver recently extracted from the
body, it is true, contains sugar ; but this sugar it has absorbed from
the tissue of the organ in which it circulates. This is demonstrated
by the singular fact that the fresh liver of a recently killed animal,
though it may be entirely drained of blood and of the sugar which
it contained at the moment of death, will still continue for a certain
time to produce a saccharine substance. If such a liver be injected
with water by the portal vein, and all the blood contained in its
vessels washed out by the stream, the water which escapes by the
hepatic vein will still be found to contain sugar. M. Bernard has
found1 that if all the sugar contained in a fresh liver be extracted in
this manner by a prolonged watery injection, so that neither the
water which escapes by the hepatic vein, nor the substance of the
liver itself, contain any further traces of sugar, and if the organ be
then laid aside for twenty-four hours, both the tissue of the liver and
the fluid which exudes from it will be found at the end of that time
to have again become highly saccharine. The sugar, therefore, is
evidently not produced in the blood circulating through the liver,
but in the substance of the organ itself. Once having originated
in the hepatic tissue, it is absorbed thence by the blood, and trans-
ported by the circulation, as we shall hereafter show, to other parts
of the body.

The sugar which thus originates in the tissue of the liver, is pro-
duced by a mutual decomposition and transformation of various
other ingredients of the hepatic substance ; these chemical changes
being a part of the nutritive process by which the tissue of the
organ is constantly sustained and nourished. There is probably a
series of several different transformations which take place in this
manner, the details of which are not yet known to us. It has been
discovered, however, that one change at least precedes the final

1 Gazette Hebdomadaire, Paris, Oct. 5, 1855.

204 FORMATION OF SUGAR IN THE LIVER.

production of saccharine matter ; and that the sugar itself is pro-
duced by the transformation of another peculiar substance, of ante-
rior formation. This substance, which precedes the formation of
sugar, and which is itself produced in the tissue of the liver, is
known by the name of glycogenic matter, or glycogene.

This glycogenic matter may be extracted from the liver in the
following manner. The organ is taken immediately from the body
of the recently killed animal, cut into small pieces, and coagulated by
being placed for a few minutes in boiling water. This is in order
to prevent the albuminous liquids of the organ from acting upon
the glycogenic matter and decomposing it at a medium temperature.
The coagulated tissue is then drained, placed in a mortar, reduced
to a pulp by bruising and grinding, and afterward boiled in dis-
tilled water for a quarter of an hour, by which the glycogenic
matter is extracted and held in solution by the boiling water.

Thejiquid of decoction, which should be as concentrated as pos-
sible, must then be expressed, strained, and filtered, after which it
appears as a strongly opalescent fluid, of a slightly yellowish tinge.
The glycogenic matter which is held in solution may be precipi-
tated-by the addition to the filtered fluid of five times its volume
of alcohol. The precipitate, after being repeatedly washed with
alcohol in order to remove sugar and biliary matters, may then be
redissolved in distilled water. It may be precipitated from its
watery solution either by alcohol in excess or by crystallizable
acetic acid, in both of which it is entirely insoluble, and may be
afterward kept in the dry state for an indefinite time without losing
its properties.

The glycogenic matter, obtained in this way, is regarded as
intermediate in its nature and properties between hydrated starch
and dextrine. Its ultimate composition, according to M. Pelouze,1

is as follows : —

C,2H120I2.

When brought into contact with iodine, it produces a coloration
varying from violet to a deep, clear, maroon red. It does not
reduce the salts of copper in Trommer's test, nor does it ferment
when placed in contact with yeast at the proper temperature. It
does not, therefore, of itself contain sugar. It may easily be con-
verted into sugar, however, by contact with any of the animal
ferments, as, for example, those contained in the saliva, or in the

1 Journal de Physiologie, Paris, 1858, p. 552.

FORMATION OF SUGAR IN THE LIVER. 205

blood. If a solution of glycogenic matter be mixed with fresh
human saliva, and kept for a few minutes at the temperature of
100° F., the mixture will then be found to have acquired the power
of reducing the salts of copper and of entering into fermentation by
contact with jeast. The glycogenic matter has therefore been
converted into sugar by a process of catalysis, in the same manner
as vegetable starch would be transformed under similar conditions.

The glycogenic matter which is thus destined to be converted
into sugar, is formed in the liver by the processes of nutrition. It
may be extracted, as we have seen above, from the hepatic tissue
of carnivorous animals, and is equally present when they have been
exclusively confined for many days to a meat diet. It. is not in-
troduced with the food ; for the fleshy meat of the herbivora does
not contain it in appreciable quantity, though these animals so
constantly take starchy substances with their food. In them, the
starchy matters are transformed into sugar by digestion, and the
sugar so produced is rapidly destroyed after entering the circula-
tion ; so that usually neither saccharine nor starchy substances are
to be discovered in the muscular tissue. M. Poggiale1 found that in
very many experiments, performed by a commission of the French
Academy for the purpose of examining this subject, glycogenic
matter was detected in ordinary butcher's meat only once. We
have also found it to be absent from the fresh meat of the bullock's
heart, when examined in the manner described above. Neverthe-
less, in dogs fed exclusively upon this food for eight days, glycogenic
matter may be found in abundance in the liver, while it does not
exist in other parts of the body, as the spleen, kidney, lungs, &c.

Furthermore, in a dog fed exclusively for eight days upon the
fresh meat of the bullock's heart, and then killed four hours after
a meal of the same food, at which time intestinal absorption is
going on in full vigor, the liver contains, as above mentioned, both
glycogenic matter and sugar ; but neither sugar nor glycogenic mat-
ter can be found in the blood of the portal vein, when subjected to
a similar examination.

The glycogenic matter, accordingly, does not originate from any
external source, but is formed in the tissue of the liver ; where it
is soon afterward transformed into sugar, while still forming a part
of the substance of the organ.

The formation of sugar in the liver is therefore a function com-

1 Journal de Physiologie, Paris,. 1858, p. 558.

206 FORMATION OF SUGAR IN THE LIVER.

posed of two distinct and successive processes, viz : first, the forma-
tion, in the hepatic tissue, of a glycogenic matter, having some
resemblance to dextrine; and secondly, the conversion of this
glycogenic matter into sugar, by a process of catalysis and trans-
formation.

The sugar thus produced in the substance of the liver is absorbed
from it by the blood circulating in its vessels. The mechanism of
this absorption is probably the same with that which goes on in
other parts of the circulation. It is a process of transudation and
endosmosis, by which the blood in the vessels takes up the saccha-
rine fluids of the liver, during its passage through the organ.
While the blood of the portal vein, therefore, in an animal fed
exclusively upon meat, contains no sugar, the blood of the hepatic
vein, as it passes upward to the heart, is always rich in saccharine
ingredients. This difference can be easily demonstrated by exa-
mining comparatively the two kinds of blood, portal and hepatic,
from the recently killed animal. The blood in its passage through
the liver is found to have acquired a new ingredient, and shows,
upon examination, all the properties of a saccharine liquid.

The sugar produced in the liver is accordingly to be regarded as
a true secretion, formed by the glandular tissue of the organ, by a
similar process to that of other glandular secretions. It differs
from the latter, not in the manner of its production, but only in
the mode of its discharge. For while the biliary matters produced
in the liver are absorbed by the hepatic ducts and conducted down-
ward to the gall-bladder and the intestine, the sugar is absorbed by
the bloodvessels of the organ and carried upward, by the hepatic
veins, toward the heart and the general circulation.

The production of sugar in the liver during health is a constant
process, continuing, in many cases, for several days after the animal
has been altogether deprived of food. Its activity, however, like
that of most other secretions, is subject to periodical augmentation
and diminution. Under ordinary circumstances, the sugar, which
is absorbed by the blood from the tissue of the liver, disappears
very soon after entering the circulation. As the bile is transformed
in the intestine, so the sugar is decomposed in the blood. We are
not yet acquainted, however, with the precise nature of the changes
which it undergoes after entering the vascular system. It is very
probable, according to the views of Lehmann and Eobin, that it is
at first converted into lactic acid (C6H606), which decomposes in
turn the alkaline carbonates, setting free carbonic acid, and forming

FORMATION OF SUGAR IN THE LIVER. 207

lactates of soda and potassa. Bat whatever be the exact mode of
its transformation, it is certain that the sugar disappears rapidly ;
and while it exists in considerable quantity in the liver and in the
blood of the hepatic veins and the right side of the heart, it is not
usually to be found in the pulmonary veins nor in the blood of the
general circulation.

About two and a half or three hours, however, after the ingestion
of food, according to the investigations of Bernard, the circulation
of blood through the portal system and the liver becomes consider-
ably accelerated. A larger quantity of sugar is then produced in
the liver and carried away from the organ by the hepatic veins ;
so that a portion of it then escapes decomposition while passing
through the lungs, and begins to appear in the blood of the arterial
system. Soon afterward it appears also in the blood of the capil-
laries; and from four to six hours after the commencement of
digestion it is produced in the liver so much more rapidly than it
is destroyed in the blood, that the surplus quantity circulates
throughout the body, and the blood everywhere has a slightly sac-
charine character. It does not, however, in the healthy condition,
make its appearance in any of the secretions.

After the sixth hour, this unusual activity of the sugar-producing
function begins again to diminish ; and, the transformation of the
sugar in the circulation going on as before, it gradually disappears
as an ingredient of the blood. Finally, the ordinary equilibrium
between its production and its decomposition is re-established, and
it can no longer be found except in the liver and in that part of
the circulatory system which is between the liver and the lungs.
There is, therefore, a periodical increase in the amount of unde-
composed sugar in the blood, as we have already shown to be the
case with the fatty matter absorbed during digestion; but this
increase is soon followed by a corresponding diminution, and during
the greater portion of the time its decomposition keeps pace with
its production, and it is consequently prevented from appearing in
the blood of the general circulation.

There are produced, accordingly, in the liver, two different secre-
tions, viz., bile and sugar. Both of them originate by transforma-
tion of the ingredients of the hepatic tissue, from which they are
absorbed by two different sets of vessels. The bile is taken up by
the biliary ducts, and by them discharged into the intestine ; while
the sugar is carried off by the hepatic veins, to be decomposed in the
circulation, and become subservient to the nutrition of the blood.

208 THE SPLEEN.

CHAPTER X.

THE SPLEEN.

THE spleen is an exceedingly vascular organ, situated in the
vicinity of the great pouch of the stomach and supplied abund-
antly by branches of the coeliac axis. Its veins, like those of the
digestive abdominal organs, form a part of the great portal system,
and conduct the blood which has passed through it to the liver,
before it mingles again with the general current of the circulation.

The spleen is covered on its exterior by an investing membrane
or capsule, which forms a protective sac, containing the soft pulp
of which the greater part of the organ is composed. This capsule,
in the spleen of the ox, is thick, whitish, and opaque, and is com-
posed to a great extent of yellow elastic tissue. It accordingly
possesses, in a high degree, the physical property of elasticity, and
may be widely stretched without laceration ; returning readily to
its original size as soon as the extending force is relaxed.

In the carnivorous animals, on the other hand, the capsule of
the spleen is thinner, and more colorless and transparent. It con-
tains here but very little elastic tissue, being composed mostly of
smooth, involuntary muscular fibres, connected in layers by a little
intervening areolar tissue. In the herbivorous animals, accordingly,
the capsule of the spleen is simply elastic, while in the carnivora it
is contractile.

In both instances, however, the elastic and contractile properties
of the capsule subserve a nearly similar purpose. There is every
reason to believe that the spleen is subject to occasional and per-
haps regular variations in size, owing to the varying condition of
the abdominal circulation. Dr. William Dobson1 found that the
size of the organ increased, from the third hour after feeding up to
the fifth ; when it arrived at its maximum, gradually decreasing
after that period. When these periodical congestions take place,

1 In Gray, on the Structure and Uses of the Spleen. London, 1854, p. 40.

THE SPLEEN. 209

the organ becoming turgid with blood, the capsule is distended ;
and limits, by its resisting power, the degree of tumefaction to
which the spleen is liable. When the disturbing cause has again
passed away, and the circulation is about to return to its ordinary
condition, the elasticity of the capsule in the herbivora, and its con-
tractility in the carnivora, compress the soft vascular tissue within,
and reduce the organ to its original dimensions. This contractile
action of the invested capsule can be readily seen in the dog or
the cat, by opening the abdomen while digestion is going on,
exposing the spleen and removing it, after ligature of its vessels.
When first exposed, the organ is plump and rounded, and presents
externally a smooth and shining surface. But as soon as it has
been removed from the abdomen and its vessels divided, it begins
to contract sensibly, becomes reduced in size, stiff; and resisting to
the touch ; while its surface, at the same time, becomes uniformly
wrinkled, by the contraction of its muscular fibres.

In its interior, the substance of the spleen is traversed everywhere
by slender and ribbon-like cords of fibrous tissue, which radiate
from the sheath of its principal arterial trunks, and are finally
attached to the internal surface of its investing capsule. These
fibrous cords, or trabeculse, as they are called, by their frequent
branching and mutual interlacement, form a kind of skeleton or
framework by which the soft splenic pulp is embraced, and the
shape and integrity of the organ maintained. They are composed
of similar elements to those of the investing capsule, viz., elastic
tissue and involuntary muscular fibres, united with each other by
a varying quantity of the fibres of areolar tissue.

The interstices between the trabecube of the spleen are occupied
by the splenic pulp; a soft, reddish substance, which contains,
beside a few nerves and lymphatics, capillary bloodvessels in great
profusion, and certain whitish globular bodies, which may be re-
garded as the distinguishing anatomical elements of the organ, and
which are termed the Malpighian bodies of the spleen.

The Malpighian bodies are very abundant, and are scattered
throughout the splenic pulp, being most frequently attached to the
sides, or at the point of bifurcation of some small artery. They
are readily visible to the naked eye in the spleen of the ox, upon a
fresh section of the organ, as minute, whitish, rounded bodies, which
may be separated, by careful manipulation, from the surrounding
parts. In the carnivorous animals, on the other hand, and in the
human subject, it is more difficult to distinguish them by the un-
14

210 THE SPLEEN.

aided eye, though they always exist in the spleen in a healthy
condition. Their average diameter, according to Kolliker, is J.2 of
an inch. They consist of a closed sac, or capsule, containing in
its interior a viscid, semi-solid mass of cells, cell-nuclei, and homo-
geneous substance. Each Malpighian body is cqyered, on its exte-
rior, by a network of fine capillary bloodvessels ; and it is now
perfectly well settled, by the observations of various anatomists
(Kolliker, Busk, Huxley, &c.), that bloodvessels also penetrate into
the substance of the Malpighian body, and there form an internal
capillary plexus.

The spleen is accordingly a glandular organ, analogous in its
minute structure to the solitary and agrninated glands of the small
intestine, and to the lymphatic glands throughout the body. Like
them, it is a gland without an excretory duct ; and resembles, also,
in this respect, the thyroid and thymus glands and the supra-renal
capsules. All these organs have a structure which is evidently
glandular in its nature, and yet the name of glands has been some-
times refused to them because they have, as above mentioned, no
duct, and produce apparently no distinct secretion. We have
already seen, however, that a secretion may be produced in the
interior of a glandular organ, like the sugar in the substance of the
liver, and yet .not be discharged by its excretory duct. The j^eins
of the gland, in this instance, perform the part of excretory ducts.
They absorb the new materials, and convey them, through the
medium of the blood, to other parts of the body, where they suffer
subsequent alterations, and are finally decomposed in the circula-
tion.

The action of such organs is consequently to modify the consti-
tution of the blood. As the blood passes through their tissue, it
absorbs from the glandular substance certain materials which it did
not previously contain, and which are necessary to the perfect con-
stitution of the circulating fluid. The blood, as it passes out from
the organ, has therefore a different composition from that which it
possessed before its entrance ; and on this account the name of vas-
cular glands has been applied to all the glandular organs above
mentioned, which are destitute of excretory ducts, and is eminently
applicable to the spleen.

The precise alteration, however, which is effected in the blood
during its passage through the splenic tissue, has not yet been
discovered. Various hypotheses have been advanced from time to
time, as to the processes which go on in this organ ; many of them

THE SPLEEN. 211

vague and indefinite in character, and some of them directly con-
tradictory of each other. None, however, have yet been offered
which are entirely satisfactory in themselves, or which rest on suf-
ficiently reliable evidence.

A very remarkable fact with regard to the spleen is that it' may
be entirely removed in many of the lower animals, without its loss
producing any serious permanent injury. This experiment has
been frequently performed by various observers, and we have our-
selves repeated it several times with similar results. The organ
may be easily removed, in the dog or the cat, by drawing it out of
the abdomen, through an opening in the median line, placing a few
ligatures upon the vessels of the gastro-splenic omentum, and then
dividing the vessels between the ligatures and the spleen. The
wound usually heals without difficulty'; and if the animal be killed
some weeks afterward, the only remaining trace of the operation
is an adhesion of the omentum to the inner surface of the abdomi-
nal parietes, at the situation of the original wound.

The most constant and permanent effect of a removal of the
spleen is an unusual increase of the appetite. This symptom we
have observed in some instances to be excessively developed ; so
that the animal would at all times throw himself, with an unnatural
avidity, upon any kind of food offered him. We have seen a dog,
subjected to this operation, afterward feed without hesitation upon
the flesh of other dogs ; and even devour greedily the entrails, taken
warm from the abdomen of the recently killed animal. The food
taken in this unusual quantity is, however, perfectly well digested ;
and the animal will often gain very perceptibly in weight. In one
instance, a cat, in whom the unnatural appetite was marked though
not excessive, increased in weight from five to six pounds, in the
course of a little less than two months ; and at the same time the
fur became sleek and glossy, and there was a considerable improve-
ment in the general appearance of the animal.

Another symptom, which usually follows removal of the spleen,
is an unnatural ferocity of disposition. The animal will frequently
attack others, of its own or a different species, without any appa-
rent cause, and without any regard to the difference of size, strength,
&c. This symptom is sometimes equally excessive with that of an
unnatural appetite ; while in other instances it shows itself only in
occasional outbursts of irritability and violence.

Neither of the symptoms, however, which we have just de-
scribed, appears to exert any permanently injurious effect upon the

212 THE SPLEEN.

animal which has been subjected to the operation ; and life may be
prolonged for an indefinite period without any serious disturbance
of the nutritive process, after the spleen has been completely
extirpated.

We must accordingly regard the spleen, not as a single organ,
but as associated with others, which may .completely, or to a great
extent, perform its functions after its entire removal. We have
already noticed the similarity in structure between the spleen and
the mesenteric and lymphatic glands ; a similarity which has led
some writers to regard them as more or less closely associated with
each other in function, and. to consider the spleen as an unusually
developed lymphatic or mesenteric gland. It is true that this
organ is provided with a comparatively scanty supply of lymphatic
vessels ; and the chyle, which is absorbed from the intestine, does
not pass through the spleen, as it passes through the remaining
mesenteric glands. Still, the physiological action of the spleen
may correspond with that of the other lymphatic glands, so far as
regards its influence on the blood ; and there can be little doubt
that its function is shared, either by them or by some other glan-
dular organs, which become unnaturally active, and more or less
perfectly supply its place after its complete removal.

BLOOD-GLOBULES. 213

CHAPTER XI.

THE BLOOD.

THE blood, as it exists in its natural condition, while circulating
in the vessels, is a thick opaque fluid, varying in color in different
parts of the body from a brilliant scarlet to a dark purple. It has
a slightly alkaline reaction, and a specific gravity of 1055. It
is not; however, an entirely homogeneous fluid, but is found on
microscopic examination to consist, first, of a nearly colorless,
transparent, alkaline fluid, termed the plasma, containing water,
fibrin, albumen, salts, &c., in a state of mutual solution; and,
secondly, of a large number of distinct cells, or corpuscles, the
blood- globules, swimming freely in the liquid plasma. These glo-
bules, which are so small as not to be distinguished by the naked
eye, by being mixed thus abundantly with the fluid plasma, give
to the entire mass of the blood an opaque appearance and a uniform
red color.

BLOOD-GLOBULES. — On microscopic examination it is found that
the globules of the blood are of two kinds, viz., red and white ; of
these the red are by far the most abundant.

The red globules of the blood present, under the microscope, a
perfectly circular outline and a smooth exterior. (Fig. 54.) Their
size varies somewhat, in human blood, even in the same specimen.
The greater number of them have a transverse diameter of ^^0 of
an inch ; but there are many smaller ones to be seen, which are
not more than -5^17 or even s^W °f an inca in diameter. Their
form is that of a spheroid, very much flattened on its opposite
surfaces, somewhat like a round biscuit, or a thick piece of money
with rounded edges. The blood-globule accordingly, when seen
flatwise, presents a comparatively broad surface and a circular out-
line («); but if it be made to roll over, it will present itself edge-
wise during its rotation and assume the flattened form indicated at
b. The thickness of the globule, seen in this position, is about

THE BLOOD.

Fig. 54.

of an inch, or a little less than one-fifth of its transverse
diameter.

When the globules are examined lying upon their broad sur-
faces, it can be seen that these surfaces are not exactly flat, but that

there is on each side a slight
central depression, so that
the rounded edges of the
blood-globule are evidently
thicker than its middle por-
tion. This inequality pro-
duces a remarkable optical
effect. The substance of
which the blood-globule is
composed refracts light more
strongly than the fluid plas-
ma. Therefore, when exa-
mined with the microscope,
by transmitted light, the

HUMAN BLOOD-GLOBULES. -«. Red globules, thick edges of the globules
seen flatwise, b. Red globules, seen edgewise, c. ac{; as double COnVCX lenses,
White globule.

and concentrate the light

above the level of the fluid. Consequently, if the object-glass be
carried upward by the adjusting screw of the microscope, and lifted

away from the stage, so that
the blood-globules fall be-
yond its focus, their edges
will appear brighter. But
the central portion of each
globule, being excavated on
both sides, acts as a double
concave lens, and disperses
the light from a point below
the level of the fluid. It,
therefore, grows brighter as
the object-glass is carried
downward, and the object
falls within its focus. An
alternating appearance of the
blood-globules may, there-
fore, be produced by view-
ing them first beyond and then within the focus of the instrument.

Fig. 55.

RED GLOBULES OF THE BLOOD, seen a

beyond the focus of the microscope.

little

BLOOD-GLOBULES.

215

Fie.

THE SAME, seen a little within the focus.

When beyond the focus, the globules will be seen with a bright
rim and a dark centre. (Fig. 55.) When within it they will appear
with a dark rim and a bright
centre. (Fig. 56.)

The blood-globules accord-
ingly have the form of a
thickened disk with rounded
edges and a double central
excavation. They have, con-
sequently, been sometimes
called " blood-disks," instead
of blood -globules. The term
'disk/' however, does not in-
dicate their exact shape, any
more than the other; and
the term "blood-corpuscle."
which is also sometimes used,
does not indicate it at all.
And although the term "blood-globule" may not be precisely a
correct one, still it is the most convenient ; and need not give rise
to any confusion, if we remember the real shape of the bodies de-
signated by it. This term will, consequently, be employed when-
ever we have occasion to
speak of the blood-globules
in the following pages.

Within a minute after being
placed under the microscope,
the blood-globules, after a
fluctuating movement of
short duration, very often
arrange themselves in slight-
ly curved rows or chains, in
which they adhere to each
other by their flat surfaces,
presenting an appearance
which has been aptly com-
pared with that of rolls of

m, . . •,•,-, BLOOD-GLOBULES adhering together, like rolls

coin. This is probably ow- of coin>

ing merely to the coagulation

of the blood, which takes place very rarjidly when it is spread out

in thin layers and in contact with glass surfaces ; and which, by

Fig. 57.

216 THE BLOOD.

compressing the globules, forces them into such a position that they
may occupy the least possible space. This position is evidently
that in which they are applied to each other by their flat surfaces,
as above described.

The color of the blood-globules, when viewed by transmitted
light and spread out in a thin layer, is a light amber or pale yellow.
It is, on the contrary, deep _ red when they are seen by reflected
light, or piled together in comparatively thick layers. When viewed
singly, they are so transparent that the outlines of those lying under-
neath can be easily seen, showing through the substance of the
superjacent globules. Their consistency is peculiar. They are not
solid bodies, as they have been sometimes inadvertently described ;
but on the contrary have a consistency which is very nearly fluid.
They are in consequence exceedingly flexible, and easily elongated,
bent, or otherwise distorted by accidental pressure, or in passing
through the narrow currents of fluid which often establish them-
selves accidentally in a drop of blood under microscopic examina-
tion. This distortion, however, is only temporary, and the globules
regain their original shape, as soon as the accidental pressure is
taken off. The peculiar flexibility and .elasticity thus noticed are
characteristic of the red globules of the blood, and may always
serve to distinguish them from any other free cells which may be
found in the animal tissues or fluids.

In structure the blood-globules are homogeneous. They have
been sometimes erroneously described as consisting of a closed
vesicle or cell-wall, containing in its cavity some fluid or semi-fluid
substance of a different character from that composing the wall of
the vesicle itself. No such structure, however, is really to be seen
in them. Each blood-globule consists of a mass of organized ani-
mal substance, perfectly or nearly homogeneous in appearance, and
of the same color, consistency and composition throughout. In
some of the lower animals (birds, reptiles, fish) it contains also a
granular nucleus, imbedded in the substance of the globule ; but
in no instance is there any distinction to be made out between an
external cell- wall and an internal cavity.

The appearance of the blood-globules is altered by the addition
of various foreign substances. If water be added, so as to dilute
the plasma, the globules absorb it by imbibition, swell, lose their
double central concavity and become paler. If a larger quantity
of water be added, they finally dissolve and disappear altogether.
When a moderate quantity of water is mixed with the blood, the

BLOOD-GLOBULES.

217

Fig. 58.

BLOOD-GLOBULES, swollei
water.

by the imbibition of

edges of the globules, being thicker than the central portions, and
absorbing water more abundantly, become turgid, and encroach
gradually upon the central
part. (Fig. 58.) It is very
common to see the central
depression under these cir-
cumstances, disappear on one
side before it is lost on the
other, so that the globule, as
it swells up, curls over to-
wards one side, and assumes
a peculiar cup-shaped form
(a). This form may often be
seen in blood-globules that
have been soaking for some
time in the urine, or in any
other animal fluid of a less
density than the plasma of
the blood. Dilute acetic acid

dissolves the blood-globules more promptly than water, and solu-
tions of the caustic alkalies more promptly still.

If a drop of blood be allowed partially to evaporate while under
the microscope, the globules
near the edges of the prepa-
ration often diminish in size,
and at the same time present
a shrunken and crenated ap-
pearance, as if minute gran-
ules were projecting from
their surfaces (Fig. 59); an
effect apparently produced
by the evaporation of part
of their watery ingredients.
For some unexplained rea-
son, however, a similar dis-
tortion is often -produced in
some of the globules by the
addition of certain other ani-
mal fluids, as for example the
saliva; and a few can even be seen in this condition after the
addition of pure water.

Fig. 59.

BLOOD-GLOBULES, shrunken, with their margins
crenated.

*

218 THE BLOOD.

The entire mass of the blood- globules, in proportion to the rest
of the circulating fluid, can only be approximately measured by
the eye in a microscopic examination. In ordinary analyses the
globules are usually estimated as amounting to about fifteen per
cent., by weight, of the entire blood. This estimate, however, refers,
properly speaking, not to the globules themselves, but only to their
dry residue, after the water which they contain has been lost by
evaporation. It is easily seen, by examination with the microscope,
that the globules, in their natural semi-fluid condition, are really
much more abundant than this, and constitute fully one-half the
entire mass of the blood • that is, the intercellular fluid, or plasma, is
not more abundant than the globules themselves which are sus-
pended in it. When separated from the other ingredients of the
blood and examined by themselves, the globules are found, ac-
cording to Lehmann, to present the following composition : —

COMPOSITION OF THE BLOOD-GLOBULES IN 1000 PARTS.

Water 688.00

Globuline 282.22

Haematine ........... 16.75

Fatty substances 2.31

Undetermined (extractive) matters 2.60

Chloride of sodium ........

" potassium ........

Phosphates of soda and potassa ......

Sulphate " "

Phosphate of lime

" " magnesia .......

1000.00

The most important of these ingredients is the globuline. This
is an organic substance, nearly fluid in its natural condition by
union with water, and constituting the greater part of the mass of
the blood- globules. It is soluble in water, but insoluble in the
plasma of the blood, owing to the presence in that fluid of albumen
and saline matters. If the blood be largely diluted, however, the
globuline is dissolved, as already mentioned, and the blood-globules
are destroyed. Globuline coagulates by heat; but, according to
Kobin and Yerdeil, only becomes opalescent at 160°, and requires
for its complete coagulation a temperature of 200° F.

The hsematine is the coloring matter of the globules. It is, like
globuline, an organic substance, but is present in much smaller quan-
tity than the latter. It is not contained in the form of a powder,

BLOOD-GLOBULES. 219

mechanically deposited in the globuline, but the two substances are
intimately mingled throughout the mass of the blood-globule, just
as the fibrin and albumen are mingled in the plasma. Haematine
contains, like the other coloring matters, a small proportion of iron.
This iron has been supposed to exist under the form of an oxide;
and to contribute directly in this way to the red color of the sub-
stance in question. But it is now ascertained that although the
iron is found in an oxidized form in the ashes of the blood-globules
after they have been destroyed by heat, its oxidation probably takes
place during the process of incineration. So far as we know, there-
fore, the iron exists originally in the haematine as an ultimate
element, directly combined with the other ingredients of this sub-
stance, in the same manner as the carbon, the hydrogen, or the

nitrogen.

The blood-globules of all the warm-blooded quadrupeds, with
the exception of the family of the camelidae, resemble those of the
human species in shape and structure. They differ, however, some-
what in size, being usually rather smaller than in man. There are
but two species in which they are known to be larger than in man,
viz., the Indian elephant, in which they are ?•>?$•$ °^ an incn» and
the two-toed sloth (Bradypus didactylus), in which they are 3BV^ of
an inch in diameter. In the musk deer of Java they are smaller
than in any other known species, measuring rather less than T2 Jnir
of an inch. The following is a list showing the size of the red
globules of the blood in the principal mammalian species, taken
from the measurement of Mr. Gulliver.1

DIAMETER OF RED GLOBULES IN THE

Ape . . . j^gof an inch. Cat . . . ?Jff5of an inch.

Horse . . . „>„ " Fox ... ^ «

Ox - . . ifa « Wolf . . . ^ «

Sheep. . . ^j " Elephant . .

Goat . . . WJSV " Red deer . .

Dog ... ^ " Musk deer. .

In all these instances the form and general appearance of the
globules are the same. The only exception to this rule among the
mammalians is in the family of the camelidae (camel, dromedary,
lama), in which the globules present an oval outline instead of a
circular one. In other respects they resemble the foregoing.

In the three remaining classes of vertebrate animals, viz., birds,

1 In Works of William Hevrson, Syrtenham edition, London, 1846, p. 327.

220

THE BLOOD.

rjj.pti.les, and fish, the blood-globules differ so much from the above
that they can be readily distinguished by microscopic examination.
They are oval in form, and contain a colorless granular nucleus
imbedded in their substance. They are also considerably larger
than the blood-globules of the mammalians, particularly in the

class of reptiles. In the frog

Fig. 60. (Fig. 60) they measure T^T

of an inch in their long
diameter ; and in Menobran-
chus, the great water lizard
of the northern lakes, 7^^ of
an inch. In Proteus angui-
nus they attain the size, ac-
cording to Dr. Carpenter,1 of
•5^7 of an inch.

Beside the corpuscles de-
scribed above, there are glo-
bules of another kind found
in the blood, viz., the white
globules. These globules are
very much less numerous
than the red; the proportion

between the two, in human blood, being one white to two or three
hundred red globules. In reptiles, the relative quantity of the
white globules is greater, but they are always considerably less
abundant than the red. They differ also from the latter in shape,
size, color, and consistency. They are globular in form, white or
colorless, and instead of being homogeneous like the others, their
substance is filled everywhere with minute dark molecules, which
give them a finely granular appearance. (Fig. 54, c.) In size they
are considerably larger than the red globules, being about 25V<r of
an inch in diameter. They are also more consistent than the others,
and do not so easily glide along in the minute currents of a drop of
blood under examination, but adhere readily to the surfaces of the
glass. If treated with dilute acetic acid, they swell up and become
smooth and circular in outline ; and at the same time a separation
or partial coagulation seems to take place in the substance of which
they are composed, so that an irregular collection of granular
matter shows itself in their interior, becoming more divided and

BLOOD-GLOBUL KS OF FROG.
seen edgewise, b. White-globule.

a. Blood-globule

The Microscope and its Revelations, Philadelphia edition, p. 600.

BLOOD- GLOBULES.

221

Fig. 61.

broken up as the action of the acetic acid upon the globule is
longer continued. (Fig. 61.) This collection of granular matter
often assumes a curved or crescentic form, as at a, and sometimes
various other irregular shapes. It does not indicate the existence
of a nucleus in the white globule, but it is merely an appearance
produced by the coagulating
and disintegrating action of
acetic acid upon the substance
of which it is composed.

The chemical constitution
of the white globules, as
distinguished from the red,
has never been determined ;
owing to the small quantity
in which they occur, and the
difficulty of separating them
from the others for purposes
of analysis.

The two kinds of blood-
globules, white and red, are
to be regarded as distinct
and independent anatomical
forms. It has been sometimes supposed that the white globules
were converted, by a gradual transformation, into the red. There
is, however, no direct evidence of this ; as the transformation has
never been seen to take pla%e, either in the human subject or in
the mammalia, nor even its intermediate stages satisfactorily ob-
served. When, therefore, in default of any such direct evidence,
we are reduced to the surmise which has been adopted by some
authors, viz., that the change " takes place too rapidly to be de-
tected by our means of observation,"1 it must be acknowledged
that the above opinion has no solid foundation. It has been stated
by some authors (Kolliker, Gerlach) that in the blood of the
batrachian reptiles there are to be seen certain bodies intermediate
in appearance between the white and the red globules, and which
represent different stages of transition from one form to the other ;
but this is not a fact which is generally acknowledged. We have
repeatedly examined, with reference to this point, the fresh blood
of the frog, as well as that of the menobranchus, in which the large

WHITK GLOBULES OF THE BLOOD; altered by
dilute acetic acid.

Kolliker, Handbuch der Gewebelehre, Leipzig, 1652, p. 582.

222 THE BLOOD.

size of the globules would give every opportunity for detecting any
such changes, did they really exist ; and it is our unavoidable con-
clusion from these observations, that there is no good evidence, even
in the blood of reptiles, of any such transformation taking place.
There is simply, as in human blood, a certain variation in size and
opacity among the red globules; but no such connection with, or
resemblance to, the white globules as to indicate a passage from one
form to the other. The red and white globules are therefore to be
regarded as distinct and independent anatomical elements. They
are mingled together in the blood, just as capillary bloodvessels and
nerves are mingled in areolar tissue ; but there is no other connection
between them, so far as their formation is concerned, than that of
juxtaposition.

Neither is it at all probable that the red globules are produced or
destroyed in any particular part of the body. One ground for the
belief that these bodies were produced by a metamorphosis of the
white globules was a supposition that they were continually and
rapidly destroyed somewhere in the circulation ; and as this loss
must be as rapidly counterbalanced by the formation of new glo-
bules, and as no other probable source of their reproduction ap-
peared, they were supposed to be produced by transformation of
the white globules. But there is no reason for believing that the
red globules of the blood are any less permanent, as anatomical
forms, than the muscular fibres or the nervous filaments. They
undergo, it is true, like all the constituent parts of the body, a
constant interstitial metamorphosis. They absorb incessantly nu-
tritious materials from the blood, and give up to the circulating
fluid, at the same time, other substances which result from their
internal waste and disintegration. But they do not, so far as we
know, perish bodily in any part of the circulation. It is not the
anatomical forms, anywhere, which undergo destruction and reno-
vation in the nutritive process ; but only the proximate principles of
which they are composed. The effect of this interstitial nutrition,
therefore, in the blood-globules as in the various solid tissues, is
merely to maintain them in a natural and healthy condition of
integrity. Their ingredients are incessantly altered, by transforma-
tion and decomposition, as they pass through various parts of the
vascular system; but the globules themselves retain their form
and texture, and still remain as constituent parts of the circulating
fluid.

PLASMA.

223

8.55

PLASMA. — The plasma of the blood, according to Lehmann, has
the following constitution : —

COMPOSITION OF THE PLASMA i>* 1,000 PARTS.

Water 902.90

Fibrin 4.05

Albumen 78.84

Fatty matters 1.72

Undetermined (extractive) matters ...... 3.94

Chloride of sodium '.

potassium ....

Phosphates of soda and potassa .
Sulphates " "...

Phosphate of lime .....

magnesia ....

1000. 00

The above ingredients are all intimately mingled in the blood-
plasma, in a fluid form, by mutual solution; but they may be sepa-
rated from each other for examination by appropriate means. The
two ingredients belonging to the class of organic substances are the
fibrin and the albumen.

The fibrin, though present in small quantity, is evidently an Jm-
portant element in the constitution of the blood. It may be ob-
tained in a tolerably pure form by gently stirring freshly drawn
blood with a glass rpd or a bundle of twigs ; upon which the fibrin
coagulates, and adheres to the twigs in the form of slender threads
and flakes. The fibrin, thus coagulated, is at first colored red by
the haematine of the blood-globules entangled in it ; but it may be
washed colorless by a few hours' soaking in running water. The
fibrin then presents itself

under the form of nearly
white threads and flakes,
having a semi-solid consist-
ency, and a considerable de-
gree of elasticity.

The coagulation of fibrin
takes place in a peculiar
manner. It does not solidify
in a perfectly homogeneous
mass; but if examined by the
microscope in thin layers it
is seen to have a fibroid or
filamentous texture. In this
condition it is said to be
"fibrillated.v(Fig.62.) The

Fig. 62.

showing its fibrillated con-

dition.

22-i THE BLOOD.

filaments of which it is composed are colorless and elastic, and when
isolated are seen to be exceedingly minute, being not more than
4¥tio(j or even 5 (j no IT °f an mcn i*1 diameter. They are in part
arranged so as to lie parallel with each other ; but are more gene-
rally interlaced in a kind of irregular network, crossing each other
in every direction. On the addition of dilute acetic acid, they swell
up and fuse together into a homogeneous mass, but do not dissolve.
They are often interspersed everywhere with minute granular mole-
cules, which render their outlines more or less obscure.

Once coagulated, fibrin is insoluble in water and can only be
again liquefied by the action of an alkaline or strongly saline solu-
tion, or by prolonged boiling at a very high temperature. These
agents, however, produce a complete alteration in the properties of
the fibrin, and after being subjected to them it is no longer the
same substance as before.

The quantity of fibrin in the blood varies in different parts of the
body. According to the observations of various writers,1 there is
more fibrin generally in arterial than in venous blood. The blood
of the veins near the heart, again, contains a smaller proportion of
fibrin than those at a distance. The blood of the portal vein con-
tains less than that of the jugular ; and that of the hepatic vein less
than that of the portal.

The albumen is undoubtedly the most important ingredient of the
plasma, judging both from its nature and the abundance in which
it occurs. It coagulates at once on being heated to 160° F., or by
contact with alcohol, the mineral acids, the metallic salts, or with
ferrocyanide of potassium in an acidulated solution. It exists natu-
rally in the plasma in a fluid form by reason of its union with
water. The greater part of the water of the plasma, in fact, is in
union with the albumen ; and when the albumen coagulates, the
water remains united with it, and assumes at the same time the
solid form. If the plasma of the blood, therefore, after the removal
of the fibrin, be exposed to the temperature of 160° F., it solidifies
almost completely ; so that only a few drops of water remain that
can be drained away from the coagulated mass. The phosphates
of lime and magnesia are also held in solution principally by the
albumen, and are retained by it in coagulation.

The fatty matters exist in the blood mostly in a saponified form,
excepting soon after the digestion of food rich in fat. At that
period, as we have already mentioned, the emulsioned fat finds its

Robin and VerJeil, op. cit., vol. ii. p. 202.

COAGULATION OF THE BLOOD. 225

way into the blood, and circulates for a time uncoanged. After-
ward it disappears as free fat, and remains partly in the saponified
condition.

The saline ingredients of the plasma are of the same nature with
those existing in the globules. The chlorides of sodium and potas-
sium, and the phosphates of soda and potassa are the most abundant
in both, while the sulphates are present only in minute quantity.
The proportions in which the various salts are present are very dif-
ferent, according to Lehmann,1 in the blood-globules and in the
plasma. Chloride of potassium is most abundant in the globules,
chloride of sodium in the plasma. The phosphates of soda and
potassa are more abundant in the globules than in the plasma. On
the other hand, the phosphates of lime and magnesia are more
abundant in the plasma than in the globules.

The substances known under the name of extractive matters consist
of a mixture of different ingredients, belonging mostly to the class
of organic substances, which have not yet been separated in a state
of sufficient purity to admit of their being thoroughly examined
and distinguished from each other. They do not exist in great
abundance, but are undoubtedly of considerable importance in the
constitution of the blood. Beside the substances enumerated in the
above list, there are still others which occur in small quantity as
ingredients of the blood. Among the most important are the alka-
line carbonates, which are held in solution in the serum. It has
already been mentioned that while the phosphates are most abun-
dant in the blood of the carnivora, the carbonates are most abun-
dant in that of the herbivora. Thus Lehmann2 found carbonate of
soda in the blood of the ox in the proportion of 1.628 per thousand
parts. There are also to be found, in solution in the blood, urea,
urate of soda, creatine, creatinine, sugar, &c. ; all of them crystalliza-
ble substances derived from the transformation of other ingredients
of the blood, or of the tissues through which it circulates. The
relative quantity, however, of these substances is very minute, and
has not yet been determined with precision.

COAGULATION OF THE BLOOD. — A few moments after the blood
has been withdrawn from the vessels, a remarkable phenomenon
presents itself, viz., its coagulation or clotting. This process com-
mences at nearly the same time throughout the whole mass of the
blood. The blood becomes first somewhat diminished in fluidity,

1 Op. cit., vol. i. p. 546. 2 Op. cit., vol. i. p. 393.

15

226 THE BLOOD.

so that it will not run over the edge of the vessel, when slightly
inclined ; and its surface may be gently depressed with the end of
the finger or a glass rod. It then becomes rapidly thicker, and at
last solidifies into a uniformly red, opaque, consistent, gelatinous
mass, which takes the form of the vessel in which the blood was
received. Its coagulation is then complete. The process usually
commences, in the case of the human subject, in about fifteen min-
utes after the blood has been drawn, and is completed in about
twenty minutes.

The coagulation of the blood is dependent entirely upon the
presence of the fibrin. This fact has been demonstrated in various
ways. In the first place, if frog's blood be filtered, so as to separate
the globules and leave them upon the filter, while the plasma is
allowed to run through, the colorless filtered fluid which contains
the fibrin soon coagulates ; while no coagulation takes place in the
moist globules remaining on the filter. Again, if the freshly drawn
blood be stirred with a bundle of rods, as we have already de-
scribed above, the fibrin coagulates upon them by itself, while the
rest of the plasma, mixed with the globules, remains perfectly fluid.
It is the fibrin, therefore, which, by its own coagulation, induces
the solidification of the entire blood. As the fibrin is uniformly
distributed throughout the blood, when its coagulation takes place
the minute filaments which make their appearance in it entangle
in their meshes the globules and the albuminous fluids of the
plasma. A very small quantity of fibrin, therefore, is sufficient to
entangle by its coagulation all the fluid and semi-fluid parts of the
blood, and convert the whole into a volumi-
Fig. 63. nous, trembling, jelly-like mass, which is

known by the name of the "erassamenturn,"
or "clot." (Fig. 63.)

As soon as the clot has fairly formed, it
begins to contract and diminish in size. Ex-
actly how this contraction of the clot is pro-
duced, we are unable to say; but it is proba-
bly a continuation of the same process by
of recently Co AOU- which its solidificationis atfirst accomplished,
BLOOD showing the Qr t j t similar to it. As the

whole mass uniformly sohdi- *

fied contraction proceeds, the albuminous fluids

begin to be pressed out from the meshes in

which they were entangled. A few isolated drops first appear on
the surface of the clot. These drops soon increase in size and be-

COAGULATION OF THE BLOOD.

227

Fig. 64.

come more numerous. They run together and coalesce with each
other, as more and more fluid exudes from the coagulated mass,
until the whole surface of the clot is covered with a thin layer of
fluid. The clot at first adheres pretty strongly to the sides of the
vessel into which the blood was drawn ; but as its contraction goes
on, its edges are separated, and the fluid continues to exude between
it and the sides of the vessel. This exudation
continues for ten or twelve hours ; the clot
growing constantly smaller and firmer, and
the expressed fluid more and more abundant.
The globules, owing to their greater con-
sistency, do not escape with the albuminous
fluids, but remain entangled in the fibrinous
coagulum. Finally, at the end of ten or
twelve hours the whole of the blood has
usually separated into two parts, viz., the clot Bowl of
which is a red, opaque, dense and resisting BI.OOD, after twelve hours;

•<_ . ™ showing the clot contracted

semi-solid mass, consisting of the fibrin and ami floating in the fluid serum,
the blood-globules ; and the serum, which is a

transparent, nearly colorless fluid, containing the water, albumen^
and saline matters of the plasma. (Fig. 64.)

The change of the blood in coagulation may therefore be ex-
pressed as follows : —

Before coagulation the blood consists of

1st. GLOBULES ; and 2d. PLASMA — containing

Fibrin,
Albumen,
Water,
[ Salts.

After coagulation it is separated into

r Albumen,

1st. CLOT, containing | ! ™" *x and 2d. SERCM, containing ] Water,

' Salts.

The coagulation of the blood is hastened or retarded by various
physical conditions, which have been studied with care by various
observers, but more particularly by Robin and Yerdeil. The con-
ditions which influence the rapidity of coagulation are as follows :
First, the rapidity with which the blood is drawn from the vein,
and the size of the orifice from which it flows. If blood be drawn
rapidly, in a full stream, from a large orifice, it remains fluid for a
comparatively long time ; if it be drawn slowly, from a narrow
orifice, it coagulates quickly. Thus it usually happens that in the
operation of venesection, the blood drawn immediately after the

228 THE BLOOD.

opening of the vein runs freely and coagulates slowly ; while that
which is drawn toward the end of .the operation, when the tension
of the veins has been relieved and the blood trickles slowly from
the wound, coagulates quickly. Secondly, the shape of the vessel
into which the blood is received and the condition of its internal
surface. The greater, the extent of surface over which the blood
comes in contact with the vessel, the more is its coagulation
hastened. Thus, if the blood be allowed to flow into a tall, narrow,
cylindrical vessel, or into a shallow plate, it coagulates more rapidly
than if it be received into a hemispherical bowl, in which the ex-
tent of surface is less, in proportion to the entire quantity of blood
which it contains. For the same reason, coagulation takes place
more rapidly in a vessel with a roughened internal surface, than in
one which is smooth and polished. The blood coagulates most
rapidly when spread out in thin layers, and entangled among the
fibres of cloth or sponges. For the same reason, also, hemorrhage
continues longer from an incised wound than from a lacerated one ;
because the blood, in flowing over the ragged edges of the lace-
rated bloodvessels and tissues, solidifies upon them readily, and thus
blocks up the wound.

In all these cases, there is an inverse relation between the rapidity
of coagulation and the firmness of the clot. When coagulation
takes place slowly, the clot afterward becomes small and dense, and
the serum is abundant. When coagulation is rapid, there is but
little contraction of the coagulum, an imperfect separation of the
serum, and the clot remains large, soft, and gelatinous.

It is well known to practical physicians that a similar relation
exists when the coagulation of the blood is hastened or retarded by
disease. In cases of lingering and exhausting illness, or in diseases
of a typhoid or exanthernatous character, with much depression of
the vital powers, the blood coagulates rapidly and the clot remains
soft. In cases of active inflammatory disease, as pleurisy or pneu-
monia, occurring in previously healthy subjects, the blood coagulates
slowly, and the clot becomes very firm. In every instance, the
blood which has coagulated liquefies again at the commencement of
putrefaction.

The coagulation of the fibrin is not a commencement of organization.
The filaments already described, which show themselves in the clot
(Fig. 62), are not, properly speaking, organized fibres, and are en-
tirely different in their character from the fibres of areolar tissue, or
any other normal anatomical elements. They are simply the ulti-

COAGULATION OF THE BLOOD. 229

mate form which fibrin assumes in coagulating, just as albumen
takes the form of granules under the same circumstances. The
coagulation of fibrin does not differ in character from that of any
other organic substance ; it merely differs in the physical conditions
which give rise to it. All the coagulable organic substances are
naturally fluid, and coagulate only when they are placed under
certain unusual conditions. But the particular conditions neces-
sary for coagulation vary with the different organic substances.
Thus albumen coagulates by the application of heat. Casein, which
is not affected by heat, coagulates by contact with an acid Jaody.
Pancreatine, again, is coagulated by contact with sulphate of mag-
nesia, which has no effect on albumen. So fibrin, which is naturally
fluid, and which remains fluid so long as it is circulating in the
vessels, coagulates when it is withdrawn from them and brought in
contact with unnatural surfaces. Its coagulation, therefore, is no
more "spontaneous," properly speaking, than that of any other
organic substance. Still less does it indicate anything like organ-
ization, or even a commencement of it. On the contrary, in the
natural process of nutrition, fibrin is assimilated by the tissues
and takes part in their organization, only when it is absorbed by
them from the bloodvessels in a fluid form. As soon as it is once
coagulated by any means, it passes into an unnatural condition, and
must be again liquefied and absorbed into the blood before it can
be assimilated.

As the fibrin, therefore, is maintained in its natural condition of
fluidity by the movement of the circulating blood in the interior of
the vessels, anything which interferes with this circulation will in-
duce its coagulation. If a ligature be placed upon an artery in the
living subject, the blood which stagnates above the ligature coagu-
lates, just as it would do if entirely removed from the circulation.
If the vessel be ruptured or lacerated, the blood which escapes from
it into the areolar tissue coagulates, because here also it is with-
drawn from the circulation. It coagulates also in the interior of
the vessels after death owing to the same cause, viz : stoppage of
the circulation. During the last moments of life, when the flow of
blood through the cavities of the heart is impeded, the fibrin often
coagulates, in greater or less abundance, upon the moving chordas
tendinea? and the edges of the valves, just as it would do if with-
drawn from the body and stirred with a bundle of twigs. In every
instance, the coagulation of the fibrin is a morbid phenomenon, de-
pendent on the cessation or disturbance of the circulation.

230

TIIE BLOOD.

Fig. 65.

Vertical section of a RE-
CENT CoAauLUM, showing
the greater accumulation of
blood-globules at the bottom.

If the blood be allowed to coagulate in a bowl, and the clot be
then divided by a vertical section, it will be seen that its lower
portion is softer and of a deeper red than the upper. (Fig. 65.)
This is because the globules, which are of
greater specific gravity than the plasma, sink
toward the bottom of the vessel before coagu-
lation takes place, and accumulate in the
lower portion of the blood. This deposit of
the globules, however, is only partial; be-
cause they are soon fixed and entangled by
the solid mass of the coagulum, and are thus
retained in the position in which they hap-
pen to be at the moment that coagulation
takes place.

If the coagulation, however, be delayed
longer than usual, or if the globules sink more rapidly than is cus-
tomary, they will have time to subside entirely from the upper por-
tion of the blood, leaving a layer at the surface which is composed
of plasma alone. When coagulation then takes place, this upper
portion solidifies at the same time with the rest, and the clot then
presents two different portions, viz., a lower portion of a dark red
color, in which the globules are accumulated, and an upper portion
from which the globules have subsided, and which is of a grayish
white color and partially transparent. This whitish layer on the
surface of the clot is termed the " buffy coat ;" and the blood pre-
senting it is said to be " buffed." It is an appearance which often
presents itself in cases of acute inflammatory disease, in which the
coagulation of the blood is unusually retarded.

When a clot with a buffy coat begins to contract, the contrac-
tion takes place perfectly well in its upper
portion, but in the lower part it is impeded
by the presence of the globules which have
accumulated in large quantity at the bottom
of the clot. While the lower part of the
coagulum, therefore, remains voluminous,
and hardly separates from the sides of the
vessel, its upper colorless portion diminishes
very much in size ; and as its edges separate

Bowl of COAGULATED J

BLOOD, showing the clot from the sides of the vessel, they curl over
buffed and cupped. toward each other, so that the upper surface

of the clot becomes more or less excavated or cup-shaped. (Fig. 66.)

Fig. 66.

COAGULATION OF TIIE BLOOD. 231

The blood is then said to be " buffed and cupped." These appear-
ances do not present themselves under ordinary conditions, but only
when the blood has become altered by disease.

The entire quantity of blood existing in the body has never been
very accurately ascertained. It is not possible to extract the whole
of it by opening the large vessels, since a certain portion will always
remain in the cavities of the heart, in the veins, and in the capil-
laries of the head and abdominal organs. The other methods
which have been practised or proposed from time to time are all
liable to some practical objection. We have accordingly only
been able thus far to ascertain the minimum quantity of blood
existing in the body. Weber and Lehmann1 ascertained as nearly
as possible the quantity of blood in two criminals who suffered
death by decapitation ; in both of which cases they obtained essen-
tially similar results. The body weighed before decapitation 133
pounds avoirdupois. The blood which escaped from the vessels at
the time of decapitation amounted to 12.27 pounds. In order to
estimate the quantity of blood which remained in the vessels, the
experimenters then injected the arteries of the head and trunk with
water, collected the watery fluid as it escaped from the veins, and
ascertained how much solid matter it held in solution. This
amounted to 477.22 grains, which corresponded to 4.38 pounds of
blood. The result of the experiment is therefore as follows : —

Blood which escaped from the vessels 12.27 pounds.

" remained in the body 4.38 "

Whole quantity of blood in the living body, 16.65

The weight of the blood, then, in proportion to the entire weight
of the body, was as 1 : 8 ; and the body of a healthy man, weighing
140 pounds, will therefore contain on the average at least 17 J
pounds of blood.

1 Physiological Chemistry, vol. i. p. 638.

232 RESPIRATION.

CHAPTEE XII.

BESPIRATION.

THE blood as it circulates in the arterial system has a bright
scarlet color ; but as it passes through the capillaries it gradually
becomes darker, and on its arrival in the veins its color is a deep
purple, and in some parts of the body nearly black. There are,
therefore, two kinds of blood in the body ; arterial blood, which is
of a bright color, and venous blood, which is dark. Now it is found
that the dark-colored venous blood, which has been contaminated
by passing through the capillaries, is unfit for further circulation.
It is incapable, in this state, of supplying the organs with their
healthy stimulus and nutrition, and has become, on the contrary,
deleterious and poisonous. It is accordingly carried back to the
heart by the veins, and thence sent to the lungs, where it is recon-
verted into arterial blood. The process by which the venous blood
is thus arterialized and renovated, is known as the process of
respiration.

This process takes place very actively in the higher animals, and
probably does so to a greater or less extent in all animals without
exception. Its essential conditions are that the circulating fluid
should be exposed to the influence of atmospheric air, or of an
aerated fluid ; that is, of a fluid holding atmospheric air or oxygen
in solution. The respiratory apparatus consists essentially of a
moist and permeable animal membrane, the respiratory membrane,
with the bloodvessels on one side of it, and the air or aerated fluid
on the other. The blood and the air, consequently, do not come in
direct contact with each other, but absorption and exhalation take
place from one to the other through the thin membrane which lies
between.

The special anatomical arrangement of the respiratory apparatus
differs in different species of animals. In most of those inhabiting
the water, the respiratory organs have the form of gills or branchiae ;
that is, delicate filamentous prolongations of some part of the

RESPIRATION. 233

integument or mucous membranes, which contain an abundant
supply of bloodvessels, and which hang out freely into the sur-
rounding water. In many kinds of aquatic lizards, as, for exam-
ple, in menobranchu-s (Fig. 67),
there are upon each side of the
neck three delicate feathery
tufts of thread-like prolonga-
tions from the mucous mem-
brane of the pharynx, which
pass out through fissures in
the side of the neck. Each
tuft is composed of a prin-
cipal stem, upon which^the HEAD AXD GILLS OF MEXOBBAircHi;-.
filaments are arranged in a

pinnated form, like the plume upon the shaft of a feather. Each
filament, when examined by itself, is seen to consist of a thin, rib-
bon-shaped fold of mucous membrane, in the interior of which
there is a plentiful network of minute bloodvessels. The dark
blood, as it comes into the filament from the branchial artery, is
exposed to the influence of the water in which the filament is
bathed, and as it circulates through the capillary network of the
gills is reconverted into arterial blood. It is then carried away by
the branchial vein, and passes into the general current of the cir-
culation. The apparatus is further supplied with a cartilaginous
framework, and a set of muscles by which the gills are gently waved
about in the surrounding water, and constantly brought into con-
tact with fresh portions of the aerated fluid.

Most of the aquatic animals breathe by gills similar in all their
essential characters to those described above. In terrestrial and
air-breathing animals, however, the respiratory apparatus is situated
internally. In them, the air is made to penetrate into the interior
of the body, into certain cavities or sacs called the lungs, which
are lined with a vascular mucous membrane. In the salamanders,
for example, which, though aquatic in their habits, are air-breathing
animals, the lungs are two long cylindrical sacs, running nearly the
entire length of the body, commencing anteriorly by a communi-
cation with the pharynx, and terminating by rounded extremities
at the posterior part of the abdomen. These lungs, or air-sacs,
have a smooth internal surface ; and the blood which circulates
through their vessels is arterialized by exposure to the air contained
in their cavities. The air is forced into the lungs by a kind of

234 BKSPIBATiON.

swallowing movement, and is after a time regurgitated and dis-
charged, in order to make room for a fresh supply.

In frogs, turtles, serpents, &c., the structure of the lung is a
little more complicated, since respiration is more active in these
animals, and a more perfect organ is requisite to accomplish the
arterial ization of the blood. In these animals, the cavity of the
lung, instead of being simple, is divided by incomplete partitions
into a number of smaller cavities or " cells." The cells all commu-
nicate with the central pulmonary cavity ; and the partitions, which
join each other at various angles, are all composed of thin, pro-
jecting folds of the lining membrane, with bloodvessels ramifying
between them. (Fig. 68.) By this arrangement,
Fig. 68. tne extent Of surface presented to the air by the

pulmonary membrane is much increased, and the
arterialization of the blood takes place with a
corresponding degree of rapidity.

In the human subject, and in all the warm-
blooded quadrupeds, the lungs are constructed
on a plan which is essentially similar to the
above, and which differs from it only in the
greater extent to which the pulmonary cavity is
subdivided, and the surface of the respiratory
membrane increased. The respiratory apparatus
(Fig. 69) commences with the larynx, which
communicates with the pharynx at the upper part of the neck.
Then follows the trachea, a membranous tube with cartilaginous
rings ; which, upon its entrance into the chest, divides into the right
and left bronchus. These again divide successively into secondary
and tertiary bronchi; the subdivision continuing, while the bron-
chial tubes grow smaller and more numerous, and separate con-
stantly from each other. As they diminish in size, the tubes grow
more delicate in structure, and the cartilaginous rings and plates
disappear from their walls. They are finally reduced, according to
Kolliker, to the size of 2V °f an mcn in diameter ; and are com-
posed only of a thin mucous membrane, lined with pavement epi-
thelium, which rests upon an elastic fibrous layer. They are then
known as the " ultimate bronchial tubes."

Each ultimate bronchial tube terminates in a division or islet of
the pulmonary tissue, about T'2 of an inch in diameter, which is
termed a " pulmonary lobule." Each pulmonary lobule resembles
in its structure the entire frog's lung in miniature. It consists of a

RESPIRATION.

_ Fig. 69.

235

Fig. 70.

HUMAN LARYNX, TRACHEA, BRONCHI, AND LUNGS; showing the ramification of the
bronchi, and the division of the lungs into lobules.

vascular membrane inclosing a cavity; which cavity is divided
into a large number of secondary compartments by thin septa or
partitions, which project from its internal surface. (Fig. 70.) These
secondary cavities are the "pulmonary
cells," or " vesicles." Each vesicle is about
7*5 of an inch in diameter ; and is covered
on its exterior with a close network of ca-
pillary bloodvessels, which dip down into
the spaces between the adjacent vesicles, and
expose in this way a double surface to the
air which is contained in their cavities.
Between the vesicles, and in the interstices
between the lobules, there is a large quan-
tity of yellow elastic tissue, which gives
firmness and resiliency to the pulmonary
structure. The pulmonary vesicles, accord-

.-, i , n T7-.-1T1 SlNGT.ELOBCLEOFHu-

ing to the observations of Kolhker, are MAMLlJNG._a. ultimate bn>n-
lined everywhere with a layer of pa3£einent chial tube- 6- cavitv of icbnie.

J . c,c,c. Pulmonary cells, or vest-

epithelium, continuous with that in the cies.

236 RESPIRATION.

ultimate bronchial tubes. The whole extent of respiratory sur-
face in both lungs has been calculated by Lieberkiihn1 at fourteen
hundred square feet. It is plainly impossible to make a precisely
accurate calculation of this extent; but there is every reason to
believe that the estimate adopted by Lieberkiihn, regarded as
approximative, is not by any means an exaggerated one. The
great multiplication of the minute pulmonary vesicles, and of the
partitions between them, must evidently increase to an extraor-
dinary degree the extent of surface over which the blood, spread
out in a thin layer, is exposed to the action of the air. These
anatomical conditions are, therefore, the most favorable for its rapid
and complete arterialization.

EESPIRATORY MOVEMENTS OF THE CHEST. — The air which is con-
tained in the pulmonary lobules and vesicles becomes rapidly vitiated
in the process of respiration, and requires therefore to be expelled
and replaced by a fresh supply. This exchange or renovation of
the air is effected by alternate movements of the chest, of expansion
and collapse, which are termed the " respiratory movements of the
chest." The expansion of the chest is effected by two sets of mus-
cles, viz., first, the diaphragm, and, second, the intercostals. While
the diaphragm is in a state of relaxation, it has the form of a vaulted
partition between the thorax and abdomen, the edges of which are
attached to the inferior extremity of the sternum, the inferior
costal cartilages, the borders of the lower ribs and the bodies of
the lumbar vertebra^ while its convexity rises high into the cavity
of the chest, as far as the level of the fifth rib. When the fibres
of the diaphragm contract, their curvature is necessarily dimi-
nished ; and they approximate a straight line, exactly in proportion
to the extent of their contraction. Consequently, the entire con-
vexity of the diaphragm is diminished in the same proportion,
and it descends toward the abdomen, enlarging the cavity of the
chest from above downward. (Fig. 71.) At the same time the inter-
costal muscles enlarge it in a lateral direction. For the ribs, arti-
culated behind with the bodies of the vertebra?, and joined in front
to the sternum by the flexible and elastic costal cartilages, are so
arranged that, in a position of rest, their convexities look obliquely
outward and downward. When the movement of inspiration is
about to commence, the first rib is fixed by the contraction of the

1 In Simon's Chemistry of Man, Philada ed., 1846, p. 109.

RESPIRATORY MOVEMENTS OF THE CHEST.

237

Fig. 71.

scaleni muscles, and the intercostal muscles then contracting simul-
taneously, the ribs are drawn upward. In this movement, as each
rib rotates upon its articulation with the
spinal column at one extremity, and with
the sternum at the other, its convexity is
necessarily carried outward at the same
time that it is drawn upward, and the pa-
rietes of the chest are, therefore, expanded
laterally. The sternum itself rises slightly
with the same movement, and enlarges to
some extent the antero-posterior diameter
of the thorax. By the simultaneous action,
therefore, of the diaphragm which descends,
and of the intercostal muscles which lift
the ribs and the sternum, the cavity of the
chest is expanded in every direction, and
the air passes inward, through the trachea
and bronchial tubes, by the simple force of
aspiration.

After the movement of inspiration is ac-
complished, and the lungs are filled with
air, the diaphragm and intercostal muscles
relax, and a movement of expiration takes
place, by which the chest is partially col-
lapsed, and a portion of the air contained
in the pulmonary cavity expelled. The
movement of expiration is entirely a passive
one, and is accomplished by the action of
three different forces. First, the abdominal
organs, which have been pushed out of their
usual position by the descent of the diaphragm, fall backward by
their own weight and carry upward the relaxed diaphragm before
them. Secondly, the costal cartilages, which are slightly twisted
out of shape when the ribs are drawn upward, resume their natural
position as soon as the muscles are relaxed, and, drawing the ribs
down again, compress the sides of the chest. Thirdly, the pul-
monary tissue, as we have already remarked, is abundantly sup-
plied with yellow elastic fibres, which retract by virtue of their
own elasticity, in every part of the lungs, after they have been
forcibly distended, and, compressing the pulmonary vesicles, drive
out a portion of the air which they contained. By the constant

DIAGRAM ILLUSTRATIKO
THE RESPIRATORY MOVE-
MEXTS. — a. Cavity of tbe chest.
b. Diaphragm. The dark out-
lines show the figure of the chest
when collapsed ; the dotted lines
show the same when expauded.

238 RESPIRATION.

recurrence of these alternating movements of inspiration and expi-
ration, fresh portions of air are constantly introduced into and
expelled from the chest.

The average quantity of atmospheric air, taken into and dis-
charged from the lungs with each respiratory movement, is, ac-
cording to the results of various observers, twenty cubic inches. At
eighteen respirations per minute, this amounts to 360 cubic inches
of air inspired per minute, 2.1,600 cubic inches per hour, and 518,400
cubic inches per day. But as the movements of respiration are
increased both in extent and rapidity by every muscular exertion,
the entire quantity of air daily used in respiration is not less than
600,000 cubic inches, or 350 cubic feet.

The whole of the air in the chest, however, is not changed at each
movement of respiration. On the contrary, a very considerable
quantity remains in the pulmonary cavity after the most complete
expiration ; and even after the lungs have been removed from the
chest, they still contain a large quantity of air which cannot be
entirely displaced by any violence short of disintegrating and dis-
organizing the pulmonary tissue. It is evident, therefore, that only
a comparatively small portion of the air in the lungs passes in and
out with each respiratory movement ; and it will require several
successive respirations before all the air in the chest can be entirely
changed. It has not been possible to ascertain with certainty the
exact proportion in volume which exists between the air which is
alternately inspired and expired, or "tidal" air, and that which
remains constantly in the chest, or " residual" air, as it is called.
It has been estimated, however, by Dr. Carpenter,1 from the reports
of various observers, that the volume of inspired and expired air
varies from 10 to 13 per cent, of the entire quantity contained in
the chest. If this estimate be correct, it will require from eight to
ten respirations to change the whole quantity of air in the cavity
of the chest.

It is evident, however, from the foregoing, that the inspiratory
and expiratory movements of the chest cannot be sufficient to
change the air at all in the pulmonary lobules and vesicles. The
air which is drawn in with each inspiration penetrates only into
the trachea and bronchial tubes, until it occupies the place of that
which was driven out by the last expiration. By the ordinary
respiratory movements, therefore, only that small portion of the

1 Human Physiology, Philada. ed., 1855, p. 300.

RESPIRATORY MOVEMENTS OF THE GLOTTIS. 239

air Iving nearest the exterior, in the trachea and large bronchi,
would fluctuate backward and forward, without ever penetrating
into the deeper parts of the lung, were there no other means pro-
vided for its renovation. There are, however, two other forces in
play for this purpose. The first of these is the diffusive power of
the gases themselves. The air remaining in the deeper parts of
the chest is richer in carbonic acid and poorer in oxygen than that
which has been recently inspired ; and by the laws of gaseous dif-
fusion there must be a constant interchange of these gases between
the pulmonary vesicles and the trachea, tending to mix them
equally in all parts of the lung. This mutual diffusion and inter-
mixture of the gases will therefore tend to renovate, partially at
least, the air in the pulmonary lobules and vesicles. Secondly, the
trachea and bronchial tubes, down to those even of the smallest
size, are lined with a mucous membrane which is covered with
ciliated epithelium. The movement of those cilia is found to be
directed always from below upward • and, like ciliary motion
wherever it occurs, it has the effect of producing a current in tl.e
same direction, in the fluids covering the mucous membrane. The
air in the tubes must partici-
pate, to a certain extent, in Fig. 72.
this current, and a double
stream of air therefore is estab-
lished in each bronchial tube ;
one current passing from with-
in outward along the walls of
the tube, and a return current
passing from without inward,

. SM AT, L BRONCHI AT, TUBE, showing ontward

along the Central part Of its and iuward current, produced by ciliary motion.

cavity. (Fig. 72.) By this

means a kind of aerial circulation is constantly maintained in the
interior of the bronchial tubes ; which, combined with the mutual
diffusion of the gases and the alternate expansion and collapse of
the chest, effectually accomplishes the renovation of the air contained
in all parts of the pulmonary cavity.

EESPIRATORY MOVEMENTS OF THE GLOTTIS. — Beside the move-
ments of expansion and collapse already described, belonging to
the chest, there are similar respiratory movements which take place
in the larynx. If the respiratory passages be examined after death,
in the state of collapse in which they are usually found, it will be

240

RESPIRATION.

noticed that the opening of the glottis is very much smaller than
the cavity of the trachea below. The glottis itself presents the
appearance of a narrow chink, while the passage for the inspired
air widens in the lower part of the larynx, and in the trachea
constitutes a spacious tube, nearly cylindrical in shape, and over
half an inch in diameter. We have found, for instance, that in
the human subject the space included between the vocal chords
has an area of only 0.15 to 0.17 square inch ; while the calibre
of the trachea in the middle of its length is 0.45 square inch.
This disproportion, however, which is so evident after death, does
not exist during life. While respiration is going on, there is a
constant and regular movement of the vocal chords, synchronous
with the inspiratory and expiratory movements of the chest, by

Fig. 73.

Fie. 74.

HUMANLAKYNX, viewed from above
in its ordinary post-mortern condition. — a,
Vocal chords, b. Thyroid cartilage, cc. Ary-
tenoid cartilages, o. Opening of theglottis.

The *amc, with the glottis opened by
separation of the vocal chords. — a. Vocal
chords. 6. Thyroid cartilage, cc. Aryte-
noid cartilages, o. Opening of the glottis.

which the -size of the glottis is alternately enlarged and diminished.
At every inspiration, the glottis opens and allows the air to pass
freely into the trachea ; at every expiration it collapses, and the
air is driven out through it from below. These movements are
called the " respiratory movements of the glottis." They correspond
in every respect with those of the chest, and are excited or retarded
by similar causes. Whenever the general movements of respiration
are hurried and labored, those of the glottis become accelerated and
increased in intensity at the same time ; and when the movements
of the chest are slower or fainter than usual, owing to debility,
coma, or the like, those of the glottis are diminished in the same
proportion.

CHANGES IN THE AIR DURING RESPIRATION.

241

Fig.75.

In the respiratory motions of the glottis, as in those of the chest,
the movement of inspiration is an active one, and that of expira-
tion passive. In inspiration, the glottis
is opened by contraction of the posterior
crico-arytenoid muscles. (Fig. 75.)
These muscles originate from the pos-
terior surface of the cricoid cartilage,
near the median line ; and their fibres,
running upward and outward, are in-
serted into the external angle of the
arytenoid cartilages. By the contrac-
tion of these muscles, during the move-
ment of inspiration, the arytenoid car-
tilages are rotated upon their articula-
tions with the cricoid, so that their
anterior extremities are carried outward,
and the vocal chords stretched and sepa-
rate from each other. (Fig. 74.) In this
way, the size of the glottis may be in- glottis. «?. Arytenoid cartilages, a.

-IP f\ ^ ~ ^ (\ ci*r • i Cricoid cartilage, ee. Posterior crico-

creased from O.lo to 0.27 square inch. arytenoid mu.scies. /. Trachea.

In expiration, the posterior crico-
arytenoid muscles are relaxed, and the elasticity of the vocal chords
brings them back to their former position.

The motions of respiration consist, therefore, of two sets of move-
ments : viz., those of the chest and those of the glottis. These move-
ments, in the natural condition, correspond with each other both in
time and intensity. It is at the same time and by the same nervous
influence, that the chest expands to inhale the air, while the glottis
opens to admit it ; and in expiration, the muscles of both chest and
glottis are relaxed ; while the elasticity of the tissues, by a kind of
passive contraction, restores the parts to their original condition.

CHANGES IN THE AIR DURING KESPIRATION. — The atmospheric
air, as it is drawn into the cavity of the lungs, is a mixture of oxy-
gen and nitrogen, in the proportion of about 21 per cent., by volume,
of oxygen, to 79 per cent, of nitrogen. It also contains about one-
twentieth per cent, of carbonic acid, a varying quantity of watery
vapor, and some traces of ammonia. The last named ingredients,
however, are quite insignificant in comparison with the oxygen and
nitrogen, which form the principal parts of its mass.

If collected and examined, after passing through the lungs, the
16

242 RESPIRATION.

air is found to have become altered in the following essential par-
ticulars, viz : —

1st. It has lost oxygen.

2d. It has gained carbonic acid. And

3d. It has absorbed the vapor of water.

Beside the two latter substances, there are also exhaled with the
expired air a very small quantity of nitrogen, over and above what
was taken in with inspiration, and a little animal matter in a
gaseous form, which communicates a slight but peculiar odor to
the breath. The air is also somewhat elevated in temperature, by
contact with the pulmonary mucous membrane.

The watery vapor, which is exhaled with the breath, is given off
by the pulmonary mucous membrane, by which it is absorbed from
the blood. At ordinary temperatures it is transparent and invisi-
ble ; but in cold weather it becomes partly condensed, on leaving
the lungs, and appears under the form of a cloudy vapor discharged
with the breath. According to the researches of Valentin, the
average quantity of water, exhaled daily from the lungs, is 8100
grains, or about l£ pounds avoirdupois.

By far the most important part, however, of the changes suffered
by the air in respiration, consists in its loss of oxygen, and its
absorption of carbonic acid.

According to the researches of Valentin, Vierordt, Regnault and
Reiset, &c., the air loses during respiration, on an average,five per
cent, of its volume of oxygen. At each inspiration, therefore,
about one cubic inch of oxygen is removed from the air and ab-
sorbed by the blood ; and as we have seen that the entire daily
quantity of air used in respiration is about 350 cubic feet, the entire
quantity of oxygen thus consumed in twenty-four hours is not less
than seventeen and a half cubic feet. This is, by weight, 7,134
grains, or a little over one pound avoirdupois.

The oxygen which thus disappears from the inspired air is not
entirely replaced in the carbonic acid exhaled ; that is, there is less
oxygen in the carbonic acid which is returned to the air by expira-
tion than has been lost during inspiration.

There is even more oxygen absorbed than is given off again in
both the carbonic acid and aqueous vapor together, which are
exhaled from the lungs.1 There is, then, a constant disappearance
of oxygen from the air used in respiration, and a constant accumu-
lation of carbonic acid.

1 Lehmann's Physiological Chemistry, Philada. ed., vol. ii. p. 432.

CHANGES IN THE BLOOD DURING RESPIRATION. 243

The proportion of oxygen which disappears in the interior of the
body, over and above that which is returned in the breath under
the form of carbonic acid, varies in different kinds of animals. . In
the herbivora, it is about 10 per cent, of the whole amount of oxy-
gen inspired ; in the carnivora, 20 or 25 per cent, and even more.
It is a very remarkable fact, also, and an important one, as regards
the theory of respiration, that, in the same animal, the proportion of
oxj^gen absorbed, to that of carbonic acid exhaled, varies according
to the quality of the food. In dogs, for instance, while fed on ani-
mal food, according to the experiments of Eegnault and Reiset, 25
per cent, of the inspired oxygen disappeared in the body of the
animal ; but when fed on starchy substances, all but 8 per cent,
reappeared in the expired carbonic acid. It is already evident,
therefore, from these facts, that the oxygen of the inspired air is
not altogether employed in the formation of carbonic acid.

CHANGES IN THE BLOOD DURING RESPIRATION. — If we pass from
the consideration of the changes produced in the air by respiration
to those which take place in the blood during the same process, we
find, as might have been expected, that the latter correspond
inversely with the former. The blood, in passing through the
lungs, suffers the following alterations : —

1st. Its color is changed from venous to arterial.

2d. It absorbs oxygen. And

3d. It exhales carbonic acid and the vapor of water.

The interchange of gases, which takes place during respiration
between the air and the blood, is a simple phenomenon of absorp-
tion and exhalation. The inspired oxygen does not, as Lavoisier
once supposed, immediately combine with carbon in the lungs, and
return to the atmosphere under the form of carbonic acid. On the
contrary, almost the first fact of importance which has been estab-
lished by the examination of the blood in this respect is the fol-
lowing, viz : that carbonic acid exists ready formed in the venous blood
before its entrance into the lungs ; and, on the other hand, that the
oxygen which is absorbed during respiration passes off in a free state
with the arterial blood. The real process, as it takes place in the
lung, is, therefore, for the most part, as follows : The blood comes to
the lungs already charged with carbonic acid. In passing through
the pulmonary capillaries, it is exposed to the influence of the air
in the cavity of the pulmonary cells, and a transudation of gases
takes place through the moist animal membranes of the lung.

RESPIRATION.

Since the blood in the capillaries contains a larger proportion of
carbonic acid than the air in the air- vesicles, a portion of this gas
leaves the blood and passes out through the pulmonary membrane;
while the oxygen, being more abundant in the air of the vesicles
than in the circulating fluid, passes inward at the same time, and is
condensed by the blood.

In this double phenomenon of exhalation and absorption, which
takes place in the lungs, both parts of the process are equally
necessary to life. It is essential for the constant activity and nutri-
tion of the tissues that they be steadily supplied with oxygen by the
blood ; and if this supply be cut off, their functional activity ceases.
On the other hand, the carbonic acid which is produced in the body
by the processes of nutrition becomes a poisonous substance, if it
be allowed to collect in large quantity. Under ordinary circum-
stances, the carbonic acid is removed by exhalation through the
lungs as fast as it is produced in the interior of the body ; but if
respiration be suspended, or seriously impeded, since the production
of carbonic acid continues, while its elimination is prevented, it
accumulates in the blood and in the tissues, and terminates life in a
few moments, by a rapid deterioration of the circulating fluid, and
more particularly by its poisonous effect on the nervous system.

The deleterious effects of breathing in a confined space will
therefore very soon become apparent. As respiration goes on, the
oxygen of the air constantly diminishes, and the carbonic acid,
mingled with it by exhalation, increases in quantity. After a time
the air becomes accordingly so poor in oxygen that, by that fact
alone, it is incapable of supporting life. At the same time, the
carbonic acid becomes so abundant in the air vesicles that it pre-
vents the escape of that which already exists in the blood ; and the
deleterious effect of its accumulation in the circulating fluid is
added to that produced by a diminished supply of oxygen. An
increased proportion of carbonic acid in the atmosphere is therefore
injurious in a similar manner, although there may be no diminution
of oxygen ; since by its presence it impedes the elimination of the
carbonic acid already formed in the blood, and induces the poison-
ous effects which result from its accumulation.

Examination of the blood shows furthermore that the interchange
of gases in the lungs is not complete but only partial in its extent.
It results from the experiments of Magendie, Magnus, and others,
that both oxygen and carbonic acid are contained in both venous

CHANGES IN THE BLOOD DURING RESPIRATION. 245

and arterial blood. Magnus1 found that the proportion of oxygen
to carbonic acid, by volume, in arterial blood was as 10 to 25 ; in
venous blood as 10 to 40. The venous blood, then, as it arrives at
the lungs, still retains a remnant of the oxygen which it had pre-
viously absorbed ; and in passing through the pulmonary capil-
laries it gives off only a part of the carbonic acid with which it has
become charged in the general circulation.

The oxygen and carbonic acid of the blood exist in a state of
solution in the circulating fluid, and not in a state of intimate chemi-
cal combination. This is shown by the fact that both of these
substances may be withdrawn from the blood by simple exhaustion
with an air-pump, or by a stream of any other indifferent gas, such
as hydrogen, which possesses sufficient physical displacing power.
Magnus found' that freshly drawn arterial blood yielded by simple
agitation with carbonic acid more than 10 per cent, of its volume
of oxygen. The carbonic acid may also be expelled from venous
blood by a current of pure oxygen, or of hydrogen, or, in great
measure, by simple agitation with atmospheric air. There is some
difficulty in determining, however, whether the carbonic acid of
the blood be altogether in a free state, or whether it be partly in a
state of loose chemical combination with a base, under the form of
an alkaline bicarbonate. A solution of bicarbonate of soda itself
will lose a portion of its carbonic acid, and become reduced to the
condition of a carbonate by simple exhaustion under the air-pump,
or by agitation with pure hydrogen at the temperature of the body.
Lehmann has found3 that after the expulsion of all the carbonic
acid removable by the air-pump and a current of hydrogen, there
still remains, in ox's blood, 0.1628 per cent, of carbonate of soda ;
and he estimates that this quantity is sufficient to have retained all
the carbonic acid, previously given off, in the form of a bicarbonate.
It makes little or no difference, however, so far as regards the pro-
cess of respiration, whether the carbonic acid of the blood exist in
an entirely free state, or under the form of an alkaline bicarbonate ;
since it may be readily removed from this combination, at the tem-
perature of the body, by contact with an indifferent gas.

The oxygen and carbonic acid of the blood are in solution prin-~
cipally in the blood- globules, and not in the plasma. The researches
of Magnus have shown4 that the blood holds in solution 2J times

1 In Lehmann, op. cit., vol. i. p. 570.

2 In Robin and Verdeil, op. cit., vol. ii. p. 34.

3 Op. cit., vol i. p. 393.

« In Robin and Verdeil, op. cit., vol. ii. pp. 28—32.

246 RESPIRATION.

as much oxygen as pure water could dissolve at the same tempera-
ture ; and that while the serum of the blood, separated from the
globules, exerts no more solvent power on oxygen than pure water,
defibrinated blood, that is, the serum and globules mixed, dissolves
quite as much oxygen as the fresh blood itself. The same thing is
true with regard to the carbonic acid. It is therefore the semi-
fluid blood-globules which retain these two gases in solution ; and
since the color of the blood depends entirely upon that of the glo-
bules, it is easy to understand why the blood should alter its hue
from purple to scarlet in passing through the lungs, where the
globules give up carbonic acid, and absorb a fresh quantity of
oxygen. The above change may readily be produced outside the
body. If freshly drawn venous blood be shaken in a bottle with
pure oxygen, its color changes at once from purple to red ; and the
same change will take place, though more slowly, if the blood be
simply agitated with atmospheric air. It is for this reason that the
surface of defibrinated venous blood, and the external parts of a
dark-colored clot, exposed to the atmosphere, become rapidly red-
dened, while the internal portions retain their original color.

The process of respiration, so far as we have considered it, con-
sists in an alternate interchange of carbonic acid and oxygen in the
blood of the general and pulmonary circulations. In the pulmonary
circulation, carbonic acid is given off and oxygen absorbed ; while
in the general circulation the oxygen gradually disappears, and is
replaced, in the venous blood, by carbonic acid. The oxygen which
thus disappears from the blood in the general circulation does not,
for the most part, enter into direct combination in the blood itself.
On the contrary, it exists there, as we have already stated, in the
form of a simple solution. It is absorbed, however, from the blood
of the capillary vessels, and becomes fixed in the substance of the
vascular tissues. The blood may be regarded, therefore, in this
respect, as a circulating fluid, destined to transport oxygen from the
lungs to the tissues ; for it is the tissues themselves which finally
appropriate the oxygen, and fix it in their substance.

The next important question which presents itself in the study
of the respiratory process relates to the origin of the carbonic acid in
the venous blood. It was formerly supposed, when Lavoisier first
discovered the changes produced in the air by respiration, that the
production of the carbonic acid could be accounted for in a very
simple manner. It was thought to be produced in the lungs by a

CHANGES IN THE BLOOD DURING RESPIRATION. 247

direct union of the inspired oxygen with the carbon of the blood
in the pulmonary vessels. It was found afterward, however, that
this could not be the case ; since carbonic acid exists already formed
in the blood, previously to its entrance into the lungs. It was then
imagined that the oxidation of carbon, and the consequent produc-
tion of carbonic acid, took place in the capillaries of the general
circulation, since it could not be shown to take place in the lungs,
nor between the lungs and the capillaries. The truth is, however,
that no direct evidence exists of such a direct oxidation taking
place anywhere. The formation of carbonic acid, as it is now
understood, takes place in three different modes : 1st, in the lungs ;
2d, in the blood ; and 3d, in the tissues.

First, in the lungs. There exists in the pulmonary tissue a pecu-
liar acid substance, first described by Yerdeil1 under the name of
"pneumic" or "pulmonic" acid. It is a crystallizable body, soluble
in water, which is produced in the substance of the pulmonary
tissue by transformation of some of its other ingredients, in the
same manner as sugar is produced in the tissue of the liver. It is
on account of the presence of this substance that the fresh tissue of
the lung has usually an acid reaction to test-paper, and that it has
also the property, which has been noticed by several observers, of
decomposing the metallic cyanides, with the production of hydro-
cyanic acid ; a property not possessed by sections of areolar tissue,
the internal surface of the skin, &c. &c. When the blood, there-
fore, comes in contact with the pulmonary tissue, which is
permeated everywhere by pneumic acid in a soluble form, its
alkaline carbonates and bicarbonates, if any be present, are decom-
posed with the production on the one hand of the pneumates of
soda and potassa, and on the other of free carbonic acid, which is
exhaled. M. Bernard has found3 that if a solution of bicarbonate
of soda be rapidly injected into the jugular vein of a rabbit, it
becomes decomposed in the lungs with so rapid a development of
carbonic acid, that the gas accumulates in the pulmonary tissue,
and even in the pulmonary vessels and the cavities of the heart, to
such an extent as to cause immediate death by stoppage of the
circulation. In the normal condition, however, the carbonates and
bicarbonates of the blood arrive so slowly at the lungs that as fast
as they are decomposed there, the carbonic acid is readily exhaled
by expiration, and produces no deleterious effect on the circulation.

1 Robin and Verdeil, op. cit., vol. ii. p. 460.

2 Arclm-es Gen. de Med., xvi. 222.

248 RESPIKAT1OX.

Secondly, in the b7ood. There is little doubt, although the fact has
not been directly proved, that some of the oxygen definitely dis-
appears, and some of the carbonic acid is also formed, in the sub-
stance of the blood-globules during their circulation. Since these
globules are anatomical elements, and since they undoubtedly go
through with nutritive processes analogous to those which take
place in the elements of the solid tissues, there is every reason for
believing that they also require oxygen for their support, and that
they produce carbonic acid as one of the results of their interstitial
decomposition. While the oxygen and carbonic acid, therefore,
contained in the globules, are for the most part transported by
these bodies from the lungs to the tissues, and from the tissues back
again to the lungs, they probably take part, also, to a certain extent,
in the nutrition of the blood-globules themselves.

Thirdly, in the tissues. This is by far the most important source
of the carbonic acid in the blood. From the experiments of Spal-
lanzani, W. Edwards, Marchand and others, the following very
important fact has been established, viz., that every organized tissue
and even every organic substance, when in a recent condition, has the
power of absorbing oxygen and of exhaling carbonic acid. Or. Liebig,
for example,1 found that frog's muscles, recently prepared and com-
pletely freed from blood, continued to absorb oxygen and discharge
carbonic acid. Similar experiments with other tissues have led
to a similar result. The interchange of gases, therefore, in the
process of respiration, takes place mostly in the tissues themselves.
It is in their substance that the oxygen becomes fixed and assimi-
lated, and that the carbonic acid takes its origin. As the blood in
the lungs gives up its carbonic acid to the air, and absorbs oxygen
from it, so in the general circulation it gives up its oxygen to the
tissues, and absorbs from them carbonic acid.

We come lastly to examine the exact _mpde by which the car-
bonic acid originates in the animal tissues. Investigation shows
that e" ven here it is not produced by a process of oxidation, or direct
union of oxygen with the carbon of the tissues, but in some other and more
indirect mode. This is proved by the fact that animals and fresh
animal tissues will continue to exhale carbonic acid in an atmo-
sphere of hydrogen or of nitrogen, or even when placed in a vacuum.
Marchand found2 that frogs would live for from half an hour to an
hour in pure hydrogen gas ; and that during this time they exhaled
even more carbonic acid than in atmospheric air, owing probably

1 In Lehmann, op. cit., vol. ii. p. 474. 2 Ibid., p. 442.

CHANGES IN THE BLOOD DURING RESPIRATION. 249

to the' superior displacing power of hydrogen for carbonic acid.
For while 15,500 grains' weight of frogs exhaled about 1.13 grain
of carbonic acid per hour in atmospheric air, they exhaled during
the same time in pure hydrogen as much as 4.07 grains. The same
observer found that frogs would recover on the admission of air
after remaining for nearly half an hour in a nearly complete
vacuum ; and that if they were killed by total abstraction of the
air, 15,500 grains' weight of the animals were found to have
eliminated 9.3 grains of carbonic acid. The exhalation of carbonic
acid by the tissues does not, therefore, depend directly upon the
access of free oxygen. It cannot go on, it is true, for an indefinite
time, any more than the other vital processes, without the presence
of oxygen. But it may continue long enough to show that the
carbonic acid exhaled is not a direct product of oxidation, but that
it originates, on the contrary, in all probability, by a decomposi-
tion of the organic ingredients of the tissues, resulting in the pro-
duction of carbonic acid on the one hand, and of various other
substances on the other, with which we are not yet fully acquainted :
in very much the same manner as the decomposition of sugar
during fermentation gives rise to alcohol on the one hand and to
carbonic acid on the other. The fermentation of sugar, when it has
once commenced, does not require the continued access of air. It
will go on in an atmosphere of hydrogen, or even when confined in
a close vessel over mercury; since its carbonic acid is not produced
by direct oxidation, but by a decomposition of the' sugar already
present. For the same reason, carbonic acid will continue to be
exhaled by living or recently dead animal tissues, even in an atmo-
sphere of hydrogen, or in a vacuum.

Carbonic acid makes its appearance, accordingly, in the tissues,
as one product of their decomposition in the nutritive process.
From them it is taken up by the blood, either in simple solution or
in loose combination as a bicarbonate, transported by the circulation
to the lungs, and finally exhaled from the pulmonary mucous mem-
brane in a gaseous form.

The carbonic acid exhaled from the lungs should accordingly be
studied by itself as one of the products of the animal organism, and
its quantity ascertained in the different physiological conditions of
the body. The expired air usually contains about four per cent, of
its volume of carbonic acid. According to the researches of Yier-
ordt,1 which are regarded as the most accurate on this subject, an

1 In Lehmann, op. cit., vol. ii. p. 439.

250 RESPIRATION.

adult man gives off 1.62 cubic inch of carbonic acid with each nor-
mal expiration. This amounts to very nearly 1,150 cubic inches
per hour, or fifteen and a half cubic feet per day. This quantity
is, by weight, 10,740 grains, or a little over one pound and a half.
The amount of carbonic acid exhaled, however, varies from time to
time, according to many different circumstances ; so that no such
estimate can represent correctly its quantity at all times. These
variations have been very fully investigated by Andral and Gavar-
ret,1 who found that the principal conditions modifying the amount
of this gas produced were age, sex, constitution and development.
The variations were very marked in different individuals, notwith-
standing that the experiments were made at the same period of the
day, and with the subject as nearly as possible in the same condi-
tion. Thus they found that the quantity of carbonic acid exhaled
per hour in five different individuals was as follows : —

QUANTITY OF CARBONIC ACID PER HOUR.

In subject No. 1 1207 cubic inches.

" " " 2 970 " "

" " " 3 1250 "

" " " 4 1250 " "

" " « 5 1591 « "

With regard to the difference produced by age, it was found that
from the period of eight years up to puberty the quantity of car-
bonic acid increases constantly with the age. Thus a boy of eight
years exhales, on the average, 564 cubic inches per hour ; while a
boy of fifteen years exhales 981 cubic inches in the same time.
Boys exhale during this period more carbonic acid than girls of the
same age. In males this augmentation of the quantity of carbonic
acid continues till the twenty-fifth or thirtieth year, when it reaches,
on the average, 1398 cubic inches per hour. Its quantity then
remains stationary for ten or fifteen years ; then diminishes slightly
from the fortieth to the sixtieth year ; and after sixty years dimi-
nishes in a marked degree, so that it may fall so low as 1038 cubic
inches. In one superannuated person, 102 years of age, Andral
and Gavarret found the hourly quantity of carbonic acid to be
only 665 cubic inches.

In women, the increase of carbonic acid ceases at the period of
puberty ; and its production then remains constant until the cessa-
tion of menstruation, about the fortieth or forty-fifth year. At that
time it increases again until after fifty years, when it subsequently

1 Annales de Chimie et de Thai-made, 1843, vol. viii. p. 129.

CHANGES IX THE BLOOD DURING RESPIRATION. 251

diminishes with the approach of old age, as in men. Pregnancy,
occurring at any time in the above period, immediately produces a
temporary increase in the quantity of carbonic acid.

The strength of the constitution, and more particularly the deve-
lopment of the muscular system, was found to have a very great in-
fluence in this respect ; increasing the quantity of carbonic acid
very much in proportion to the weight of the individual. The
largest production of carbonic acid observed was in a young man,
26 years of age, whose frame presented a remarkably vigorous and
athletic development, and who exhaled 1591 cubic inches per hour.
This large quantity of carbonic acid, moreover, in well developed
persons, is not owing simply to the size of the entire body, but
particularly to the development of the muscular system, since an
unusually large skeleton, or an abundant deposit of adipose tissue,
is not accompanied by any such increase of the carbonic acid.

Andral and Gavarret finally sum up the results of their investiga-
tions as follows : —

1. The quantity of carbonic acid exhaled from the lungs in a given
time varies with the age, the sex, and the constitution of the subject.

2. In the male, as well as in the female, the quantity of carbonic
acid varies according to the age ; and that independently of the
weight of the individual subjected to experiment.

3. During all the periods of life, from that of eight years up to
the most advanced age, the male and female may be distinguished
by the different quantities of carbonic acid which they exhale in a
given time. Other things being equal, the male exhales always a
larger quantity than the female. This difference is particularly
marked between the ages of 16 and 40 years, during which period
the male usually exhales twice as much carbonic acid as the female.

4. In the male, the quantity of carbonic acid increases constantly
from eight to thirty years ; and the rate of this increase undergoes
a rapid augmentation at the period of puberty. Beyond thirty
years the exhalation of carbonic acid begins to decrease, and its
diminution is more marked as the individual approaches extreme
old age, so that near the termination of life, the quantity of carbonic
acid produced may be no greater than at the age of ten years.

5. In the female, the exhalation of carbonic acid increases accord-
ing to the same law as in the male, from the age of eight years
until puberty. But at the period of puberty, at the same time with
the appearance of menstruation, the exhalation of carbonic acid,

252 EESPIRATION.

contrary to what happens in the male, ceases to increase ; and it
afterward remains stationary so long as the menstrual periods recur
with regularity. At the cessation of the menses, the quantity of
carbonic acid exhaled increases in a notable manner ; then it de-
creases again, as in the male, as the woman advances toward old age.

6. During the whole period of pregnancy, the exhalation of car-
bonic acid rises, for the time, to the same standard as in women
whose menses have ceased.

7. In both sexes, and at all ages, the quantity of carbonic acid is
greater as the constitution is stronger, and the muscular system
more fully developed.

Prof. Scharling, in a similar series of investigations,1 found that
the quantity of carbonic acid exhaled was greater during the diges-
tion of food than in the fasting condition. It is greater, also, in the
waking state than during .sleep; and in a state of activity than in
one of quietude. It is diminished, also, by fatigue, and by most
conditions which interfere with perfect health.

The process of respiration is not altogether confined to the lungs,
but the interchange of gases takes place, also, to some extent through
the skin. It has been found, by inclosing one of the limbs in an
air-tight case, that the air in which it is confined loses oxygen and
gains in carbonic acid. By an experiment of this sort, performed by
Prof. Scharling,2 it was ascertained that the carbonic acid given off
from the whole cutaneous surface, in the human subject, is from
one-sixtieth to one-thirtieth of that discharged during the same
period from the lungs. In the true amphibious animals, that is,
those which breathe by lungs, and can yet remain under water for
an indefinite period without injury (as frogs, and salamanders), the
respiratory function of the skin is very active. In these animals,
the integument is very vascular, moist, and flexible ; and is covered,
not with dry cuticle, but with a very thin and delicate layer of
epithelium. It, therefore, presents all the conditions necessary for
the accomplishment of respiration ; and while the animal remains
beneath the surface, and the lungs are in a state of inactivity, the
exhalation and absorption of gases continue to take place through
the skin, and the process of respiration goes on in a nearly unin-
terrupted manner.

1 Annales de Chirai« et <\e Pharmacia, vol. viii. p. 490.

2 In Carpenter's Human Physiology, Philaria. ed., 1855, p. 308.

ANIMAL HEAT. 253

CHAPTER XIII.

ANIMAL HEAT.

OXE of the most important phenomena presented by animals and
vegetables is the property which they possess of maintaining, more
or less constantly, a standard temperature, notwithstanding the
external vicissitudes of heat and cold to which they may be sub-
jected. If a bar of iron, or a jar of water, be heated up to 100° or
200° F., and then exposed to the air at 50° or 60°, it will imme-
diately begin to lose heat by radiation and conduction ; and this
loss of heat will steadily continue, until, after a certain time, the
temperature of the heated body has become reduced to that of the
surrounding atmosphere. It then remains stationary at this point,
unless the temperature of the atmosphere should happen to rise or
fall : in which case, a similar change takes place in the inorganic
body, its temperature remaining constant, or varying with that of
the surrounding medium.

With living animals the case is different. If a thermometer be
introduced into the stomach of a dog, or placed under the tongue
of the human subject, it will indicate a temperature of 100° F., very
nearly, whatever may be the condition of the surrounding atmo-
sphere at the time. This internal temperature is the same in sum-
mer and in winter. If the individual upon whom the experiment
has been tried be afterward exposed to a cold of zero, or even of 20°
or 30° below zero, the thermometer introduced into the interior of
the body will still stand at 100° F. As the body, during the whole
period of its exposure, must have been losing heat by radiation and
conduction, like any inorganic mass, and has, notwithstanding, main-
tained a constant temperature, it is plain that a certain amount of
heat has been generated in the interior of the body by means of the
vital processes, sufficient to compensate for the external loss. The
internal heat, so produced, is known by the name of vital or animal
heat. x

There are two classes of animals in which the production of vital

254 ANIMAL HEAT.

heat takes place with such activity that their blood and internal
organs are nearly always very much above the external temper-
ature; and which are therefore called "warm-blooded animals."
These are mammalia and birds. Among the birds, some species,
as the gull, have a temperature as low as 100° F. ; but in most of
them, it is higher, sometimes reaching as high as 110° or 111°. In
the mammalians, to which -class man belongs, the animal tempera-
ture is never far from 100°. In the seal and the Greenland whale,
it has been found to be 104° ; and in the porpoise, which is an air-
breathing animal, 99°.5. In the human subject it is 98° to 100°.
When the temperature of the air is below this, the external parts
of the body, being most exposed to the cooling influences of radia-
tion and conduction, fall a little below the standard, and may indi-
cate a temperature of 97°, or even several degrees below this point.
Thus, on a very cold day, the thinner and more exposed parts, such
as the nose, the ears, and the ends of the fingers, may become
cooled down considerably below the standard temperature, and may
even be congealed, if the cold be severe ; bat the temperature of
the internal organs and of the blood still remains the same under
all ordinary exposures.

If the cold be so intense and long continued as to affect the
general temperature of the blood, it at once becomes fatal. It has
been found that although a warm-blooded animal usually preserves
its natural temperature when exposed to external cold, yet if the
actual temperature of the blood become reduced by any means
more than 5° or 6° below its natural standard, death inevitably
results. The animal, under these circumstances, gradually becomes
torpid and insensible, and all the vital operations finally cease.
Birds, accordingly, whose natural temperature is about 110°, die if
the blood be cooled down to 100°, which is the natural temperature
of the mammalia ; and the mammalians die if their blood be cooled
down below 94° or 95°. Each of these different classes has there-
fore a natural temperature, at which the blood must be maintained
in order to sustain life ; and even the different species of animals,
belonging to the same class, have each a specific temperature which
is characteristic of them, and which cannot be raised or lowered, to
any considerable extent, without producing death.

While in the birds and mammalians, however, the internal pro-
duction of heat is so active, that their temperature is nearly always
considerably above that of the surrounding media, and suffers but
little variation ; in reptiles and fish, on the other hand, its produc- •

ANIMAL HEAT. 255

tion is much less rapid, and the temperature of their bodies differs
but little from that of the air or water which they inhabit. Birds
and mammalians are therefore called " warm-blooded," and reptiles
and fish " cold-blooded" animals. There is, however, no other dis-
tinction between them, in this respect, than one of degree. - In
reptiles and fish there is also an internal source of heat ; only this
is not so active as in the other classes. Even in these animals a
difference is usually found to exist between the temperature of their
bodies and that of the surrounding media. John Hunter, Sir
Humphrey Davy, Czermak, and others,1 have found the temperature
of Proteus anguinus to be 63°.5, when that of the air was 55°.4;
that of a frog 48U, in water at 4A°A ; that of a serpent 88°.46, in
air at 81°.5 ; that of a tortoise 84°, in air at 79°.5 ; and that of fish
to be from 1°.7 to 2°.5 above that of the surrounding water.

The following list2 shows the mean temperature belonging to
animals of different classes and species.

ANIMAL. MEAN TEMPERATURE.

f Swallow ...... 1110.25

Heron ....... llic.2

B,RDS. ' Raven ....... 108°'5

Pigeon ....... 107°.6

I Fowl ....... 1060.7

I Gull ....... 1000.0

quirrel ...... 105O

k>at . . ..... 1020.5

at ....... 1010.3

Dog ....... 990.4

Man ....... 980.6

[Ape ....... 950.9

REPTILE. Toad ....... 51O.6 *

r Carp ....... 510.25

\ Tench ....... 520.10

In the invertebrate animals, as a general rule, the internal heat
is produced in too small quantity to be readily estimated. In some
of the more active kinds, however, such as insects and arachnida,
it is occasionally generated with such activity that it may be
appreciated by the thermometer. Thus, the temperature of the
butterfly, when in a state of excitement, is from 5° to 9° above
that of the air; and that of the humble-bee from 3° to 10° higher

1 Simon's Chemistry of Man, Philadelphia edition, p. 124.

2 Ibid., pp. 123—126.

256 ANIMAL HEAT.

than the exterior. According to the experiments of Mr. Newport,1
the interior of a hive of bees may have a temperature of 48°.o.
when the external atmosphere is at 34°.5, even while the insects
are quiet ; but if they be excited, by tapping on the outside of the
hive, it may rise to 102°. In all cases, while the insect is at rest,
the temperature is very moderate ; but if kept in rapid motion in
a confined space, it may generate heat enough to affect the thermo-
meter sensibly, in the course of a few minutes.

Even in vegetables a certain degree of heat-producing power is
occasionally manifest. Usually, the exposed surface of a plant is
so extensive in proportion to its mass, that whatever caloric may
be generated is too rapidly lost by radiation and evaporation, to be
appreciated by ordinary means. Under some circumstances, how-
ever, it may accumulate to such an extent as to become readily
perceptible. In the process of malting, for example, when a large
quantity of germinating grain is piled together in a mass, its ele-
vated temperature may be readily distinguished, both by the hand
and the thermometer. During the flowering process, also, an un-
usual evolution of heat takes place in plants. The flowers of the
geranium have been found to have a temperature of 87°, while
that of the air was 81°; and the thermometer, placed in the centre
of a clump of blossoms of arum cordifolium, has been seen to rise
to 111°, and even 121°, while the temperature of the external air
was only 66°.7

Dutrochet has moreover found, by a series of very ingenious and
delicate experiment,3 that nearly all parts of a living plant gene-
rate a certain amount of heat. The proper heat of the plant is
usually so rapidly dissipated by the continuous evaporation of its
fluids, that it is mostly imperceptible by ordinary means ; but if
this evaporation be prevented, by keeping the air charged with
watery vapor, the heat becomes sensible and can be appreciated by
a delicate thermometer. Dutrochet used for this purpose a thermo-
electric apparatus, so constructed that an elevation of temperature
of 1° F., in the substances examined, would produce a deviation in
the needle of nearly nine degrees. By this means he found that he
could appreciate, without difficulty, the proper temperature of the
plant. A certain amount of heat was constantly generated, during

1 Carpenter's General and Comparative Physiology, Philadelphia, 1851, p. 852.

2 Carpenter's Gen. and Comp. Physiology, p. 846.

3 Annales des Sciences Naturelles, 2d series, xii. p. 277.

ANIMAL HEAT. 257

the day, in the green stems, the leaves, the buds, and even the
roots and fruit. The maximum temperature of these parts, above
that of the surrounding atmosphere, was sometimes a little over
one-half a degree Fahrenheit; though it was often considerably
less than this.

The different parts of the vegetable fabric, therefore, generate
different quantities of caloric. In the same manner, the heat-
producing power is not equally active in different species of ani-
mals; but its existence is nevertheless common to both animals
and vegetables.

With regard to the mode of generation of this internal or vital
heat, \ve may start with the assertion that its production depends
upon changes of a chemical nature, and is so far to be regarded as
a chemical phenomenon. The sources of heat which we meet with
in external nature are of various kinds. Sometimes the heat is of
a physical origin ; as, for example, that derived from the rays of
the sun, the friction of solid substances, or the passage of electric
currents. In other instances it is produced by chemical changes ;
and the most abundant and useful source of artificial heat is the
oxidation, or combustion, of carbon and carbonaceous compounds.
Wood and coal, substances rich in carbon, are mostly used for this
purpose ; and charcoal, which is nearly pure carbon, is frequently
employed by itself. These substances, when burnt, or oxidized,
evolve a large amount of heat ; and produce, as the result of their
oxidation, carbonic acid. In order that the process may go on, it
is of course necessary that oxygen, or atmospheric air, should have
free access to the burning body; otherwise the combustion and
evolution of heat cease, for want of a necessary agent in the chemi-
cal combination. In all these instances, the quantity of heat gene-
rated is in direct proportion to the amount of oxidation ; and may
be measured, either by the quantity of carbon consumed, or by that
of carbonic acid produced. It may be made to go on, also, either
rapidly or slowly, according to the abundance and purity in which
oxygen is supplied to the carbonaceous substance. Thus, if char-
coal be ignited in an atmosphere of pure oxygen, it burns rapidly
and violently, raises the temperature to a high point, and is soon
entirely consumed. On the other hand, if it be shut up in a close
stove, to which the air is admitted but slowly, it produces only a
slight elevation of temperature, and may require a much longer
time for its complete disappearance. Nevertheless, for the same
quantity of carbon consumed, the amount of heat generated, and
17

258 ANIMAL HEAT.

that of carbonic acid produced, will be equal in the two cases. In
one instance we have a rapid combustion, in the other a slow com-
bustion ; the total effect being the same in both.

Such is the mode in which heat is commonly produced by artifi-
cial means, its evolution is here dependent upon two principal
conditions, which are essential to it, and by which it is always
accompanied, viz., the consumption of oxygen, and the production
of carbonic acid.

Now, since the two phenomena just mentioned are presented
also by the living body, and since they are accompanied here, too,
by the production of animal heat, it was very natural to suppose
that in the animal organization, as well as elsewhere, the internal
heat must be owing to an oxidation or combustion of carbon. Ac-
cording to Lavoisier, the oxygen taken into the lungs was sup-
posed to combine immediately with the carbon of the pulmonary
tissues and fluids, producing carbonic acid, and to be at once re-
turned under that form to the atmosphere ; the same quantity of
heat resulting from the above process as would have been produced
by the oxidation of a similar quantity of carbon in wood or coal.
Accordingly, he regarded the lungs as a sort of stove or furnace,
by which the rest of the body was warmed, through the medium of
the circulating blood.

It was soon found, however, that this view was altogether erro-
neous ; for the slightest examination shows that the lungs are not
perceptibly warmer than the rest of the body ; and that the heat-
producing power, whatever it may be, does not reside exclusively
in the pulmonary tissue. Furthermore, subsequent investigations
showed the following very important facts, which we have already
mentioned, viz., that the carbonic acid is not formed in the lungs,
but exists in the blood before its arrival in the pulmonary capilla-
ries ; and that the oxygen of the inspired air, so far from combining
with carbon in the lungs, is taken up in solution by the blood-
globules, and carried away by the current of the general circulation.
It is evident, therefore, that this oxidation or combustion of the
blood must take place, if at all, not in the lungs, but in the capil-
laries of the various organs and tissues of the body.

Liebig accordingly adopted Lavoisier's theory of the production
of animal heat, with the above modification. He believed the heat
of the animal body to be produced by the oxidation or combustion
of certain elements of the food while still circulating in the blood ;
these substances being converted into carbonic acid and water by

AXIMAL HKAT. 259

the oxidation of their carbon and hydrogen, and immediately ex-
pelled from the body without ever having formed a part of the solid
tissues. He therefore divided the food into two different classes of
alimentary substances ; viz., 1st, the nitrogenous or plastic elements,
which are introduced in comparatively small quantity, and which
are to be actually converted into the substance of the tissues, such as
albumen, muscular flesh, &c.; and 2d, the hydro-carbons or respiratory
elements, such as sugar, starch, and fat ; which, according to his view,
are taken into the blood solely to be burned, never being assimilated
or converted into the tissues, but only oxidized in the circulation,
and immediately expelled, as above, under the form of carbonic
acid and water. He therefore regarded these elements of the food
only as so much fuel ; destined simply to maintain the heat of the
body, but taking no part in the proper function of nutrition.

The above theory of animal heat has been very generally adopted
and acknowledged by the medical profession until within a recent
period. A few years ago, however, some of its deficiencies and
inconsistencies were pointed out, by Lehmann in Germany, and by
Eobin and Yerdeil in France ; and since that time it has begun to
lose ground and give place to a different mode of explanation, more
in accordance with the present state of physiological science. We
believe it, in fact, to be altogether erroneous; and incapable of
explaining, in a satisfactory manner, the phenomena of animal heat,
as exhibited by the living body. We shall now proceed to pass in
review the principal objections to the theory of combustion, con-
sidered as a physiological doctrine.

I. It is not at all necessary to regard the evolution of heat as
dependent solely on direct oxidation. This is only one of its
sources, as we see constantly in external nature. The sun's rays,
mechanical friction, electric currents, and more particularly a great
variety of chemical actions, such as various saline combinations and
decompositions, are all capable of producing heat; and even simple
solutions, such as the solution of caustic potassa in water, the mixture
of sulphuric acid and water, or of alcohol and water, will often pro-
duce a very sensible elevation of temperature. Now we know that
in the interior of the body a thousand different actions of this
nature are constantly going on ; solutions, combinations and decom-
positions in endless variety, all of which, taken together, are amply
sufficient to account for the production of animal heat, provided the
theory of combustion should be found insufficient or improbable.

260 ANIMAL HEAT.

II. In vegetables there is an internal production of heat, as well
as in animals ; a fact which has been fully demonstrated by the
experiments of Dutrochet and others, already described. In vege-
tables, however, the absorption of oxygen and exhalation of car-
bonic acid do not take place ; excepting, to some extent, during the
night. On the contrary, the diurnal process in vegetables, it is well
known, is exactly the reverse of this. Under the influence of the
solar light they absorb carbonic acid and exjiale oxygen. And it
is exceedingly remarkable that, in Dutrochet's experiments, he
found that the evolution of heat by plants was always accompanied
by the disappearance of carbonic acid and the exhalation of oxygen.
Plants which, in the daylight, exhale oxygen and evolve heat, if
placed in the dark, immediately begin to absorb oxygen and exhale
carbonic acid ; and, at the same time, the evolution of heat is sus-
pended. Datrochet even found that the evolution of heat by plants
presented a regular diurnal variation ; and that its maximum of
intensity was about the middle of the day, just at the time when the
absorption of carbonic acid and the exhalation of oxygen are going on
with the greatest* activity. The proper heat of plants, therefore, can-
not be the result of oxidation or combustion, but must be dependent
on an entirely different orocess.

III. In animals, the quantities of oxygen absorbed and of carbonic
acid exhaled do not correspond with each other. Most frequently
a certain amount of oxygen disappears in the body, over and above
that which is returned in the breath under the form of carbonic
acid. This overplus of oxygen has been said to unite with the
hydrogen of the food, so as to form water which also passes out
by the lungs : but this is a pure assumption, resting on no direct
evidence whatever, for we have no experimental proof that any
more watery vapor is exhaled from the lungs than is supplied by
the fluids taken into the stomach. It is superfluous, therefore, to
assume that any of it is produced by the oxidation of hydrogen.

Furthermore, the proportion of overplus oxygen which disap-
pears in the body, beside that which is exhaled in the carbonic acid
of the breath, varies greatly in the same animal according to the
quality of the food. Eegnault and Reiset1 found that in dogs, fed
on meat, the oxygen which reappeared under the form of carbonic
,acid was only 75 per cent, of the whole quantity absorbed ; while

1 Annales de Chimie et de Physique, 3d series, xxvi. p. 428.

ANIMAL HEAT. 2t)l

in dogs fed on vegetable substances it amounted to over 90 per
cent. In some instances,1 where the animals (rabbits and fowls)
were fed on bread and grain exclusively, the proportion of expired
oxygen amounted to 101 or even 102 per cent; that is, more oxygen
was actually contained in the carbonic acid exhakd, than had been ab-
sorbed in a free state from the atmosphere. A portion, at least, of the
carbonic acid must therefore have been produced by other means
than direct oxidation.

IY. It has already been shown, in a previous chapter, that the
carbonic acid which is exhaled from the lungs is not primarily
formed in the blood, but makes its appearance in the substance of
the tissues themselves ; and furthermore, that even here it does not
originate by a direct oxidation, but rather by a process of decom-
position, similar to that by which sugar, in fermentation, is resolved
into alcohol and carbonic acid. We understand from this how to
explain the singular fact alluded to in the last paragraph, viz., the
abundant production of carbonic acid, under some circumstances,
with a comparatively small supply of free oxygen. The statement
made by Liebig, therefore, that starchy and oily matters taken with
the food are immediately oxidized in the circulation without ever
being assimilated by the tissues, is without foundation. It never,
in fact, rested on any other ground than a supposed probability ;
and as we see that carbonic acid is abundantly produced in the
body by other means, we have no longer any reason for assuming,
without direct evidence, the existence of a combustive process in
the blood.

Y. The evolution of heat in the animal body is not general, as it
would be if it resulted from a combustion of the blood ; but local,
since it takes place primarily in the substance of the tissues them-
selves. Yarious causes will therefore produce a local elevation or
depression of temperature, by modifying the nutritive changes
which take place in the tissues. Thus, in the celebrated experiment
of Bernard, which we have often verified, division of the sympa-
thetic nerve in the middle of the neck produces very soon a marked
elevation of temperature in the corresponding side of the head and
face. Local inflammations, also, increase very sensibly the tempera-
ture of the part in which they are seated, while that of the general

1 Annales de Chimie et de Physique, 3d series, xxvi. pp. 4C9— 451.

262 ANIMAL HEAT.

mass of the blood is not altered. Finally it has been demonstrated
by Bernard that in the natural state of the system there is a marked
difference in the temperature of the different organs and of the blood
returning from them.1 The method adopted by this experimenter
was to introduce, in the living animal, the bulb of a fine thermo-
meter successively into the bloodvessels entering and those leaving
the various internal organs. The difference of temperature in these
two situations showed whether the blood had lost or gained in heat
while traversing the capillaries of the organ. Bernard found, in
the first place, that the blood in passing through the lungs, so far
from increasing, was absolutely diminished in temperature; the
blood on the left side of the heart being sometimes a little more
and sometimes a little less than one-third of a degree Fahr. lower
than on the right side. This slight cooling of the blood in the
lungs is owing simply to its exposure to the air through the pul-
monary membrane, and to the vaporization of water which takes
place in these organs. In the abdominal viscera, on the contrary,
the blood is increased in temperature. It is sensibly warmer in the
portal vein than in the aorta ; and very considerably warmer in the
hepatic vein than in either the portal or the vena cava. The blood
of the hepatic vein is in fact warmer than that of any other part
of the body. The production of heat, therefore, according to Ber-
nard's observations, is more active in the liver than in any other
portion of the system. As the chemical processes of nutrition are
necessarily different in the different tissues and organs, it is easy to
understand why a specific amount of heat should be produced in
each of them. A similar fact, it will be recollected, was noticed by
Dutrochet, in regard to the different parts of the vegetable organ-
ization.

YI. Animal heat has been supposed to stand in a special relation
to the production of carbonic acid, because in warm-blooded animals
the respiratory process is more active than in those of a lower
temperature; and because, in the same anirrial, an increase or di-
minution in the evolution of heat is accompanied by a correspond-
ing increase or diminution in the products of respiration. But
this is also true of all the other excretory products of the body. An
elevation of temperature is accompanied by an increased activity
of all the nutritive processes. Not only carbonic acid, but the

1 Gazette Hebdomadaire, Aug. 29 and Sept. 26, 1856.

ANIMAL HEAT. 263

ingredients of the urine and the perspiration are discharged in larger
quantit y than usual. An increased supply of food also is required,
as well as a larger quantity of oxygen; and the digestive and
secretory processes both go on, at the same time, with unusual
activity.

Animal heat, then, is a phenomenon which results from the
simultaneous activity of many different processes, taking place in
many different organs, and dependent, undoubtedly, on different
chemical changes in each one. The introduction of oxygen and
the exhalation of carbonic acid have no direct connection with each
other, but are only the beginning and the end of a long series of
continuous changes, in which all the tissues of the body successively
take a part. Their relation is precisely that which exists between
the food introduced through the stomach, and the urinary ingre-
dients eliminated by the kidneys. The tissues require for their
nutrition a constant supply of solid and liquid food which is intro-
duced through the stomach, and of oxygen which is introduced
through the lungs. The disintegration and decomposition of the
tissues give rise, on the one hand, to urea, uric acid, &c., which are
discharged with the urine, and on the other hand to carbonic acid,
which is exhaled from the lungs. But the oxygen is not directlv
converted into carbonic acid, any more than the food is directly
converted into urea and the urates.

Animal heat is not to be regarded, therefore, as the result of a
combustive process. There is no reason for believing that the
greater part of the food is " burned" in the circulation. It is, on
the contrary, assimilated by the substance of the tissues ; and these,
in their subsequent disintegration, give rise to several excretory
products, one of which is carbonic acid.

The numerous combinations and decompositions which follow
each other incessantly during the nutritive process, result in the
production of an internal or vital heat, which is present in both
animals and vegetables, and which varies in amount in different
species, in the same individual at different times, and even in
different parts and organs of the same body.

26-i THE CIRCULATION.

CHAPTER XIV.

THE CIRCULATION.

THE blood may be regarded as a nutritious fluid, holding in
solution all the ingredients necessary for the formation of the
tissues. In some animals and vegetables, of the lowest organization,
such as infusoria, polypes, alga3, and the like, neither blood nor
circulation is required ; since all parts of the body, having a similar
structure, absorb nourishment equally from the surrounding media,
and carry on nearly or quite the same chemical processes of growth
and assimilation. In the higher animals and vegetables, however,
as well as in the human subject, the case is different. In them, the
structure of the body is compound. Different organs, with widely
different functions, are situated in different parts of the frame ; and
each of these functions is more or less essential to the continued
existence of the whole. In the intestine, for example, the process
of digestion takes place ; and the prepared ingredients of the food
are thence absorbed into the bloodvessels, by which they are
transported to distant tissues and organs. In the lungs, again,
the blood absorbs oxygen which is afterward to be appropriated by
the tissues ; and carbonic acid, which was produced in the tissues,
is exhaled from the lungs. In the liver, the kidneys, and the skin,
other substances again are produced or eliminated, and these local
processes are all of them necessary to the preservation of the general
organization. The circulating fluid is, therefore, in the higher
animals, a means of transportation, by which the substances pro-
duced in particular organs are dispersed throughout the body, or
by which substances produced generally in the tissues are conveyed
to particular organs, in order to be eliminated and expelled.

The circulatory apparatus consists of four different parts, viz :
1st. The heart ; a hollow, muscular organ, which receives the blood
at one orifice and drives it out, in successive impulses, at another.
2d. The arteries ; a series of branching tubes, which convey the
blood from the heart to the different tissues and organs of the body.

THE HEART.

265

3d. The capillaries ; a network of minute inosculating tubules,
which are interwoven with the substance of the tissues, and which
bring the blood into intimate contact with the cells and fibres of
which they are composed ; and 4th. The veins ; a set of converg-
ing vessels, destined to collect the blood from the capillaries, and
return it to the heart. In each of these four different parts of the
circulatory apparatus, the movement of the blood is peculiar and
dependent on special conditions. It will therefore require to be
studied in each one of them separately.

Fig

THE HEART.

The structure of the heart, and of the large vessels connected
with it, varies considerably in different classes of animals, owing to
the different arrangement of the respiratory organs. For the respi-
ratory apparatus being one of the most important in the body, and
the one most closely connected
by anatomical relations with
the organs of circulation, the
latter are necessarily modified
in structure to correspond with
the former. In fish, for exam-
ple (Fig. 76), the heart is an
organ consisting of two princi-
pal cavities ; an auricle (a) into
which the blood is received from
the central extremity of the
vena cava, and a ventricle (b)
into which the blood is driven
by the contraction of the auricle.
The ventricle is considerably
larger and more powerful than
the auricle, and by its contrac-
tion drives the blood into the
main artery supplying the gills.
In the gills (cc) the blood is

. ,. , . . CIRCULATION OF FISH. — a. Anncle. r>.

arteriallZed ; after Which it IS Ventricle, cc. Gills, d. Aorta, ee. Venae cava.

collected by the branchial veins.

These veins unite upon the median line to form the aorta (d) by

which the blood is finally distributed throughout the frame. In

266

THE CIRCULATION.

Fig. 77.

these animals the respiratory process is not a very active one ; but
the gills, which are of small size, being the only respiratory organs,
all the blood requires to pass through them for purposes of aeration.
The heart here is a single organ, destined only to drive the blood
from the termination of the venous system to the capillaries of the
gills.

In reptiles, the heart is composed of two auricles, placed side by
side, and one ventricle. (Fig. 77.) The venas cavse discharge their

blood into the right auricle (a),
whence it passes into the ventricle
(t-). From the ventricle, a part of it
is carried into the aorta and distri-
buted throughout the body, while a
part is sent to the lungs through the
pulmonary artery. The arterialized
blood, returning from the lungs by
the pulmonary vein, is discharged
into the left auricle (b), and thence
into the ventricle (c), where it
mingles with the venous blood
which has just arrived by the vense
cava3. In the reptile, therefore, the
ventricle is a common organ of pro-
pulsion, both for the lungs and for
the general circulation. In these
animals the aeration of the blood in
the lungs is only partial ; a certain
portion of the blood which leaves
the heart being carried to these organs, just as in the human subject
it is only a portion of the blood which is carried to the kidney by
the renal artery. This arrangement is sufficient for the reptiles,
because in many of them, such as serpents and turtles, the lungs
are much more extensive and efficient, as respiratory organs, than
the gills of fish ; while in others, such as frogs and water-lizards,
the integument itself, which is moist, smooth, and naked, takes an
important share in the aeration of the blood.

In quadrupeds and the human species, however, the respi-
ratory process is not only exceedingly active, but the lungs
are, at the same time, the only organs in which the aeration of
the blood can be fully accomplished. In them, accordingly, we
find the two circulations, general and pulmonary, entirely dis-

ClRCULATION OF REPTILES. — a.

Right auricle. 6. Left auricle, c. Ventricle.
d. Lungs, e. Aorta. /. Veua cava.

THE HEART.

267

Fig. 78.

tinct from each other. (Fig. 78.) All the blood returning from
the body by the veins must pass through the lungs before it is
again distributed through the
arterial system. We have
therefore a double circula-
tion, and also a double heart;
the two sides of which,
though united externally,
are separate internally. The
mammalian heart consists of
a right auricle and ventricle
(a, b), receiving the blood
from the vena cava (i), and
driving it to the lungs ; and
a left auricle and ventricle
C/» 9} receiving the blood
from the lungs and driving
it outward through the arte-
rial system.

In the complete or double
mammalian heart, the differ-
ent parts of the organ present
certain peculiarities and bear

certain relations to each other, which it is necessary to understand
before we can properly appreciate its action and movements. The
entire organ has a more or less conical form, its base being situated
on the median line, directed upward and backward ; the whole being
suspended in the chest, and loosely fixed to the spinal column, by
the great vessels which enter and leave it at this point. The apex,
on the contrary, is directed downward, forward, and to the left, sur-
rounded by the pericardium and the pericardial fluid, but capable
of a very free lateral and rotatory motion. The auricles, which
have a smaller capacity and thinner walls than the ventricles, are
situated at the upper and posterior part of the organ (Figs. 79 and
80) ; while the ventricles occupy its anterior and lower portions.
The two ventricles, moreover, are not situated on the same plane,
but the right ventricle occupies a position somewhat in front and
above that of the left ; so that in an anterior view of the heart the
greater portion of the left ventricle is concealed by the right (Fig.
79), and in a posterior view the greater portion of the right ven-
tricle is concealed by the left (Fig. 80) ; while in both positions the

CIRCCI. ATir>5 IN MAMMA MANS. — n. Right
auricle. 6. Right ventricle, c. Pulmonary artery.
d. Lungs, e. Pulmonary vein. /. Left auricle, y.
Left ventricle, h. Aorta, i. Vena cava.

268

THE CIRCULATION".

apex of the heart is constituted altogether by the point of the left
ventricle.

Fig. 79.

Fig. 80.

HUMAN UK ART, anterior view. —
a. Right ventricle. 6. Left ventricle.
c. Right auricle, d. Left auricle, e.
Pulmonary artery. /. Aorta.

II UMAX Hi: ART, posterior view. —
a. Right ventricle. 6. Left ventricle.
c. Right auricle, d. Left auricle.

The different cavities of the heart and of the adjacent blood-
vessels, though continuous with each other, are partially separated
by certain constrictions. These constricted orifices, by which the
different cavities communicate, are known by the names of the

Fig. 81.

RIGHT AURICLE AND VENTRICLE; Auriculo-ventricular Valves open, Arterial Valves closed.

auricular, auriculo-ventricular, and aortic and pulmonary orifices ;
the auricular orifices being the passages from the venas cavoe and

THE HEART. 269

pulmonary veins into the right and left auricles; the auriculo-
ventricular orifices leading from the auricles into the ventricles;
and the aortic and pulmonary orifices leading from the ventricles
into the aortic and pulmonary arteries respectively.

The auriculo- ventricular, aortic, and pulmonary orifices are fur-
nished with valves, which allow the blood to pass readily from the
auricles to the ventricles, and from the ventricles to the arteries,
but shut back, with the contractions of the organ, so as to prevent
its return in an opposite direction. The course of the blood
through the heart is, therefore, as follows. From the vena cava it
passes into the right auricle ; and from the right auricle into the
right ventricle. (Fig. 81.) On the contraction of the right ventricle,
the tricuspid valves shut back, preventing its return into the auricle
(Fig. 82); and it is thus driven through the pulmonary artery to the

Fig. 82.

KIOHT A CHICLE AXD VENTRICLE; Attricalo-veatricular Valves closed, Arterial Valves open.

lungs. Eeturning from the lungs, it enters the left auricle, thence
passes into the left ventricle, from which it is finally delivered into
the aorta, and distributed throughout the body. (Fig. S3.) This
movement of the blood, however, through the cardiac cavities, is
not a continuous and steady flow, but is accomplished by alternate
contractions and relaxations of the muscular parietes of the heart
so that with every impulse, successive portions of blood are received
by the auricles, delivered into the ventricles, and by them dis-

270 THE CIRCULATION.

charged into the arteries. Each one of these successive actions is
called a beat, or pulsation of the heart.

Fig. 83.

COURSE OF BLOOD THROUGH THE HEART. — a, a. Vena cava, superior and inferior.
6. Right ventricle, c. Pulmonary artery, d. Pulmonary vein. e. Left ventricle. /. Aorta.

Each pulsation of the heart is accompanied by certain important
phenomena, which require to be studied in detail. These are the
sounds, the movements, and the impulse.

The sounds of the heart are two in number. They can readily be
heard by applying the ear over the cardiac region, when they are
found to be quite different from each other in position, in tone, and
in duration. They are distinguished as the first and second sounds
of the heart. The first sound is heard with the greatest intensity
over the anterior surface of the heart, and more particularly over
the fifth rib and the fifth intercostal space. It is long, dull, and
smothered in tone, and occupies one-half the entire duration of a
single beat. It corresponds in time with the impulse of the heart
in the precordial region, and the stroke of the large arteries in the
immediate vicinity of the chest. The second sound follows imme-
diately upon the first. It is heard most distinctly at the situation
of the aortic and pulmonary valves, viz., over the sternum at the
level of the third costal cartilage. It is short, sharp, and distinct
in tone, and occupies only about one-quarter of the whole time of

THE HEART. 271

a pulsation. It is followed by an equal interval of silence ; after
which the first sound again recurs. The whole time of a cardiac
pulsation may then be divided into four quarters, of which the first
two are occupied by the first sound, the third by the second sound,
and the fourth by an interval of silence, as follows : —

f 1st quarter

ist quarter |

Time of pulsation, j 3d „ gecond

^ 4th " Interval of silence.

The cause of the second sound is universally acknowledged to be
the sudden closure and tension of the aortic and pulmonary valves.
This fact is established by the following proofs: 1st, this sound is
heard with perfect distinctness, as we have already mentioned,
direct*1- over tho situation of the above-mentioned valves; 2d, the
farther we recede in any direction from this point, the fainter be-
comes the sound ; and 3d, in experiments upon the living animal,
often repeated by different observers, it has been found that if a
curved needle be introduced into the base of the large vessels, so
as to hook back the semilunar valves, the second sound at once dis-
appears, and remains absent until the valve is again liberated. These
valves consist of fibrous sheets, covered with a layer of endocardial
epithelium. They have the form of semilunar festoons, the free
edge of which is directed away from the cavity of the ventricle,
while the attached edge is fastened to the inner surface of the base
of the artery. While the blood is passing from the ventricle to the
artery, these valves are thrown forward and relaxed ; but when the
artery reacts upon its contents they shut back, and their fibres, be-
coming suddenly tense, yield a clear, characteristic, snapping sound.

The production of the first sound has been attributed by some
writers to a combination of various causes; such as the rush of
blood through the cardiac orifices, the muscular contraction of the
parietes of the heart, the tension of the auriculo- ventricular valves,
the collision of the particles of blood with each other and with the
surface of the ventricle, &c. &c. We believe, however, with Andry1
and some others, that the first sound of the heart has a similar
origin with the second ; and that it is dependent altogether on t1>e
closure of the auricula-ventricular valves. The reasons for this con-
clusion are the following : —

1st. The second sound is undoubtedly caused by the closure of

1 Diseases of the Heart, Kneeland's translation, Boston, 1846.

272 THE CIRCULATION.

the semilunar valves, and in the action of the heart the shutting
back of the two sets of valves alternate with each other precisely
as do the first and second sounds ; and there is every probability,
to say the least, that the sudden tension of the valvular fibres pro-
duces a similar effect in each instance.

2d. The first sound is heard most distinctly over the anterior
surface of the ventricles, where the tendinous cords supporting the
auriculo- ventricular valves are inserted, and where the sound pro-
duced by the tension of these valves would be most readily con-
ducted to the ear.

3d. There is no reason to believe that the current of blood
through the cardiac orifices could give rise to an appreciable sound,
so long as these orifices, and the cavities to which they lead, have
their normal dimensions. An unnatural souffle may indeed origi-
nate from this cause when the orifices of the heart are diminished
in size, as by calcareous or fibrinous deposits; and it may also
occur in cases of aneurism. A souffle may even be produced at
will in any one of the large arteries by pressing firmly upon it
with the end of a stethoscope, so as to diminish its calibre. But in
all these instances, the abnormal sound occurs only in consequence
of a disturbance in the natural relation existing between the volume
of the blood and the size of the orifice through which it passes.
In the healthy heart, the different orifices of the organ are in exact
proportion to the quantity of the circulating blood ; and there is no
more reason for believing that its passage should give rise to a
sound in the cardiac cavities than in the larger arteries or veins.

4th. The difference in character between the two sounds of the
heart depends, in all probability, on the different arrangement of
the two sets of valves. The second sound is short, sharp, and dis-
tinct, because the semilunar valves are short and narrow, superficial
in their situation, and supported by the highly elastic, dense and
fibrous bases of the aortic and pulmonary arteries. The first sound
is dull and prolonged, because the auriculo- ventricular valves are
broad and deep-seated, and are attached, by their long chordas
tendineae to the comparatively soft and yielding fleshy columns of
the heart. The difference between the first and second sounds can,
in fact, be easily imitated, by simply snapping between the fingers
two pieces of tape or ribbon, of the same texture but of different
lengths. (Fig. 84.) The short one will give out a distinct and sharp
sound ; the long one a comparatively dull and prolonged sound.

Together with the first sound of the heart there is also to be

THE HEART. 273

heard a slight friction sound, produced by the collision of the point
of the heart against the parietes of the chest. This sound, which is
heard in the fifth intercostal space, is very faint, and is more or less

Fig. 84.

masked by the strong valvular sound which occurs at the same
time. It is different, however, in character from the latter, and
may usually be distinguished from it by careful examination.

The movements of the heart during the time of a pulsation are
of a peculiar character, and have been very often erroneously
described. In fact altogether the best description of the move-
ments of the heart which has yet appeared, is that given by "Wil-
liam Harvey, in his celebrated work on the Motion of the Heart and
Blood, published in 1628. He examined the motion of the heart
by opening the chest of the living animal ; and though the same or
similar experiments have been frequently performed since his time,
the descriptions given by subsequent observers have been for the
most part singularly inferior to his, both in clearness and fidelity.
The method which we have adopted for examining the motions of
the heart in the dog is as follows : The animal is first rendered
insensible by ether, or by the inoculation of woorara. The latter
mode is preferable, since a long-continued etherization seems to
exert a sensibly depressing effect on the heart's action, which is
not the case with woorara. The trachea is then exposed and
opened just below the larynx, and the nozzle of a bellows inserted
and secured by ligature. Finally, the chest is opened on the me-
dian line, its two sides widely separated, so as to expose the heart
and lungs, the pericardium slit up and carefully cut away from its
attachments, and the lungs inflated by insufflation through the
trachea. By keeping up a steady artificial respiration, the move-
18

274 THE CIRCULATION.

ments of the heart may be made to continue, in favorable cases, for
more than an hour ; and its actions may be studied by direct obser-
vation, li ke those of any external organ.

The examination, however, requires to be conducted with certain
precautions, which are indispensable to success. When the heart
is first exposed, its movements are so complicated, and recur with
such rapidity, that it is difficult to distinguish them perfectly from
each other, and to avoid a certain degree of confusion. Singular
as it may seem, it is even difficult at first to determine what period
in the heart's pulsation corresponds to contraction, and what to
relaxation of the organ. We have even seen several medical men,
watching together the pulsations of the same heart, unable to agree
upon this point. It is very evident, indeed, that several English
and continental observers have mistaken, in their examinations, the
contraction for the relaxation, and the relaxation for the contrac-
tion. The first point, therefore, which it is necessary to decide, in
examining the successive movements of a cardiac pulsation, is the
following, viz : Which is the contraction and which the relaxation of
the ventricles ? The method which we have adopted is to pass a
small silver canula directly through the parietes of the left ven-
tricle into its cavity. The blood is then driven from the external
orifice of the canula in interrupted jets ; each jet indicating the
time at which the ventricle contracts upon its contents. The
canula is then withdrawn, and the different muscular layers of the
ventricular walls, crossing each other obliquely, close the opening,
so that there is little or no subsequent hemorrhage.

When the successive actions of contraction and relaxation have
by this means been fairly recognized and distinguished from each
other, the cardiac pulsations are seen to be characterized by the
following phenomena. The changes in form and position of the
entire heart are mainly dependent on those of the ventricles, which
contract simultaneously with each other, and which constitute much
the largest portion of the entire mass of the organ.

1. At the time of its contraction the heart hardens. This pheno-
menon is exceedingly well marked, and is easily appreciated by
placing the finger upon the ventricles, or by grasping them between
the finger and thumb. The muscular fibres become swollen and
indurated, and, if grasped by the hand, communicate the sensation
of a somewhat sudden and powerful shock. It is this forcible indu-
ration of the heart, at the time of contraction, which has been mis-
taken by some writers for an active dilatation, and described as

THE HEART. 275

such. It is, however, a phenomenon precisely similar to that which
takes place in the contraction of a voluntary muscle, which becomes
swollen and indurated at the same moment and in the same propor-
tion that it diminishes in length.

2. At the time of contraction, the ventricles elongate and the
point of the heart protrudes. This phenomenon was very well
described by Dr. Harvey.1 " The heart," he says, " is erected, and
rises upward to a point, so that at this time it strikes against the
breast and the pulse is felt externally." The elongation of the
ventricles during contraction has, however, been frequently denied
by subsequent writers. The only modern observers, so far as we
are aware, who have recognized its existence, are Drs. C. W. Pen-
nock and Edward M. Moore, who performed a series of very careful
and interesting experiments on the action of the heart, in Philadel-
phia, in the year 1839.2 These -experimenters operated upon calves,
sheep, and horses, by stunning the animal with a blow upon the
head, opening the chest, and keeping up artificial respiration. They
observed an elongation of the ventricle at the time of contraction,
and were even able to measure its extent by applying a shoemaker's
rule to the heart while in active motion. We are able to corroborate
entirely the statement of these observers by the result of our own
experiments on dogs, rabbits, frogs, &c. The ventricular contrac-
tion is an active movement, the relaxation entirely a passive one.
When contraction occurs and a stream of blood is thrown out of
the ventricle, its sides approximate each other and its point elon-
gates ; so that the transverse diameter of the heart is diminished,
and its longitudinal diameter increased. This can be readily felt
by grasping the base of the heart and the origin of the large vessels
gently between the first and middle fingers, and allowing the end
of the thumb of the same hand to rest lightly upon its apex.
With every contraction the thumb is sensibly lifted and separated
from the fingers, by a somewhat forcible elevation of the point of
the heart.

The same thing can be seen, and even measured by the eye,
in the following manner : If the heart of the frog or even of any
small warm-blooded animal, as the rabbit, be rapidly removed from
the chest, it will continue to beat for some minutes afterward ; and
when the rhythmical pulsations have finally ceased, contractions

1 Works of William Harvey, M. D. Sydenham ed., London, 1847, p. 21.

2 Philadelphia Medical Examiner, No. 44.

276

THE CIRCULATION.

can still be readily excited by touching the heart with the point of
a steel needle. If the heart be now held by its base between the
thumb and finger, with its point directed upward, it will be seen
to have a pyramidal or conical form, representing very nearly in
its outline an equilateral triangle (Fig. 85) ; its base, while in a
condition of rest, bulging out laterally, while the apex is compara-
tively obtuse.

Fig! 85.

Fig. 815.

HEAKT op FROO
in a state of relaxa-
tion.

HEAKT OF FKOO in cont action.

Fig. 87,

"\Yhen the heart, held in this position, is touched with the point
of a needle (Fig. 86), it starts up, becomes instantly narrower and
longer, its sides approximating and its point rising to an acute
angle. This contraction is immediately followed by a relaxation ;
the point of the heart sinks down, and its sides again bulge out-
ward.

Let us now see in what manner this change in the figure of the
ventricles during contraction is produced. If the muscular fibres

of the heart were arranged in the form of
simple loops, running parallel with the
axis of the organ, the contraction of these
fibres would merely have the effect of di-
minishing the size of the heart in every
direction. This effect can be seen in the
accompanying hypothetical diagram (Fig.
87), where the white outline represents
such simple looped fibres in a state of re-
laxation, and the dotted internal line indi-
cates the form which they would take in
contraction. In point of fact, however,
none of the muscular fibres of" the heart

run parallel to its longitudinal axis. They are disposed, on the
contrary, in a direction partly spiral and partly circular. The most
superficial fibres start from the base of the ventricles, and pass

Diagram of SIMPLE LOOPED
FIBRES, in relaxation and Con-
traction.

THE HEART.

277

toward the apex, curling round the heart in such a manner as to
pass over its anterior surface in an obliquely spiral direction, from
above downward, and from right to left. (Fig. 88.) They converge

toward the point of the heart, curl-
ing round the centre of its apex, and
then, changing their direction, be-
come deep-seated, run upward along

Fig. 89.

BULLOCK'S HK AKT, anterior view,
showing thesupe.ficial muscular fibres.

T- E F T V E x T R r r r. E OF
Bp i. LOCK'S HEAKT, show-
iug the deep fibres.

the septum and internal surface of the ventricles, and terminate
in the columns earner, and in the inner border of the auriculo-
ventricular ring. The deepest layers of fibres, on the contrary, a*re
wrapped round the ventricles in a nearly circular direction (Fig.
89) ; their points of origin and attachment being still the auriculo-
ventricular ring, and the points of the fleshy columns. The entire
arrangement of the muscular bundles may be readily seen in a
heart which has been boiled for six or eight hours, so as to soften
the connecting areolar tissue, and enable the fibrous layers to be
easily separated from each other.

By far the greater part of the mass of the fibres have therefore
a circular instead of a longitudinal direction. When they contract,
their action tends to draw the lateral walls of the ventricles together,
and thus to diminish the transverse diameter of the heart; but as
each muscular fibre becomes thickened in direct proportion to its
contraction, their combined lateral swelling necessarily pushes out
the apex of the ventricle, and the heart elongates at the same time
that its sides are drawn together. This effect is illustrated in the
accompanying diagram (Fig. 90), where the white lines show the
figure of the heart during relaxation, with the course of its circular

278

THE CIRCULATION.

fibres, while the dotted line shows the narrowed and elongated
figure necessarily produced by their contraction. This phenomenon,

therefore, of the protrusion of the apex
Fig. 90. of the heart at the time of contraction, is

not only fully established by observation,
but is readily explained by the anatomical
structure of the organ.

3. Simultaneously with the hardening
and elongation of the heart, its apex moves
slightly from left to right, and rotates also
upon its own axis in the same direction.
Both these movements result from the
peculiar spiral arrangement of the cardiac
fibres. If we refer again to the preceding
Diagram of CIRCULAR FIBRES diagrams, we shall see that, provided the

OF THE HEAKT.aud their con- „, ,..,,.,.

traction. fibres were arranged in simple longitudi-

nal loops (Fig. 87), their contraction would

merely have the effect of drawing the point of the heart directly
upward in a straight line toward its base. On the other hand, if
they were arranged altogether in a circular direction (Fig. 90),
the apex would be simply protruded, also in a direct line,
without deviating or twisting either to the
Fig. 91. right or to the left. But in point of fact,

the superficial fibres, as we have already
described, run spirally, and, curling round
the point of the heart, turn inward toward
its base ; so that if the apex of the organ be
viewed externally, it will be seen that the
superficial fibres converge toward its cen-
tral point in curved lines, as in Fig. 91. It
is well known that every curved muscular
fibre, at the time of its shortening, necessa-
rily approximates more or less to a straight

line. Its curvature is diminished in exact proportion to the extent
of its contraction ; and if arranged in a spiral form, its contraction
tends in the same degree to untwist the spiral. During the con-
traction of the heart, therefore, its apex rotates on its own axis in
the direction indicated by the arrows in Fig. 91, viz., from left to
right anteriorly, and from right to left posteriorly. This produces
a twisting movement of the apex in the above direction, which is

CONVERGING FIBRKSJIT
THE APEX OF THE HEART.

THE HEAKT. 279

very perceptible to the eye at each pulsation of the heart, when
exposed in the living animal.

4. The protrusion of the point of the heart at the time of con-
traction, together with its rotation upon its axis from left to right,
brings the apex of the organ in contact with the parietes of the
chest, and produces the shock or impulse of the heart, which is
readily perceptible externally, both to the eye and to the touch.
In the human subject, when in an erect position, the heart strikes
the chest in the fifth intercostal space, midway between the edge
of the sternum and a line drawn perpendicularly through the left
nipple. In a supine position of the body, the heart falls away from
the anterior parietes of the chest so much that the impulse may
disappear for the time altogether. This alternate recession and
advance of the point of the heart, in relaxation and contraction,
is provided for by the anatomical arrangement of the pericardium,
and the existence of the pericardial fluid. As the heart plays back-
ward and forward, the pericardial fluid constantly follows its
movements, receding as the heart advances, and advancing as the
heart recedes. It fulfils, in this respect, the same purpose as the
sy no vial fluid, and the folds of adipose tissue in the cavity of the
large articulations ; and allows the cardiac movements to take place
to their full extent without disturbing or injuring in any way the
adjacent organs.

5. The rhythm of the heart's pulsations is peculiar and somewhat
complicated. Each pulsation is made up of a double series of con-
tractions and relaxations. The two auricles contract together, and
afterward the two ventricles ; and in each case the contraction is
immediately followed by a relaxation. The auricular contraction
is short and feeble, and occupies the first part of the time of a
pulsation. The ventricular contraction is longer and more powerful,
and occupies the latter part of the same period. Following the
ventricular contraction there comes a short interval of repose, after
which the auricular contraction agains recurs. The auricular and
ventricular contractions, however, do not alternate so distinctly
with each other (like the strokes of the two pistons of a fire engine)
as we should be led to believe from the accounts which have been
given by some observers. On the contrary, they are connected and
continuous. The contraction, which commences at the auricle, is
immediately propagated to the ventricle, and runs rapidly from the
base of the heart to its apex, very much in the manner of a peri-
staltic motion, except that it is more sudden and vigorous.

280 THE CIRCULATION.

William Harvey, again, gives a better account of this part of the
heart's action than has been published by any subsequent writer.
The following exceedingly graphic and appropriate description,
taken from his book, shows that he derived his knowledge, not
from any secondary or hypothetical sources, but from direct and
careful study of the phenomena in the living animal.

"First of all," he says,1 "the auricle contracts, and in the course
of its contraction throws the blood (which it contains in ample
quantity as the head of the veins, the storehouse and cistern of the
blood) into the ventricle, which being filled, the heart raises itself
straightway, makes all its fibres tense, contracts the ventricles, and
performs a beat, by which beat it immediately sends the blood
supplied to it by the auricle, into the arteries ; the right ventricle
sending its charge into the lungs by the vessel which is called vena
arteriosa, but which, in structure and function, and all things else,
is an artery ; the left' ventricle sending its charge into the aorta,
and through this by the arteries to the body at large.

" These two motions, one of the ventricles, another of the auricles,
take place consecutively, but in such a manner that there is a kind
of harmony or rhythm preserved between them, the two concurring
in such wise that but one motion is apparent, especially in the
warmer blooded animals, in which the movements in question are
rapid. Nor is this for any other reason than it is in a piece of
machinery, in which, though one wheel gives motion to another,
yet all the wheels seem tQ move simultaneously; or in that
mechanical contrivance which is adapted to fire-arms, where the
trigger' being touched, down comes the flint, strikes against the
steel, elicits a spark, which falling among the powder, it is ignited,
upon which the flame extends, enters the barrel, causes the explo-
sion, propels the ball, and the mark is attained ; all of which inci-
dents, by reason of the celerity with which they happen, seem to
take place in the twinkling of an eye."

The above description indicates precisely the manner in which
the contraction of the ventricle follows successively and yet con-
tinuously upon that of the auricle. The entire action of the auricles
and ventricles during a pulsation is accordingly as follows : The
contraction begins, as we have already stated, at the auricle.
Thence it runs immediately forward to the apex of the heart. The
entire ventricle contracts vigorously, its walls harden, its apex

1 Op. cit., p. 31.

THE ARTERIES AND THE ARTERIAL CIRCULATION. 281

protrudes, strikes against the walls of the chest, and twists from
left to right, the auriculo-ventricular valves shut back, the first
sound is produced, and the blood is driven into the aorta and
pulmonary artery. These phenomena occupy about one-half the
time of an entire pulsation. Then the ventricle is immediately
relaxed, and a short period of repose ensues. During this period
the blood flows in a steady stream from the large veins into the
auricle, and through the auriculo-ventricular orifice into the ven-
tricle ; filling the ventricle, by a kind of passive dilatation, about
two-thirds or three-quarters full. Then the auricle contracts with a
quick sharp motion, forces the last drop of blood into the ventricle,
distending it to its full capacity, and then the ventricular contraction
follows, as above described, driving the blood into the large arteries.
These movements of contraction and relaxation continue to alter-
nate with each other, and form, by their recurrence, the successive
cardiac pulsations.

THE ARTERIES AND THE ARTERIAL CIRCULATION".

The arteries are a series of branching tubes which commence
with the aorta and ramify throughout the body, distributing the
blood to all the vascular organs. They are composed of three
coats, viz : an internal homogeneous tunic, continuous with the
endocardium; a middle coat, composed of elastic and muscular
fibres ; and an external or " cellular" coat, composed of condensed
layers of areolar tissue. The essential anatomical difference be-
tween the larger and the smaller arteries consists in the structure
of their middle coat. In the smaller arteries this coat is composed
exclusively of smooth muscular fibres, arranged in a circular man-
ner around the vessel, like the circular fibres of the muscular coat
of the intestine. In arteries of medium size the middle coat con-
tains both muscular and elastic fibres ; while in those of the largest
calibre it consists of elastic tissue alone. The large arteries, ac-
cordingly, possess a remarkable degree of elasticity and little or no
contractility ; while the smaller are contractile, and but little or not
at all elastic.

It is found, by measuring the diameters of the successive arte-
rial ramifications, that the combined area of all the branches given
off from a trunk is somewhat greater than that of the original
vessel ; and therefore that the combined area of all the small arte-
ries must be considerably larger than that of the aorta, from which

282 THE CIRCULATION.

the arterial system originates. As the blood, consequently, in its
passage from the heart outward, flows successively through larger
and larger spaces, the rapidity of its circulation must necessarily
be diminished, in the same proportion as it recedes from the heart.
It is driven rapidly through the larger trunks, more slowly through
those of medium size, and more slowly still as it approaches the
termination of the arterial system and the commencement of the
capillaries.

The movement of the Hood through the arteries is primarily caused
by the contractions of the heart ; but is, at the same time, regulated
and modified by the elasticity of the vessels. The mode in which
the arterial circulation takes place is as follows. The arterial sys-
tem is, as we have seen, a vast and connected ramification of tubular
canals, which may be regarded as a great vascular cavity, divided
and subdivided from within outward by the successive branching
of its vessels, but communicating freely with the heart and aorta
at one extremity, and with the capillary plexus at the other;
and this vascular system is filled everywhere with the circulating
fluid. At the time of the heart's contraction, the muscular walls of
the ventricle act powerfully upon its fluid contents. The auriculo-
ventricular valves at the same time shutting back and preventing
the blood from regurgitating into the ventricle, it is forced out
through the aortic orifice. A charge of blood is therefore driven
into the arterial ramifications, distending their walls by the addi-
tional quantity of fluid forced into their cavities. When the ven-
tricle immediately afterward relaxes, the active distending force is
removed ; and the elastic arterial walls, reacting upon their contents,
would force the blood back again into the heart, were it not for the
semilunar valves, which shut together and close the aortic orifice.
The blood is therefore urged onward, under the pressure of the
arterial elasticity, into the capillary system. When the arteries
have thus again partially emptied themselves, and returned to their
original dimensions, they are again distended by another contraction
of the heart. In this manner a succession of impulses or distensions
is produced, which alternates with the reaction or subsidence of the
vessels, and which can be felt throughout the body, wherever the
arterial ramifications penetrate. This phenomenon is known by
the name of the arterial pulse.

When the blood is thus driven by the cardiac pulsations into the
arteries, the vessels are not only distended laterally, but are elongated
as well as widened, and enlarged in every direction. Particularly

THE ARTERIES AND THE ARTERIAL CIRCULATION. 283

Flgt 9:

when the vessel takes a curved or serpentine course, its elongation
and the increase of its curvatures may be observed at every pulsa-
tion. This may be seen, for example, in the temporal, or even
in the radial arteries, in emaciated persons. It is also very well
seen in the mesenteric arteries, when the abdomen is opened in the
living animal. At every contraction of the heart the curves of
the artery on each side become more strongly pronounced. (Fig.
92.) The vessel even rises up partially out of its
bed, particularly where it runs over a bony sur-
face, as in the case of the radial artery. In old
persons the curves of the vessels become perma-
nently enlarged from frequent distension ; and all
the arteries tend to assume, with the advance of
age, a more serpentine and even spiral course.

But the arterial pulse has certain other pecu-
liarities which deserve a special notice. In the
first place, if we place one finger upon the chest
at the situation of the apex of the heart, and an-
other upon the carotid artery at the middle of
the neck, we can distinguish little or no difference
in time between the two impulses. The disten-
sion of the carotid seems to take place at the
same instant with the contraction of the heart.
But if the second finger be placed upon the temporal artery, instead
of the carotid, there is a perceptible interval between the two beats.
The impulse of the temporal artery is felt a little later than that of
the heart. In the same way the pulse of the radial artery at the
wrist seems a little later than that of the carotid, and that of the
posterior tibial at the ankle joint a little later than that of the radial.
So that, the greater the distance from the heart at which the artery
is examined, the later is the pulsation perceived by the finger laid
upon the vessel.

But it has been conclusively shown, particularly by the investi-
gations of M. Marey,1 that this difference in time of the arterial
pulsations, in different parts of the body, is rather relative than
absolute. By the contraction of the heart, the impulse is commu-
nicated at the same instant to all parts of the arterial system ; but
the apparent difference between them, in this respect, depends upon
the fact, that, although all the arteries begin to be distended at the

Elongation and curva-

Dr. Brown-Sequard's Journal de Phvsiologie, April, 1859.

284 THE CIRCULATION.

same moment, yet those nearest the heart are distended suddenly
and rapidly, while for those at a distance, the distension takes place
more slowly and gradually. Thus the impulse given to the finger,
which marks the condition of maximum distension of the vessel,
occurs a little later at a distance from the heart, than in its imme-
diate proximity.

This modification of the arterial pulse is produced in the follow-
ing way : —

The contraction of the left ventricle is a brusque, vigorous and
sudden motion. The charge of blood, thus driven into the arterial
system, meeting with a certain amount of resistance from the fluid
already filling the vessels, does not instantly displace and force
onward a quantity of blood equal to its own mass, but a large
proportion of its force is used in expanding the distensible walls
of the vessels. In the immediate neighborhood, therefore, the
expansion of the arteries is sudden and momentary, like the con-
traction of the heart itself. But this expansion requires for its
completion a certain expenditure, both of force and time ; so that
at a little distance farther on, the vessel is neither distended to the
same degree nor with the same rapidity. At the more distant
point, accordingly, the arterial impulse is less powerful and arrives
more slowly at its maximum.

On the other hand, when the heart becomes relaxed, the artery
in its immediate neighborhood contracts upon the blood by its own
elasticity ; and as its contraction at this time meets with no other
resistance than that of the blood in the smaller vessels beyond, it
drives a portion of its own blood into them, and thus supplies these
vessels with a certain degree of distending force even in the inter-
vals of the heart's action. Thus the difference in size of the carotid
artery, at the two periods of the heart's contraction and its relaxa-
tion, is very marked ; for the degree of its distension is great when
the heart contracts, and its own reaction afterward empties it of
blood to a very considerable extent. But in the small branches of
the radial or ulnar artery, there is less distension at the time of the
cardiac contraction, because this force has been partly expended in
overcoming the elasticity of the larger vessels ; and there is less
emptying of the vessel afterward, because it is still kept partially
filled by the reaction of the aorta and its larger branches. In other
words, there is progressively less variation in size, at the periods of
distension and collapse, for the smaller and distant arteries than for
those which are larger and nearer the heart.

THE ARTERIES AND THE ARTERIAL CIRCULATION. 285

Mr. Marey has illustrated these facts by an exceedingly ingenious
and effectual contrivance. He attached to the pipe of a small forcing
pump, to be worked by alternate strokes of the piston, a long elastic
tube open at the farther extremity. At different points upon this
tube there rested little movable levers, which were raised by the
distension of the tube whenever water was driven into it by the
forcing pump. Each lever carried upon its extremity a small pen-
cil, which marked upon a strip of paper, revolving with uniform
rapidity, the lines produced by its alternate elevation and depression.
Bv these curves, therefore, both the extent and rapidity of distension
of different parts of the elastic tube were accurately registered.
The curves thus produced are as follows : —

Fig. 93.

('. KVKS OF THE A R T K R i A T, P r T, s A T i n s , as il 1 n*t ratf>d hv M. Marpy'n experiment. — 1. Is'ear
the distending force. 2. At a distance from it. 3. Still farther removed.

It will be seen that the whole time of pulsation is everywhere of
equal length, and that the distension everywhere begins at the same
moment. But at the beginning of the tube the expansion is wide
and sudden, and occupies only a sixth part of the entire pulsation,
while all the rest is taken up by a slow reaction. At the more
remote points, however, the. period of expansion becomes longer
and that of collapse shorter ; until at 3 the two periods are com-
pletely equalized, and the amount of expansion is at the same time
reduced one-half. Thus, the farther the blood passes from the heart
outward, ihe more uniform is its flow, and the more moderate the
distension of the arteries.

Owing to the alternating contractions and relaxations of the heart,
accordingly, the blood passes through the arteries, not in a steady
stream, but in a series of welling impulses ; and the hemorrhage
from a wounded artery is readily distinguished from venous or
capillary hemorrhage by the fact that the blood flows in successive
jets, as well as more rapidly and abundantly. If a puncture be
made in the walls of the ventricle, and a slender canula introduced,

286 THE CIRCULATION.

the flow of the blood through it is seen to be entirely intermittent.
A strong jet takes place at each ventricular contraction, and at each-
relaxation the flow is completely interrupted. If the puncture be
made, however, in any of the large arteries near the heart, the flow
of blood through the orifice is no longer intermittent, but is con-
tinuous ; only it is very much stronger at the time of ventricular
contraction, and diminishes, though it does not entirely cease, at
the time of relaxation. If the blood were driven through a series
of perfectly rigid and unyielding tubes, its flow would be every-
where intermittent ; and it would be delivered from an orifice situ-
ated at any point, in perfectly interrupted jets. But the arteries
are yielding and elastic; and this elasticity, as we have already
explained, moderates the force of the separate arterial pulsations,
and gradually fuses them with each other. The interrupted or
pulsating character of the arterial current, therefore, which is
strongly pronounced in the immediate vicinity of the heart, becomes
gradually lost and equalized, during its passage through the vessels,
until in the smallest arteries it is nearly imperceptible.

The same effect of an elastic medium in equalizing the force of
an interrupted current may be shown by fitting to the end of a
common syringe a long glass or metallic tube. Whatever be the
length of the inelastic tubing, the water which is thrown into one
extremity of it by the syringe will be delivered from the other end
in distinct jets, corresponding with the strokes of the piston ; but if
the metallic tube be replaced by one of India rubber, of sufficient
length, the elasticity of this substance merges the force of the sepa-
rate impulses into each other, and the water is driven out from the
farther extremity in a continuous stream.

The elasticity of the arteries, however, never entirely equalizes
the force of the separate cardiac pulsations, since a pulsating cha-
racter can be seen in the flow of the blood through even the smallest
arteries, under the microscope ; but this pulsating character dimi-
nishes very considerably from the heart outward, and the current
becomes much more continuous in the smaller vessels than in the
larger.

The primary cause, therefore, of the motion of the blood in the
arteries is the contraction of the ventricles, which, by driving out
the blood in interrupted impulses, distends at every stroke the
whole arterial system. But the arterial pulse is not exactly syn-
chronous everywhere with the beat of the heart ; since a certain
amount of time is required to propagate the blood-wave from the

THE ARTERIES AND THE ARTERIAL CIRCULATION. 287

centre of the circulation outward. The pulse of the radial artery
at the wrist is perceptibly later than that of the heart ; and the
pulse of the posterior tibial at the ankle, again, perceptibly later
than that at the wrist. The arterial circulation, accordingly, is not
an entirely simple phenomenon ; but is made up of the combined
effects of two different physical forces. In the first place, there is
the elasticity of the entire arterial system, by which the blood is
subjected to a constant and uniform pressure, quite independent of
the action of the heart. Secondly, there is the alternating contrac-
tion and relaxation of the heart, by which the blood is driven in
rapid and successive impulses from the centre of the circulation, to
be thence distributed throughout the body.

The passage of the blood through the arterial system takes place
under a certain degree of constant pressure. For these vessels being
everywhere elastic, and filled with blood, they constantly tend to
react, more or less vigorously, and to compress the circulating fluid
which they contain. If any one of the arteries, accordingly, be
opened in the living animal, and a glass tube inserted, the blood
will immediately be seen to rise in the tube to a height of about
five and a half or six feet, and will remain at that level ; thus indi-
cating the pressure to which it was subjected in the interior of the
vessels. This constant pressure, which is thus due to the reaction
of the entire arterial system, is known as the arterial pressure.

The degree of arterial pressure may be easily measured by con-
necting the open artery, by a flexible tube, with a small reservoir
of mercury, which is provided with a narrow upright glass tube,
open at its upper extremity. "When the blood, therefore, urged by
the reaction of the arterial walls, presses upon the surface of the
mercury in the receiver, the mercury rises in the upright tube, to
a corresponding height. By the use of this instrument it is seen,
in the first place, that the arterial pressure is nearly the same all
over the body. Since the cavity of the arterial system is every-
where continuous, the pressure must necessarily be communicated,
by the blood in its interior, equally in all directions. Accordingly,
the constant pressure is the same, or nearly so, in the larger and the
smaller arteries, in those nearest the heart, and those at a distance.
This constant pressure averages, in the higher quadrupeds, six
inches of mercury, which is equivalent to from five and a half to
six feet of blood.

It is also seen, however, in employing such an instrument, that
the level of the mercury, in the upright tube, is not perfectly steady,

288 THE CIRCULATION.

but rises and falls with the pulsations of the heart. Thus, at every
contraction of the ventricle, the mercury rises for about half an
inch, and at every relaxation it falls to its previous level. Thus the
instrument becomes a measure, not only for the constant pressure of
the arteries, but also for the intermitting pressure of the heart ; and
on that account it has received the name of the cardiometer. It is
seen, accordingly, that each contraction of the heart is superior in
force to the reaction of the arteries by about one-twelfth ; and these
vessels are kept filled by a succession of cardiac pulsations, and
discharge their contents in turn into the capillaries, by their own
elastic reaction.

The rapidity with which the blood circulates through the arterial
system is very great. Its velocity is greatest in the immediate
neighborhood of the heart, and diminishes somewhat as the blood
recedes farther and farther from the centre of the circulation. This
diminution in the rapidity of the arterial current is due to the suc-
cessive division of the aorta and its primary branches into smaller
and smaller ramifications, by which the total calibre of the arterial
system, as we have already mentioned, is somewhat increased. The
blood, therefore, flowing through a larger space as it passes outward,
necessarily moves more slowly. At the same time the increased
extent of the arterial parietes with which the blood comes in con-
tact, as well as the mechanical obstacle arising from the division of
the vessels and the separation of the streams, undoubtedly contri-
butes more or less to retard the currents. The mechanical obstacle,
however, arising from the friction of the blood against the walls of
the vessels, which would be very serious in the case of water or any
similar fluid flowing through glass or metallic tubes, has compara-
tively little effect on the rapidity of the arterial circulation. This
can readily be seen by microscopic examination of any transparent
and vascular tissue. The internal surface of the arteries is so smooth
and yielding, and the consistency of the circulating fluid so accu-
rately adapted to that of the vessels which contain it, that the
retarding effects of friction are reduced to a minimum, and the
blood in flowing through the vessels meets with the least possible
resistance.

It is owing to this fact that the arterial circulation, though some-
what slower toward the periphery than near the heart, yet retains
a very remarkable velocity throughout ; and even in arteries of the
minutest size it is so rapid that the shape of the blood-globules can-
not be distinguished in it on microscopic examination, but only a

THE ARTERIES AND THE ARTERIAL CIRCULATION. 289

mingled, current shooting forward with increased velocity at every
cardiac pulsation. Volkmann, in Germany, has determined, by a
very ingenious contrivance, the velocity of the current of blood in
some of the large sized arteries in dogs, horses, and calves. The
instrument which he employed (Fig. 94) consisted of a metallic
cylinder (a), with a perforation running from end to end, and cor-
responding in size with the artery to be examined. The artery
was divided transversely, and its cardiac extremity fastened to the
upper end (b) of the instrument, while its peripheral extremity was

Fig. 94.

Fig. 95.

VOI,KMAK»'S APPARATUS for measnring the rapidity of the artorlal circulation.

fastened in the same manner to the lower end (c). The blood
accordingly still kept on its usual course ; only passing for a short
distance through the artificial tube (a), between the divided extremi-
ties of the artery. The instrument, however, was provided, as shown
in the accompanying figures, with two transverse cylindrical plugs,
also perforated ; and arranged in such a manner, that when, at a
19

290 THE CIRCULATION.

given signal, the two plugs were suddenly turned in opposite
directions, the stream of blood would be turned out of its course
(Fig. 95), and made to traverse a long bent tube of glass (d, d, d),
before again finding its way back to the lower portion of the artery.
In this way the distance passed over by the blood in a given time
could be readily measured upon a scale attached to the side of the
glass tube. Yolkmann found, as the average result of his obser-
vations, that the blood moves in the carotid arteries of warm-blooded
quadrupeds with a velocity of 12 inches per second.

VENOUS CIRCULATION.

The veins, which collect the blood from the tissues and return it
to the heart, are composed, like the arteries, of three coats; an inner,
middle, and exterior. In structure, they differ from the arteries in
containing a much smaller quantity of muscular and elastic fibres,
and a larger proportion of simple condensed areolar tissue. They
are consequently more flaccid and compressible than the arteries,
and less elastic and contractile. They are furthermore distin-
guished, throughout the limbs, neck, and external portions of the
head and trunk, by being provided with valves, consisting of fibrous
sheets arranged in the form of festoons, and so placed in the cavity
of the vein as to allow the blood to pass readily from the periphery
toward the heart, while they prevent altogether its reflux in an
opposite direction.

Although the veins are provided with walls which are very much
thinner and less elastic than those of the arteries, yet, contrary to
what we might expect, their capacity for resistance to pressure is
equal, or even superior, to that of the arterial tubes. Milne Ed-
wards1 has collected the results of various experiments, which show
that the veins will sometimes resist a pressure which is sufficient to
rupture the walls of the arteries. In one instance the jugular vein
supported, without breaking, a pressure equal to a column of water
148 feet in height ; and in another, the iliac vein of a sheep resisted
a pressure of more than four atmospheres. The portal vein was
found capable of resisting a pressure of six atmospheres ; and in
one case, in which the aorta of a sheep was ruptured by a pressure
of 158 pounds, the vena cava of the same animal supported a pres-
sure equal to 176 pounds.

.' Lemons sur la Physiologie, &c., vol. iv. p. 301.

VENOUS CIRCULATION. 291

This resistance of the veins is to be attributed to the large pro-
portion of white fibrous tissue which enters into their composition ;
the same tissue which forms nearly the whole of the tendons and
fasciae, and which is distinguished by its density and unyielding
nature.

The elasticity of the veins, however, is much less than that of the
arteries. When they are filled with blood, they enlarge to a certain
size, and collapse again when the pressure is taken off; but they do
not react by virtue of an elastic resilience, or, at least, only to a
slight extent, as compared with the arteries. Accordingly, when
the arteries are cut across, and emptied of blood, they still remain
open and pervious, retaining the tubular form, on account of the
elasticity of their walls; while, if the veins be treated in the same
way, their sides simply fall together and remain in contact with each
other.

Another peculiarity of the venous system is the abundance of
the separate channels, which it affords, for the flow of blood from
the periphery towards the centre. The arteries pass directly from
the heart outward, each separate branch, as a general rule, going
to a separate region, and supplying that part of the body with
all the blood which it requires ; so that the arterial system is kept
constantly filled to its entire capacity with the blood which passes
through it. But that is not the case with the veins. In injected
preparations of the vascular system, we have often two, three,
four, or even five veins, coming together from the same region of
the body. There are also abundant inosculations between the dif-
ferent veins. The deep veins which accompany the brachial artery
inosculate freely with each other, and also with the superficial veins
of the arm. In the veins, coming from the head, we have the ex-
ternal jugular communicating with the thyroid veins, the anterior
jugular, and the brachial veins. The external and internal jugulars
communicate with each other, and the two thyroid veins also form
an abundant plexus in front of the trachea.

Thus the blood, coming from the extremities toward the heart,
flows, not in a single channel, but in many channels ; and as these
channels communicate freely with each other, the blood passes some-
times through one of them, and sometimes through another.

The flow of blood through the veins is less powerful and regular
than that through the arteries. It depends on the combined action
of three different forces.

292 THE CIRCULATION.

1. The force, of aspiration of the thorax. — When the chest expands
by the lifting of the ribs and the descent of the diaphragm, its
movement, of course, tends to diminish the pressure exerted upon
its contents, and so has the effect of drawing into the thoracic cavity
all the fluids which can gain access to it. The expanded cavity is
principally filled by the air, which passes in through the trachea
and fills the bronchial tubes and the pulmonary vesicles. But the
blood in the veins is also drawn into the chest at the same time and
by the same force. This force of aspiration, exerted by the expan-
sion of the chest, is gentle and uniform in character, like the move-
ments of respiration themselves. Accordingly its influence is ex-
tended, without doubt, to the farthest extremities of the venous
system, the blood being gently solicited toward the heart,' at each
expansion of the chest, without any visible alteration in the size of
the veins, which are filled up from behind as fast as they are emptied
in front.

But if the movement of inspiration be sudden and violent, instead
of gentle and easy, a different effect is produced. For then the walls
of the veins, which are thin and flaccid, cannot retain their position,
but collapse under the external pressure too rapidly to allow the
blood to flow in from behind. In this case, therefore, the vein is
simply emptied in the immediate neighborhood of the chest, but
the entire venous circulation is not assisted by the movement.

The same difference in the effect of an easy and a violent suction
movement, may be readily shown by attaching to the nozzle of an
air-tight syringe a flexible elastic tube with thin walls, and placing
the other extremity of the tube under water. If the piston of the
syringe be now withdrawn with a gentle and gradual motion, the
water will be readily drawn up into the tube, while the tube itself
suffers no visible change ; but if the suction movement be made
rapid and violent, the tube will collapse instantly under the pres-
sure of the air, and will fail to draw the water into its cavity.

A similar effect shows itself in the living body. If the jugular
or subclavian vein be exposed in a dog or cat, it will be seen that
while the movements of respiration are natural and easy no fluc-
tuation in the vein can be perceived. But as soon as the respira-
tion becomes disturbed and laborious, then at each inspiration the
vein is collapsed and emptied ; while during expiration, the chest
being strongly compressed and the inward flow of the blood arrested,
the vein becomes turgid with blood which accumulates in it from
behind. In young children, also, the spasmodic movements of res-

VENOUS CIRCULATION. 293

piration in crying produce a similar turgescence and engorgement
of the large veins during expiration, while they are momentarily
emptied during the hurried and forcible inspiration.

In natural and quiet respiration, therefore, the movements of the
chest hasten and assist the venous circulation ; but in forced or
laborious respiration, they do not assist and may even retard its flow.

2. The contraction of the voluntarg muscles. — The veins which
convey the blood through the limbs, and the parietes of the head
and trunk, lie among voluntary muscles, which are more or less
constantly in a state of alternate contraction and relaxation. At
even- contraction these muscles become swollen laterally, and, of
course, compress the veins which are situated between them. The
blood, driven out from the vein by this pressure, cannot regurgitate
toward the capillaries, owing to the valves, already described, which
shut back and prevent its reflux. It is accordingly forced onward
toward the heart ; and when the muscle relaxes and the vein is
liberated from pressure, it again fills up from behind, and the cir-
culation goes on as before. This force is a very efficient one in
producing the venous circulation ; since the voluntary muscles are
more or less active in every position of the body, and the veins
constantly liable to be compressed by them. It is on this account

Fig. 96. Fig. 97.

VEI.V with valves opeu. VEIN with valves closed: stream of

blood passing otfby a lateral channel.

that the veins, in the external parts of the body, communicate so
freely with each other by transverse branches ; in order that the
current of blood, which is momentarily excluded from one vein by

294 THE CIRCULATION.

the pressure of the muscles, may readily find a passage through
others, which communicate by cross branches with the first. (Figs.
96 and 97.)

3. The force of the capillary circulation. — This last cause of the
motion of the blood through the veins is the most important of all,
as it is the only one which is constantly and universally active. In
fish, for example, respiration is performed altogether by gills ; and
in reptiles the air is forced down into the lungs by a kind of deglu-
tition, instead of being drawn in by the expansion of the chest. In
neither of these classes, therefore, can the movements of respiration
assist mechanically in the circulation of the blood. In the splanch-
nic cavities, again, of all the vertebrate animals, the veins coming
from the internal organs, as, for example, the cerebral, pulmonary,
portal, hepatic, and renal veins, are unprovided with valves; and
the passage of the blood through them cannot therefore be effected
by any lateral pressure. The circulation, however, constantly going
on in the capillaries, everywhere tends to crowd the radicles of the
veins with blood ; and this vis a tergo, or pressure from behind, fills
the whole venous system by a constant and steady accumulation.
So long, therefore, as the veins are relieved of blood at their cardiac
extremity by the regular pulsations of the heart, there is no back-
ward pressure to oppose the impulse derived from the capillary cir-
culation ; and the movement of the blood through the veins continues
in a steady and uniform course.

With regard to the rapidity of the venous circulation, no direct
results have been obtained by experiment. Owing to the flaccidity
of the venous parietes, and the readiness with which the flow of
blood through them is disturbed, it is not possible to determine this
point for the veins, in the same manner as it has been determined
for the arteries. The only calculation which has been made in this
respect is based upon a comparison of the total capacity of the
arterial and venous systems. As the same blood which passes out-
ward through the arteries, passes inward again through the veins,
the rapidity of its flow in each must be in inverse proportion to the
capacity of the two sets of vessels. That is to say, a quantity of
blood which would pass in a given time, with a velocity of x,
through an opening equal to one square inch, would pass during
the same time through an opening equal to two square inches, with
a velocity of J ; and would require, on the other hand, a velocity
of 2 x, to pass in the same time through an opening equal to one-
half a square inch. Now the capacity of the entire venous system,

THE CAPILLAEY CIRCULATION.

295

when distended by injection, is about twice as great as that of the
entire arterial system. During life, however, the venous system is
at no time so completely filled with blood as is the case with the
arteries, and, making allowance for this difference, we find that the
entire quantity of venous blood is to the entire quantity of arterial
blood nearly as three to two. The velocity of the venous blood,
as compared with that of the arterial, is therefore as two to three :
or about 8 inches per second. It will be understood, however, that
this calculation is altogether approximative, and not exact ; since
the venous current varies, according to many different circumstances,
in different parts of the body ; being slower near the capillaries,
and more rapid near the heart. It expresses, however, with suffi-
cient accuracy, the relative velocity of the arterial and venous cur-
rents, at corresponding parts of their course.

THE CAPILLARY CIRCULATION.

The capillary bloodvessels are minute inosculating tubes, which
permeate the vascular organs in every direction, and bring the
blood into intimate contact with the substance of the tissues. They
are continuous with the terminal ramifications of the arteries on
the one hand, and with the com-
mencing rootlets of the veins on
the other. They vary somewhat
in size in different organs, and in
different species of animals ; their
average diameter in the human
subject being a little over ^Va of
an inch. They are composed of
a single, transparent, homogene-
ous, somewhat elastic, tubular
membrane, which is provided at
various intervals with flattened,
oval nuclei. As the smaller arte-
ries approach the capillaries, they
diminish constantly in size by
successive subdivision, and lose
first their external or fibrous
tunic. They are then composed

only of the internal or homogeneous coat, and the middle or muscu-
lar. (Fig. 98, a.) The middle coat then diminishes in thickness,

SMALL ABTKRT, with its muscular tunic
(n}, breaking up into capillaries. From the jt/ut
•muter.

296

THE CIRCULATION.

Fig. 99.

until it is reduced to a single layer of circular, fusiform, unstriped,
muscular fibres, which in their turn disappear altogether, as the
artery merges at last in the capillaries ; leaving only, as we have
already mentioned, a simple, homogeneous, nucleated, tubular mem-
brane, which is continuous with the internal arterial tunic.

The capillaries are further distinguished from b<>th arteries and
veins by their frequent inosculation. The arteries constantly
divide and subdivide, as they pass from within outward; while
the veins as constantly unite with each other to form larger and
less numerous branches and trunks, as they pass from the circum-
ference toward the centre. But the capillaries simply inosculate
with each other in every direction, in such a manner as to form an
interlacing network or plexus, the capillary plexus (Fig. 99), which
is exceedingly rich and abundant in some organs, less so in others.
The spaces included between the meshes of the capillary network
vary also, in shape as well as in size, in different parts of the body.

In the muscular tissue they
form long parallelograms ; in
the areolar tissue, irregular
shapeless figures, correspond-
ing with the direction of the
fibrous bundles of which the
tissue is composed. In the
mucous membrane of the
large intestine, the capillaries
include hexagonal or nearly
circular spaces, inclosing the
orifices of the follicles. In
the papilla3 of the tongue and
of the skin, and in the tufts
of the placenta, they are
arranged in long spiral loops,
and in the adipose tissue in wide meshes, among which the fat
vesicles are entangled.

The motion of the blood in the capillaries may be studied by
examining under the microscope any transparent tissue, of a
sufficient degree of vascularity. One of the most convenient parts
for this purpose is the web of the frog's foot. When properly
prepared and kept moistened by the occasional addition of water
to the integument, the circulation will go on in its vessels for an
indefinite length of time. The blood can be seen entering the

CAPILLARY NETWORK from web of frog's foot.

THE CAPILLARY CIRCULATION. 297

field by the smaller arteries, shooting through them with great
rapidity and in successive impulses, and flowing off again by the
veins at a somewhat slow rate. In the capillaries themselves
the circulation is considerably less rapid than in either the arteries
or the veins. It is also perfectly steady and uninterrupted in its
flow. The blood passes along in u uniform and continuous current,
without any apparent contraction or dilatation of the vessels, very

much as if it were flowing

Fig. 100.

through glass tubes. An-
other very remarkable pe-
culiarity of the capillary
circulation is that it has no
definite direction. The nu
merous streams of which it
is composed (Fig. 100) do
not tend to the right or to
the left, nor toward any one
particular point. On the
contrary, they pass above
and below each other, at
right angles to each other's
course, or even in opposite

-,. , ^ - , , , CAPILLARY CIRCCLAIIOJJ iu web of f.og's foot.

directions ; so that the blood,

while in the capillaries, merely circulates promiscuously among
the tissues, in such a manner as to come intimately in contact with
every part of their substance.

The motion of the white and red globules in the circulating blood
is also peculiar, and shows very distinctly the difference in their
consistency and other physical properties. In the larger vessels
the red globules are carried along in a dense column, in the central
part of the stream; while near the edges of the vessel there is a
transparent space occupied only by the clear plasma of the blood,
in which no red globules are to be seen. In the smaller vessels,
the globules pass along in a narrower column, two by two, or
following each other in single file. The flexibility and semi-fluid
consistency of these globules are here very apparent, from the
readiness with which they become folded up, bent or twisted in
turning corners, and the ease with which they glide through minute
branches of communication, smaller in diameter than themselves.
The white globules, on the other hand, flow more slowl} and with
greater difficulty through the vessels. They drag along the exter-

298 THE CIRCULATION.

nal portions of the current, and are sometimes momentarily arrested ;
apparently adhering for a few seconds to the internal surface of the
vessel. Whenever the current is obstructed or retarded in any
manner, the white globules accumulate in the affected portion, and
become more numerous there in proportion to the red.

It is during the capillary circulation that the blood serves for
the nutrition of the vascular organs. Its fluid portions slowly
transude through the walls of the vessels, and are absorbed by the
tissues in such proportion as is 'requisite for their nourishment.
The saline substances enter at once into the composition of the
surrounding parts, generally without undergoing any change. The
phosphate of lime, for example, is taken up in large quantity by
the bones and cartilages, and in smaller quantity by the softer parts ;
while the chlorides of sodium and potassium, the carbonates, sul-
phates, &c., are appropriated in special proportions by the different
tissues, according to the quantity necessary for their organization.
The albuminous ingredients of the blood, on the other hand, are
not only absorbed in a similar manner by the animal tissues, but at
the same tim o transformed by catalysis, and converted into new
materials, characteristic of the different tissues. In this way are
produced the musculine of the muscles, the osteine of the bones, the
cartilagine of the cartilages, &c. &c. It is probable that this trans-
formation does not take place in the interior of the vessels them-
selves ; but that the organic ingredients of the blood are absorbed
by the tissues, and at the same moment converted into new mate-
rials, by contact with their substance. The blood in this way fur-
nishes, directly or indirectly, all the materials necessary for the
nutrition of the body.

The physical conditions which influence the movement of the
blood in the capillaries, are somewhat different from those which
regulate the arterial and venous circulations. We must remember
that, as the arteries pass from the heart outward, they subdivide and
ramify to such an extent that the surface of the arterial walls is
very much increased in proportion to the quantity of blood which
they contain. It is on this account that the arterial pulsation is so
much equalized at a distance from the heart, since the influence of
the elasticity of the arterial coats is thus constantly increased from
within outward. But as these vessels finally reach the confines
of the arterial system, having already been very much increased
in number and diminished in size, they suddenly break up into

THE CAPILLARY CIRCULATION. 299

a terminal ramification of still smaller and more numerous vessels,
and so lose themselves at last in the capillary network.

By this final increase of the vascular surface, the equalization of
the heart's action is completed. There is no longer any intermitting
or pulsatile character in the force which acts upon the circulating
fluid ; and the blood, accordingly, is delivered from the arteries into
the capillaries under a perfectly continuous and uniform pressure.

This pressure is sufficient to cause the blood to pass with con-
siderable rapidity, through the capillary plexus, into the commence-
ment of the veins. This fact was first demonstrated by Prof.
Sharpey,1 of London, who employed an injecting syringe with a
double nozzle, one extremity of which was connected with a mercu-
rial gauge, while the other was inserted into the artery of a recently
killed animal. When the syringe, filled with defibrinated blood,
was fixed in this position and the vessels of the animal injected, the
defibrinated blood would press with equal force upon the mercury
in the gauge and upon the fluid in the bloodvessels ; and thus it
was easy to ascertain the exact amount of pressure required to force
the defibrinated blood through the capillaries of the animal, and to
make it return by the corresponding vein. In this way Prof.
Sharpey found that when the free end of the injecting tube was
attached to the mesenteric artery of the dog, a pressure of 90 milli-
metres of mercury caused the blood to pass through the capillaries
of the intestine and of the liver ; and that under a pressure of 130
millimetres, it flowed in a full stream from the divided extremity
of the vena cava.

We have also performed a similar experiment on the vessels of
the lower extremity. A full grown healthy dog was killed, and
the lower extremity immediately injected with defibrinated blood,
by the femoral artery, in order to prevent coagulation in the smaller
vessels. A syringe with a double flexible nozzle was then filled
with defibrinated blood, and one extremity of its injecting tube
attached to the femoral artery, the other to the mouthpiece of a
cardiometer. By making the injection, it was then found that the
defibrinated blood ran from the femoral vein in a continuous stream
under a pressure of 120 millimetres, and that it was discharged very
freely under a pressure of 130 millimetres.

Since, as we have already seen, the arterial pressure upon the

1 Todd and Bowmann, Physiological Anatomy and Physiology of man, vol. ii. p.
350.

300 THE CIRCULATION.

blood is equal to six inches, or 150 millimetres, of mercury, it is
evident that this pressure is sufficient to propel the blood through
the capillary circulation.

Beside, the blood is not altogether relieved from the influence of
elasticity, after it has left the arteries. For the capillaries them-
selves are elastic, notwithstanding the delicate texture of their
walls; and even the tissues of the organs which they traverse
possess, in many instances, a considerable share of elasticity, owing
to the minute elastic fibres which are scattered through their sub-
stance. These elastic fibres are found in considerable quantity in
the lungs, the spleen, the skin, the lobulated glands, and more or
less in the mucous membranes. They are abundant, of course, in
the fibrous tissues of the extremities, in the fascia3, the tendons, and
the intermuscular substance.

In the experiment of injecting the vessels of the lower extremity
with defibrinated blood, if the injection be stopped, the blood does
not instantly cease flowing from the extremity of the femoral vein,
but continues for a short time, until the elasticity of the intervening
parts is exhausted.

The same thing may be observed even in the liver. If the end
of a water-pipe be inserted into the portal vein, and the liver in-
jected with water under the pressure of a hydrant, the liquid will
distend the vessels of the organ, and pass out by the hepatic veins.
But if the portal vein be suddenly tied or compressed, so as to shut
off the pressure from behind, the stream will continue to run, for
several seconds afterward, from the hepatic vein, owing to the re-
action of the organ itself upon the fluid contained in its vessels.

As a general rule, also, the capillaries do not suffer any backward
pressure from the venous system. On the contrary, as soon as the
blood has been delivered into the veins, it is hurried onward toward
the heart by the compression of the muscles and the action of the
venous valves. The right side of the heart itself continues the same
process, by its regular contractions, and by the action of its own
valvular apparatus ; so that the blood is constantly lifted away from
the capillaries, by the muscular action of the surrounding parts.

These are the most important of the mechanical influences under
which the blood moves through the continuous round of the circu-
lation. The heart, by its alternating contractions and relaxations,
and by the backward play of its valves, continually urges the blood
forward into the arterial system. The arteries, by their dilatable
and elastic walls, convert the cardiac pulsations into a uniform and

THE CAPILLARY CIRCULATION. 3CU.

steady pressure. Under this pressure, the blood passes through the
capillary vessels; and it is then carried backward to the heart
through the veins, assisted by the action of the muscles and the
respiratory movements of the chest.

At the same time there are certain phenomena which are very
important in this respect, and which show that various local in-
fluences will either excite or retard the capillary circulation in par-
ticular parts, independently of the heart's action. The pallor or
suffusion of the face under mental emotion, the congestion of the
mucous membranes during the digestive process, the local and de-
fined redness produced in the skin by an irritating application, are
all instances of this sort. These phenomena are usually explained
by the contraction or dilatation of the smaller arteries immediately
supplying the part with blood, under the influence of nervous
action. As we know that the smaller arteries are in fact provided
with organic muscular fibres, this may undoubtedly have something
to do with the local variations of the capillary circulation ; but the
precise manner in which these effects are produced is at present
unknown.

The rapidity of the circulation in the capillary vessels is much
less than in the arteries or the veins. It may be measured, with a
tolerable approach to accuracy, during the microscopic examination
of transparent and vascular tissues, as, for example, the web of the
frog's foot, or the mesentery of the rat. The results obtained in
this way by different observers (Valentine, Weber, Volkmann, &c.)
show that the rate of movement of the blood through the capil-
laries is rather less than one-thirtieth of an inch per second ; or not
quite two inches per minute. Since the rapidity of the current, as
we have mentioned above, must be in inverse ratio to the entire
calibre of the vessels through which it moves, it follows that the
united calibre of all the capillaries of the body must be from 350 to
4uO times greater than that of the arteries. It must not be sup-
posed from this, however, that the whole quantity of blood contained
in the capillaries at any one time is so much greater than that in
the arteries ; since, although the united calibre of the capillaries is
very large, their length is very small. The effect of the anatomical
structure of the capillary system is, therefore, merely to disseminate
a comparatively small quantity of blood over a very large space, so
that the chemico-physiological reactions, necessary to nutrition, may
take place with promptitude and energy. For the same reason,
although the rate of movement of the blood in these vessels is very

302 THE CIRCULATION.

slow, yet as the distance to be passed over between the arteries and
veins is very small, the blood really requires but a short time to
traverse the capillary system, and to commence its returning passage
by the veins.

GENERAL CONSIDERATIONS.

The rapidity with which the blood passes through the entire round
of the circulation is a point of great interest, and one which has
received a considerable share of attention. The results of such
experiments, as have been tried, show that this rapidity is much
greater than would have been anticipated. Hering, Poisseuille, and
Matteucci,1 have all experimented on this subject in the following
manner. A solution of ferrocyanide of potassium was injected
into the right jugular vein of a horse, at the same time that a liga-
ture was placed upon the corresponding vein on the left side, and
an opening made in it above the ligature. The blood flowing from
the left jugular vein was then received in separate vessels, which
were changed every five seconds, and the contents afterward exa-
mined. It was thus found that the blood drawn from the first to
the twentieth second contained no traces of the ferrocyanide ; but
that which escaped from the vein at the end of from twenty to
twenty-five seconds, showed unmistakable evidence of the presence
of the foreign salt. The ferrocyanide of potassium must, therefore,
during this time, have passed from the point of injection to the
right side of the heart, thence to the lungs and through the pulmo-
nary circulation, returned to the heart, passed out again through
the arteries to the capillary system of the head and neck, and
thence have commenced its returning passage to the right side of
the heart, through the jugular vein.

By extending these investigations to different animals, it was
found that the duration of the circulatory movement varied, to
some extent, with the size and species. In the larger quadrupeds,
as a general rule, it was longer ; in the smaller, the time required
was less.

In the Horse,2 the mean duration was 28 seconds.
" Dog " " " " 15 "

" Goat " " " " 13 "

w. FOX c< « u t< 12$ "

« Rabbit " " " " 7 "

1 Physical Phenomena of Living Beings, Pereira's translation, Philada. ed., 1848,
p. 317.

2 In Milne Edwards, Logons sur la Physiologie, &c., vol. iv. p. 364.

LOCAL VARIATIONS. 303

When these results were first published, it was thought to be
doubtful whether the circulation were really as rapid as they would
make it appear. It was thought that the saline matter which was
injected, " travelled faster than the blood ;" that it became " diffused''
through the circulating fluid; that it transuded through dividing
membranes ; or passed round to the point at which it was detected,
by some short and irregular route.

But none of these explanations have ever been found to be cor-
rect. They are all really more improbable than the fact which
they are intended to explain. The physical diffusion of liquids
does not take place with such rapidity as that manifested by the
circulation ; and there is no other route so likely to give passage to
the injected fluid, as the bloodvessels and the movement of the blood
itself. Beside, the first experiments of Poisseuille and others have
not been since invalidated, in any essential particular. It was found,
it is true, that certain other substances, injected at the same time
with the saline matter, might hasten or retard the circulation to a
certain degree. But these variations were not very marked, and
never exceeded the limits of from eighteen to forty-five seconds.
There is no doubt that the blood itself makes the same circuit in
very nearly the same interval of time.

The truth is, however, that we cannot fix upon any absolutely
uniform rate which shall express the time required by the entire
blood to pass the round of the whole vascular system, and return
to a given point. The circulation of the blood, far from being a
simple phenomenon, like a current of water through a circular tube,
is, on the contrary, extremely complicated in all its anatomical and
physiological conditions ; and it differs in rapidity, as well as in its
physical and chemical phenomena, in different parts of the circu-
latory apparatus. We have already seen how much the form of
the capillary plexus varies in different organs. In some the vascu-
lar network is close, in others comparatively open. In some its
meshes are circular in shape, in others polygonal, in others rectan-
gular. In some the vessels are arranged in twisted loops, in others
they communicate by irregular but abundant inosculations. The
mere distance from the heart at which an organ is situated must
modify to some extent the time required for its blood to return
again to the centre of the circulation. The blood which passes
through the coronary arteries and the capillaries of the heart,
for example, must be returned to the right auricle in a compara-
tively short time; while that which is carried by the carotids into

30-i THE CIRCULATION.

the capillary system of the head and neck, to return by the jugulars,
will require a longer interval. That, again, which descends by the
abdominal aorta and its divisions to the lower extremities, and
which, after circulating through the tissues of the leg and foot,
mounts upward through the whole course of the saphena, femoral,
iliac and abdominal veins, must be still longer on its way ; while
that which circulates through the abdominal digestive organs and
is then collected by the portal .system, to be again dispersed through
the glandular tissue of the liver, requires undoubtedly a longer
period still to perform its double capillary circulation. The blood,
therefore, arrives at the right side of the heart, from different parts
of the body, at successive intervals; and may pass several times
through one organ while performing a single circulation through
another.

Furthermore, the chemical phenomena taking place in the blood
and the tissues vary to a similar extent in different organs. The
actions of transformation and decomposition, of nutrition and secre-
tion, of endosmosis and exosmosis, which go on simultaneously
throughout the body, are yet extremely varied in their character,
and produce a similar variation in the phenomena of the circula-
tion. In one organ the blood loses more fluid than it absorbs ; in
another it absorbs more than it loses. The venous blood, conse-
quently, has a different composition as it returns from different
organs. In the brain and spinal cord it gives up those ingredients
necessary for the nutrition of the nervous matter, and absorbs cho-
lesterine and other materials resulting from its waste ; in the muscles
it loses those substances necessary for the supply of the muscular
tissue, and in the bones those which are requisite for the osseous
system. In the parotid gland it yields the ingredients of the saliva ;
in the kidneys, those of the urine. In the intestine it absorbs in
large quantity the nutritious elements of the digested food ; and in
the liver, gives up substances destined finally to produce the bile,
at the same time that it absorbs sugar, which has been produced
in the hepatic tissue. In the lungs, again, it is the elimination of
carbonic acid and the absorption of oxygen that constitute its prin-
cipal changes. It has been already remarked that the temperature
of the blood varies in different veins, according to the peculiar
chemical and nutritive changes going on in the organs from which
they originate. Its color, even, which is also dependent on the
chemical and nutritive actions taking place in the capillaries, varies
in a similar manner. In the lungs it changes from blue to red ;

LOCAL VARIATIONS.

305

Fig. 101,

in the capillaries of the general system, from red to blue. But its

tinge also varies very considerably in different parts of the general

circulation. The blood of the hepatic

veins is darker than that of the femoral

or brachial vein. In the renal veins

it is very much brighter than in the

vena cava ; and when the circulation

through the kidneys is free, the blood

returning from them is nearly as red

as arterial blood.

We must regard the circulation of
the blood, therefore, not as a simple
process, but as made up of many differ-
ent circulations, going on simultane-
ously in different organs. It has been
customary to illustrate it, in diagram,
by a double circle, or figure of 8, of
which the upper arc is used to repre-
sent the pulmonary, the lower the gen-
eral circulation. This, however, gives
but a very imperfect idea of the entire
circulation, as it really takes place. It
would be much more accurately re-
presented by such a diagram as that
in Fig. 101, in which its variations
in different parts of the body are
indicated in such a manner as to show,
in some degree, the complicated cha-
racter of its phenomena. The circula-
tion is modified in these different parts,
not only in its mechanism, but also in
its rapidity and quantity, and in the
nutritive functions performed by the
blood. In one part, it stimulates the
nervous centres and the organs of
special sense ; in others it supplies the
fluid secretions, or the ingredients of Dia?ram of ti,e
the solid tissues. One portion, in H™rr- 2 L"n^ 3 Head and nppeT

* extremities. 4. Spleen. 5. Intestine. 6.

paSSing tlirOUgh the digestive appara- Kiduey. 7. Lower extremities. S. Liver.

tus, absorbs the materials requisite

for the nourishment of the body ; another, in circulating through
20

306 THE CIKCULATION.

the lungs, exhales the carbonic acid which it has accumulated else-
where, and absorbs the oxygen which is afterward transported to
distant tissues by the current of arterial blood. The phenomena of
the circulation are even liable, as we have already seen, to periodical
variations in the same organ ; increasing or diminishing in intensity
with the condition of rest or activity of the whole body, or of the
particular organ which is the subject of observation.

IMBIBITION AND EXHALATION. 307

CHAPTER XV.

IMBIBITION AND EX HAL ATI ON.— THE LYMPHATIC

SYSTEM.

DURING the passage of the blood through the capillaries of the
circulatory system, a very important series of changes takes place
by which its ingredients are partly transferred to the tissues by
exhalation, and at the same time replaced by others which the blood
derives by absorption from the adjacent parts. These phenomena
depend upon the property, belonging to animal membranes, of
imbibing or absorbing certain fluid substances in a peculiar way.
They are known more particularly as the phenomena of endosmosis
and exosmosis.

These phenomena may be demonstrated in the following way. If
we take two different liquids, for example a solution of salt and an
equal quantity of distilled water, and inclose them in a glass vessel
with a fresh animal membrane stretched between, so that there is
no direct communication from one to the other, the two liquids
being in contact with opposite sides of the membrane, it will be
found after a time that the liquids have become mixed, to a cer-
tain extent, with each other. A part of the salt will have passed
into the distilled water, giving it a saline taste ; and & part of the
water will have passed into the saline solution, making it more
dilute than before. If the quantities of the two liquids, which
have become so transferred, be measured, it will be found that a
comparatively large quantity of the water has passed into the
saline solution, and a comparatively small quantity of the saline
solution has passed out into the water. That is, the water passes
inward to the salt more rapidly than the salt passes outward to the
water. The consequence is, that an accumulation soon begins to
show itself on the side of the salt. The saline solution is increased
in volume and diluted, while the water is diminished in volume,
and acquires a saline ingredient. This abundant passage of the
water, through the membrane, to the salt, is called endosmosis ; and

308 IMBIBITION AND EXHALATION.

the more scanty passage of the salt outward to the water is called
exosmosis.

The mode usually adopted for measuring the rapidity of endos-
mosis is to take a glass vessel, shaped somewhat like an inverted
funnel, wide at the bottom and narrow at the top. The bottom of
the vessel is closed by a thin animal membrane, like the mucous
membrane of an ox -bladder, which is stretched tightly over its edge
and secured by a ligature. From the top of the vessel there rises
a very narrow glass tube, open at its upper extremity. When the
instrument is thus prepared, it is filled with a solution of sugar
and placed in a vessel of distilled water, so that the animal mem-
brane, stretched across its mouth, shall be in contact with pure
water on one side and with the saccharine solution on the other.
The water then passes in through the membrane, by endosmosis,
faster than the saccharine solution passes out. An accumulation
therefore takes place inside the vessel, and the level of the fluid
rises in the upright tube. The height to which the fluid thus rises
in a given time is a measure of the intensity of the endosmosis, and
of its excess over exosmosis. By varying the constitution of the
two liquids, the arrangement of the membrane, &c., the variation
in endosmotic action under different conditions may be easily
ascertained. Such an instrument is called an endosmometer.

If the extremity of the upright tube be bent over, so as to point
downward, as endosmosis continues to go on after the tube has
become entirely filled by the rising of the fluid, the saccharine solu-
tion will be discharged in drops from the end of the tube, and fall
back into the vase of water. A steady circulation will thus be
kept up for a time by the force of endosmosis. The water still
passes through the membrane, and accumulates in the endosmo-
meter ; but, as this is already full of fluid, the surplus immediately
falls back into the outside vase, and thus a current is established
which will go on until the two liquids have become intimately
mingled.

The conditions which influence the rapidity and extent of endos-
mosis have been most thoroughly investigated by Dutrochet, who
was the first to make a systematic examination of the subject.

The first of these conditions is the freshness of the membrane itself.
This is an indispensable requisite for the success of the experiment.
A membrane that has been dried and moistened again, or one that
has begun to putrefy, will not produce the desired effect. It has
been also found that if the membrane of the endosmometer be

THE LYMPHATIC SYSTEM. 309

allowed to remain and soak in the fluids, after the column has risen
to a certain height in the upright tube, it begins to descend again
as soon as putrefaction commences, and the two liquids finally sink
to the same level.

The next condition is the extent of contact between the membrane
and the two liquids. The greater the extent of this contact, the
more rapid and forcible is the current of endosmosis. An endos-
mometer with a wide mouth will produce more effect than with a
narrow one, though the volume of the liquid contained in it may
be the same in both instances. The action takes place at the
surface of the membrane, and is proportionate to its extent.

Another very important circumstance is the constitution of the two
liquids, and their relation to each other. As a general thing, if we
use water and a saline solution in our experiments, endosmosis is
more active, the more concentrated is the solution in the endosmo-
meter. A larger quantity of water will pass inward toward a dense
solution than toward one which is already dilute. But the force of
endosmosis varies with different liquids, even when they are of the
same density. Dutrochet measured the force with which water
passed through the mucous membrane of an ox-bladder into differ-
ent solutions of the same density. He found that the force varies
with different substances, as follows i1 —

Endosmosis of water, with a solution of albumen . . 12

sugar ... 11

" " " gum ... 5

" " " gelatine . . 3

The position of the membrane also makes a difference. With some
fluids, endosmosis is more rapid when the membrane has its mucous
surface in contact with the dense solution, and its dissected surface
in contact with the water. With other substances the more favor-
able position is the reverse. Matteucci found that, in using the
mucous membrane of the ox-bladder with water ard a solution of
sugar, if the mucous surface of the membrane were in contact with
the saccharine solution, the liquid rose in the endosmometer between
four and five inches. But if the same surface were turned outward
toward the water, the column of fluid was less than three inches in
height. Different membranes also act with different degrees of force.
The effect produced is not the same with the integument of different
animals, nor with mucous membranes taken from different parts of
the body.

1 In Matteucci 's Lectures on the Physical Phenomena of Living Beings. Philada.,
1848, p. 48.

310 IMBIBITION AND EXHALATION.

Generally speaking, endosmosis is more active when the temper-
ature is moderately elevated. Dutrochet noticed that an endosmo-
meter, containing a solution of gum, absorbed only one volume of
water at a temperature of 32° Fahr.; but absorbed three volumes
at a temperature a little above 90°. Variations of temperature will
sometimes even change the direction of the endosmosis altogether,
particularly with dilute solutions of hydrochloric acid. Dutrochet
found, for example,1 that when the endosmometer was filled with
dilute hydrochloric acid and placed in distilled water, at the tem-
perature of 50° F., endosmosis took place from the acid to the water,
if the density of the acid solution were less than 1.020 ; but that it
took place from the water to the acid, if its density were greater
than this. On the other hand, at the temperature of 72° F., the
current was from within outward when the density of the acid solu-
tion was below 1.003, and from without inward when it was above
that point.

Finally, the pressure which is exerted upon the fluids and the
membrane favors their endosmosis. Fluids that pass slowly under
a low pressure will pass more rapidly with a higher one. Different
liquids, too, require different degrees of pressure to make them
pass the same membrane. Liebig2 has measured the pressure re-
quired for several different liquids, in order to make them pass
through the same membrane. He found that this pressure was

INCHES OF MERCURY.

For alcohol 52

For oil . 37

For solution of salt 20

For water 13

There are some cases in which endosmosis takes place without
being accompanied by exosmosis. This occurs, for example, when
we use water and albumen as the two liquids. For while water
readily passes in through the animal membrane, the albumen does
not pass out. If an opening be made, for example, in the large
end of an egg, so as to expose the shell-membrane, and the whole
be then placed in a goblet of water, endosmosis will take place very
freely from the water to the albumen, so as to distend the shell-
membrane and make it protrude, like a hernia, from the opening in
the shell. But the albumen does not pass outward through the
membrane, and the water in the goblet remains pure. After a time,

1 In Milne Edwards, Lemons sur la Physiologie, &c., vol. v. p. 164.

2 In Longet's Traite de Physiologie, vol. i. p. 384.

THE LYMPHATIC SYSTEM. 311

however, the accumulation of fluid in the interior becomes so ex-
cessive as to* burst the shell- membrane, and then the two liquids
become mixed indiscriminately together.

These are the principal conditions by which endosmosis is influ-
enced and regulated. Let us now see what is the nature of the
process, and upon what its phenomena depend.

Endosmosis is not dependent upon the simple force of diffusion
or admixture of two different liquids. For sometimes, as in the
case of albumen and water, all the fluid passes in one direction and
none in the other. It is true that the activity of the process de-
pends very much, as we have already seen, upon the difference in
constitution of the two liquids. With water and a saline solution,
for instance, the stronger the solution of salt, the more rapid is the
endosmosis of the water. And if two solutions of salt be used,
with a membranous septum between them, endosmosis takes place
from the weaker solution to the stronger, and is proportionate in
activity to the difference in their densities. From this fact, Dutro-
chet was at first led to believe that the direction of endosmosis was
determined by the difference in density of the two liquids, and that
the current of accumulation was always directed from the lighter
liquid to the denser. But we now know that this is not the case.
For though, with solutions of salt, sugar, and the like, the current
of endosmosis is from the lighter to the denser liquid ; in other
instances it is the reverse. With water and alcohol, for example,
endosmosis takes place, not from the alcohol to the water, but from
the water to the alcohol ; that is, from the denser liquid to the lighter.
The difference in density of the liquids, therefore, is not the only
condition which regulates the direction of the endosmotic current.
In point of fact, the process of endosmosis does not depend princi-
pally upon the attraction of the two liquids for each other, but
upon the attraction of the animal membrane for the two liquids. The
membrane is not a passive filter through which the liquids mingle,
but it is the active agent which determines their passage. The
membrane has the power of absorbing liquids, and of taking them
up into its own substance. This power of absorption, belonging to
.the membrane, depends upon the organic or albuminous ingredients
of which it is composed ; and, with different animal substances, the
power of absorption is different. The tissue of cartilage, for exam-
ple, will absorb more water, weight for weight, than that of the
tendons ; and the tissue of the cornea will absorb nearly twice as
much as that of cartilage.

312 IMBIBITION AND EXHALATION.

Beside, the power of absorption of an animal membrane is dif-
ferent for different liquids. Nearly all animal membranes absorb
pure water more freely than a solution of salt. If a membrane,
partly dried, be placed in a saturated saline solution, it will absorb
the water in larger proportion than the salt, and a part of the salt
will, therefore, be deposited in the form of crystals on the surface
of the membrane.

Oily matters, on the other hand, are usually absorbed less readily
than either water or saline solutions.

Chevreuil has investigated the absorbent power of different
animal substances for different liquids, by taking definite quanti-
ties of the animal substance and immersing it for twenty-four
hours in different liquids. At the end of that time, the substance
was removed and weighed. Its increase in weight showed the
quantity of liquid which it had absorbed. The results which were
obtained are given in the following table : — l

100 PARTS OP WATER. SALINE SOLUTION. OIL.

Cartilage,

Tendon,

Elastic ligament,

Cornea,

Cartilaginous ligament,

Dried fibrin,

absorb in
24 hours,

f 231 parts. 125 parts.

178 " 114 " 8. 6 parts.

148 " 30 " 7.2 «

461 " 370 " 9.1 "

319 " 3.2 "

I 301 " 154 "

The same substance, therefore, will take up different quantities
of water, saline solutions, and oil.

Accordingly, when an animal membrane is placed in contact
with two different liquids, it absorbs one of them more abundantly
than the other ; and that which is absorbed in the greatest quantity
is also diffused most abundantly into the liquid on the opposite side
of the membrane. A rapid endosmosis takes place in one direc-
tion, and a slow exosmosis in the other. Consequently, the least
absorbable fluid increases in volume by the constant admixture of
that which is taken up more rapidly.

The process of endosmosis, therefore, is essentially one of im-
bibition or absorption of the liquid by an animal membrane, com-
posed of organic ingredients. We have already shown, in de-
scribing the organic proximate principles in a previous chapter,
that these substances have the power of absorbing watery and
serous fluids in a peculiar way. In endosmosis, accordingly, the

1 In Longet's Traite de Physiologic, vol. i. p. 383.

THE LYMPHATIC SYSTEM. 313

imbibed fluid penetrates the membrane by a kind of chemical
combination, and unites intimately with the substance of which its
tissues are composed.

It is in this way that all imbibition and transudation take place
in the living body. Under the most ordinary conditions, the transu-
dation of certain fluids is accomplished with great rapidity. It has
been shown by M. Gosselin,1 that if a watery solution of iodide of
potassium be dropped upon the cornea of a living rabbit, the
iodine passes into the cornea, aqueous humor, iris, lens, sclerotic
and vitreous body, in the course of eleven minutes; and that it
will penetrate through the cornea into the aqueous humor in three
minutes, and into the substance of the cornea in a minute and a
half. In these experiments it was evident that the iodine actually
passed into the deeper portions of the eye by simple endosmosis,
and was not transported by the vessels of the general circulation ;
since no trace of it could be found in the tissues of the opposite
eye, examined at the same time.

The same observer showed that the active principle of belladonna
penetrates the tissues of the eyeball in a similar manner. M. Gos-
selin applied a solution of sulphate of atropine to both eyes of two
rabbits. Half an hour afterward, the pupils were dilated. Three
quarters of an hour later, the aqueous humor was collected by
puncturing the cornea with a trocar; and this aqueous humor,
dropped upon the eye of a cat, produced dilatation and immobility
of the pupil in half an hour. These facts show that the aqueous
humor of the affected eye actually contains atropine, which it
absorbs from without through the cornea, and this atropine then
acts directly and locally upon the muscular fibres of the iris.

But in all the vascular organs, the processes of endosmosis and
exosmosis are very much accelerated by two important conditions,
viz., first, the movement of the blood in circulating through the
vessels, and secondly the minute dissemination and distribution of
these vessels through the tissue of the organs.

The movement of a fluid in a continuous current always favors
endosmosis through the membrane with which it is in contact. For
if the two liquids be stationary, on the opposite sides of an animal
membrane, as soon as endosmosis commences they begin to ap-
proximate in constitution to each other by mutual admixture ; and,
as this admixture goes on, endosmosis of course becomes less active,

1 Gazette Hebdomad aire, Sept. 7, 1855.

314: IMBIBITION AND EXHALATION.

and ceases entirely when the two liquids have become perfectly
alike in composition. But if one of the liquids be constantly
renewed by a continuous current, those portions of it which have
become contaminated are immediately carried away by the stream,
and replaced by fresh portions in a state of purity. Thus the
difference in constitution of the two liquids is preserved, and
transudation will continue to take place between them with una-
bated rapidity.

Matteucci demonstrated the effect of a current in facilitating
endosmosis by attaching to the stopcock of a glass reservoir filled
with water, a portion of a vein also filled with water. The vein
was then immersed in a very dilute solution of hydrochloric acid.
So long as the water remained stationary in the vein it did not give
any indications of the presence of the acid, of did so only very
slowly ; but if a current were allowed to pass through the vein by
opening the stopcock of the reservoir, then the fluid running from
its extremity almost immediately showed an acid reaction.

The same thing may be shown even more distinctly upon the
living animal. If a solution of the extract of nux vomica be in-
jected into the subcutaneous areolar tissue of the hind leg of two
rabbits, in one of which the bloodvessels of the extremity have
been left free, while in the other they have been previously tied,
so as to stop the circulation in that part — in the first rabbit, the
poison will be absorbed and will produce convulsions and death in
the course of a few minutes; but in the second animal, owing to the
stoppage of the local circulation, absorption will be much retarded,
and the poison will find its way into the general circulation so
slowly, and in such small quantities, that its specific effects will show
themselves only at a late period, or even may not be produced at all.

The anatomical arrangement of the bloodvessels and adjacent
tissues is the second important condition regulating endosmosis
and exosmosis. We have already seen that the network of capil-
lary bloodvessels results from the excessive division and ramifica-
tion of the smaller arteries. The blood, therefore, as it leaves the
arteries and enters the capillaries, is constantly divided into smaller
and more numerous currents, which are finally disseminated in the
most intricate manner throughout the substance of the organs and
tissues. Thus, the blood is brought into intimate contact with the
surrounding tissues, over a comparatively very large extent of sur-
face. It has already been stated, as the result of Dutrochet's inves-
tigations, that the activity of endosmosis is in direct proportion to

THE LYMPHATIC SYSTEM. 315

the extent of surface over which the two liquids come in contact
with the intervening membrane. It is very evident, therefore, that
it will be very much facilitated by the anatomical distribution of
the capillary bloodvessels.

It is in some of the glandular organs, however, that the transu-
dation of fluids can be shown to take place with the greatest rapi-
dity. For in these organs the exhaling and absorbing surfaces are
arranged in the form of minute ramifying tubes and follicles, which
penetrate everywhere through the glandular substance ; while the
capillary bloodvessels form an equally complicated and abundant
network, situated between the adjacent follicles and ducts. In this
way, the union and interlacement of the glandular membrane, on
the one hand, and the bloodvessels on the other, become exceed-
ingly intricate and extensive ; and the ingredients of the blood are
almost instantaneously subjected, over a very large surface, to the
influence of the glandular membrane.

The rapidity of transudation through the glandular membranes
has been shown in a very striking manner by Bernard.1 This ob-
server injected a solution of iodide of potassium into the dnct of
the parotid gland on the right side, in a living dog, and immediately
afterward found iodine to be present in the saliva of the correspond-
ing gland on the opposite side. In the few instants, therefore, re-
quired to perform the experiment, the salt of iodine must have
been taken up by the glandular tissue on one side, carried by the
blood of the general circulation to the opposite gland, and there
transuded through the secreting membrane.

We have also found the transudation of iodine through the
glandular tissue to be exceedingly rapid, by the following experi-
ment. The parotid duct was exposed and opened, upon one side,
in a living dog, and a canula inserted into it, and secured by liga-
ture. The secretion of the parotid saliva was then excited, by in-
troducing a little vinegar into the mouth of the animal, and the
saliva, thus obtained, found to be entirely destitute of iodine. A
solution of iodide of potassium being then injected into the jugu-
lar vein, and the parotid secretion again immediately excited by
the introduction of vinegar, as before, the saliva first discharged
from the canula showed evident traces of iodine, by striking a blue
color on the addition of starch and nitric acid.

The processes of exosmosis and endosmosis, therefore, in the living

1 Lemons de Physiologie Exp&imentale, Paris, 1856, p. 107.

316 IMBIBITION AND EXHALATION.

body, are regulated by the same conditions as in artificial experi-
ments, but they take place with infinitely greater rapidity, owing to
the movement of the circulating blood, and the extent of contact
existing between the bloodvessels and adjacent tissues. We have
already seen that the absorption of the same fluid is accomplished
with different degrees of rapidity by different animal substances.
Accordingly, though the arterial blood is everywhere the same in
composition, yet its different ingredients are imbibed in varying
quantities by the different tissues. Thus, the cartilages absorb
from the circulating fluid a larger proportion of phosphate of lime
than the softer tissues, and the bones a larger proportion than the
cartilages; and the watery and saline ingredients generally are
found in different quantities in different parts of the body. The
same animal membrane, also, as it has been shown by experiment,
will imbibe different substances with different degrees of facility.
Thus, the blood, for example, contains more chloride of sodium
than chloride of potassium ; but the muscles, which it supplies with
nourishment, contain more chloride of potassium than chloride of
sodium. In this way, the proportion of each ingredient derived
from the blood is determined, in each separate tissue, by its special
absorbing or endosmotic power.

Furthermore, we have seen that albumen, under ordinary condi-
tions, is not endosmotic ; that is, it will not pass by transudation
through an animal membrane. For the same reason, the albumen
of the blood, in the natural state of the circulation, is not exhaled
from the secreting surfaces, but is retained within the circulatory
system, while the watery and saline ingredients transude in varying
quantities. But the degree of pressure to which a fluid is subjected
has great influence in determining its endosmotic action. A sub-
stance which passes but slowly under a low pressure, may pass
much more rapidly if the force be increased. Accordingly, we find
that if the pressure upon the blood in the vessels be increased, by
obstruction to the venous current and backward congestion of the
capillaries, then not only the saline and watery parts of the blood
pass out in larger quantities, but the albumen itself transudes, and
infiltrates the neighboring parts. It is in this way that albumen
makes its appearance in the urine, in consequence of obstruction to
the renal circulation, and that local oedema or general anasarca
may follow upon venous congestion in particular regions, or upon
general disturbance of the circulation.

The processes of imbibition and exudation, which thus take

THE LYMPHATIC SYSTEM. 317

place incessantly throughout the body, are intimately connected
with the action of the great absorbent or lymphatic system of ves-
sels, which is to be considered as secondary or complementary to
that of the sanguiferous circulation.

The lymphatics may be regarded as a system of vessels, com-
mencing in the substance of the various tissues and organs, and
endowed with the property of absorbing certain of their ingredi-
ents. Their commencement has been demonstrated by injections,
more particularly in the membranous parts of the body ; viz., in
the skin, the mucous membranes, the serous and synovial surfaces,
and the inner tunic of the arteries and veins. They originate in
these situations by vascular networks, not very unlike those of the
capillary bloodvessels. Notwithstanding this resemblance in form
between the capillary plexuses of the lymphatics and the blood-
vessels, it is most probable that they are anatomically distinct from
each other. It has been supposed, at various times, that there
might be communications between them, and even that the lymph-
atic plexus might be a direct continuation of that originating from
the smaller arteries ; but this has never been demonstrated, and it
is now almost universally conceded that the anatomical evidence is
in favor of a complete separation between the two vascular systems.

Commencing in this way in the substance of the tissues, by a
vascular network, the minute lymphatics unite gradually with each
other to form larger vessels ; and, after continuing their course for
a certain distance from without inward, they enter and are distri-
buted to the substance of the lymphatic glands. According to M.
Colin,1 beside the more minute and convoluted vessels in each gland,
there are always some larger branches which pass directly through
its substance, from the afferent to the efferent vessels ; so that only
a portion of the lymph is distributed to its ultimate glandular
plexus. This portion, however, in passing through the organ, is
evidently subjected to some glandular influence, which may serve
to modify its composition.

After passing through these glandular organs, the lymphatic
vessels unite into two great trunks (Fig. 43) : the thoracic duct, which
collects the fluid from the absorbents of the lower extremities, the
intestines and other abdominal organs, the chest, the left upper
extremity, and the left side of the head and neck, and terminates
in the left subclavian vein, at the junction of the internal jugular ;
and the right lymphatic duct, which collects the fluid from the right

1 Physiologic comparer des Animaux domestiques, Paris, 185H, vol. ii. p. 68.

818 IMBIBITION AND EXHALATION.

upper extremity and right side of the head and neck, and joins the
right subclavian vein at its junction with the corresponding jugular.
Thus nearly all the lymph from the external parts, and the whole
of that from the abdominal organs, passes, by the thoracic duct,
into the left subclavian vein.

We already know that the lymphatic vessels are not to be re-
garded as the exclusive agents of absorption. On the contrary,
absorption takes place by the bloodvessels even more rapidly and
abundantly than by the lymphatics. Even the products of diges-
tion, including the chyle, are taken up from the intestine in large
proportion by the bloodvessels, and are only in part absorbed by
the lymphatics. But the main peculiarity of the lymphatic system
is that its vessels all pass in one direction, viz., from without inward,
and none from within outward. Consequently there is no circula-
tion of the lymph, strictly speaking, like that of the blood, but it
is all supplied by exudation and absorption from the tissues.

The lymph has been obtained, in a state of purity, by various
experimenters, by introducing a canula into the thoracic duct, at
the root of the neck, or into large lymphatic trunks in other parts
of the body. It has been obtained by Rees from the lacteal vessels
and the lymphatics of the leg in the ass, by Colin from the lacteals
and thoracic duct of the ox, and from the lymphatics of the neck
in the horse. We have also obtained it, on several different occa-
sions, from the thoracic duct of the dog and of the goat.

The analysis of these fluids shows a remarkable similarity in
constitution between them and the plasma of the blood. They
contain water, fibrin, albumen, fatty matters, and the usual saline
substances of the animal fluids. At the same time, the lymph is
very much poorer in albuminous ingredients than the blood. The
following is an analysis by Lassaigne,1 of the fluid obtained from

the thoracic duct of the cow : —

PARTS PER THOUSAND.

Water 964.0

Fibrin 0.9

Albumen . 28.0

Fat . 0.4

Chloride of sodium 5.0

Carbonic \

Phosphate and > of soda 1.2

Sulphate J

Phosphate of lime . . . . . . . 0.5

1000.0

Colin, Physiologie comparee des Animaux domestiques, vol. ii. p. 111.

THE LYMPHATIC SYSTEM. 319

It tli us appears that both the fibrin and the albumen of the blood
actually transude to a certain extent from the bloodvessels, even in
the ordinary condition of the circulatory system. But this transuda-
tion takes place in so small a quantity that the albuminous matters
are all taken up again by the lymphatic vessels, and do not appear
in the excreted fluids.

The first important peculiarity which is noticed in regard to the
fluid of the lymphatic system, especially in the carnivorous animals,
is that it varies very much, both in appearance and constitution, at
different times. In the ruminating and graminivorous animals,
such as the sheep, ox, goat, horse, &c., it is either opalescent in
appearance, with a slight amber tinge, or nearly transparent and
colorless. In the carnivorous animals, such as the dog and cat, it
is also opaline and amber colored, in the intervals of digestion, but
soon after feeding becomes of a dense, opaque, milky white, and con-
tinues to present that appearance until the processes of digestion
and intestinal absorption are complete. It then regains its original
aspect, and remains opaline or semi-transparent until digestion is
again in progress.

The cause of this variable constitution of the fluid discharged
by the thoracic duct is the absorption of fatty substances from the
intestine during digestion. Whenever fatty substances exist in con-
siderable quantity in the food, they are reduced, by the process of
digestion, to a white, creamy mixture of molecular fat, suspended
in an albuminous menstruum. The mixture is then absorbed by
the lymphatics of the mesentery, and transported by them through
the thoracic duct to the subclavian vein. While this absorption is
going on, therefore, the fluid of the thoracic duct alters its appear-
ance, becomes white and opaque, and is then called chyle; so that
there are two different conditions, in which the contents of the great
lymphatic trunks present different appearances. In the fasting
condition, these vessels contain a semi-transparent, or opaline and
nearly colorless lymph; and during digestion, an opaque, milky
chyle. It is on this account that the lymphatics of the mesentery
are called " lacteals."

The chyle, accordingly, is nothing more than the lymph which
is constantly absorbed by the lymphatic system everywhere, with
the addition of more or less fatty ingredients taken up from the
intestine during the digestion of food.

The results of analysis show positively that the varying appear-
ance of the lymphatic fluids is really due to this cause ; for though

320 IMBIBITION AND EXHALATION.

the chyle is also richer than the lymph in albuminous matters, the
principal difference between them consists in the proportion of fat.
This is shown by the following comparative analysis of the lymph
and chyle of the ass, by Dr. Bees:' —

LYMPH.
965.36

CHYLE.

902.37

. • . . . 12.00

35.16

Fibrin .
Spirit extract

1.20
240

3.70
3.32

Water extract

Fat
Saline matter

13.19
. traces.

5.85

12.33
36.01
7.11

1,000.00 1,000.00

When a canula, accordingly, is introduced into the thoracic duct
at various periods after feeding, the fluid which is discharged varies
considerably, both in appearance and quantity. We have found
that, in the dog, the fluid of the thoracic duct never becomes quite
transparent, but retains a very marked opaline tinge even so late
as eighteen hours after feeding, and at least three days and a half
after the introduction of fat food. Soon after feeding, however, as
we have already seen, it becomes whitish and opaque, and remains
so while digestion and absorption are in progress. It also becomes
more abundant soon after the commencement of digestion, but
diminishes again in quantity during its latter stages. We have
found the lymph and chyle to be discharged from the thoracic duct,
in the dog, in the following quantities per hour, at different periods
of digestion. The quantities are calculated in proportion to the
entire weight of the animal.

PER THOUSAND PARTS.
3£ hours after feeding . . . , . .2.45

7 « « « 2.20

13 « « « 0.99

18 " " " 1.15

18} "" " 1.99

It would thus appear that the hourly quantity of lymph, after
diminishing during the latter stages of digestion, increases again
somewhat, about the eighteenth hour, though it is still considera-
bly less abundant than while digestion was in active progress.

The lymph obtained from the thoracic duct at all periods coagu-
lates soon after its withdrawal, owing to the fibrin which it contains

1 In Colin, op. cit., vol. ii. p. 18.

THE LYMPHATIC SYSTEM. 321

in small quantity. After coagulation, a separation takes place be-
tween the clot and serum, precisely as in the case of blood.

The movement of the lymph in the lymphatic vessels, from the
extremities toward the heart, is accomplished by various forces.
The first and most important of these forces is that by which the
fluids are originally absorbed by the lymphatic capillaries. Through-
out the entire extent of the lymphatic system, an extensive process
of endosmosis is incessantly going on, by which the ingredients of
the lymph are imbibed from the surrounding tissues, and com-
pelled to pass into the lymphatic vessels. The lymphatics are thus
filled at their origin ; and, by mere force of accumulation, the fluids
are then compelled, as their absorption continues, to discharge
themselves into the large veins in which the lymphatic trunks
terminate.

The movement of the fluids through the lymphatic system is
also favored by the contraction of the voluntary muscles and the
respiratory motions of the chest. For as the lymphatic vessels are
provided with valves, arranged like those of the veins, opening
toward the heart and shutting backward toward the extremities,
the alternate compression and relaxation of the adjacent muscles,
and the expansion and collapse of the thoracic parietes, must have
the same effect upon the movement of the Lymph as upon that of
the venous blood. By these different influences the chyle and
lymph are incessantly carried from without inward, and discharged,
in a slow but continuous stream, into the returning current of the
venous blood.

The entire quantity of the lymph and chyle has been found, by
direct experiment, to be very much larger than was previously
anticipated. M. Colin1 measured the chyle discharged from the
thoracic duct of an ox during twenty -four hours, and found it to
exceed eighty pounds. In other experiments of the same kind, he
obtained still larger quantities.2 From two experiments on the
horse, extending over a period of twelve hours each, he calculates
the quantity of chyle and lymph in this animal as from twelve to
fifteen thousand grains per hour, or between forty and fifty pounds
per day. But in the ruminating animals, according to his observa-
tions, the quantity is considerably greater. In an ordinary-sized
cow, the smallest quantity obtained in an experiment extending over

1 Gazette Hebdoinadaire, April 24, 1857, p. 2S5.

2 Colin, op. cit., vol. ii. p. 100.

21

322 IMBIBITION AND EXHALATION.

a period of twelve hours, was a little over 9,000 grains in fifteen
minutes ; that is, five pounds an hour, or 120 pounds per day. In
another experiment, with a young bull, he actually obtained a little
over 100 pounds from a fistula of the thoracic duct, in twenty-four
hours.

We have also obtained similar results by experiments upon the
dog and goat. In a young kid, weighing fourteen pounds, we have
obtained from the thoracic duct 1890 grains of lymph in three
hours and a half. This quantity would represent 540 grains in an
hour, and 12,690 grains, or 1.85 pounds in twenty-four hours; and
in a ruminating animal weighing 1000 pounds, this would corre-
spond to 132 pounds of lymph and chyle discharged by the thoracic
duct in the course of twenty-four hours.

The average of all the results obtained by us, in the dog, at dif-
ferent periods after feeding, gives very nearly four and a half per
cent, of the entire weight of the animal, as the total daily quantity
of lymph and chyle. This is substantially the same result as that
obtained by Colin, in the horse ; and for a man weighing 140
pounds, it would be equivalent to between six and six and a half
pounds of lymph and chyle per day.

But of this quantity a considerable portion consists of the chyle
which is absorbed from the intestines during the digestion of fatty
substances. If we wish, therefore, to ascertain the total amount of
the lymph, separate from that of the chyle, the calculation should
be based upon the quantity of fluid obtained from the thoracic
duct in the intervals of digestion, when no chyle is in process of
absorption. We have seen that in the dog, eighteen hours after
feeding, the lymph, which is at that time opaline and semi-transpa-
rent, is discharged from the thoracic duct, in the course of an hour,
in a quantity equal to 1.15 parts per thousand of the entire weight
of the animal. In twenty-four hours this would amount to 27.6
parts per thousand ; and for a man weighing 140 pounds this would
give 3.864 pounds as the total daily quantity of the lymph alone.

It will be seen, therefore, that the processes of exudation and
absorption, which go on in the interior of the body, produce a very
active interchange or internal circulation of the animal fluids, which
may be considered as secondary to the circulation of the blood.
For all the digestive fluids, as we have found, together with the bile
discharged into the intestine, are reabsorbed in the natural process
of digestion and again enter the current of the circulation. These
fluids, therefore, pass and repass through the mucous membrane of

THE LYMPHATIC SYSTEM. 323

the alimentary canal and adjacent glands, becoming somewhat
altered in constitution at each passage, but still serving to renovate
alternately the constitution of the blood and the ingredients of the
digestive secretions. Furthermore the elements of the blood itself
also transude in part from the capillary vessels, and are again taken
up, by absorption, by the lymphatic vessels, to be finally restored
to the returning current of the venous blood, in the immediate
neighborhood of the heart.

The daily quantity of all the fluids, thus secreted and reabsorbed
during twenty-four hours, will enable us to estimate the activity
with which endosmosis and exosmosis go on in the living body.
In the following table, the quantities are all calculated for a man
weighing 140 pounds.

SECRETED AND REABSORBED DURING 24 HOURS.
Saliva 20,164 grains, or 2.880 pounds.

Gastric juice 98,000 " " 14.000 "
Bile 16.940 " " 2.420 "

Pancreatic juice 13,104 " " 1.872 "
Lymph 27,048 " " 3.864 •'

1 25.036

A little over twenty-five pounds, therefore, of the animal fluids
transude through the internal membranes and are restored to the
blood by reabsorption in the course of a single day. It is by this
process that the natural constitution of the parts, though constantly
changing, is still maintained in its normal condition by the move-
ment of the circulating fluids, and the incessant renovation of their
nutritious materials.

324 SECRETION.

CHAPTER XYI.

SECRETION.

WE have already seen, in a previous chapter, how the elements of
the blood are absorbed by the tissues during the capillary circula-
tion, and assimilated by them or converted into their own substance.
In this process, the inorganic or saline matters are mostly taken up
unchanged, and are merely appropriated by the surrounding parts in
particular quantities ; while the organic substances are transformed
into new compounds, characteristic of the different tissues by which
they are assimilated. In this way the various tissues of the body,
though they have a different chemical composition from the blood,
are nevertheless supplied by it with appropriate ingredients, and
their nutrition constantly maintained.

Beside this process, which is known by the name of "assimila-
tion," there is another somewhat similar to it, which takes place in
the different glandular organs, known as the process of secretion. It
is the object of this function to supply certain fluids, differing in
chemical constitution from the blood, which are required to assist
in various physical and chemical actions going on in the body.
These secreted fluids, or "secretions," as they are called, vary in
consistency, density, color, quantity, and reaction. Some of them
are thin and watery, like the tears and the perspiration ; others are
viscid and glutinous, like mucus and the pancreatic fluid. They
are alkaline like the saliva, acid like the gastric juice, or neutral
like the bile. Each secretion contains water and the inorganic salts
of the blood, in varying proportions; and is furthermore distin-
guished by the presence of some peculiar animal substance which
does not exist in the blood, but which is produced by the secreting
action of the glandular organ. As the blood circulates through the
capillaries of the gland, its watery and saline constituents transude
in certain quantities, and are discharged into the excretory duct.
At the same time, the glandular cells, which have themselves been
nourished by the blood, produce a new substance by the catalytic

SECRETION. 325

transformation of their organic constituents ; and this new substance
is discharged also into the excretory duct and mingled with the
other ingredients of the secreted fluid. A true secretion, therefore,
is produced only in its own particular gland, and cannot be formed
elsewhere, since the glandular cells of that organ are the only
ones capable of producing its most characteristic ingredient. Thus
pepsine is formed only in the tubules of the gastric mucous mem-
brane, pancreatine only in the pancreas, tauro-cholate of soda only
in the liver.

One secreting gland, consequently, can never perform vicariously
the office of another. Those instances which have been from time
to time reported of such an unnatural action are not, properly
speaking, instances of "vicarious secretion;" but only cases in
which certain substances, already existing in the blood, have made
their appearance in secretions to which they do not naturally belong.
Thus cholesterine, which is produced in the brain and is taken up
from it by the blood, usually passes out with the bile; but it may
also appear in the fluid of hydrocele, or in inflammatory exuda-
tions. The sugar, again, which is produced in the liver and taken
up by the blood, when it accumulates in large quantity in the cir-
culating fluid, may pass out with the urine. The coloring matter
of the bile, in cases of biliary obstruction, may be reabsorbed, and
so make its appearance in the serous fluids, or even in the perspira-
tion. In these instances, however, the unnatural ingredient is not
actually produced by the kidneys, or the perspiratory glands, but
is merely supplied to them, already formed, by the blood. Cases
of "vicarious menstruation" are simply capillary hemorrhages
which take place from various mucous membranes, owing to the
general disturbance of the circulation in amenorrhoea. A true
secretion, however, is always confined to the gland in which it
naturally originates.

The force by which the different secreted fluids are prepared in
the glandular organs, and discharged into their ducts, is a peculiar
one, and resident only in the glands themselves. It is not simply
a process of filtration, in which the ingredients of the secretion
exude from the bloodvessels by exosmosis under the influence of
pressure ; since the most characteristic of these ingredients, as we
have already mentioned, do not pre-exist in the blood, but are
formed in the substance of the gland itself. Substances, even,
which already exist in the blood in a soluble form, may not have
the power of passing out through the glandular tissue. Bernard

326 SECRETION.

has found1 that ferrocyanide of potassium, when injected into the
jugular vein, though it appears with great facility in the urine,
does not pass out with the saliva ; and even that a solution of
the same salt, injected into the duct of the parotid gland, is ab-
sorbed, taken up by the blood, and discharged with the urine ; but
does not appear in the saliva, even of the gland into which it has
been injected. The force with which the secreted fluids accumulate
in the salivary ducts has also been shown by Ludwig's experi-
ments2 to be sometimes greater than the pressure in the bloodves-
sels. This author found, by applying mercurial gauges at the same
time to the duct of Steno and to the artery of the parotid gland, that
the pressure in the duct from the secreted saliva was considerably
greater than that in the artery from the circulating blood ; so that
the passage of the secreted fluids had really taken place in a direc-
tion contrary to that which would have been caused by the simple
influence of pressure.

The process of secretion, therefore, is one which depends upon
the peculiar anatomical and chemical constitution of the glandular
tissue and its secreting cells. These cells have the property of
absorbing and transmitting from the blood certain inorganic and
saline substances, and of producing, by chemical metamorphosis,
certain peculiar animal matters from their own tissue. These sub-
stances are then mingled together, dissolved in the watery fluids
of the secretion, and discharged simultaneously by the excretory
duct.

All the secreting organs vary in activity at different periods.
Sometimes they are nearly at rest ; while at certain periods they
become excited, under the influence of an occasional or periodical
stimulus, and then pour out their secretion with great rapidity and in
large quantity. The perspiration, for example, is usually so slowly
secreted that it evaporates as rapidly as it is poured out, and the
surface of the skin remains dry ; but under the influence of unusual
bodily exercise or mental excitement it is secreted much faster
than it can evaporate, and the whole integument becomes covered
with moisture. The gastric juice, again, in the intervals of digestion,
is either not secreted at all, or is produced in a nearly inappreciable
quantity ; but on the introduction of food into the stomach, it is
immediately poured out in such abundance, that between two and
three ounces may be collected in a quarter of an hour.

1 Legons de Physiologie Experiinentale. Paris, 1856, tome ii. p. 96 et seq.

2 Ibid., p. 106.

MUCUS. 327

The principal secretions met with in the animal body are as
follows : —

1. Mucus. 6. Saliva.

2. Sebaceous matter. 7. Gastric juice.

3. Perspiration. 8. Pancreatic juice.

4. The tears. 9. Intestinal juice.

5. The milk. 10. Bile.

The last five of these fluids have already been described in the
preceding chapters. We shall therefore only require to examine
at present the five following, viz., mucus, sebaceous matter, per-
spiration, the tears, and the milk, together with some peculiarities
in the secretion of the bile.

1. Mucus. — Nearly all the mucous membranes are provided with
follicles or glandulae, in which the mucus is prepared. These folli-
cles are most abundant in the lining membrane of the mouth, nares,
pharynx, oesophagus, trachea and bronchi, vagina, and male urethra.
They are generally of a compound form, consisting of a number of
secreting sacs or cavities, terminating at one end in a blind ex-
tremity, and opening by the other into a common duct by which
the secreted fluid is discharged. Each ultimate secreting sac or
follicle is lined with glandular epithelium (Fig. 102), and surround-
ed on its external surface by a network of capillary bloodvessels.
These vessels, penetrating deeply into the F. 1Q2

interstices between the follicles, bring the
blood nearly into contact with the epithelial
cells lining its cavity. It is these cells
which prepare the secretion, and discharge
it afterward into the commencement of the

excretory duct. "FOLLICLES OF A COM-

The mucus, produced in the manner POUND MCCOUS GLANDULE.

, , ., , . , ,, n • t From the human subject. (After

above described, is a clear, colorless fluid, Ko inker.)-*. Membrane of the
which is poured out in larger or smaller foiiscie. j, c. Epithelium of the

t n fl i same.

quantity on the surface ot the mucous

membranes. It is distinguished from other secretions by its vis-
cidity, which is its most marked physical property, and which
depends on the presence of a peculiar animal matter, known under
the name of mucosine. When unmixed with other animal fluids,
this viscidity is so great that the mucus has nearly a semi-solid or
gelatinous consistency. Thus, the mucus of the mouth, when ob-
tained unmixed with the secretions of the salivary glands, is so

ff

328 SECRETION.

tough and adhesive that the vessel containing it may be turned
upside down without its running out. The mucus of the cervix
uteri has a similar firm consistency, so as to block up the cavity
of this part of the organ with a semi-solid gelatinous mass. Mucus
is at the same time exceedingly smooth and slippery to the touch,
so that it lubricates readily the surfaces upon which it is exuded,
and facilitates the passage of foreign substances, while it defends
the mucus membrane itself from injury.

The composition of mucus, according to the analyses of Nasse,1

is as follows : —

COMPOSITION OF PULMONARY Mucus.

Water

Animal matter .........

Fat

Chloride of sodium

Phosphates of soda and potassa .

Sulphates " "

Carbonates " " ,

1000.00

The animal matter of mucus is insoluble in water ; and conse-
quently mucus, when dropped into water, does not mix with it, but
is merely broken up by agitation into gelatinous threads and flakes,
which subside after a time to the bottom. It is miscible, however,
to some extent, with other animal fluids, and may be incorporated
with them, so as to become thinner and more dilute. It readily
takes on putrefactive changes, and communicates them to other
organic substances with which it may be in contact.

The varieties of mucus found in different parts of the body are
probably not identical in composition, but differ a little in the cha-
racter of their principal organic ingredient, as well as in the pro-
portions of their saline constituents. The function of mucus is for
the most part a physical one, viz., to lubricate the mucous surfaces,
to defend them from injury, and to facilitate the passage of foreign
substances through their cavities.

2. SEBACEOUS MATTER. — The sebaceous matter is distinguished
by containing a very large proportion of fatty or oily ingredients.
There are three varieties of this secretion met with in the body,
viz., one produced by the sebaceous glands of the skin, another
by the ceruminous glands of the external auditory meatus, and
a third by the Meibomian glands of the eyelid. The sebaceous

1 Simon's Chemistry of Man, Philada., 1846, p. 352.

SEBACEOUS MATTEK.

329

Fig. 103.

glands of the skin are found most abundantly in those parts which
are thickly covered with hairs, as well as on the face, the labia
nrinora of the female generative organs, the glans penis, and the
prepuce. They consist sometimes of a simple follicle, or flask-
shaped cavity, opening by a single orifice ; but more frequently of
a number of such follicles grouped round a common excretory duct.
The duct nearly always opens just at the root of one of the hairs,
which is smeared more or less abundantly
with its secretion. Each follicle, as in the
case of the mucous glandules, is lined
with epithelium, and its cavity is filled
with the secreted sebaceous matter.

In the Meibomian glands of the eye-
lid (Fig. 103), the follicles are ranged
along the sides of an excretory duct,
situated just beneath the conjunctiva, on
the posterior surface of the tarsus, and
opening upon its free edge, a little be-
hind the roots of the eyelashes. The
ceruminous glands of the external audi-
tory meatus, again, have the form of long
tubes, which terminate, at the lower part
of the integument lining the meatus, in
a globular coil, or convolution, covered
externally by a network of capillary bloodvessels.

The sebaceous matter of the skin has the following composition,
according to Esenbeck.1

MEIBOMIAN
Ludovic.

GLANDS, after

COMPOSITION OF SEBACEOUS MATTER.
Animal substances . . .
Fatty matters .......

Phosphate of lime

Carbonate of lime ......

Carbonate of magnesia

Chloride of sodium \
Acetate of soda, &c. »

358

368

200

21

16

37

1000

Owing to the large proportion of stearine in the fatty ingredients
of the sebaceous matters, they have a considerable degree of con-
sistency. Their office is to lubricate the integument and the hairs,
to keep them soft and pliable, and to prevent their drying up by

Simon's Chemistry of Man, p. 379.

330

SECRETION.

too rapid evaporation. When the sebaceous glands of the scalp
are inactive or atrophied, the hairs become dry and brittle, are
easily split or broken off, and finally cease growing altogether.
The cerurainous matter of the ear is intended without doubt partly
to obstruct the cavity of the meatus, and by its glutinous consist-
ency and strong odor to prevent small insects from accidentally
introducing themselves into the meatus. The secretion of the
Meibomian glands, by being smeared on the edges of the eyelids,
prevents the tears from running over upon the cheeks, and confines
them within the cavity of the lachrymal canals.

3. PERSPIRATION. — The perspiratory glands of the skin are scat-
tered everywhere throughout the integument, being most abundant
on the anterior portions of the body. They consist each of a slender
tube, about 7£<y of an inch in diameter, lined with glandular epi-
thelium, which penetrates nearly through the entire thickness of
the skin, and terminates below in a globular coil, very similar in

appearance to that of the cerumi-
Fig. 104. nous glands of the ear. (Fig. 104.)

Yt A network of capillary vessels

envelops the tubular coil and sup-
plies the gland with the materials
necessary to its secretion.

These glands are very abundant
in some parts. On the posterior
portion of the trunk, the cheeks,
and the skin of the thigh and leg
there are, according to Krause,1
about 500 to the square inch ; on
the anterior part of the trunk, the
forehead, the neck, the forearm,
and the back of the hand and foot
1000 to the square inch ; and on
the sole of the foot and the palm

of the hand about 2700 in the same space. According to the same
observer, the whole number of perspiratory glands is not less than
2,300,000, and the length of each tubular coil, when unravelled,
about YS of an inch. The entire length of the glandular tubing
must therefore be not less than 153,000 inches, or about two miles
and a half.

A PERSPIRATORY G LAND, with its ves-
sels ; magnified 35 times. (After Todd and Bow-
man.)— a. Glandular coil: b. Plexus of vessels.

Kolliker, Handbuch der Gewebelehre, Leipzig, 1852. p. 147.

PERSPIRATION. 331

It is easy to understand, therefore, that a very large quantity of
fluid may be supplied from so extensive a glandular apparatus. It
results from the researches of Lavoisier and Seguin1 that the ave-
rage quantity of fluid lost by cutaneous perspiration during 24
hours is 13,500 grains, or nearly two pounds avoirdupois. A still
larger quantity than this may be discharged during a shorter time,
when the external temperature is high and the circulation active.
Dr. Southwood Smith2 found that the laborers employed in gas
works lost sometimes as much as 3J pounds' weight, by both cuta-
neous and pulmonary exhalation, in less than an hour. In these
cases, as Seguin has shown, the amount of cutaneous transpiration
is about twice as great as that which takes place through the lungs.

The perspiration is a colorless watery fluid, generally with a
distinctly acid reaction, and having a peculiar odor, which varies
somewhat according to the part of the body from which the speci-
men is obtained. Its chemical constitution, according to Ansel-
mino,3 is as follows : —

COMPOSITION OF THE PERSPIRATION.

Water 995.00

Animal matters, with lime ........ .10

Sulphates, and substances soluble in water .... 1.05

Chlorides of sodium and potassium, and spirit-extract . . 2.40

Acetic acid, acetates, lactates, and alcohol-extract . . . 1.45

1000.00

The office of the cutaneous perspiration is principally to regulate
the temperature of the body. "We have already seen, in a preced-
ing chapter, that the living body will maintain the temperature of
100° F., though subjected to a much lower temperature by the
surrounding atmosphere, in consequence of the continued genera-
tion of heat which takes place in its interior ; and that if, by long
continued or severe exposure, the blood become cooled down much
below its natural standard, death inevitably results. But the body
has also the power of resisting an unnaturally high temperature,
as well as an unnaturally low one. If exposed to the influence of
an atmosphere warmer than 100° F., the body does not become
heated up to the temperature of the air, but remains at its natural
standard. This is provided for by the action of the cutaneous
glands, which are excited to unusual activity, and pour out a large
quantity of watery fluid upon the skin. This fluid immediately

1 Milne Edwards, LeQons sur la Physiologie, &c., vol. ii. p. 623.

2 Philosophy of Health, London, 1838, chap. xiii.

3 Simon. Op. cit., p. 374.

332 SECRETION.

evaporates, and in assuming the gaseous form causes so much heat
to become latent that the cutaneous surfaces are cooled down to
their natural temperature.

So long as the air is dry, so that evaporation from the surface
can go on rapidly, a very elevated temperature can be borne with
impunity. The workmen of the sculptor Chantrey were in the
habit, according to Dr. Carpenter, of entering a furnace in which
the air was heated up to 350° ; and other instances have been known
in which a temperature of 4'00° to 600° has been borne for a time
without much inconvenience. But if the air be saturated with
moisture, and evaporation from the skin in this way retarded, the
body soon becomes unnaturally warm ; and if the exposure be long
continued, death is the result. It is easily seen that horses, when
fast driven, suffer much more from a warm and moist atmosphere
than from a warm and dry one. The experiments of Magendie and
others have shown1 that quadrupeds confined in a dry atmosphere
suffer at first but little inconvenience, even when the temperature
is much above that of their own bodies ; but as soon as the atmo-
sphere is loaded with moisture, or the supply of perspiration is ex-
hausted, the blood becomes heated, and the animal dies. Death
follows in these cases as soon as the blood has become heated up to
8° or 9° F., above its natural standard. The temperature of 110°,
therefore, which is the natural temperature of birds, is fatal to quad-
rupeds ; and we have found that frogs, whose natural temperature
is 50° or 60°, die very soon if they are kept in water at 100° F.

The amount of perspiration is liable to variation, as we have
already intimated, from the variations in temperature of the sur-
rounding atmosphere. It is excited also by unusual muscular
exertion, and increased or diminished by various nervous condi-
tions, such as anxiety, irritation, lassitude, or excitement.

4. THE TEARS. — The tears are produced by lobulated glands
situated at the upper and outer part of the orbit of the eye, and
opening, by from six to twelve ducts, upon the surface of the con-
junctiva, in the fold between the eyeball and the outer portion of
the upper lid. The secretion is extremely watery in its composition,
and contains only about one part per thousand of solid matters,
consisting mostly of chloride of sodium and animal extractive
matter. The office of the lachrymal secretion is simply to keep the

1 Bernard, Lectures on the Blood. Atlee's translation, Phila., 1854, p. 25.

THE MILK.

333

surfaces of the cornea and conjunctiva moist and polished, and to
preserve in this way the transparency of the parts. The tears,
which are constantly secreted, are spread out uniformly over the
anterior part of the eyeball by the movement of the lids in wink-
ing, and are gradually conducted to the inner angle of the eye.
Here they are taken up by the puncta lachrymalia, pass through
the lachrymal canals, and are finally discharged into the nasal pas-
sages beneath the inferior turbinated bones. A constant supply of
fresh fluid is thus kept passing over the transparent parts of the
eyeball, and the bad results avoided which would follow from its
accumulation and putrefactive alteration.

5. THE MILK. — The mammary glands are conglomerate glands^
resembling closely in their structure the pancreas, the salivary, and
the lachrymal glands. They consist of numerous secreting sacs or
follicles, grouped together in lobules, each lobule being supplied
with a common excretory duct, which joins those coming from
adjacent parts of the gland.

(Fig. 105.) In this way, by Fig. 105.

their successive union, they
form larger branches and
trunks, until they are reduced
in numbers to some 15 or 20
cylindrical ducts, the lactifer-
ous ducts, which open finally
by as many minute orifices
upon the extremity of the
nipple.

The secretion of the milk
becomes fairly established at
the end of two or three days
after delivery, though the
breasts often contain a milky

fluid during the latter part of pregnancy. At first the fluid dis-
charged from the nipple is a yellowish turbid mixture, which is
called the colostrum. It has the appearance of being thinner than
the milk, but chemical examinations have shown1 that it really con-
tains a larger amount of solid ingredients than the perfect secre-
tion. When examined under the microscope it is seen to contain,
beside the milk-globules proper, a large amount of irregularly glo-

1 Lehmann, op. cit., vol. ii. p. 63.

GLANDULAR STRUCTURE OF MAMMA.

334

SECRETION.

106.

bular or oval bodies, from T7f5ir to 5 Jo of an inch in diameter,

which are termed the " colostrum corpuscles." (Fig. 106.) These

bodies are more yellow and
opaque than the true milk-
glob ules, as well as being very
much larger. They have a
well defined outline, and con-
sist apparently of a group of
minute oily granules or glo-
bules, imbedded in a mass
of organic substance. The
milk-globules at this time
are less abundant than after-
ward, and of larger size,
measuring mostly from soW
to TsVff °f an inCR in dia-
meter.

At the end of a day or
two after its first appearance,

the colostrum ceases to be discharged, and is replaced by the true

milky secretion.

The milk, as it is discharged from the nipple, is a white, opaque

fluid, with a slightly alkaline reaction, and a specific gravity of

about 1030. Its proximate chemical constitution, according to

Pereira and Lehmann, is as follows : —

COLOSTRUM COKPTSCLES, with milk-globules
from a woman, one day after delivery.

COMPOSITION OF Cow's MILK.

Water

Casein

Butter

Sugar ........

Soda

Chlorides of sodium and potassium .
Phosphates of soda and potassa

Phosphate of lime

" magnesia .....

" " iron

Alkaline carbonates ......

870.2
44.8
31.3
47.7

6.0

1000.0

Human milk is distinguished from the above by containing less
casein, and a larger proportion of oily and saccharine ingredients.
The entire amount of solid ingredients is also somewhat less than
in cow's milk.

THE MILK.

335

The casein is one of the most important ingredients of the milk.
It is an extremely nutritious organic substance, which is held in a
fluid form by union with the water of the secretion. Casein is not
coagulable by heat, and consequently, milk may be boiled without
changing its consistency to any considerable extent. It becomes
a little thinner and more fluid during ebullition, owing to the melt-
ing of its oleaginous ingredients; and a thin, membranous film
forms upon its surface, consisting probably of a very little albumen,
which the milk contains, mingled with the casein. The addition of
any of the acids, however, mineral, animal, or vegetable, at once
coagulates the casein, and the milk becomes curdled. Milk is
coagulated, furthermore, by the gastric juice in the natural process
of digestion, immediately after being taken into the stomach ; and
if vomiting occur soon after a meal containing milk, it is thrown
off in the form of semi-solid, curd-like flakes.

The mucous membrane of the calves' stomach, or rennet, also
has the power of coagulating casein; and when milk has been
curdled in this way, and its watery, saccharine, and inorganic in-
gredients separated by mechanical pressure, it is converted into
cheese. The peculiar flavor of the different varieties of cheese
depends on the quantity and quality of the oleaginous ingredients
which have been entangled with the coagulated casein, and on the
alterations which these sub-
stances have undergone by
the lapse of time and ex-
posure to the atmosphere.

The sugar and saline sub-
stances of the milk are in
solution, together with the
casein and water, forming a
clear, colorless, homogene-
ous, serous fluid. The but-
ter, or oleaginous ingredient,
however, is suspended in
this serous fluid in the form
of minute granules and
globules, the true "milk-

fflobules" (Fig" 107 ^ These MILK-GLOBCLKS; from same woman as above,
et>. ^r Ig. IU i .) ID „ four days after delivery> secretion fully established.

globules are nearly fluid at

the temperature of the body, and have a perfectly circular out-
line. In the perfect milk, they are very much more abundant and

Fig. 107.

SECRETION.

smaller in size than in the colostrum ; as the largest of them are
not over 2uVo °f an inc^ in diameter, and the greater number
about yeiffTj of an inch.

The following is the composition of the butter of cow's milk,
according to Robin and Yerdeil : —

Margarine .......... 68

Oleine 30

Butyrine .......... 2

100

It is the last of these ingredients, the butyrine, which gives the
peculiar flavor to the butter of milk.

The milk-globules have sometimes been described as if each one
were separately covered with a thin layer of coagulated casein or
albumen. No such investing membrane, however, is to be seen.
The milk-globules are simply small masses of semi-fluid fat, sus-
pended by admixture in the watery and serous portions of the
secretion, so as to make an opaque, whitish emulsion. They do
not fuse together when they come in contact under the microscope,
simply because they are not quite fluid, but contain a large pro-
portion of margarine, which is solid at ordinary temperatures of the
body, and is only retained in a partially fluid form by the oleine
with which it is associated. The globules may be made to fuse with
each other, however, by simply heating the milk and subjecting it
to gentle pressure between two slips of glass.

When fresh milk is allowed to remain at rest for twelve to twenty-
four hours, a large portion of its fatty matters rise to the surface,
and form there a dense and rich-looking yellowish-white layer, the
cream, which may be removed, leaving the remainder still opaline,
but less opaque than before. At the end of thirty-six to forty-eight
hours, if the weather be warm, the casein begins to take on a
putrefactive change. In this condition it exerts a catalytic action
upon the other ingredients of the milk, and particularly upon the
sugar. A pure watery solution of milk-sugar (C24H24O24) may be
kept for an indefinite length of time, at ordinary temperatures,
without undergoing any change. But if kept in contact with the
partially altered casein, it suffers a catalytic transformation, and is
converted into lactic acid (C6H6Ofi). This unites with the free soda,
and decomposes the alkaline carbonates, forming lactates of soda
and potassa. After the neutralization of these substances has been
accomplished, the milk loses its alkaline reaction and begins to turn
sour. The free lactic acid then coagulates the casein, and the milk

SECRETION OF THE BILE. 337

is curdled. The altered organic matter also acts upon the olea-
ginous ingredients, which are partly decomposed; and the milk
begios to give off a rancid odor, owing to the development of
various volatile fatty acids, among which are butyric acid, and the
like. These changes are very much hastened by a moderately
elevated temperature, and also by a highly electric state of the
atmosphere.

The production of the milk, like that of other secretions, is liable
to be much influenced by nervous impressions. It may be increased
or diminished in quantity, or vitiated in quality by sudden emo-
tions ; and it is even said to have been sometimes so much altered
in this way as to produce indigestion, diarrhoea, and convulsions in
the infant.

Simon found1 that the constitution of the milk varies from day to
day, owing to temporary causes ; and that it undergoes also more
permanent modifications, corresponding with the age of the infant.
He analyzed the milk of a nursing woman during a period of nearly
six months, commencing with the second day after delivery, and
repeating his examinations at intervals of eight or ten days. It
appears, from these observations, that the casein is at first in small
quantity ; but that it increases during the first two months, and
then attains a nearly uniform standard. The saline matters also
increase in a nearly similar manner. The sugar, on the contrary,
diminishes during the same period ; so that it is less abundant in
the third, fourth, fifth and sixth months, than it is in the first and
second. These changes are undoubtedly connected with the in-
creasing development of the infant, which requires a corresponding
alteration in the character of the food supplied to it. Finally, the
quantity of butter in the milk varies so much from day to day,
owing to incidental causes, that it cannot be said to follow any
regular course of increase or diminution.

6. SECRETION OF THE BILE. — The anatomical peculiarities in the
structure of the liver are such as to distinguish it in a marked
degree from the other glandular organs. Its first peculiarity is
that it is furnished principally with venous blood. For, although
it receives its blood from the hepatic artery as well as from the
portal vein, the quantity of arterial blood with which it is supplied
is extremely small in comparison with that which it receives from

1 Op. cit., p. 337.
22

338

SECRETION.

Fig. 108.

the portal system. The blood which has circulated through the
capillaries of the stomach, spleen, pancreas, and intestine is col-
lected by the roots of the corresponding veins, and discharged into
the portal vein, which enters the liver at the great transverse
fissure of the organ. Immediately upon its entrance, the portal
vein divides into two branches, right and left, which supply the
corresponding portions of the liver; and these branches success-
ively subdivide into smaller twigs and ramifications, until they are
reduced to the size, according to Kolliker, of 1^-^ of an inch in
diameter. These veins, with their terminal branches, are arranged
in such a manner as to include between them pentagonal or
hexagonal spaces, or portions of the hepatic substance, -J$ to ylj
of an inch in diameter in the human subject, which can readily be
distinguished by the naked eye, both on the exterior of the organ
and by the inspection of cut surfaces. The portions of hepatic
substance included in this way between the terminal branches

of the portal vein (Fig. 108)
are termed the "acini" or
"lobules" of the liver; and
the terminal venous branches,
occupying the spaces between
the adjacent lobules, are the
"interlobular" veins. In the
spaces between the lobules
we also find the minute
branches of the hepatic ar-
tery, and the commencing
rootlets of the hepatic ducts.
As the portal vein, the he-
patic artery, and the hepatic
duct enter the liver at the
transverse fissure, they are
closely invested by a fibrous

sheath, termed Glisson's capsule, which accompanies them in their
divisions and ramifications. In some of the lower animals, as in the
pig, this sheath extends even to the interlobular spaces, inclosing
each lobule in a thin fibrous investment, by which it is distinctly
separated from the neighboring parts. In the human subject, how-
ever, Glisson's capsule becomes gradually thinner as it penetrates
the liver, and disappears altogether before reaching the interlobular
spaces ; so that here the lobules are nearly in contact with each

Ranrfication of PORTAL VEIN IN LIVER.— a.
Twig of portal vein. 6,6. I uteri obular veins, c. Aciui.

SECRETION OF THE BILE. 339

other by their adjacent surfaces, being separated only by the inter-
lobular veins and the minute branches of the hepatic artery and
duct previously mentioned.

From the sides of the interlobular veins, and also from their
terminal extremities, there are given off capillary vessels, which
penetrate the substance of each lobule and converge from its cir-
cumference toward its centre, inosculating at the same time freely
with each other, so as to form a minute vascular plexus, the " lobu-
lar" capillary plexus. (Fig. 109.) At the centre of each lobule, the

Fig. 109.

LOBTLE OF LIVER, showing distribution of bloodvessels ; magnified 22 diameters.— n. a. In-
terlobular veins. 6. Intralobular vein, c, c, c. Lobular capillary plexus, d, d. Twigs of inter-
lobular vein passing to adjacent lobules.

converging capillaries unite into a small vein (b), the " intralobu-
lar" vein, which is one of the commencing rootlets of the hepatic
vein. These rootlets, uniting successively with each other, so as
to form larger and larger branches, finally leave the liver at its
posterior edge, to empty into the ascending vena cava.

Beside the capillary bloodvessels of the lobular plexus, each
acinus is made up of an abundance of minute cellular bodies, about
T^Vtf of an inch in diameter, the "hepatic cells." (Fig. 110.) These
cells have an irregularly pentagonal figure, and a soft consistency.
They are composed of a homogeneous organic substance, in the
midst of which are imbedded a large number of minute granules,
and generally several well defined oil-globules. There is also a
round or oval nucleus, with a nucleolus, imbedded in the substance

340

SECRETION.

Fig. 110.

of the cell, sometimes more or less obscured by the granules and
oil drops with which it is surrounded.

The exact mode in which these cells are connected with the
hepatic duct was for a long time the most obscure point in the

minute anatomy of the liver.
It has now been ascertained,
however, by the researches of
Dr. Leidy, of Philadelphia,1
and Dr. Beale, of London,7
that they are really contained
in the interior of secreting
tubules, which pass off from
the smaller hepatic ducts, and
penetrate everywhere the
substance of the lobules.
The cells fill nearly or com-
pletely the whole cavity of
the tubules, and the tubules,
themselves lie in close proxi-
mity with each other, so as
to leave no space between them except that which is occupied by
the capillary bloodvessels of the lobular plexus.

These cells are the active agents in accomplishing the function of
the liver. It is by their influence that the blood which is brought
in contact with them suffers certain changes which give rise to the
secreted products of the organ. The ingredients of the bile first
make their appearance in the substance of the cells. They are
then transuded from one to the other, until they are at last dis-
charged into the small biliary ducts seated in the interlobular
spaces. Each lobule of the liver must accordingly be regarded as
a mass of secreting tubules, lined with glandular cells, and invested
with a close network of capillary bloodvessels. It follows, there-
fore, from the abundant inosculation of the lobular capillaries, and
the manner in which they are entangled with the hepatic tissue,
that the blood, in passing through the circulation of the liver,
comes into the most intimate relation with the glandular cells of
the organ, and gives up to them the nutritious materials which are
afterward converted into the ingredients of the bile.

HEPATIC CELLS. From the human subject.

1 American Journal Med. Sci., January, 1848.

2 On Some Points in the Minute Anatomy of the Liver. London, 1856.

EXCRETION". 341

CHAPTER XVII.

EXCRETION.

WE have now come to the last division of the great nutritive
function, viz., the process of excretion. In order to understand fairly
the nature of this process we must remember that all the component
parts of a living organism are necessarily in a state of constant
change. It is one of the essential conditions of their existence and
activity that they should go through with this incessant transforma-
tion and renewal of their component substances. Every living
animal and vegetable, therefore, constantly absorbs certain materials
from the exterior, which are modified and assimilated by the pro-
cess of nutrition, and converted into the natural ingredients of the
organized tissues. But at the same time with this incessant growth
and supply, there goes on in the same tissues an equally incessant
process of waste and decomposition. For though the elements of
the food are absorbed by the tissues, and converted into musculine,
osteine, hasmatine and the like, they do not remain permanently in
this condition, but almost immediately begin to pass over, by a con-
tinuance of the alterative process, into new forms and combinations,
which are destined to be expelled from the body, as others continue
to be absorbed. Thus Spallanzani and Edwards found that every
organized tissue not only absorbs oxygen from the atmosphere
and fixes it in its own substance; but at the same time exhales
carbonic acid, which has been produced by internal metamorphosis.
This process, by which the ingredients of the organic tissues, al-
ready formed, are decomposed and converted into new substances,
is called the process of Destructive Assimilation.

Accordingly we find that certain substances are constantly mak-
ing their appearance in the tissues and fluids of the body, which
did not exist there originally, and which have not been introduced
with the food, but which have been produced by the process of in-
ternal metamorphosis. These substances represent the waste, or
physiological detritus of the animal organism. They are the forms

342 EXCRETION".

under which those materials present themselves, which have once
formed a part of the living tissues, but which have become altered
by the incessant changes characteristic of organized bodies, and
which are consequently no longer capable of exhibiting vital pro-
perties, or of performing the vital functions. They are, therefore,
destined to be removed and discharged from the animal frame, and
are known accordingly by the name of Excrementitious Substances.

These excrementitious substances have peculiar characters by
which they may be distinguished from the other ingredients of the
living body ; and they might, therefore, be made to constitute a
fourth class of proximate principles, in addition to the three which
we have enumerated in the preceding chapters. They are all sub-
stances of definite chemical composition, and all susceptible of
crystallization. Some of the most important of them contain nitro-
gen, while a few are non-nitrogenous in their composition. They
originate in the interior of living bodies, and are not found else-
where, except occasionally as the result of decomposition. They
are nearly all soluble in water, and are soluble without exception in
the animal fluids. They are formed in the substance of the tissues,
from which they are absorbed by the blood, to be afterward conveyed
by the circulating fluid to certain excretory organs, particularly the
kidneys, from which they are finally discharged and expelled from
the body. This entire process, made up of the production of the
excrementitious substances, their absorption by the blood, and their
final elimination, is known as the process of excretion.

The importance of this process to the maintenance of life is readily
shown by the injurious effects which follow upon its disturbance.
If the discharge of the excrementitious substances be in any way
impeded or suspended, these substances accumulate, either in the
blood or in the tissues, or in both. In consequence of this retention
and accumulation, they become poisonous, and rapidly produce a
derangement of the vital functions. Their influence is principally
exerted upon the nervous system, through which they produce
most frequent irritability, disturbance of the special senses, deli-
rium, insensibility, coma, and finally death. The readiness with
which these effects are produced depends on the character of the
excrementitious substance, and the rapidity with which it is pro-
duced in the body. Thus, if the elimination of carbonic acid be
stopped, by overloading the atmosphere with an abundance of the
same gas, death takes place at the end of a few minutes ; but if the
elimination of urea by the kidneys be checked, it requires three or

UREA.

343

CO,

C2H4N202

C8H9N304

C8H7N302
NaO,C5HN202+HO

KO,C5HN202
NH40,2C5HN202+HO

four days to produce a fatal result. A fatal result, however, is cer-
tain to follow, at the end of a longer or shorter time, if any one of
these substances be compelled to remain in the body, and accumu-
late in the animal tissues and fluids.

The principal excrementitious substances known to exist in the
human body are as follows : —

1. Carbonic acid .

2. Urea

3. Creatine ....

4. Creatinine

5. Urate of soda .

6. Urate of potassa

7. Urate of ammonia

The physiological relations of carbonic acid have already been
studied, at sufficient length, in the preceding chapters.

The remaining excrementitious substances may be examined
together with the more propriety, since they are all ingredients of
a single excretory fluid, viz., the urine.

UREA. — This is a neutral, crystallizable, nitrogenous substance,
very readily soluble in water, and easily decomposed by various
external influences. It occurs
in the urine in the proportion
of 30 parts per thousand; in
the blood, according to Picard,1
in the proportion of 0.16 per
thousand. The blood, how-
ever, is the source from which
this substance is supplied to
the urine; and it exists, ac-
cordingly, in but small quan-
tity in the circulating fluid, for
the reason that it is constantly
drained off by the kidneys.
But if the kidneys be extir-

, n ,, , . n UREA, prepared from urine, and crystallized by

pated, Or the renal arteries tied, 8iow evaporation. (After Lehmann.)

or the excretion of urine sus-
pended by inflammation or otherwise, the urea then accumulates in
the blood, and presents itself there in considerable quantity. It has
been found in the blood, under these circumstances, in the propor-

Fig. Ill

In Milne Edwards, Logons sur la Physiologie, &c., vol. i. p. 297.

344: EXCRETION.

tion of 1.4 per thousand.1 It is not yet known from what source
the urea is originally derived ; whether it be produced in the blood
itself, or whether it is formed in some of the solid tissues, and thence
taken up by the blood. It has not yet been found, however, in any
of the solid tissues, in a state of health.

Urea is obtained most readily from the urine. For this purpose
the fresh urine is evaporated in the water bath until it has a syrupy
consistency. It is then mixed with an equal volume of nitric acid,
which forms nitrate of urea. This salt, being less soluble than pure
urea, rapidly crystallizes, after which it is separated by filtration
from the other ingredients. It is then dissolved in water and decom-
posed by carbonate of lead, forming nitrate of lead which remains
in solution, and carbonic acid which escapes. The solution is then
evaporated, the urea dissolved out by alcohol, and finally crystal-
lized in a pure state.

Urea has no tendency to spontaneous decomposition, and may
be kept, when perfectly pure, in a dry state or dissolved in water,
for an indefinite length of time. If the watery solution be boiled,
however, the urea is converted, during the process of ebullition,
into carbonate of ammonia. One equivalent of urea unites with
two equivalents of water, and becomes transformed into two equiva-
lents of carbonate of ammonia, as follows : —

C2H4N202=Urea.
0,=Water.

Various impurities, also, by acting as catalytic bodies, will in-
duce the same change, if water be present. Animal substances in
a state of commencing decomposition are particularly liable to act
in this way. In order that the conversion of the urea be thus pro-
duced, it is necessary that the temperature of the mixture be not
far from 70° to 100° F.

The quantity of urea produced and discharged daily by a healthy
adult is, according to the experiments of Lehmann, about 500
grains. It varies to some extent, like all the other secreted and
excreted products, with the size and development of the body.
Lehmann, in experiments on his own person, found the average
daily quantity to be 487 grains. Prof. William A. Hammond,2
who is a very large man, by similar experiments found it to be

1 Robin and Verdeil, vol. ii. p. 502.

2 American Journal Med. Sci , Jan., 1855, and April, 1856.

UREA. 345

670 grains. Dr. John C. Draper1 found it 408 grains. No urea is
to be detected in the urine of very young children ;2 but it soon
makes its appearance, and afterward increases in quantity with the
development of the body.

The daily quantity of urea varies also with the degree of mental
and bodily activity. Lehmann and Hammond both found it very
sensibly increased by muscular exertion and diminished by repose.
It has been thought, from these facts, that this substance must be
directly produced from disintegration of the muscular tissue. This,
however, is by no means certain ; since in a state of general bodily
activity it is not only the urea, but the excretions generally, carbonic
acid, perspiration, &c.. which are increased in quantity simultane-
ously. Hammond has also shown that continued mental applica-
tion will raise the quantity of urea above its normal standard,
though the muscular system remain comparatively inactive.

The quantity of urea varies also with the nature of the food.
Lehmann, by experiments on his own person, found that the quan-
tity was larger while living exclusively on animal food than with
a mixed or vegetable diet ; and that its quantity was smallest when
confined to a diet of purely non-nitrogenous substances, as starch,
sugar, and oil. The following table3 gives the result of these ex-
periments.

KIND OF FOOD. DAILY QUANTITY OF UREA.

Animal 798 grains.

Mixed 487 "

Vegetable 337 "

Non-nitrogenous ...... 231 "

Finally, it has been shown by Dr. John C. Draper4 that there is
also a diurnal variation in the normal quantity of urea. A smaller
quantity is produced during the night than during the day ; and
this difference exists even in patients who are confined to the bed
during the whole twenty-four hours, as in the case of a man under
treatment for fracture of the leg. This is probably owing to the
greater activity, during the waking hours, of both the mental and
digestive functions. More urea is produced in the latter half than
in the earlier half of the day ; and the greatest quantity is dis-
charged during the four hours from 6 J to 10 J P. M.

Urea exists in the urine of the carnivorous and many of the

1 New York Journal of Medicine, March, 1856.

2 Robin and Verdeil, vol. ii. p. 500.

3 Lehmann, op. cit., vol. ii. p. 163. 4 Loc. cit.

346

EXCRETION.

Fig. 112.

CREATIVE, crystallized from hot water. (After

herbivorous quadrupeds ; but there is little or none to be found in
that of birds and reptiles.

CREATIVE. — This is a neutral crystallizable substance, found in
the muscles, the blood, and the urine. It is soluble in water, very

slightly soluble in alcohol, and
not at all so in ether. By boil-
ing with an alkali, it is either
converted into carbonic acid
and ammonia, or is decomposed
with the production of urea and
an artificial nitrogenous crys-
tallizable substance, termed sar-
cosine. By being heated with
strong acids, it loses two equiva-
lents of water, and is converted
into the substance next to be
described, viz., creatinine.
Creatine exists in the urine,

- . , . ,

m the human subject, in the
proportion of about 1.25 parts,

and in the muscles in the proportion of 0.67 parts per thousand.
Its quantity in the blood has not been determined. In the muscu-
lar tissue it is simply in solution in the interstitial fluid of the parts,
so that it may be extracted by simply cutting the muscle into
small pieces, treating it with distilled water, and subjecting it to

pressure. Creatine evidently

Fig« 113. originates in the muscular tis-

sue, is absorbed thence by the
blood, and is finally discharged
with the urine.

CREATININE. — This is also a
crystallizable substance. It dif-
fers in composition from crea-
tine by containing two equiva-
lents less of the elements of
water. It is more soluble in
water and in spirit than crea-
tine, and dissolves slightly also
in ether. It has a distinctly

CREATININE, crystallized from hot water.
(After Lehmauu.)

CREATIXINE. — URATE OF SODA.

347

alkaline reaction. It occurs, like creatine, in the muscles, the blood,
and the urine ; and is undoubtedly first produced in the muscular
tissue, to be discharged finally by the kidneys. It is very possible
that it originates, not directly from the muscles, but indirectly, by
transformation of a part of the creatine ; since it may be artificially
produced, as we have already mentioned, by transformation of the
latter substance under the influence of strong acids, and since, fur-
thermore, while creatine is more abundant in the muscles than
creatimne, in the urine, on the contrary, there is a larger quantity
of creatinine than of creatine. Both these substances have been
found in the muscles and in the urine of the lower animals.

URATE OF SODA. — As its name implies, this substance is a neu-
tral salt, formed by the union of soda, as a base, with a nitrogenous
animal acid, viz., uric acid (C5HN202,HO). Uric acid is sometimes
spoken of as though it were itself a proximate principle, and a
constituent of the urine; but it cannot properly be regarded as
such, since it never occurs in a free state, in a natural condition of
the fluids. When present, it has always been produced by decom-
position of the urate of soda.

Urate of soda is readily soluble in hot water, from which a large
portion again deposits on cooling. It is slightly soluble in alcohol,
and insoluble in ether. It

crystallizes in small globu- Fig. 114.

lar masses, with projecting,
curved, conical, wart-like
excrescences. (Fig. 114.) It
dissolves readily in the alka-
lies ; and by most acid solu-
tions it is decomposed, with
the production of free uric
acid.

Urate of soda exists in
the urine and in the blood.
It is either produced origin-
ally in the blood, or is formed
in some of the solid tissues,
and absorbed from them by
the circulating fluid. It is

constantly eliminated by the kidneys, in company with the other
ingredients of the urine. The average daily quantity of urate of

URATE OF SODA ; from a urinary deposit.

348 EXCRETION.

soda discharged by the healthy human subject is, according to
Lehmann, about 25 grains. This substance exists in the urine of
the carnivorous and omnivorous animals, but not in that of the her-
bivora. In the^latter, it is replaced by another substance, differing
somewhat from it in composition and properties, viz., hippurate
of soda. The urine of herbivora, however, while still very young,
and living upon the milk of the mother, has been found to contain
urates. But when the young animal is weaned, and becomes her-
bivorous, the urate of soda disappears, and is replaced by the hip-
purate.

URATES OF POTASSA AND AMMONIA. — The urates of potassa and
ammonia resemble the preceding salt very closely in their physio-
logical relations. They are formed in very much smaller quantity
than the urate of soda, and appear like it as ingredients of the urine.

The substances above enumerated closely resemble each other in
their most striking and important characters. They all contain
nitrogen, are all cry stall izable, and all readily soluble in water.
They all originate in the interior of the body by the decomposition
or catalytic transformation of its organic ingredients, and are all
conveyed by the blood to the kidneys, to be finally expelled with
the urine. These are the substances which represent, to a great
extent, the final transformation of the organic or albuminoid in-
gredients of the tissues. It has already been mentioned, in a pre-
vious chapter, that these organic or albuminoid substances are not
discharged from the body, under their own form, in quantity at all
proportionate to the abundance with which they are introduced.
By far the greater part of the mass of the frame is made up of
organic substances: albumen, musculine, osteine, &c. Similar
materials are taken daily in large quantity with the food, in order
to supply the nutrition and waste of those already composing the
tissues; and yet only a very insignificant quantity of similar
material is expelled with the excretions. A minute proportion of
volatile animal matter is exhaled with the breath, and a minute
proportion also with the perspiration. A very small quantity is
discharged under the form of mucus and coloring matter, with the
urine and feces ; but all these taken together are entirely insuffi-
cient to account for the constant and rapid disappearance of organic
matters in the interior of the body. These matters, in fact, before
being discharged, are converted by catalysis and decomposition into
new substances. Carbonic acid, under which form 3500 grains of

GENERAL CHARACTERS OF THE URINE. 349

carbon are daily expelled from the body, is one of these substances ;
the others are urea, creatine, creatinine, and the urates.

We see, then, in what way the organic matters, in ceasing to form
a part of the living body, lose their characteristic properties, and
are converted into cry stall! zable substances, of definite chemical
composition. It is a kind of retrograde metamorphosis, by which
they return more or less to the condition of ordinary inorganic
materials. These excrementitious matters are themselves decom-
posed, after being expelled from the body, under the influence of
the atmospheric air and moisture ; so that the decomposition and
destruction of the organic substances are at last complete.

It will be seen, consequently, that the urine has a character
altogether peculiar, and one which distinguishes it completely
from every other animal fluid. All the others are either nutritive
fluids, like the blood and milk, or are destined, like the secretions
generally, to take some direct and essential part in the vital opera-
tions. Many of them, like the gastric and pancreatic juices, are
reabsorbed after they have done their work, and again enter the
current of the circulation. But the urine is merely a solution of
excrementitious substances. Its materials exist beforehand in the
circulation, and are simply drained away by the kidneys from
the blood. There is a wide difference, accordingly, between the
action of the kidneys and that of the true glandular organs, in
which certain new and peculiar substances are produced by the
action of the glandular tissue. The kidneys, on the contrary, do
not secrete anything, properly speaking, and are not, therefore,
glands. In their mode of action, so far as regards the excretory
function, they have more resemblance to the lungs than to any
other of the internal organs. But this resemblance is not complete ;
since the lungs perform a double function, absorbing oxygen at the
same time that they exhale carbonic acid. The kidneys alone are
purely excretory in their office. The urine is not intended to
fulfil any function, mechanical, chemical, or otherwise ; but is des-
tined only to be eliminated and expelled. Since it possesses PO
peculiar and important a character, it will require to be carefully
studied in detail.

The urine is a clear, watery, amber-colored fluid, with a distinct
acid reaction. It has, while still warm, a peculiar odor, which dis-
appears more or less completely on cooling, and returns when the
urine is gently heated. The ordinary quantity of urine discharged
daily by a healthy adult is about Jxxxv, and its mean specific

350 EXCRETION.

gravity, 1024. Both its total quantity, however, and its mean
specific gravity are liable to vary somewhat from day to day, owing
to the different proportions of water and solid ingredients entering
into its constitution. Ordinarily the water of the urine is more
than sufficient to hold all the solid matters in solution; and its pro-
portion may therefore be diminished by accidental causes without
the urine becoming turbid by the formation of a deposit. Under
such circumstances, it merely becomes deeper in color, and of a
higher specific gravity. Thus, if a smaller quantity of water than
usual be taken into the system with the drink, or if the fluid ex-
halations from the lungs and skin, or the intestinal discharges, be
increased, a smaller quantity of water will necessarily pass off by
the kidneys ; and the urine will be diminished in quantity, while its
specific gravity is increased. We have observed the urine to be
reduced in this way to eighteen or twenty ounces per day, its specific
gravity rising at the same time to 1030. On the other hand, if the
fluid ingesta be unusually abundant, or if the perspiration be dimi-
nished, the surplus quantity of water will pass off by the kidneys; so
that the amount of urine in twenty-four hours may be increased to
forty-five or forty-six ounces, and its specific gravity reduced at
the same time to 1020 or even 1017. Under these conditions the
total amount of solid matter discharged daily remains about the
same. The changes above mentioned depend simply upon the
fluctuating quantity of water, which may pass off by the kidneys
in larger or smaller quantity, according to accidental circumstances.
In these purely normal or physiological variations, therefore, the
entire quantity of the urine and its mean specific gravity vary
always in an inverse direction with regard to each other ; the former
increasing while the latter diminishes, and vice versa. If, however, it
should be found that both the quantity and specific gravity of the
urine were increased or diminished at the same time, or if either
one were increased or diminished while the other remained station-
ary, such an alteration would show an actual change in the total
amount of solid ingredients, and would indicate an unnatural and
pathological condition. This actually takes place in certain forms
of disease.

The amount of variation in the quantity of water, even, may be
so great as to constitute by itself a pathological condition. Thus,
in hysterical attacks there is sometimes a very abundant flow of
limpid, nearly colorless urine, with a specific gravity not over 1005
or 1006. On the other hand, in the onset of febrile attacks, the

DIURNAL VARIATIONS OF THE URINE. 351

quantity of water is often so much diminished that it is no longer
sufficient to retain in solution all the solid ingredients of the urine,
and the urate of soda is thrown down, after cooling, as a fine red
or yellowish sediment. So long, however, as the variation is con-
fined within strictly physiological limits, all the solid ingredients
are held in solution, and the urine remains clear.

There is also, in a state of health, a diurnal variation of the urine,
both in regard to its specific gravity and its degree of acidity.
The urine is generally discharged from the bladder five or six
times during the twenty-four hours, and at each of these periods
shows more or less variation in its physical characters. We have
found that the urine which collects in the bladder during the
night, and is first discharged in the morning, is usually dense,
highly colored, of a strongly acid reaction, and a high specific
gravity. That passed during the forenoon is pale, and of a low
specific gravity, sometimes not more than 1018 or even 1015. It
is at the same time neutral or slightly alkaline in reaction. Toward
the middle of the day, its density and depth of color increase, and
its acidity returns. All these properties become more strongly
marked during the afternoon and evening, and toward night the
urine is again deeply colored and strongly acid, and has a specific
gravity of 1028 or 1030.

The following instances will serve to show the general characters
of this variation : —

OBSERVATION FIRST. March 20th.
Urine of 1st discharge, acid, sp. gr. 1025.
" 2d " alkaline, " 1015.

" 3d " neutral, " 1018.

" 4th " acid, " 1018.

" 5th " acid, " 1027.

OBSERVATION SECOND. March 2lst.
Urine of 1st discharge, acid, sp. gr. 1029.
" 2d " neutral, " 1022.

" 3d " neutral, " 1025.

" 4th " acid, « 1027,

" 5th " acid, " 1030.

These variations do not always follow the perfectly regular
course manifested in the above instances, since they are somewhat
liable, as we have already mentioned, to temporary modification
from accidental causes during the day ; but their general tendency
nearly always corresponds with that given above.

It is evident, therefore, that whenever we wish to test the specific

352 EXCRETION.

gravity and acidity of the urine in cases of disease, it will not be
sufficient to examine any single specimen taken at random ; but all
the different portions discharged during the day should be collected
and examined together. Otherwise, we should incur the risk of
regarding as a permanently morbid symptom what might be
nothing more than a purely accidental and temporary variation.

The chemical constitution of the urine as it is discharged from the
bladder, according to the analyses of Berzelius, Lehmann, Becquerel,
and others, is as follows : —

COMPOSITION OF THE URIXE.

Water 938.00

Urea 30.00

Creatine 1.25

Creatinine .......... 1.50

Urate of soda -v

" potassa [• 1.80

" ammonia J

Coloring matter and \ , on

Mucus y

Biphosphate of soda

Phosphate of soda

potassa

12.45

magnesia
" lime

Chlorides of sodium and potassium 7.80

Sulphates of soda and potassa ....... 6.90

1000.00

We need not repeat that the proportionate quantity of these
different ingredients, as given above, is not absolute, but only
approximative; and that they vary, from time to time, within
certain physiological limits, like the ingredients of all other animal
fluids.

The urea, creatine, creatinine and urates have all been suffi-
ciently described above. The mucus and coloring matter, unlike
the other ingredients of the urine, belong to the class of organic
substances proper. They are both present, as may be seen by the
analysis quoted above, in a very small quantity. The coloring
matter, or urosacine, is in solution in a natural condition of the
urine, but it is apt to be entangled by any accidental deposits which
may be thrown down, and more particularly by those consisting of
the urates. These deposits, from being often strongly colored red
or pink by the urosacine thus thrown down with them, are known
under the name of " brick-dust" sediments.

The mucus of the urine comes from the lining membrane of the

REACTIONS OF THE URIXE. 353

urinary bladder. When first discharged it is not visible, owing to
its being uniformly disseminated through the urine by mechanical
agitation ; but if the fluid be allowed to remain at rest for some
hours in a cylindrical glass vessel, the mucus collects at the bottom,
and may then be seen as a light cottony cloud, interspersed often
with minute semi-opaque points. It plays, as we shall hereafter
see, a very important part in the subsequent fermentation and
decomposition of the urine.

Biphosphate of soda exists in the urine by direct solution, since it is
readily soluble in water. It is this salt which gives to the urine its
acid reaction, as there is no free acid present, in the recent condition.
It is probably derived from the neutral phosphate of soda in the
blood which is decomposed by the uric acid at the time of its form-
ation ; producing, on the one hand, a urate of soda, and converting
a part of the neutral phosphate of soda into the acid biphosphate.

The phosphates of lime and magnesia, or the " earthy phosphates,''
as they are called, exist in the urine by indirect solution. Though
insoluble, or very nearly so, in pure water, they are held in solu-
tion in the urine by the acid phosphate of soda, above described.
They are derived from the blood, in which they exist in considera-
ble quantity. When the urine is alkaline, these phosphates are
deposited as a light-colored precipitate, and thus communicate a
turbid appearance to the fluid. When the urine is neutral, they
may still be held in solution, to some extent, by the chloride of
sodium, which has the property of dissolving a small quantity of
phosphate of lime.

The remaining ingredients, phosphates of soda and potassa, sul-
phates and chlorides, are all derived from the blood, and are held
directly in solution by the water of the urine.

The urine, constituted by the above ingredients, forms, as we
have already described, a clear amber-colored fluid, with a reaction
for the most part distinctly acid, sometimes neutral, and occasion-
ally slightly alkaline. In its healthy condition it is affected by
chemical and physical reagents in the following manner.

Boiling the urine does not produce any visible change, provided
its reaction be acid. If it be neutral or alkaline, and if, at the same
time, it contain a larger quantity than usual of the earthy phos-
phates, it will become turbid on boiling ; since these salts are less
soluble at a high than at a low temperature.

The addition of nitric or other mineral acid produces at first onl v
23

354

EXCRETION.

Fit:. 115.

a slight darkening of the color, owing to the action of the acid upon
the organic coloring matter of the urine. If the mixture, however,
be allowed to stand for some time, the urates of soda, potassa, &cv
will be decomposed, and pure uric acid, which is very insoluble,
will be deposited in a crystalline form upon the sides and bottom
of the glass vessel. The crystals of uric acid have most frequently
the form of transparent rhomboidal plates, or oval laminaB with
pointed extremities. They are usually tinged of a yellowish hue
by the coloring matter of the urine which is united with them
at the time of their deposit. They are frequently arranged in
radiated clusters, or small spheroidal masses, so as to present the

appearance of minute calcu-
lous concretions. (Fig. 115.)
The crystals vary very much
in size and regularity, ac-
cording to the time occupied
in their formation.

If a free alkali, such as
potassa or soda, be added to
the urine so as to neutralize
its acid reaction, it becomes
immediately turbid from a
deposit of the earthy phos-
phates, which are insoluble
in alkaline fluids.

The addition of nitrate of
baryta, chloride of barium

or subacetate of lead to healthy urine, produces a dense precipi-
tate, owing to the presence of the alkaline sulphates.

Nitrate of silver produces a precipitate with the chlorides of
sodium and potassium.

Subacetate of lead and nitrate of silver precipitate also the or-
ganic substances, mucus and coloring 'matter, present in the urine.
All the above reactions, it will be seen, are owing to the presence
of the natural ingredients of the urine, and do not, therefore, indi-
cate any abnormal condition of the excretion.

Beside the properties mentioned above, the urine has several
others which are of some importance, and which have not been
usually noticed in previous descriptions. It contains, among other
ingredients, certain organic substances which have the power of
interfering with the mutual reaction of starch and iodine, and even

URIC ACID; deposited from urine.

REACTIONS OF THE URINE. 355

of decomposing the iodide of starch, after it has once been formed.
This peculiar action of the urine was first noticed and described
by us in 1856.1 If 3j of iodine water be mixed with a solution
of starch, it strikes an opaq ue blue color ; but if 3j of fresh urine
be afterward added to the mixture, the color is entirely destroyed
at the end of four or five seconds. If fresh urine be mixed with
four or five times its volume of iodine water, and starch be
subsequently added, no union takes place between the starch and
iodine, and no blue color is produced. In these instances, the iodine
unites with the animal matters of the urine in preference to com-
bining with the starch, and is consequently prevented from striking
its ordinary blue color with the latter. This interference occurs
whether the urine be acid or alkaline in reaction. In all cases in
which iodine exists in the urine, as for example where it has been
administered as a medicine, it is under the form of an organic com-
bination ; and in order to detect its presence by means of starch, a
few drops of nitric acid must be added at the same time, so as to
destroy the organic matters, after which the blue color immediately
appears, if iodine be present. This reaction with starch and iodine
belongs also, to some extent, to most of the other animal fluids, as
the saliva, gastric and pancreatic juices, serum of the blood, &c. ;
but it is most strongly marked in the urine.

Another remarkable property of the urine, also dependent on its
organic ingredients, is that of interfering with Trommer's test for
grape sugar. If clarified honey be mixed with fresh urine, and sul-
phate of copper with an excess of potassa be afterward added, the
mixture takes a dingy, grayish-blue color. On boiling, the color
turns yellowish or yellowish-brown, but the suboxide of copper is
not deposited. In order to remove the organic matter and detect
the sugar, the urine must be first treated with an excess of animal
charcoal and filtered. By this means the organic substances are
retained upon the filter, while the sugar passes through in solution,
and may then be detected as usual by Trommer's test.

ACCIDENTAL INGREDIENTS OF THE URINE. — Since the urine, in
its natural state, consists of materials which are already prepared in
the blood, and which merely pass out through the kidneys by a
kind of filtration, it is not surprising that most medicinal and
poisonous substances, introduced into the circulation, should be

1 American Journal Me<l. Sci., April, 1S56.

356 EXCRETION.

expelled from the body by the same channel. Those substances
which tend to unite strongly with the animal matters, and to form
with them insoluble compounds, such as the preparations of iron,
lead, silver, arsenic, mercury, &c., are least liable to appear in the
urine. They may occasionally be detected in this fluid when they
have been given in large doses, but when administered in moderate
quantity are not usually to be found there. Most other substances,
however, accidentally present in the circulation, pass off' readily by
the kidneys, either in their original form, or after undergoing cer-
tain chemical modifications.

The salts of the organic acids, such as lactates, acetates, malates,
&c., of soda and potassa, when introduced into the circulation, are
replaced by the carbonates of the same bases, and appear under
that form in the urine. The urine accordingly becomes alkaline
from the presence of the carbonates, whenever the above salts have
been taken in large quantity, or after the ingestion of fruits and
vegetables which contain them. We have already spoken (Chap. II.)
of the experiments of Lehmann, in which he found the urine exhi-
biting an alkaline reaction, a very few minutes after the administra-
tion of lactates and acetates. In one instance, by experimenting
upon a person with congenital extroversion of the bladder, in whom
the orifices of the ureters were exposed,1 he found that the urine
became alkaline in the course of seven minutes after the ingestion
of half an ounce of acetate of potassa.

The pure alkalies and their carbonates, according to the same ob-
server, produce a similar effect. Bicarbonate of potassa, for example,
administered in doses of two or three drachms, causes the urine
to become neutral in from thirty to forty-five minutes, and alkaline
in the course of an hour. It is in this way that certain " anti-cal-
culous" or " anti-lithic" nostrums operate, when given with a view
of dissolving concretions in the bladder. These remedies, which
are usually strongly alkaline, pass into the urine, and by giving it
an alkaline reaction, produce a precipitation of the earthy phos-
phates. Such a precipitate, however, so far from indicating the
successful disintegration and discharge of the calculus, can only
tend to increase its size by additional deposit.

Ferrocyanide of potassium, when introduced into the circulation,
appears readily in the urine. Bernard2 observed that a solution of

' Physiological Chemisty, vol. ii. p. 133.

2 Leqons de Physiologie Experiruentale, 1856, p. 111.

ACCIDENTAL INGREDIENTS OF THE URINE. 357

this salt, after being injected into the duct of the submaxillary
gland, could be detected in the urine at the end of twenty minutes.

Iodine, in all its combinations, passes out by the same channel.
We have found that after the administration of half a drachm of
the syrup of iodide of iron, iodine appears in the urine at the end
of thirty minutes, and continues to be present for nearly twenty-
four hours. In the case of two patients who had been taking iodide
of potassium freely, one of them for two months, the other for six
weeks, the urine still contained iodine at the end of three days
after the suspension of the medicine. In three days and a half,
however, it was no longer to be detected. Iodine appears also,
after being introduced into the circulation, both in the saliva and
the perspiration.

Quinine, when taken as a remedy, has also been detected in the
urine. Ether passes out of the circulation in the same way. "We
have observed the odor of this substance very perceptibly in the
urine, after it had been inhaled for the purpose of producing anaes-
thesia. The bile-pigment passes into the urine in great abundance
in some cases of jaundice, so that the urine may have a deep yellow
or yellowish brown tinge, and may even stain linen clothes, with
which it comes in contact, of a similar color. The saline biliary
substances, viz., glyko-cholate and tauro-cholate of soda, have occa-
sionally, according to Lehmann, been also found in the urine. In
these instances the biliary matters are reabsorbed from the hepatic
ducts, and afterward conveyed by the blood to the kidneys.

Sugar. — When sugar exists in unnatural quantity in the blood,
it passes out with the urine. We have repeatedly found that if
sugar be artificially introduced into the circulation in rabbits, or
injected into the subcutaneous areolar tissue so as to be absorbed by
the blood, it is soon discharged by the kidneys. It has been shown
by Bernard1 that the rapidity with which this substance appears in
the urine under these circumstances varies with the quantity in-
jected and the kind of sugar used for the experiment. If a solution
of 15 grains of glucose be injected into the areolar tissue of a rabbit
weighing a little over two pounds, it is entirely destroyed in the
circulation, and does not pass out with the urine. A dose of 23
grains, however, injected in the same way, appears in the urine at
the end of two hours, 30 grains in an hour and a half, 38 grains in
an hour, and 188 grains in fifteen minutes. Again, the kind of

1 Le.onsde Phys. Exp.. 1855, p. 214 et seq.

358 EXCRETION.

sugar used makes a difference in this respect. For while 15 grains
of glucose may be injected without passing out by the kidneys,
7 J grains of cane sugar, introduced in the same way, fail to be com-
pletely destroyed in the circulation, and may be detected in the
urine. In certain forms of disease (diabetes), where sugar accu-
mulates in the blood, it is eliminated by the same channel ; and a
saccharine condition of the urine, accompanied by an increase in
its quantity and specific gravity, constitutes the most characteristic
feature of the disease.

Finally, albumen sometimes shows itself in the urine in conse-
quence of various morbid conditions. Most acute inflammations
of the internal organs, as pneumonia, pleurisy, &c., are liable to be
accompanied, at their outset, by a congestion of the kidneys, which
produces a temporary exudation of the albuminous elements of the
blood. Albumen has been found in the urine, according to Simon,
Becquerel, and others, in pericarditis, pneumonia, pleurisy, bron-
chitis, hepatitis, inflammation of the brain, peritonitis, metritis, &c.
We have observed it, as a temporary condition, in pneumonia and
after amputation of the thigh. Albuminous urine also occurs fre-
quently in pregnant women, and in those affected with abdominal
tumors, where the pressure upon the renal veins is sufficient to
produce passive congestion of the kidneys. "When the renal con-
gestion is spontaneous in its origin, and goes on to produce actual
degeneration of the tissue of the kidneys, as in Bright's disease, the
same symptom occurs, and remains as a permanent condition. In
all such instances, however, as the above, where foreign ingredients
exist in the urine, these substances do not originate in the kidneys
themselves, but are derived from the blood, in the same manner as
the natural ingredients of the excretion.

CHANGES IN THE URINE DURING DECOMPOSITION. — When the
urine is allowed to remain exposed, after its discharge, at ordinary
temperatures, it becomes decomposed, after a time, like any other
animal fluid; and this decomposition is characterized by certain
changes which take place in a regular order of succession, as fol-
lows : —

After a few hours of repose, the mucus of the urine, as we have
mentioned above, collects near the bottom of the vessel as a light,
nearly transparent, cloudy layer. This mucus, being an organic
substance, is liable to putrefaction; and if the temperature to which
it is exposed be between 60° and 100° F., it soon becomes altered,

ACID FERMENTATION OF THE URINE. 359

and communicates these alterations more or less rapidly to the super-
natant fluid. The first of these changes is called the acid fermenta-
tion of the urine. It consists in the production of a free acid, usually
lactic acid, from some of the undetermined animal matters con-
tained in the excretion. This fermentation takes place very early ;
within the first twelve, twenty-four, or forty-eight hours, according
to the elevation of the surrounding temperature. Perfectly fresh
urine, as we have already stated, contains no free acid, its acid
reaction with test paper being dependent entirely on the presence
of biphosphate of soda. Lactic acid nevertheless has been so fre-
quently found in nearly fresh urine as to lead some eminent
chemists (Berzelius, Lehmann) to regard it as a natural constituent
of the excretion. It has been subsequently found, however, that
urine, though entirely free from lactic acid when first passed, may
frequently present traces of this substance after some hours' expo-
sure to the air. The lactic acid is undoubtedly formed, in these
cases, by the decomposition of some animal substance contained in
the urine. Its production in this way, though not constant, seems
to be sufficiently frequent to be regarded as a normal process.

In consequence of the presence of this acid, the urates are par-
tially decomposed ; and a crystalline deposit of free uric acid slowly
takes place, in the same manner as if a little nitric or muriatic acid
had been artificially mixed with the urine. It is for this reason
that urine which is abundant in the urates frequently shows a de-
posit of crystallized uric acid some hours after it has been passed,
though it may have been perfectly free from deposit at the time
of its emission.

During the period of the " acid fermentation," there is reason to
believe that oxalip acid is also sometimes produced, in a similar
manner with the lactic. It is very certain that the deposit of oxa-
late of lime, far from \>eing a dangerous or even morbid symptom,
as it was at one time regarded, is frequently present in perfectly
normal urine after a day or two of exposure to the atmosphere.
We have often observed it, under these circumstances, when no
morbid symptom could be detected in connection either with the
kidneys or with any other bodily organ. Now, whenever oxalic
acid is formed in the urine, it must necessarily be deposited under
the form of oxalate of lime ; since this salt is entirely insoluble
both in water and in the urine, even when heated to the boiling
point. It is difficult to understand, therefore, when oxalate of lime
is found as a deposit in the urine, how it can previously have been

360

EXCKETION.

Fig. 116.

held in solution. Its oxalic acid is in all probability gradually
formed, as we have said, in the urine itself; uniting, as fast as it is
produced, with the lime previously in solution, and thus appearing
as a crystalline deposit of oxalate of lime. It is much more probable
that this is the true explanation, since, in the cases to which we
allude, the crystals of oxalate of lime grow, as it were, in the cloud
of mucus which collects at the bottom of the vessel, while the
supernatant fluid remains clear. These crystals are of minute size,

transparent, and colorless,
and have the form of regular
octohedra, or double quad-
rangular pyramids, united
base to bise. (Fig. 116.) They
make their appearance usu-
ally about the commence-
ment of the second day, the
urine at the same time con-
tinuing clear and retaining
its acid reaction. This depo-
sit is of frequent occurrence
when no substance contain-
ing oxalic acid or oxalates
has been taken with the food.

OXALATE OF LIME ; deposited from healthy urine, AT j /?

during the acid fermentation. At the end OI SOIHC days

the changes above described

come to an end, and are succeeded by a different process known as
the alkaline fermentation. This consists essentially in the decom-
position or metamorphosis of urea into carbonate of ammonia.
As the alteration of the mucus advances, it loses the power of pro-
ducing lactic and oxalic acids, and becomes a ferment capable of
acting by catalysis upon the urea, and of exciting its decomposition
as above. We have already mentioned that urea may be converted
into carbonate of ammonia by prolonged boiling or by contact
with decomposing animal substances. In this conversion, the urea
unites with the elements of two equivalents of water ; and conse-
quently it is not susceptible of the transformation when in a dry
state, but only when in solution or supplied with a sufficient quan-
tity of moisture. The presence of mucus, in a state of incipient
decomposition, is also necessary, to act the part of a catalytic
body. Consequently if the urine, when first discharged, be passed
through a succession of close filters, so as to separate its mucus, it

ALKALINE FERMENTATION OF THE URINE. 361

may be afterward kept, for an indefinite time, without alteration.
But under ordinary circumstances, the mucus, as soon as its putre-
faction has commenced, excites the decomposition of the urea, and
carbonate of ammonia begins to be developed.

The first portions of the ammoniacal salt thus produced begin to
neutralize the biphosphate of soda, so that the acid reaction of the
urine diminishes in intensity. This reaction gradually becomes
weaker, as the fermentation proceeds, until it at last disappears
altogether, and the urine becomes neutral. The production of
carbonate of ammonia still continuing, the reaction of the fluid
then becomes alkaline, and its alkalescence grows more strongly
pronounced with the constant accumulation of the ammoniacal salt.

The rapidity with which this alteration proceeds depends on the
character of the urine, the quantity and quality of the mucus which
it contains, and the elevation of the surrounding temperature. The
urine passed early in the forenoon, which is often neutral at the
time of its discharge, will of course become alkaline more readily
than that which has at first a strongly acid reaction. In the summer,
urine will become alkaline, if freely exposed, on the third, fourth,
oj fifth day ; white in the winter, a specimen kept in a cool place
may still be neutral at the end of fifteen days. In cases of paralysis
of the bladder, on the other hand, accompanied with cystitis, where
the mucus is increased in quantity and altered in quality, and the
urine is retained in the bladder for ten or twelve hours at the tem-
perature of the body, the change may go on much more rapidly, so
that the urine may be distinctly alkaline and ammoniacal at the
time of its discharge. In these cases, however, it is really acid
when first secreted by the kidneys, and becomes alkaline while
retained in the interior of the bladder.

The first effect of the alkaline condition of the urine, thus pro-
duced, is the precipitation of the earthy phosphates. These salts,
being insoluble in neutral and alkaline fluids, begin to precipitate as
soon as the natural acid reaction of the urine has fairly disappeared,
and thus produce in the fluid a whitish turbidity. This precipitate
slowly settles upon the sides and bottom of the vessel, or is partly
entangled with certain animal matters which rise to the surface and
form a thin, opaline scum upon the urine. There are no crystals
to be seen at this time, but the deposit is entirely amorphous and
granular in character.

The next change consists in the production of two new double
salts by the action of carbonate of ammonia on the phosphates of

362

EXCRETION.

Pier. 117.

soda and magnesia. One of these is the "triple phosphate," phos-
phate of magnesia and ammonia (2MgO,lSrH40,PO54- 2 HO). The
other is the phosphate of soda and ammonia (NaO,NH40,HO,POo 4-
8HO). The phosphate of magnesia and ammonia is formed from
the phosphate of magnesia in the urine (3MgO,P05-f 7HO) by
the replacement of one equivalent of magnesia by one of am-
monia. The crystals of this salt are very elegant and charac-
teristic. They show themselves throughout all parts of the mix-
ture ; growing gradually in the mucus at the bottom, adhering to

the sides of the glass, and
scattered abundantly over
the film which collects upon
the surface. By their refract-
ive power, they give to this
film a peculiar glistening
and iridescent appearance,
which is nearly always visi-
ble at the end of six or seven
days. The crystals are per-
fectly colorless and transpa-
rent, and have the form of
triangular prisms, generally
with bevelled extremities.
(Fig. 117.) Frequently, also,
their edges and angles are
replaced by secondary facets.
They are insoluble in alkalies, but are easily dissolved by acids,
even in a very dilute form. At first they are of minute size, but
gradually increase, so that after seven or eight days they may
become visible to the naked eye.

The phosphate of soda and ammonia is formed, in a similar
manner to the above, by the union of ammonia with the phosphate
of soda previously existing in the urine. Its crystals resemble
very much those just described, except that their prisms are of a
quadrangular form, or some figure derived from it. They are
intermingled with the preceding in the putrefying urine, and are
affected in the same way by chemical reagents.

As the putrefaction of the urine continues, the carbonate of am-
monia which is produced, after saturating all the other ingredients
with which it is capable of entering into combination, begins to
be given off in a free form. The urine then acquires a strong

PHOSPHATE OF M A u N t: s i A AND AMMONIA;
deposited from healthy urine, duriug alkaline fermen-
tation.

RENOVATION BY NUTRITIVE PROCESS. St33

ammoniacal odor ; and a piece of moistened test paper, held a little
above its surface, will have its color immediately turned by the
alkaline gas escaping from the fluid. This is the source of the
ammoniacal vapor which is so freely given off from stables and from
dung heaps, or wherever urine is allowed to remain and decompose.
This process continues until all the urea has been destroyed, and
until the products of its decomposition have either united with
other substances, or have finally escaped in a gaseous form.

RENOVATION OF THE BODY BY THE NUTRITIVE PROCESS. — We
can now estimate, from the foregoing details, the entire quantity of
material assimilated and decomposed by the living body. For we
have already seen how much food is taken into the alimentary canal
and absorbed by the blood after digestion, and how much oxygen
is appropriated from the atmosphere in the process of respiration.
"We have also learned the amount of carbonic acid evolved with the
breath, and that of the various excretory substances discharged from
the body. The following table shows the absolute quantity of these
different ingredients of the ingesta and egesta, compiled from the
results of direct experiment which have already been given in the
foregoing pages.

ABSORBED DURING 24 HOURS. DISCHARGED DURING 24 HOURS.

Oxygen . . . 1.019 Ibs. Carbonic acid . . 1.535 Ibs.

Water . . . 4.735 " Aqueous vapor . 1.155 "

Albuminous matter . .396 " Perspiration . . 1.930 "

Starch . . . .660 " Water of the urine . 2.020 "

Fat 220 " Urea and salts . .110 "

Salts .040 " Feces . . . .320 "

7.070 7.070

Rather more than seven pounds, therefore, are absorbed and dis-
charged daily by the healthy adult human subject ; and, for a man
having the average weight of 140 pounds, a quantity of material,
equal to the weight of the entire body, thus passes through the
system in the course of twenty days.

It is evident, also, that this is not a simple phenomenon of the
passage, or filtration, of foreign substances through the animal
frame. The materials which are absorbed actually combine with
the tissues, and form a part of their substance ; and it is only after
undergoing subsequent decomposition, that they finally make their
appearance in the excretions. None of the solid ingredients of the
food are discharged under their own form in the urine, viz., as

364 EXCRETION.

starch, fat, or albumen ; but they are replaced by urea and other
crystallizable substances, of a different nature. Even the carbonic
acid exhaled by the breath, as experience has taught us, is not pro-
duced by a direct oxidation of carbon ; but originates by a steady
process of decomposition, throughout the tissues of the body, some-
what similar to that by which it is generated in the decomposition
of sugar by fermentation. These phenomena, therefore, indicate an
actual change in the substance of which the body is composed, and
show that its entire ingredients are incessantly renewed under the
influence of the vital operations.

SECTION II.
NERYOUS SYSTEM.

CHAPTER I.

GENERAL STRUCTURE AND FUNCTIONS OF THE
NERYOUS SYSTEM.

Ix entering upon the study of the nervous system, we commence
the examination of an entirely different order of phenomena from
those which have thus far engaged our attention. Hitherto we
have studied the physical and chemical actions taking place in the
body and constituting together the process of nutrition. We have
seen how the lungs absorb and exhale different gases; how the
stomach dissolves the food introduced into it, and how the tissues
produce and destroy different substances by virtue of the varied
transformations which take place in their interior. In all these
instances, we have found each organ and each tissue possessing
certain properties and performing certain functions, of a physical
or chemical nature, which belong exclusively to it, and are charac-
teristic of its action.

The functions of the nervous system, however, are neither phy-
sical nor chemical in their nature. They do not correspond, in
their mode of operation, with any known phenomena belonging to
these two orders. The nervous system, on the contrary, acts only
upon other organs, -in some unexplained manner, so as to excite or
modify the functions peculiar to them. It is not therefore an appa-
ratus which acts for -itself, but is, intended entirely for the purpose
of influencing, in an indirect manner, the action of other organs.
Its object is to connect" and associate the functions of different

( 365 )

366 GENERAL STRUCTURE AND FUNCTIONS

parts of the body, and to cause them to act in harmony with each
other.

This object may be more fully exemplified as follows : — •
Each organ and tissue in the body has certain properties peculiar
to it, which may be called into activity by the operation of a stimu-
lus or exciting cause. This capacity, which all the organs possess,
of reacting under the influence of a stimulus, is called their excita-
bility, or irritability. We have often had occasion to notice this pro-
perty of irritability, in experiments related in the foregoing pages.
We have seen, for example, that if the heart of a frog, after being
removed from the body, be touched with the point of a needle, it
immediately contracts, and repeats the movement of an ordinary
pulsation. If the leg of a frog be separated from the thigh, its
integument removed, and the poles of a galvanic battery brought
in contact with the exposed surface of the muscles, a violent con-
traction takes place every time the electric circuit is completed.
In this instance, the stimulus to the muscles is supplied by the
electric discharge, as, in the case of the heart above mentioned, it is
supplied by the contact of the steel needle ; and in both, a muscu-
lar contraction is the immediate consequence. If we introduce a
metallic catheter into the empty stomach of a dog through a gastric
fistula, and gently irritate with it the mucous membrane, a secretion
of gastric juice at once begins to take place ; and if food be intro-
duced the fluid is poured out in still greater abundance. We know
also that if the integument be exposed to contact with a heated
body, or to friction with an irritating liquid, an excitement of the
circulation is at once produced, which again passes away after the
removal of the irritating cause.

In all these instances we find that the organ which is called into
activity is excited by the direct application of some stimulus to its
own tissues. But^this is noj usually the manner in which the dif-
ferent functions are excited during life. The stimulus which calls
into action the organs of the living body is usually not direct, but
indirect in its operation. Very often, two organs which are situ-
ated in distant parts of the body are connected with each other by
such a sympathy, that the activity of one is influenced by the
condition of the other. The muscles, for example, are almost never
called into action by an external stimulus operating directly upon
their own fibres, but by one which is applied to some other organ,
either adjacent or remote. Thus the peristaltic action of the mus-
cular coat of the intestine commences when the food is brought in

OF THE NERVOUS SYSTEM. 367

contact with its mucous membrane. The lachrymal gland is excited
to increased activity by anything which causes irritation of the
conjunctiva. In all such instances, the physiological connection
between two different organs is established through the medium of
the nervous system.

The function of the nervous system may therefore be defined, in
the simplest terms, as follows : It is intended to associate the different 1
parts of the body in such a manner, that stimulus. applied to one organ ^
may excite the activity of another.

The instances of this mode of action are exceedingly numerous.
Thus, the light which falls upon the retina produces a contraction
of the pupil. The presence of food in the stomach causes the gall-
bladder to discharge its contents into the duodenum. The expul-
sive efforts of coughing are excited by a foreign body entangled in
the glottis.

It is easy to understand the great importance of this function,
particularly in the higher animals and in man, whose organization
is an exceedingly complicated one. For the different organs of
the body, in order to preserve the integrity of the whole frame,
must not only act and perform their functions, but they must act in
harmony with each other, and at the right time, and in the right
direction. The functions of circulation, of respiration, and of
digestion, are so mutually dependent, that if their actions do not
take place harmoniously, and in proper order, a serious disturb-
ance must inevitably follow. When the muscular system is ex-
cited by unusual exertion, the circulation is also quickened. The
blood arrives more rapidly at the heart, and is sent in greater
quantity to the lungs. If the movements of respiration were not
accelerated at the same time, through the connections of the nerv-
ous system, there would immediately follow deficiency of aeration,
vascular congestion, and derangement of the circulation. If the
iris were not stimulated to contract by the influence of the light
falling- on the retina,, the delicate expansion of the optic nerve
would be dazzled by any. unusual brilliancy, and vision would be
obscured or confused. In all the higher animals, therefore, where
the different functions of the body are performed by distinct organs,
situated ia- different parts of the frame, it is necessary that their
action should be thus regulated and harmonized by the operation
of the nervous system.

363 GENERAL STRUCTURE AND FUNCTIONS

The manner in which this is accomplished is as follows : —

The nervous system, however simple or however complicated it
may be, consists always of two different kinds of tissue, which are
distinguished from each other by their color, their structure, and
their mode of action. One of these is known as the white substance,
or the fibrous tissue. It constitutes the whole of the substance of
the nervous trunks and branches, and is found in large quantity on
the exterior of the spinal cord, and in the central parts of the brain
and cerebellum. In the latter situations, it is of a soft consistency,
like curdled cream, and of a uniform, opaque white color. In
the trunks and branches of the nerves it has the same opaque
white color, but is at the same time of a firmer consistency, owing
to its being mingled with condensed areolar tissue. Examined by
the microscope, the white substance is seen to be composed every-
where of minute fibres or filaments, the "ultimate nervous fila-
ments," running in a direction very nearly parallel with each other.
These filaments are cylindrical in shape, and vary considerably in
size. Those which are met with in the spinal cord and the brain
are the smallest, and have an average diameter of T<j^<j(7 °f an
inch. In the trunks and branches of the nerves they average ^W
of an inch.

The structure of the ultimate nervous filament is as follows:
The exterior of each filament consists of a colorless, transparent
tubular membrane, which is seen with some difficulty in the natural
condition of the fibre, owing to the extreme delicacy of its texture,
and to its cavity being completely filled^with a substance very
similar to it in refractive power. In the interior of this tubular
membrane there is contained a thick, semi-fluid nervous matter,
which is white and glistening by reflected light, and is called the
"white substance of Schwann." Finally, running longitudinally
through the centrab part of each filament, is a narrow ribbon-
shaped cord, of rather firm consistency, and of a semi-transparent
grayish color. This central portion is called the "axis cylinder,"
or the " flattened band." It is enveloped everywhere by the semi-
fluid white substance, and the whole invested by the external tubu-
lar membrane.

When nervous matter is prepared for the microscope and exa-
mined by transmitted light, two remarkable appearances are ob-
served in its filaments, produced by the contact of foreign sub-
stances. In the first place the unequal pressure, to which the fila-
ments are accidentally subjected in the process of dissection and

OF THE NERVOUS SYSTEM.

369

Fig. 118.

NKRVOCS FILAMESTS from white substance of

preparation, produces an irregularly bulging or varicose appearance
in them at various points, owing to the readiness with which the
semi-fluid white substance in their interior is displaced in different
directions. (Fig. 118.) Sometimes spots may be seen here and
there, where the nervous matter has been entirely pressed apart in
the centre of a filament, so
that there appears to be an
entire break in its continuity,
while the investing mem-
brane may be still seen, pass-
ing across from one portion
to the other. When a nerv-
ous filament is torn across
under the microscope and
subjected to pressure, a cer-
tain quantity of the semi-
fluid white substance is
pressed out from its torn
extremity, and may be en-
tirely separated from it, so
as to present itself under the

. brain. — a, a, a. Sott substance of tlie filaments pressed

form Of irregularly rOUnded Out, and flojUuig in irregularly ruuuded drops.

drops of various sizes (a, a,

a), scattered over the field of the microscope. The varicose appear-
ance above alluded to is more frequently seen in the smaller nerv-
ous filaments from the brain and spinal cord, owing to their soft
consistency and the readiness with which they yield to pressure.

The second effect produced by the artificial preparation of the
nervous matter is a partial coagulation of the white substance of
Schwann. , In its natural condition this, substance has the same
consistency throughout, and appears perfectly transparent and
homogeneous by transmitted light. As soon, however, as the nerv-
ous filament is removed from its natural situation, and brought in
contact with air, water, or other unnatural fluids, the soft substance
immediately under the investing membrane begins to coagulate.
It increases in consistency, and at the same time becomes more
highly refractive; so that it presents on each side, immediately
underneath the investing membrane, a thin layer of a peculiar
glistening aspect. (Fig. 119.) At first, this change takes place
only in the outer portions of the white substance of Schwann.
The coagulating process, however, subsequently goes on, and
24

370

GENERAL STRUCTURE AND FUNCTIONS

119-

gradually advances from the edges of the filament toward its
centre, until its entire thickness after a time presents the same
appearance. The effect of this process can also be seen in those
portions of the white substance which have been pressed out from
the interior of the filaments, and which float about in the form of

drops. (Fig. 118, a.) These
drops are always covered
with a layer of coagulated
material which is thicker
and more opaque in propor-
tion to the length of time
which has elapsed since the
commencement of the alter-
ation.

The nervous filaments
have essentially the same
structure in the brain and
spinal cord as in the nervous
trunks and branches ; only
they are of much smaller
size in the former than in
the latter situation. In the
nervous trunks and branches,
however, outside the cranial
and spinal cavities, there
exists, superaclded to the

nervous filaments and interwoven with them, a large amount of
condensed areolar or fibrous tissue, which protects them from
injury, and gives to this portion of the nervous system a peculiar
density and resistance. This difference in consistency between the
white substance of the nerves and that of the brain and spinal cord
is owing, therefore, exclusively to the presence of ordinary fibrous
tissue in the nerves, while it is wanting in the brain and spinal
cord. The consistency of the nervous filaments themselves is the
same in each situation.

The nervous filaments are arranged, in the nervous trunks and
branches, in a direction nearly parallel with each other. A certain
number of them are collected in the form of a bundle, which is
invested with a layer of fibrous tissue, in which run the small
bloodvessels, destined for the nutrition of the nerve. These pri-
mary bundles are again united into secondary, the secondary into

NERVOUS FII.AM ENTS from sciatic nerve, showing
tbeir coagulation. — At », th.) torn extremity of a
nervous filament with the axis cylinder (b) protruding
from it. At c, the white substance of Sch wann is nearly
separated by accidental compression, but the axis-
cylinder passes across the ruptured portion. The out-
line of the tubular membrane is also seen at c on the
outside of the nervous filament.

OF THE NERVOUS SYSTEM.

371

Fig. 120.

tertiary, &c. A nerve, therefore, consists of a large bundle of ulti-
mate filaments, associated with each other in larger or smaller
packets, and bound together by the investing fibrous layers. When
a nerve is said to become branched or " divided" in any part of its
course, this division merely implies that some of its filaments leave
the bundles with which they were
previously associated, and pursue
a different direction. (Fig. 120.)
A nerve which originates, for ex-
ample, from the spinal cord in the
region of the neck, and runs down
the upper extremity, dividing and
subdividing, to be finally distri-
buted to the integument and mus-
cles of the hand, contains at its
point of origin all the filaments
into which it is afterward divided,
and which are merely separated
at successive points from the
main bundle. The ultimate fila-
ments, accordingly, are continu-
ous throughout, and do not them-
selves divide at any point between
their origin and their final distri-
bution.

When a nerve, furthermore, is
said to " inosculate" with another
nerve, as when the infra-orbital
inosculates with the facial, or the
cervical nerves inosculate with

each other, this means simply that some of the filaments composing
the first nervous bundle separate from it, and cross over to form a
part of the second, while some of those belonging to the second
cross over and join the first (Fig. 121) ; but the individual filaments
in each instance remain continuous and preserve their identity
throughout. This fact is of great physiological importance; since
the white or fibrous nerve-substance is everywhere simply an
organ of transmission. It serves to convey the nervous impulse in
various directions, from without inward, or from within outward ;
and as each nervous filament acts independently of the others, it
will convey an impression or a stimulus continuously from its

Division of a NERVE, showing portion of
nervous trunk (a), aud the separation of its
filauieuts (b, c, d, e).

372

GENERAL STRUCTURE AND FUNCTIONS

origin to its termination, and will always have the same character
and function in every part of its course.

The other variety of nervous matter is known as the gray sub-
stance. It is sometimes called " cineritious matter," and sometimes

Fig. 121.

Inosculation of NERVES.

Fig. 122.

"vesicular neurine." It is found in the central parts of the spinal
cord, at the base of the brain in isolated masses, and is also spread

out as a continuous layer on
the external portions of the
cerebrum and cerebellum.
It also constitutes the sub-
stance of all the ganglia of
the great sympathetic. Ex-
amined by the microscope, it
consists of vesicles or cells, of
various forms and sizes, im-
bedded in a grayish, granular,
intercellular substance, and
containing, also, very fre-
quently, granules of grayish
pigmentary matter. It is to
the presence of this granular

NERVK CKM.R, intermingled with fibres; from . , . , . , „

M^miUmar ganglion of cat. pigment that thlS kind of

OF THE NERVOUS SYSTEM. 373

nervous matter owes the ashy or " cineritious" color from which it
derives its name. The cells composing it vary in size, according
to Kolliker, from 4^0 to 3^5 of an inch. The largest of them have
a very distinct nucleus and nucleolus. (Fig. 122.) Many of them
are provided with long processes or projections, which are sometimes
divided into two or three smaller branches. These cells are inter-
mingled, in all the collections of gray matter, with nervous filaments,
and are entangled with their extremities in such a manner that it
is exceedingly difficult to ascertain the exact nature of the anato-
mical relations existing between them. It is certain that in some
instances the slender processes running out from the nervous vesi-
cles become at last continuous with the filaments; but it is not
known whether this be the case in all or even in a majority of
instances. The extremities of the filaments, however, are at all
events brought into very close relation with the vesicles or cells of
the gray matter.

Every collection of gray matter, whatever be its situation or
relative size in the nervous system, is called a ganglion or nervous
centre. Its function is to receive impressions conveyed to it by the
nervous filaments, and to send out by them impulses which are to
be transmitted to distant organs. The ganglia, therefore, originate
nervous power, so to speak ; while the filaments and the nerves
only transmit it. Now we shall find that, in the structure of every
nervous system, the ganglia are connected, first with the different
organs, by bundles of filaments which
are called nerves ; and secondly with Fig- 123.

each other, by other bundles which
are termed commissures. The entire
system is accordingly made up of
ganglia, nerves, and commissures.

The simplest form of nervous
system is probably that found in
the five-rayed starfish. This animal
belongs to the type known as radiata;
that is, animals whose organs radiate
from a central point, so as to form a
circular series of similar parts, each
organ being repeated at different NERVOUS SYSTEM OF STARFISH.
points of the circumference. The

starfish (Fig. 123) consists of a central mass, with five arms or
limbs radiating from it. In the centre is the mouth, and immedi-

374 GENERAL STRUCTURE AND FUNCTIONS

ately beneath it the stomach or digestive cavity, which sends pro-
longations into every one of the projecting limbs. There is also
contained in each limb a portion of the glandular and muscular
systems, and the whole is covered by a sensitive integument. The
nervous system consists of five similar ganglia, situated in the
central portion, at the base of the arms. These ganglia are con-
nected with each other by commissures, so as to form a nervous
collar or chain, surrounding the orifice of the digestive cavity.
Each ganglion also sends off nerves, the filaments of which are
distributed to the organs contained in the corresponding limb.

"We have already stated that the proper function of the nervous
system is to enable a stimulus, acting upon one organ, to produce
motion or excitement in another. This is accomplished, in the
starfish, in the following manner : —

When any stimulus or irritation is applied to the integument of
one of the arms, it is transmitted by the nerves of the integument
to the ganglion situated near the mouth. Arrived here, it is
received by the gray matter of the ganglion, and immediately con-
verted into an impulse which is sent out by other filaments to the
muscles of the corresponding limb; and a muscular contraction and
movement consequently take place. The muscles therefore contract
in consequence of an irritation which has been applied to the skin.
This is called the "reflex action" of the nervous system ; because the
stimulus is first sent inward by the nerves of the integument, and
then returned or reflected back from the ganglion upon the muscles.
It must be recollected that this action does not necessarily indicate
any sensation or volition, nor even any consciousness on the part of
the animal. The function of the gray matter is simply to receive
the impulse conveyed to it, and to reflect or send back another ;
and this may be accomplished altogether involuntarily, and without
the existence of any conscious perception.

Where the irritation applied to the integument is of an ordinary
character and not very intense, it is simply reflected, as above
described, from the corresponding ganglion back to the same limb.
But if it be of a peculiar character, or of greater intensity than usual,
it may be also transmitted by the commissures to the neighboring
ganglia ; and so two, three, four, or even all five of the limbs may
be set in motion by a stimulus applied to the integument of one of
them. Now, as all the limbs of the animal have the same structure
and contain the same organs, their action will also be the same;
and the effects of this communication of the stimulus from one to

OF THE NERVOUS SYSTEM.

375

the other by means of commissures will be a repetition, or rather
a simultaneous production of similar movements in different parts
of the body. According to the character and intensity, therefore,
of the original stimulus, it will be followed by a response from
one, several, or all of the different parts of the animal frame.

It will be seen also that there are two kinds of nervous filaments,
differing essentially in their functions. One set of these fibres run
from the sensitive surfaces to the ganglion, and convey the nervous
impression inward. These are called sensitive fibres. The other
set run from the ganglion to the muscles, and carry the nervous
impression outward. These are called motor fibres.

In the starfish, where the body is composed of a repetition of simi-
lar parts arranged round a common centre, and where all the limbs
are precisely alike in structure, the several ganglia composing the
nervous system are also similar to each other, and act in the same
way. But in animals which are constructed upon a different plan,
and whose bodies are composed of distinct organs, situated in dif-
ferent regions, we find that the nervous ganglia, presiding over
the function of these organs, present a corresponding degree of
dissimilarity.

In Aplysia, for example, which belongs to the type of mollusca.
or soft-bodied animals, the digestive apparatus consists of a mouth,
an ossophagus, a triple stomach, and a some-
what convoluted intestine. The liver is
large, and placed on one side of the body,
while the gills, in the form of vascular
laminae, occupy the opposite side. There
are both testicles and ovaries in the same
animal, the male and female functions co-
existing, as in many other invertebrate
species. All the organs, furthermore, are
here arranged without any reference to a
regular or symmetrical plan. The body is
covered with a muscular mantle, which ex-
pands at the ventral surface into a tolerably
well-developed " foot," or organ of locomo-
tion, by which the animal is enabled to
change its position and move from one NERVOUS SYSTEM OF

1 TJ. ^i API.YSIA. — 1. Digestive or

locality tO another. oesophageal ganglion. 2. Cere-

The nervous system of this animal is con- bral ganglion, s, s. Pedai or

, , j , . , locomotory ganglia. 4. Kespi-

structed upon a plan corresponding with ratu y gaugiiuu.

Fig. 124.

876

GENERAL STRUCTURE AND FUNCTIONS

Fig. 125.

that of the entire body. (Fig. 124.) There is a small ganglion (i)
situated anteriorly, which sends nerves to the commencement of the
digestive apparatus, and is regarded as the oesophageal or digestive
ganglion. Immediately behind it is a larger one (a) called the
cephalic or cerebral ganglion, which sends nerves to the organs of
special sense, and which is regarded as the seat of volition and
general sensation for the entire body. Following this is a pair of
ganglia (3, 3), the pedal or locomotory ganglia, which supply the
muscular mantle and its foot-like expansion, and which regulate
the movement of these organs. Finally, another ganglion (4), situ-
ated at the posterior part of the body, sends nerves to the branchiae
or gills, and is termed the branchial or respiratory ganglion. All
these nervous centres are connected by commissures with the central
or cerebral ganglion, and may therefore act either independently
or in association with each other, by means of these connecting fibres.
In the third type of animals, again, viz., the articulata, the gene-
ral plan of structure of the body is different from
the foregoing, and the nervous system is accord-
ingly modified to correspond with it. In these
animals, the body is composed of a number of
rings or sections, which are articulated with each
other in linear series. A very good example of
this type may be found in the common centipede,
or scokpendra. Here the body is composed of
twenty -two successive and nearly similar articu-
lations, each of which has a pair of legs attached,
and contains a portion of the glandular, respira-
tory, digestive and reproductive apparatuses.
The animal, therefore, consists of a repetition of
similar compound parts, arranged in a longitudi-
nal chain or series. The only exceptions to this
similarity are1 in the first and last articulations.
The first is large, and contains the mouth ; the
last is small, and contains the anus. The first
articulation, which is called the "head," is also
furnished with eyes, with antennae, and with a
pair of jaws, or mandibles.

The nervous system of the centipede (Fig. 125),
corresponding in structure with the above plan,
consists of a linear series of nearly equal and similar ganglia arranged
in pairs, situated upon the median line, along the ventral surface of

NKRVOPS SYSTEM
OF CENTIPEDE.

OF THE NERVOUS SYSTEM. 377

the alimentary canal. Each pair of ganglia is connected with the
integument and muscles of its own articulation by sensitive and
motor filaments ; and with those which precede and follow by a
double cord of longitudinal commissural fibres. In the first articu-
lation, moreover, or the head, the ganglia are larger than elsewhere,
and send nerves to the antenna and to the organs of special sense.
This pair is termed the cerebral ganglion, or the " brain."

A reflex action may take place, in these animals, through either
one or all of the ganglia composing the nervous chain. An im-
pression received by the integument of any part of the body may
be transmitted inward to its own ganglion and thence reflected
immediately outward, so as to produce a movement of the limbs
belonging to that articulation alone ; or it may be propagated,
through the longitudinal commissures, forward or backward, and
produce simultaneous movements in several neighboring articula-
tions ; or, finally, it may be propagated quite up to the anterior pair
of ganglia or " brain," where its reception will be accompanied with
consciousness, and a voluntary movement reflected back upon any
or all of the limbs at once. The organs of special sense, also, com-
municate directly with the cerebral ganglia ; and impressions con-
veyed through them may accordingly give rise to movements in
any distant part of the body. In these animals the ventral ganglia,
or those which simply stand as a medium of communication be-
tween the integument and the muscles, are nearly similar through-
out ; while the first pair, or those which receive the nerves of special
sense, and which exercise a general controlling power over the rest
of the nervous system, are distinguished from the remainder by a
well-marked preponderance in size.

In the centipede it will be noticed that nearly all the organs and
functions are distributed in an equal degree throughout the whole
length of the body. The organs of special sense alone, with those
of mastication and the functions of perception and volition, are
confined to the head. The ganglia occupying this part are there-
fore the only ones which are distinguished by any external pecu-
liarities; the remainder being nearly uniform both in size and
activity. In some kinds of articulated animals, however, particular
functions are concentrated, to a greater or less extent, in particular
parts of the body; and the nervous ganglia which preside over
them are modified in a corresponding manner. In the insects,
for example, the body is divided into three distinct sections, viz :
the head, containing the organs of prehension, mastication, tact

378 GENERAL STRUCTURE AND FUNCTIONS

and special sense ; the chest, upon which are concentrated the or-
gans of locomotion, the legs and wings ; and the abdomen, contain-
ing the greater part of the alimentary canal, together with the
glandular and generative organs. As the insects have a greater
amount of intelligence and activity than the centipedes and other
worm -like articulata, and as the organs of special sense are more
perfect in them, the cerebral ganglia are also unusually developed,
and are evidently composed of several pairs, connected by commis-
sures so as to form a compound mass. As the organs of locomo-
tion, furthermore, instead of being distributed, as in the centipede,
throughout the entire length of the animal, are concentrated upon
the chest, the locomotory ganglia also preponderate in size in this
region of the body ; while the ganglia which preside over the secre-
tory and generative functions are situated together, in the cavity of
the abdomen.

All the above parts, however, are connected, in the same manner
as previously described, with the anterior or cerebral pair of gan-
glia. In all articulate animals, moreover, the general arrangement
of the body is symmetrical. The right side is, for the most part,
precisely like the left, as well in the internal organs as in the ex-
ternal covering and the locomotory appendages. The only marked
variation between different parts of the body is in an antero-pos-
terior direction ; owing to different organs being concentrated, in
some cases, in the head, chest, and abdomen.

Finally, in the vertebrate type of animals, comprising man, the
quadrupeds, birds, reptiles, and fish, the external parts of the body,
together with the locomotory apparatus and the organs of special
sense, are symmetrical, as in the articulata ; but the internal organs,
especially those concerned in the digestive and secretory functions,
are unsymmetrical and irregular, as in the molluscs. The organs
of respiration, however, are nearly symmetrical in the vertebrata,
for the reason that the respiratory movements, upon which the
function of these organs is immediately dependent, are performed
by muscles belonging to the general locomotory apparatus. The
nervous system of the vertebrata partakes, accordingly, of the struc-
tural arrangement of the organs under its control. That portion
which presides over the locomotory, respiratory, sensitive, and in-
tellectual functions forms a system by itself, called the cerebro-spinal
system. This system is arranged in a manner very similar to that
of the articulata. It is composed of two equal and symmetrical
halves, running along the median line of the body, the different

OF THE NERVOUS SYSTEM.

379

parts of which are connected by transverse and longitudinal com-
missures. Its ganglia occupy the cavities of the cranium and the
spinal canal, and send out their nerves through openings in the
bony walls of these cavities.

The other portion of the nervous system of vertebrata is that
which presides over the functions of vegetative life. It is called
the ganglionic or great sympathetic system. Its ganglia are situated
anteriorly to the spinal column, in the visceral cavities of the body,
and are connected, like the others, by transverse and longitudinal
commissures. This part of the nervous system is symmetrical in
the neck and thorax, but is uusymmetrical in the abdomen, where
it attains its largest size and its most complete development.

The vertebrate animals, as a general rule, are very much superior
to the other classes, in intelligence and activity, as well as in the
variety and complicated character of their motions; while their
nutritive or vegetative functions,
on the other hand, are not particu- Fig. 126.

larly well developed. Accordingly
we find that in these animals the
cerebro-spinal system of nerves
preponderates very much, in im-
portance and extent, over that of
the great sympathetic. The quan-
tity of nervous matter contained
in the brain and spinal cord is,
even in the lowest vertebrate ani-
mal, very much greater than that
contained in the system of the great
sympathetic; and this preponder-
ance increases, in the higher classes,
just in proportion to their supe-
riority in intelligence, sensation,
power of motion, and other func-
tions of a purely animal character.

The spinal cord is very nearly
alike in the different classes of ver-
tebrate animals. It is a nearly
cylindrical cord, running from one
end of the spinal canal ito the other,
and connected at its anterior ex-
tremity with the ganglia of the brain. (Fig. 126.) It is divided,

CEREBRO-SiMXAL STSTEM OF MAX.

— 1. Cerebrum. 2. Cereb Hum. 3,3,3. Spin d
cord and nerves. 4, 4. Brachial nerves.
5, 5. Sacral nerves.

330 GENERAL STRUCTURE AND FUNCTIONS

by an anterior and posterior median fissure, into two lateral halves,
which still remain connected with each other by a central mass or
commissure. Its inner portions are occupied by gray matter,
which forms a continuous ganglionic chain, running from one ex-
tremity of the cord to the other. Its outer portions are composed
of white substance, the filaments of which run for the most part in
a longitudinal direction, connecting the different parts of the cord
with each other, and the cord itself with the ganglia of the brain.

The spinal nerves are given off from the spinal cord at regular
intervals, and in symmetrical pairs; one pair to each successive
portion of the body. Their filaments are distributed to the integu-
ment and muscles of the corresponding regions. In serpents, where
locomotion is performed by simple, alternate, lateral movements
of the spinal column, the spinal cord and its nerves are of the
same size throughout. But in the other vertebrate classes, where
there exist special organs of locomotion, such as fore and hind
legs, wings, and the like, the spinal cord is increased in size at
the points where the nerves of these organs are given off; and the
nerves themselves, which supply the limbs, are larger than those
originating from other parts of the spinal cord. Thus, in the hu-
man subject (Fig. 126), the cervical nerves, which go to the arms,
and the sacral nerves, which are distributed to the legs, are larger
than the dorsal and lumbar nerves. They form, also, by frequent
inosculation, two remarkable plexuses, before entering their corre-
sponding limbs, viz., the bra-

Flg> 127> chial plexus above, and the

sacral plexus below. The
cord itself, moreover, pre-
sents two enlargements at
the point of origin of these
nerves, viz., the cervical en-
largement from which the
brachial nerves (4, 4) are
given off, and the lumbar

Transverse Section of SPINAL CORD.-«,&. Spinal enlargement from which the

nerves of right and left sides, showing their two roots. sacral nerVCS (o, 5) Originate.

d. Origin of anterior root. «. Origin of posterior root. . j

c. Ganglion of posterior root. If the Spinal COrd be 6Xa-

mined in transverse section

(Fig. 127), it will be seen that the gray matter in its central portion
forms a double crescentic-shaped mass, with the concavity of the
crescents turned outward. These crescentic masses of gray matter,

OF THE NERVOUS SYSTEM. 381

occupying the two lateral halves of the cord, are united with each
other by a transverse band of the same substance, which is called
the gray commissure of the cord. Directly in front of this is a trans-
verse band of white substance, connecting in a similar manner the
white portions of the two lateral halves. It is called the white
commissure of the cord.

The spinal nerves originate from the cord on each side by two
distinct roots ; one anterior, and one posterior. The anterior root
(Fig. 127, d) arises from the surface of the cord near the extremity
of the anterior peak of gray matter. The posterior root (e) origi-
nates at the point corresponding with the posterior peak of gray
matter. Both roots are composed of a considerable number of
ultimate nervous filaments, united with each other in parallel
bundles. The posterior root is distinguished by the presence of a
small ganglion (c), which appears to be incorporated with it, and
through which its fibres pass. There is no such ganglion on the
anterior root. The two roots unite with each other shortly after
leaving the cavity of the spinal canal, and mingle their filaments
in a single trunk.

It will be seen, on referring to the diagram (Fig. 127), that each
lateral half of the spinal cord is divided into two portions, an
anterior and a posterior portion. The posterior peak of gray mat-
ter comes quite up to the surface of the cord, and it is just at this
point (e) that the posterior roots of the nerves have their origin.
The whole of the white substance included between this point and
the posterior median fissure is called the posterior column of the
cord. That which is included between the same point and the
anterior median fissure is the anterior column of the cord. The
white substance of the cord may then be regarded as consisting
for the most part of four longitudinal bundles of nervous filaments,
viz., the right and left anterior, and the right and left posterior
columns. The posterior median fissure penetrates deeply into the
substance of the cord, quite down to the gray matter, so that the
posterior columns appear entirely separated from each other in a
transverse section ; while the anterior median fissure is more shal-
low and stops short of the gray matter, so that the anterior columns
are connected with each other by the white commissure above men-
tioned.

By the encephalon we mean the whole of that portion of the
cerebro-spinal system which is contained in the cranial cavity. It
is divided into three principal parts, viz., the cerebrum, cerebellum,

382

GENERAL STRUCTURE AND FUNCTIONS

Fig. 128.

and medulla oblongata. The anatomy of these parts, though some-
what complicated, can be readily understood if it be recollected
that they are simply a double series of nervous ganglia, connected with
each other and with the spinal cord ly transverse and longitudinal
commissures. The number and relative size of these ganglia, in
different kinds of animals, depend upon the perfection of the bodily
organization in general, and more especially on that of the intelli-
gence and the special senses. They are most readily described by
commencing with the simpler forms and terminating with the more
complex.

The brain of the Alligator (Fig. 128) consists of five pair of
ganglia, ranged one behind the other in the interior of the cranium.
The first of these are two rounded masses (i), lying just above and

behind the nasal cavities, which distri-
bute their nerves upon the Schneiderian
mucous membrane. These are the olfac-
tory ganglia. They are connected with
the rest of the brain by two long and
slender commissures, the " olfactory com-
missures." The next pair (-2) are some-
what larger and of a triangular shape,
when viewed from above downward.
They are termed the " cerebral ganglia,"
or the hemispheres. Immediately follow-
ing them are two quadrangular masses (3)
which give origin to the optic nerves, and
are therefore called the optic ganglia.
They are termed also the " optic tuber-
cles ;" and in some of the higher animals,
where they present an imperfect division
into four nearly equal parts, they are
known as the " tubercula quadrigemina."

Behind them, we have a single triangular collection of nervous
matter (4), which is called the cerebellum. Finally, the upper por-
tion of the cord, just behind and beneath the cerebellum, is seen to
be enlarged and spread out laterally, so as to form a broad oblong
mass (5), the medulla oblongata. It is from this latter portion of the
brain that the pneumogastric or respiratory nerves originate, and
its ganglia are therefore sometimes termed the " pneumogastric" or
" respiratory" ganglia.

It will be seen that the posterior columns of the cord, as they

BRAIN OF ALLIGATOR. — 1. Ol-
factory ganglia. 2 Hemispheres. 3.
Optic tubercles. 4. Cerebellum. 5.
Medulla oblongata.

OF THE NERVOUS SYSTEM.

383

diverge laterally in order to form the medulla oblongata, leave be-
tween them an open space, which is continuous with the posterior
median fissure of the cord. This space is known as the " fourth
ventricle." It is partially covered in by the backward projection
of the cerebellum, but in the alligator is still somewhat open pos-
teriorly, presenting a kind of chasm or gap between the two lateral
halves of the medulla oblongata.

The successive ganglia which compose the brain, being arranged
in pairs as above described, are separated from each other on the
two sides by a longitudinal median fissure, which is continuous
with the posterior median fissure of the cord. In the brain of the
alligator this fissure appears to be interrupted at the cerebellum ;
but in the higher classes, where the lateral portions of the cerebel-
lum are more highly developed, as in the human subject (Fig. 126),
they are also separated from each other posteriorly on the median
line, and the longitudinal median fissure is complete throughout.

In birds, the hemispheres are of much larger size than in rep-
tiles, and partially conceal the optic ganglia. The cerebellum,
also, is very well developed in this class, and presents on its sur-
face a number of transverse foldings or convolutions by which
the quantity of gray matter which
it contains is considerably in-
creased. The cerebellum here
extends so far backward as almost
completely to conceal the medulla
oblongata and the fourth ven-
tricle.

In the quadrupeds, the hemis-
pheres and cerebellum attain a
still greater size in proportion to
the remaining parts of the brain.
There are also two other pairs of
ganglia, situated beneath the he-
mispheres, and between them and
the tubercula quadrigemina.
These are the corpora striata in
front and the optic thalami behind.
In Fig. 129 is shown the brain of
the rabbit, with the hemispheres
laid open and turned aside, so as to show the internal parts in their
natural situation. The olfactory ganglia are seen in front ( i ) con-

Fig. 129.

BRATX OFRABBIT. viewed from above.—
1. Olfactory ganglia. 2 Hemispheres, turned
aside. 3. Corpora striata. 4 Optic thalami.
5. Tubercula quadrigemina. 6. Cerebellum.

384

GENERAL STRUCTURE AND FUNCTIONS

nected with the remaining parts by the olfactory commissures. The
separation of the hemispheres (2, 2) shows the corpora striata (3) and
the optic thalami (4). Then come the tubercula quadrigemina (5),
which are here composed, as above mentioned, of four rounded
masses nearly equal in size. The cerebellum (e) is considerably en-
larged by the development of its lateral portions, and shows an
abundance of transverse convolutions. It conceals from view the
fourth ventricle and most of the medulla oblongata.

In other species of quadrupeds the hemispheres increase in size
so as to project entirely over the olfactory ganglia in front, and to
cover in the tubercula quadrigemina and the cerebellum behind.
The surface of the hemispheres also becomes covered with nume-
rous convolutions, which are curvilinear and somewhat irregular
in form and direction, instead of being transverse, like those of the
cerebellum. In man, the development of the hemispheres reaches
its highest point ; so that they preponderate altogether in size over
the rest of the ganglia constituting the brain. In the human brain,
accordingly, when viewed from above downward, there is nothing
to be seen but the convex surfaces of the hemispheres ; and even
in a posterior view, as seen in Fig. 126, they conceal everything
but a portion of the cerebellum. All the remaining parts, how-
ever, exist even here, and have the same connections and relative
situation as in other instances. They may
best be studied in the following order.

As the spinal cord, in the human subject,
passes upward into the cranial cavity, it en-
larges into the medulla oblongata as already
described. The medulla oblongata presents
on each side three projections, two anterior
and one posterior. The middle projections
on its anterior surface (Fig. 130, i, i), which
are called the anterior pyramids, are the con-
tinuation of the anterior columns of the cord.
They pass onward, underneath the transverse
fibres of the pons Varolii, run upward to the
corpora striata, pass through these bodies,
and radiate upward and outward from their
external surface, to terminate in the gray
matter of the hemispheres. The projections
immediately on the outside of the anterior pyramids, in the medulla
oblongata, are the olivary bodies (2, 2). They contain in their in-

Fig. 130.

MEDULLA
OF H r M A N

OBLONOATA
BRAIN, ante-

rior view — 1, 1. Anterior py-
ramids. 2, 2. Olivary bodies.
3,3. Restitbrra bodies. 4. De-
cussatiuu of the anterior co-
lumns. The medulla oblonj:-
ata is seeu terminated above
by the transverse fibres of the
pons Varolii.

OF THE NERVOUS SYSTEM. 385

terior a thin layer of gray matter folded upon itself, the functions
and connections of which are but little understood, and are not,
apparently, of very great importance.

The anterior columns of the cord present, at the lower part of the
medulla oblongata, a remarkable interchange or crossing of their
fibres (4). The fibres of the left anterior column pass across the
median line at this spot, and becoming continuous with the right
anterior pyramid, are finally distributed to the right side of the
cerebrum ; while the fibres of the right anterior column, passing
over to the left anterior pyramid, are distributed to the left side of
the cerebrum. This interchange or crossing of the nervous fibres
is known as the decussation of the anterior columns of the cord;

The posterior columns of the cord, as they diverge on each side
of the fourth ventricle, form the posterior and lateral projections of
the medulla oblongata (3, 3). They are sometimes called the "res-
tiform bodies," and are extremely important parts of the brain.
They consist in great measure of the longitudinal filaments of
the posterior columns, which pass upward and outward, and are
distributed partly to the gray matter of the cerebellum. The
remainder then pass forward, underneath the tubercula quadri-
gemina, into and through the optic thalami ; and radiating thence
upward and outward, are distributed, like the continuation of the
anterior columns, to the gray matter of the cerebrum. The resti-
form bodies, however, in passing upward to the cerebellum, are
supplied with some fibres from the anterior columns of the cord,
which, leaving the lower portion of the anterior pyramids, join the
restiform bodies, and are distributed with them to the cerebellum.
From this description it will be seen that both the cerebrum and
the cerebellum are supplied with filaments from both the anterior
and posterior columns of the cord.

In the substance of each restiform body, moreover, there is im-
bedded a ganglion which gives origin to the pneumogastric nerve,
and presides over the functions of respiration. This ganglion is
surrounded and covered by the longitudinal fibres passing upward
from the cord to the cerebellum, but may be discovered by cutting
into the substance of the restiform body, in which it is buried. It
is the first important ganglion met with, in dissecting the brain
from below upward.

While the anterior columns are passing beneath the pons Varolii,
they form, together with the continuation of the posterior columns
and the transverse fibres of the pons itself, a rounded prominence
25

386

GENERAL STRUCTURE AND FUNCTIONS

or tuberosity, which is known by the name of the tuber annulare.
In the deeper portions of this protuberance there is situated, among
the longitudinal fibres, another collection of gray matter, which
though not of large size, has very important functions and connec-
tions. This is known as the ganglion of the tuber annulare.

Situated almost immediately above these parts we have the cor-
pora striata in front, and the optic thalami behind, nearly equal in
size, and giving passage, as above described, to the fibres of the
anterior and posterior columns. Behind them still, and on a little
lower level, are the tubercula quadrigemina, giving origin to the
optic nerves. The olfactory ganglia rest upon the cribriform plate
of the ethmoid bone, and send the olfactory filaments through the
perforations in this plate, to be distributed upon the mucous mem-
brane of the upper and middle turbinated bones. The cerebellum
covers in the fourth ventricle and the posterior surface of the
medulla oblongata ; and finally the cerebrum, which has attained
the size of the largest ganglion in the cranial cavity, extends so far
in all directions, forward, backward, and laterally, as to form a con-
voluted arch or vault, completely covering all the remaining parts
of the encephalon.

The entire brain may therefore be regarded as a connected series

of ganglia, the arrangement of

Fig- 131. which is shown in the accompany-

ing diagram. (Fig. 131.) These
ganglia occur in the following
order, counting from before back-
ward: 1st. The olfactory gan-
glia. 2d. The cerebrum or hemi-
spheres. 3d. The corpora striata.
4th. The optic thalami. oth. The
tubercula quadrigemina. 6th.
The cerebellum. 7th. The gan-
glion of the tuber annulare. And
8th. The ganglion of the medulla
oblongata. Of these ganglia,
only the hemispheres and cere-
bellum are convoluted, while the
remainder are smooth and round-
ed or somewhat irregular in
shape. The course of the fibres
coming from the anterior and posterior columns of the cord is also

Diagram of HUMAN BRAIN, in vertical sec-
tion; showing the situation of the different gan-
glia, and the course of the fibres. 1. Olfactory
ganglion. 2 Hemisphere. 3. Corpus striatum.
4. Optic thalamus. 5. Tubercula quadrigemina.
6. Cerebellum. 7. Ganglion of tuber anuulare.
8. Ganglion of medulla oblongata.

OF THE NERVOUS SYSTEM. 387

to be seen in the accompanying figure. A portion of the anterior
fibres, we have already observed, pass upward and backward, with
the restiform bodies, to the cerebellum ; while the remainder run
forward through the tuber annulare and the corpus striatum, and
then radiate to the gray matter of the cerebrum. The posterior
fibres, constituting the restiform body, are distributed partly to the
cerebellum, and then pass forward, as previously described, under-
neath the tubercula quadrigemina to the optic thalmi, whence they
are also finally distributed to the gray matter of the cerebrum.

The cerebrum and cerebellum, each of which is divided into two
lateral halves or " lobes," by the great longitudinal fissure, are both
provided with transverse commissures, by which a connection is
established between their right and left sides. The great trans-
verse commissure of the cerebrum is that layer of white substance
which is situated at the bottom of the longitudinal fissure, and
which is generally known by the name of the " corpus callosum."
It consists of nervous filaments, which originate from the gray
matter of one hemisphere, converge to the centre, where they be-
come parallel, cross the median line, and are finally distributed to
the corresponding parts of the hemisphere upon the opposite side.
The transverse commissure of the cerebellum is the pons Yarolii.
Its fibres converge from the gray matter of the cerebellum on one
side, and pass across to the opposite ; encircling the tuber annulare
with a band of parallel curved fibres, to which the name of " pons
Yarolii" has been given from their resemblance to an arched bridge.

The cerebro-spinal system, therefore, consists of a series of gan-
glia situated in the cranio-spinal cavities, connected with each other
by transverse and longitudinal commissures, and sending out nerves
to the corresponding parts of the body. The spinal cord supplies
the integument and muscles of the neck, trunk, and extremities ;
while the ganglia of the brain, besides supplying the corresponding
parts of the head, preside also over the organs of special sense, and
perform various other functions of a purely nervous character.

388 OF NERVOUS IRRITABILITY

CHAPTER II.

OF NERVOUS IRRITABILITY AND ITS MODE OF

ACTION.

WE have already mentioned, in a previous chapter, that every
organ in the body is endowed with the property of irritability ; that
is, the property of reacting in some peculiar manner when subjected
to the action of a direct stimulus. Thus the irritability of a gland
shows itself by increased secretion, that of the capillary vessels by
congestion, that of the muscles by contraction. Now the irritability
of the muscles, indicated as above by their contraction, is extremely
serviceable as a means of studying and exhibiting nervous pheno-
mena. We shall therefore commence this chapter by a study of
some of the more important facts relating to muscular irritability.

The irritability of the muscles is a property inherent in the muscular
fibre itself. The existence of muscular irritability cannot be ex-
plained by any known physical or chemical laws, so far as they
relate to inorganic substances. It must be regarded simply as a
peculiar property, directly dependent on the structure and consti-
tution of the muscular fibre; just as the property of emitting light
belongs to phosphorus, or that of combining with metals to oxygen.
This property may be called into action by various kinds of stimu-
lus ; as by pinching the muscular fibre, or pricking it with the point
of a needle, the application of an acid or alkaline solution, or the
discharge of a galvanic battery. All these irritating applications
are immediately followed by contraction of the muscular fibre.
This contraction will even take place under the microscope, when
the fibre is entirely isolated, and removed from contact with any
other tissue ; showing that the properties of contraction and irrita-
bility reside in the fibre itself, and are not communicated to it by
other parts.

Muscular irritability continues for a certain time after death. The
stoppage of respiration and circulation does not at once destroy
the vital properties of the tissues, but nearly all of them retain

AND ITS MODE OF ACTION.

389

these properties to a certain extent for some time afterward. It is
only when the constitution of the tissues has become altered by
being deprived of blood, and by the consequent derangement of
the nutritive process, that their characteristic properties are finally
lost. Thus, in the muscles, irritability and contractility may be
easily shown to exist for a short time after death by applying to
the exposed muscular fibre the same kind of stimulus that we have
already found to affect it during life. It is easy to see, in the
muscles of the ox, after the animal has been killed, flayed, and
eviscerated, different bundles of muscular fibres contracting irregu-
larly for a long time, where they are exposed to the contact of the
air. Even in the human subject the same phenomenon may be
seen in cases of amputation ; the exposed muscles of the amputated
limb frequently twitching and quivering for many minutes after
their separation from the body.

The duration of muscular irritability, after death, varies consider-
ably in different classes of animals. It disappears most rapidly
in those whose circulation and respiration are naturally the most
active ; while it continues for a longer time in those whose circula-
tion and respiration are sluggish. Thus in birds the muscular
irritability continues only a few minutes after the death of the
animal. In quadrupeds it lasts somewhat longer ;
while in reptiles it remains, under favorable cir-
cumstances, for many hours. The cause of this
difference is probably that, in birds and quadrupeds,
the tissues being very vascular, and the molecular
changes of nutrition going on with rapidity, the
constitution of the muscular fibre becomes so
rapidly altered after the circulation has ceased,
that its irritability soon disappears. In reptiles,
on the other hand, the tissues are less vascular
than in birds and quadrupeds, and all the nutritive
changes go on more slowly. Kespiration and cir-
culation can therefore be dispensed with for a longer
period, before the constitution of the tissues be-
comes so much altered as to destroy altogether
their vital properties.

Owing to this peculiarity of the cold-blooded
animals, their tissues may be used with great ad-
vantage for purposes of experiment. If a frog's leg, for example,
be separated from the body of the animal (Fig. 132), the skin

Fig. 132.

FROG'S LEO, with
poles of galvanic bat-
tery applied to the
muscles at a, b.

390 OF NERVOUS IRRITABILITY

removed, and the poles of a galvanic apparatus applied to the sur-
face of the muscle (a, 1)), a contraction takes place every time the
circuit is completed and a discharge passed through the tissues of
the limb. The leg of the frog, prepared in this way, may be em-
ployed for a long time for the purpose of exhibiting the effect of
various kinds of stimulus upon the muscles. All the mechanical
and chemical irritants which we have mentioned, pricking, pinching,
cauterization, galvanism, &ov act with more or less energy and
promptitude, though the most efficient of all is the electric discharge.

Continued irritation exhausts the irritability of the muscles. It is
found that the irritability of the muscles wears out after death more
rapidly if they be artificially excited, than if they be allowed to
remain at rest. During life, the only habitual excitant of mus-
cular contraction is the peculiar stimulus conveyed by the nerves.
After death this stimulus may be replaced or imitated, to a certain
extent, by other irritants ; but their application gradually exhausts
the contractility of the muscle and hastens its final disappearance.
Under ordinary circumstances, the post-mortem irritability of the
muscle remains until the commencement of cadaveric rigidity.
When this has become fairly established, the muscles will no longer
contract under the application of an artificial stimulus.

Certain poisonous substances have the power of destroying the
irritability of the muscles by a direct action upon their tissue.
Sulphocyanide of potassium, for example, introduced into the cir-
culation in sufficient quantity to cause death, destroys entirely the
muscular irritability, so that no contraction can afterward be pro-
duced by the application of an external stimulant.

Nervous Irritability. — The irritability of the nerves is the pro-
perty by which they may be excited by an external stimulus, so as
to be called into activity and excite in their turn other organs to
which their filaments are distributed. When a nerve is irritated,
therefore, its power of reaction, or its irritability, can only be esti-
mated by the degree of excitement produced in the organ to which
the nerve is distributed. A nerve running from the integument to
the brain produces, when irritated, a painful sensation; one dis-
tributed to a glandular organ produces increased secretion ; one dis-
tributed to a muscle produces contraction. Of all these effects,
muscular contraction is found to be the best test and measure of
nervous irritability, for purposes of experiment. Sensation cannot
of course be relied on for this purpose, since both consciousness and
volition are abolished at the time of death. The activity of the

AND ITS MODE OF ACTION.

891

Fig. 133.

glandular organs, owing to the stoppage of the circulation, disappears
also very rapidly, or at least cannot readily be demonstrated. The
contractility of the muscles, however, lasts, as we have seen, for a
considerable time after death, and may accordingly be employed
with great readiness as a test of nervous irritability. The manner
of its employment is as follows : —

The leg of a frog is separated from the body and stripped of its
integument; the sciatic nerve having been previously dissected
out and cut off at its point of emergence from the
spinal canal, so that a considerable portion of it
remains in connection with the separated limb.
(Fig. 133.) If the two poles of a galvanic appa-
ratus be now placed in contact with different
points (a b) of the exposed nerve, and a discharge
allowed to pass between them, at the moment
of discharge a sudden contraction takes place in
the muscles below. It will be seen that this ex-
periment is altogether different from the one re-
presented in Fig. 132. In that experiment the
galvanic discharge passes through the muscles
themselves, and acts upon them by direct stim-
ulus. Here, however, the discharge passes only
from a to b through the tissues of the nerve, and
acts directly upon the nerve alone ; while the
nerve, acting upon the muscles by its own pecu-
liar agency, causes in this way a muscular con-
traction. It is evident that in order to produce
this effect, two conditions are equally essential : 1st.
The irritability of the muscles ; and 2d. The irri-
tability of the nerve. So long, therefore, as the
muscles are in a healthy condition, their contraction, under the
influence of a stimulus applied to the nerve, demonstrates the irri-
tability of the latter, and may be used as a convenient measure of
its intensity.

The irritability of the nerve continues after death. The knowledge
of this fact follows from what has just been said with regard to ex-
perimenting upon the frog's leg, prepared as above. The irrita-
bility of the nerve, like that of the muscle, depends directly upon
its anatomical structure and constitution ; and so long as these re-
main unimpaired, the nerve will retain its vital properties, though
respiration and circulation may have ceased. For the same reason,

FROG'S LEO. with
sciatic nerve (X) at-
tached.—a b. Pole* of
galvanic battery, ap-
plied to nerve.

392 OF NERVOUS IRRITABILITY

also, as that given above with regard to the muscles, nervous irri-
tability lasts much longer after death in the cold-blooded than in
the warm-blooded animals. Various artificial irritants may be em-
ployed to call it into activity. Pinching or pricking the exposed
nerve with steel instruments, the application of caustic liquids, and
the passage of galvanic discharges, all have this effect. The electric
current, however, is much the best means to employ for this pur-
pose, since it is more delicate in its operation than the others, and
will continue to succeed for a longer time.

The nerve is, indeed, so exceedingly sensitive to the electric cur-
rent, that it will respond to it when insensible to all other kinds of
stimulus. A frog's leg freshly prepared with the nerve attached,
as in Fig. 133, will react so readily whenever a discharge is passed
through the nerve, that it forms an extremely delicate instrument
for detecting the presence of electric currents of low intensity, and
has even been used for this purpose by Matteucci, under the name
of the "galvanoscopic frog." It is only necessary to introduce the
nerve as part of the electric circuit ; and if even a very feeble cur-
rent be present, it is at once betrayed by a muscular contraction.

The superiority of electricity over other means of exciting nerv-
ous action, such as mechanical violence or chemical agents, pro-
bably depends upon the fact that the latter necessarily alter and
disintegrate more or less the substance of the nerve, so that its irri-
tability soon disappears. The electric current, on the other hand,
excites the nervous irritability without any marked injury to the
substance of the nervous fibre. Its action may, therefore, be con-
tinued for a longer period.

Nervous irritability, like that of the muscles, is exhausted by repeated
excitement. If a frog's leg be prepared as above, with the sciatic
nerve attached, and allowed to remain at rest in a damp and cool
place, where its tissue will not become altered by desiccation, the
nerve will remain irritable for many hours ; but if it be excited,
soon after its separation from the body, by repeated galvanic shocks,
it soon begins to react with diminished energy, and becomes gra-
dually less and less irritable, until it at last ceases to exhibit any
further excitability. If it be now allowed to remain for a time at
rest, its irritability will be partially restored ; and muscular contrac-
tion will again ensue on the application of a stimulus to the nerve.
Exhausted a second time, and a second time allowed to repose, it
will again recover itself; and this may even be repeated several
times in succession. At each repetition, however, the recovery of

AXD ITS MODE OF ACTION. 393

nervous irritability is less complete, until it finally disappears alto-
gether, and can no longer be recalled.

Various accidental circumstances tend to diminish or destroy
nervous irritability. The action of the woorara poison, for example,
destroys at once the irritability of the nerves ; so that in animals
killed by this substance, no muscular contraction takes place on
irritating the nervous trunk. Severe and sudden mechanical inju-
ries often have the same effect ; as where death is produced by
violent and extensive crushing or laceration of the body or limbs.
Such an injury produces a general disturbance, or shock as it is
called, which affects the entire nervous system, and destroys or
suspends its irritability. The effects of such a nervous shock may
frequently be seen in the human subject after railroad accidents,
where the patient, though very extensively injured, may remain
for some hours without feeling the pain of his wounds. It is only
after reaction has taken place, and the activity of the nerves has
been restored, that the patient begins to be sensible of pain.

It will often be found, on preparing the frog's leg for experiment
as above, that immediately after the limb has been separated from
the body and the integument removed, the nerve is destitute of
irritability. Its vitality has been suspended by the violence in-
flicted in the preparatory operation. In a few moments, however,
if kept under favorable conditions, it recovers from the shock, and
regains its natural irritability.

The action of the galvanic current upon the nerves, as first shown
by the experiments of Matteucci, is in many respects peculiar. If
the current be made to traverse the nerve in the natural direction
of its fibres, viz., from its origin towards its distribution, as from a
to I in Fig. 133, it is called the direct current. If it be made to
pass in the contrary direction, as from b to a, it is called the inverse
current. When the nerve is fresh and exceedingly irritable, a
muscular contraction takes place at both the commencement and
termination of the current, whether it be direct or inverse. But
very soon afterward, when the activity of the nerve has become
somewhat diminished, it will be found that contraction takes place
only at the commencement of the direct and at the termination of the
inverse current. This may readily be shown by preparing the two
legs of the same frog in such a manner that they remain connected
with each other by the sciatic nerves and that portion of the spinal
column from which these nerves take their origin. The two legs,
so prepared, should be placed each in a vessel of water, with the

894: OF NERVOUS IRK1TABILTTY

nervous connection hanging between. (Fig. 134.) If the positive
pole, a. of the battery be now placed in the vessel which holds leg
No. 1, and the negative pole, b, in that containing leg No. 2, it will
be seen that the galvanic current will traverse the two legs in op-
posite directions. In No. 1, it will pass in a direction contrary to
the course of its nervous fibres, that is, it will be for this leg an

Fig. 134.

inverse current ; while in No. 2 it will pass in the same direction
with that of the nervous fibres, that is, it will be for this leg a direct
current. It will now be found that at the moment when the cir-
cuit is completed, a contraction takes place in No. 2 by the direct
current, while No. 1 remains at rest ; but at the time the circuit is
broken, a contraction is produced in No. 1 by the inverse current,
but no movement takes place in No. 2. A succession of alternate
contractions may thus be produced in the two legs by repeatedly
closing and opening the circuit. If the position of the poles, a, b,
be reversed, the effects of the current will be changed in a corre-
sponding manner.

After a nerve has become exhausted by the direct current, it is
still sensitive to the inverse ; and after exhaustion by the inverse,
it is still sensitive to the direct. It has even been found by Mat-
teucci that after a nerve has been exhausted for the time by the direct
current, the return of its irritability is hastened by the subsequent
passage of the inverse current ; so that it will become again sensi-
tive to the direct current sooner than if allowed to remain at rest.
Nothing, accordingly, is so exciting to a nerve as the passage of
direct and inverse currents, alternating with each other in rapid
succession. Such a mode of applying the electric stimulus is that

AND ITS MODE OF ACTION. 395

usually adopted in the galvanic machines used in medical practice,
for the treatment of certain paralytic affections. In these machines,
the electric circuit is alternately formed and broken with great
rapidity, thus producing the greatest effect upon the nerves with
the smallest expenditure of electricity. Such alternating currents,
however, if very powerful, exhaust the nervous irritability more
rapidly and completely than any other kind of irritation ; and in
an animal killed by the action of a battery used in this manner, the
nerves may be found to be entirely destitute of irritability from the
moment of death.

The irritability of the nerves is distinct from that of the muscles; and
the two may be destroyed or suspended independently of each other.
When the frog's leg has been prepared and separated from the
body, with the sciatic nerve attached, the muscles contract, as we
have seen, whenever the nerve is irritated. The irritability of the
nerve, therefore, is manifested in this instance only through that of
the muscle, and that of the muscle is called into action only through
that of the nerve. The two properties may be separated from each
other, however, by the action of woorara, which has the power, as
first pointed out by Bernard, of destroying the irritability of the
nerve without affecting that of the muscles. If a frog be poisoned
by this substance, and the leg prepared as above, the poles of a
galvanic battery applied to the nerve will produce no effect ; show-
ing that the nervous irritability has ceased to exist. But if the
galvanic discharge be passed directly through the muscles, contrac-
tion at once takes place. The muscular irritability has survived
that of the nerves, and must therefore be regarded as essentially
distinct from it.

It will be recollected, on the other hand, that in cases of death
from the action of sulphocyanide of potassium, the muscular irri-
tability is itself destroyed ; so that no contractions occur, even when
the galvanic discharge is made to traverse the muscular tissue.

There are, therefore, two kinds of paralysis : first, a muscular
paralysis, in which the muscular fibres themselves are directly
affected ; and second, a nervous paralysis, in which the affection is
confined to the nervous filaments, the muscles retaining their natural
properties, and being still capable of contracting under the influence
of a direct stimulus.

Nature of the Nervous Force. — The special endowment by which
a nerve acts and manifests its vitality is a peculiar one, inherent in
the anatomical structure and constitution of the nervous tissue. It is

396 OF NERVOUS IRRITABILITY

manifested, in the foregoing experiments, by its effect upon the con-
tractile muscles. But we shall hereafter see that this is, in reality,
only one of its results, and that it shows itself, during life, by a
variety of other influences. Thus it produces, in one case, sensa-
tion; in another, muscular contraction; in another, increased or
modified glandular activity; in another, alterations in the pheno-
mena of the circulation. The force, however, which is exerted by
a nerve in a state of activity, and which brings about these changes,
is not directly appreciable in any way by the senses, and can be
judged of only by its secondary effects. We understand enough
of its mode of operation, to know that it is not identical with the
forces of chemical affinity, of mechanical action, or of electricity.

And yet, by acting upon the organs to which the nerves are
distributed, it will finally produce phenomena of all these different
kinds. By the intervention of the muscles, it results in mechanical
action ; and by its influence upon the glands and bloodvessels, it
causes chemical alterations in the animal fluids of the most import-
ant character.

It will even produce well-marked electrical phenomena, which
in some cases are so decided, as to have long attracted the attention
of physiologists.

It has been fully demonstrated that certain fish (gymnotus and
torpedo) have the power of generating electricity, and of producing
electric discharges, which are often sufficiently powerful to kill
small animals that may come within their reach. That the force
generated by these animals is in reality electricity, is beyond a
doubt. It is conducted by the same bodies which serve as con-
ductors for electricity, and is stopped by those which are non-con-
ductors of the same. All the ordinary phenomena produced bj
the electric current, viz : the heating and melting of a fine con-
ducting wire, the induction of secondary currents and of magnetism,
the decomposition of saline solutions, and even the electric sparkj
have all been produced by the force generated by these animals.
There is, accordingly, no room for doubt as to its nature.

The electrical phenomena, in these cases, are produced by certain
organs which are called into activity by the nervous influence.

The electrical organs of the gymnotus and torpedo occupy a con-
siderable portion of the body, and are largely supplied with nerves
which regulate their function. If these nerves be divided, tied, or
injured in any way, the electrical organ is weakened or paralyzed,
just as the muscles would suffer if the nerves distributed to them

AND ITS MODE OF ACTION. 397

were subjected to a similar violence. The electricity produced by
these animals, accordingly, is not supplied by the nerves, but by a
special generating organ, the action of which is regulated by nerv-
ous influence.

Moreover, the experiments of Longet and Matteucci1 have shown
that no electrical current is to be detected in a living nerve, even
when in a state of activity. The electrical phenomenon, when it
exists, is only a secondary effect, and is not the active force residing
in the nervous tissue. This force is special in its nature, and is
regulated by laws peculiar to itself.

1 Longet, Traito de Physiologic. Paris, 1850, vol. ii. p. 130.

\

398 THE SPINAL COKD.

CHAPTER III.

THE SPINAL CORD.

WE have already seen that the spinal cord is a long ganglion,
covered with longitudinal bundles of nervous filaments, and occu-
pying the cavity of the spinal canal. It sends out nerves which
supply the muscles and integument of at least nine-tenths of the
whole body, viz., those of the neck, trunk, and extremities. All
these parts of the body are endowed with two very remarkable
properties, the exercise of which depends, directly or indirectly,
upon the integrity and activity of the spinal cord, viz., the power
of sensation and the power of motion. Both these properties are
said to reside in the nervous system, because they are so readily
influenced by its condition, and are so closely connected with its
physiological action. We shall therefore commence the study of
the spinal cord with an examination of these two functions, and of
the situation which they occupy in the nervous system.

SENSATION. — The power of sensation, or sensibility, is the power
by which we are enabled to receive impressions from external
objects. These impressions are usually of such a nature that we
can derive from them some information in regard to the qualities
of external objects and the effect which they may produce upon
our own systems. Thus, by bringing a foreign body into contact
with the skin, we feel that it is hard or soft, rough or smooth, cold
or warm. We can distinguish the separate impressions produced
by several bodies of a similar character, and we can perceive whe-
ther either one of them, while in contact with the skin, be at rest
or in motion. This power, which is generally distributed over the
external integument, is dependent on the nervous filaments rami-
fying in its tissue. For if the nerves distributed to any part of the
body be divided, the power of sensation in the corresponding region
is immediately lost.

SENSATION. 399

The sensibility, thus distributed over the integument, varies in
its acuteness in different parts of the body. Thus, the extremities
of the fingers are more sensitive to external impressions than the
general surface of the limbs and trunk. The surfaces of the fingers
which lie in contact with each other are more sensitive than their
dorsal or palmar surfaces. The point of the tongue, the lips, and
the orifices of most of the mucous passages are endowed with a
sensibility which is more acute than that of the general integument.

If the impression to which these parts are subjected be harsh or
violent in its character, or of such a nature as to injure the texture
of the integument or its nerves, it then produces a sensation of pain.
It is essential to notice, however, that the sensation of pain is not
a mere exaggeration of ordinary sensitive impressions, but is one
of quite a different character, which, is superadded to the others, or
takes their place altogether. Just in proportion as the contact of a
foreign body becomes painful, our ordinary perceptions of its phy-
sical properties are blunted, and the sense of suffering predominates
over ordinary sensibility. Thus if the integument be gently touched
with the blade of a knife we easily feel that it is hard, cold, and
smooth ; but if an incision be made with it in the skin, we lose all
distinct perception of these qualities, and feel only the suffering
produced by the incision. We perceive, also, the difference in
temperature between cold and warm substances brought in contact
with the skin, so long as this difference is moderate in degree ; but
if a foreign body be excessively cold or excessively hot, we can
no longer appreciate its temperature by the touch, but only its
injurious and destructive effect. Thus the sensation caused by
touching frozen carbonic acid is the same with that produced by a
red-hot metal. Both substances blister the surface, but their actual
temperatures cannot be distinguished.

It is, therefore, a very important fact in this connection, that the
sensibility to pain is distinct from the power of ordinary serration. This
distinction was first fully established by M. Beau, of Paris, who has
shown conclusively that the sensibility to pain may be diminished
or suspended, while ordinary sensation remains. This is often seen
in patients who are partially under the influence of ether or chlo-
roform. The etherization may be carried to such an extent that
the patient may be quite insensible to the pain of a surgical opera-
tion, and yet remain perfectly conscious, and even capable of feeling
the incisions, ligatures, &c., though he does not suffer from them.
It not unfrequently happens, also, when opium has been adminis-

400 THE SPINAL CORD.

tered for the relief of neuralgia, that the pain is completely abolished
by the influence of the drug, while the patient retains completely
his consciousness and his ordinary sensibility.

In all cases, however, if the influence of the narcotic be pushed
to its extreme, both kinds of sensibility are suspended together, and
the patient becomes entirely unconscious of external impressions.

MOTION. — Wherever muscular tissue exists, in any part of the
body, we find the power of motion, owing to the contractility of
the muscular fibres. But this power of motion, as we have already
seen, is dependent on the nervous system. The excitement which
causes the contraction of the muscles is transmitted to them by the
nervous filaments ; and if the nerve supplying a muscle or a limb
be divided or seriously injured, these parts are at once paralyzed
and become incapable of voluntary movement. A nerve which,
when irritated, acts directly upon a muscle, producing contraction,
is said to be excitable • and its excitability, acting through the mus-
cle, produces motion in the part to which it is distributed.

The excitability of various nerves, however, often acts -during
life upon other organs, beside the muscles ; and the ultimate effect
varies, of course, with the properties of the organ which is acted
upon. Thus, the nervous excitement transmitted to a muscle pro-
duces contraction, while that transmitted to a gland produces an
increased secretion, and that conveyed to a vascular surface causes
congestion. In all such instances, the effect is produced by an
influence transmitted by the nerve directly to the organ which is
called into activity.

But in all the external parts of the body muscular contraction
is the most marked and palpable effect produced by the direct
influence of nervous excitement. We find, therefore, that so far
as we have yet examined it, the nervous action shows itself princi-
pally in two distinct and definite forms ; first, as sensibility, or the
power of sensation, and second, as excitability or the power of pro-
ducing motion.

DISTINCT SEAT OF SENSATION AND MOTION IN THE NERVOUS
SYSTEM. — Sensation and motion are usually the first functions
which suffer by any injury inflicted on the nervous system. As a
general rule, they are both suspended or impaired at the same time,
and in a nearly equal degree. In a fainting fit, an attack of apo-
plexy, concussion or compression of the brain or spinal cord, or a

DISTINCT SEAT OF SENSATION AND MOTION. 40L

wound of any kind involving the nerves or nervous centres, insen-
sibility and loss of motion usually appear simultaneously. It is
difficult, therefore, under ordinary conditions, to trace out the
separate action of these two functions, or to ascertain the precise
situation occupied by each.

This difficulty, however, may be removed by examining sepa-
rately different parts of the nervous system. In the instances
mentioned above, the injury which is inflicted is comparatively an
extensive one, and involves at the same time many adjacent parts.
But instances sometimes occur in which the two functions, sensa-
tion and motion, are affected independently of each other, owing to
the peculiar character and situation of the injury inflicted. Sensa-
tion may be impaired without loss of motion, and loss of motion
may occur without injury to sensation. In tic douloureux, for
example, we have an exceedingly painful affection of the sensitive
parts of the face, without any impairment of its power of motion :
and in facial paralysis we often see a complete loss of motion affect-
ing one side of the face, while the sensibility of the part remains
altogether unimpaired.

The above facts first gave rise to the belief that sensation and
motion might occupy distinct parts of the nervous system ; since it
would otherwise be difficult to understand how the two could be
affected independently of each other by anatomical lesions. It has
accordingly been fully established by the labors of Sir Charles Bell,
Miiller, Panizza, and Longet, that the two functions do in reality
occupy distinct parts of the nervous system.

If any one of the spinal nerves, in the living animal, after being
exposed at any part of its course outside the spinal canal, be divided,
ligatured, bruised, or otherwise seriously injured, paralysis of motion
and loss of sensation are immediately produced in that part of the
body to which the nerve is distributed. If, on the other hand, the
same nerve be pricked, galvanized, or otherwise gently irritated, a
painful sensation and convulsive movements are produced in the
same parts. The nerve is therefore said to be both sensitive and
excitable ; sensitive, because irritation of its fibres produces a pain-
ful sensation, and excitable, because the same irritation causes mus-
cular contraction in the parts below.

The result of the experiment, however, will be different if it be

tried upon the parts situated inside the spinal canal, and particularly

upon the anterior and posterior roots of the spinal nerves. If an

irritation be applied, for example, to the anterior root of a spinal

26

402 THE SPINAL CORD.

nerve, in the living animal, convulsive movements are produced in
the parts below, but there is no painful sensation. The anterior
root accordingly is said to be excitable, but not sensitive. If the
posterior root, on the other hand, be irritated, acute pain is pro-
duced, but no convulsive movements. The posterior root is there-
fore sensitive, but not excitable. A similar result is obtained by a
complete division of the two roots. Division of the anterior root
produces paralysis of motion, but no insensibility ; division of the
posterior root produces complete loss of sensibility, but no muscular
paralysis.

"We have here, then, a separate localization of sensation and
motion in the nervous system ; and it is accordingly easy to under-
stand how one may be impaired without injury to the other, or'
how both may be simultaneously affected, according to the situation
and extent of the anatomical lesion.

The two roots of a spinal nerve differ from each other, further-
more, in their mode of transmitting the nervous impulse. If the
posterior root be divided (Fig. 135) at a b, and an irritation applied

Fig. 135.

Diagram of SPINAL CORD AND NERVES. The posterior root is seen divided at a, b, the
autedur at c, d.

to the separated extremity (a), no effect will be produced ; but if
the irritation be applied to the attached extremity (7;), a painful
sensation is immediately the result. The nervous force, therefore,
travels in the posterior root from without inward, but cannot pass
from within outward. If the anterior root, on the other hand, be
divided at c, d, and its attached extremity (d) irritated, no effect

SENSIBILITY AND EXCITABILITY IN SPINAL CORD. 403

follows ; but if the separated extremity (c) be irritated, convulsive
movements instantly take place. The nervous force, consequently,
travels in the anterior root from within outward, but cannot pass
from without inward.

The same thing is true with regard to the transmission of sensa-
tion and motion in the spinal nerves outside the spinal canal. If
one of these nerves be divided in the living animal, and its attached
extremity irritated, pain is produced, but no convulsive motion ; if
the irritation be applied to its separated extremity, muscular con-
tractions follow, but no painful sensation.

There are, therefore, two kinds of filaments in the spinal nerves,
not distinguishable by the eye, but entirely distinct in their charac-
ter and function, viz., the "sensitive" filaments, or those which
convey sensation, and the " motor" filaments, or those which excite
movement. These filaments are never confounded with each other
in their action, nor can they perform each other's functions. The
sensitive filaments convey the nervous force only in a centripetal,
the motor only in a centrifugal direction. The former preside over
sensation, and have nothing to do with motion ; the latter preside
over motion, and have nothing to do with sensation. Within the
spinal canal the two kinds of filaments are separated from each
other, constituting the anterior and posterior roots of each spinal
nerve; but externally they are mingled together in a common
trunk. While the anterior and posterior roots, therefore, are ex-
clusively sensitive or exclusively motor, the spinal nerves beyond
the junction of the roots are called mixed nerves, because they con-
tain at the same time motor and sensitive filaments. The mixed
nerves accordingly preside at the same tim£ over the functions of
movement and sensation.

DISTINCT SEAT OF SENSIBILITY AND EXCITABILITY IN THE
SPINAL CORD. — Various experimenters have demonstrated the fact
that different parts of the spinal cord, like the two roots of the
spinal nerves, are separately endowed with sensibility and excita-
bility. The anterior columns of the cord, like the anterior roots of
the spinal nerves, are excitable but not sensitive; the posterior
columns, like the posterior roots of the spinal nerves, are sensitive
but not excitable. Accordingly, when the spinal canal is opened
in the living animal, an irritation applied to the anterior columns
of the cord produces immediately convulsions in the limbs below ;
but there is no indication of pain. On the other hand, signs of

404 THE SPINAL CORD.

acute pain become manifest whenever the irritation is applied to
the posterior columns ; but no muscular contractions follow, other
than those of a voluntary character. Longet has found1 that if the
spinal cord be exposed in the lumbar region and completely divided
at that part by transverse section, the application of any irritant to
the anterior surface of the separated portion produces at once con-
vulsions below ; while if applied to the posterior columns behind
the point of division, it has no sensible effect whatever. The an-
terior and posterior columns of the cord are accordingly, so far,
analogous in their properties to the anterior and posterior roots of
the spinal nerves, and are plainly composed, to a greater or less ex-
tent, of a continuation of their filaments.

These filaments, derived from the anterior and posterior roots of
the spinal nerves, pass upward through the spinal cord toward the
brain. An irritation applied to any part of the integument is then
conveyed, along the sensitive filaments of the nerve and its pos-
terior root, to the spinal cord ; then upward, along the longitudinal
fibres of the cord to the brain, where it produces a sensation corres-
ponding in character with the original irritation. A motor im-
pulse, on the other hand, originating in the brain, is transmitted
downward, along the longitudinal fibres of the cord, passes outward
by the anterior root of the spinal nerve, and, following the motor
filaments of the nerve through its trunk and branches, produces at
last a muscular contraction at the point of its final distribution.

CROSSED ACTION OF THE SPINAL CORD. — As the anterior columns
of the cord pass upward to join the medulla oblongata, a decussa-
tion takes place between them, as we have already mentioned in
Chapter I. The fibres of the right anterior column pass over to
the left side of the medulla oblongata, and so upward to the left side
of the brain ; while the fibres of the left anterior column pass over
to the right side of the medulla oblongata, and so upward to the
right side of the brain. This decussation may be readily shown
(as in Fig. 130) by gently separating the anterior columns from each
other, at the lower extremity of the medulla oblongata, where the
decussating bundles may be seen crossing obliquely from side to
side, at the bottom of the anterior median fissure. Below this
point, the anterior columns remain distinct from each other on each
side, and do not communicate by any further decussation.

1 Traite de Physiologie, vol. ii. part 2, p 8.

CROSSED ACTION OF THE SPINAL CORD. 405

If the anterior columns of the spinal cord, therefore, be wounded
at any point in the cervical, dorsal, or lumbar region, a paralysis
of voluntary motion is produced in the limbs below, on the same
side with the injury. But if a similar lesion occur in the brain, the
paralysis which results is on the opposite side of the body. Thus
it has long been known that an abscess or an apoplectic hemorrhage
on the right side of the brain will produce paralysis of the left side
of the body; and injury of the left side of the brain will be fol-
lowed by paralysis of the right side of the body.

The spinal cord has also a crossed action in transmitting sensi-
tive as well as motor impulses. It has been recently demonstrated
by Dr. Brown-Se'quard,1 that the crossing of the sensitive fibres in
the spinal cord does not take place, like that of the motor fibres,
at its upper portion only, but throughout its entire length ; so that
the sensitive fibres of the right spinal nerves, very soon after their
entrance into the cord, pass over to the left side, and those of the
left spinal nerves pass over to the right side. For if one lateral
half of the spinal cord of a dog be divided in the dorsal region,
the power of sensation remains upon the corresponding side of the
body, but is lost upon the opposite side. It has been shown, fur-
thermore, by the same observer,2 that the sensitive fibres of the
spinal nerves when they first enter the cord join the posterior
columns, which are everywhere extremely sensitive ; but that they
very soon leave the posterior columns, and, passing through the
central parts of the cord, run upward to the opposite side of the
brain. If the posterior columns, accordingly, be alone divided at
any part of the spinal cord, sensibility is not destroyed in all the
nerves behind the seat of injury, but only in those which enter the
cord at the point of section ; since the posterior columns consist
of different nervous filaments, joining them constantly on one side
from below, and leaving them on the other to pass upward toward
the brain.

The spinal cord has therefore a crossed action, both for sensation
and motion ; but the crossing of the motor filaments occurs only at
the medulla oblongata, while that of the sensitive filaments takes
place throughout the entire length of the cord.

1 Experimental Researches applied to Physiology and Pathology. New York.
1853.

2 Memoirs sur la Physiologic de la Moelle epiniere ; Gazette Medicale de Paris,
1855.

406 THE SPINAL CORD.

There are certain important facts which still remain to be noticed
regarding the mode of action of the spinal cord and its nerves.
They are as follows : —

1. An irritation applied to a spinal nerve at the middle of its course
produces the same effect as if it traversed its entire length. Thus, if the
sciatic or median nerve be irritated at any part of its course, con-
traction is produced in the muscles to which these nerves are dis-
tributed, just as if the impulse had originated as usual from the
brain. This fact depends upon the character of the nervous fila-
ments, as simple conductors. Wherever the impulse may originate,
the final effect is manifested only at the termination of the nerve.
As the impulse in the motor nerves travels always in an outward
direction, the effect is always produced at the muscular termination
of the filaments, no matter how small or how large a portion of
their length may have been engaged in transmitting the stimulus.

If the irritation, again, be applied to a sensitive nerve in the
middle of its course, the painful sensation is felt, not at the point
of the nerve directly irritated, but in that portion of the integument
to which its filaments are distributed. Thus, if the ulnar nerve be
accidentally struck at the point where it lies behind the inner con-
dyle of the humerus, a sensation of tingling and numbness is pro-
duced in the last two fingers of the corresponding hand. It is
common to hear patients who have suffered amputation complain of
painful sensations in the amputated limb for weeks or months, and
sometimes even for years after the operation. They assert that
they can feel the separated parts as distinctly as if they were still
attached to the body. This sensation, which is a real one and not
fictitious, is owing to some irritation operating upon the divided
extremities of the nerves in the cicatrized wound. Such an irrita-
tion, conveyed to the brain by the sensitive fibres, will produce
precisely the same sensation as if the amputated parts were still
present, and the irritation actually applied to them.

It is on this account also that division of the trifacial nerve is
not always effectual for the cure of tic douloureux. If the cause of
the difficulty be seated upon the trunk of the nerve, between its
point of emergence from the bones and its origin in the brain, it is
evident that division of the nerve upon the face will be of no
avail ; since the cause of irritation will still exist behind the point
of section, and the same painful sensations will still be produced in
the brain.

2. The irritability of the motor filaments disappears from within out-

INDEPENDENCE OF NERVOUS FILAMENTS. 407

•ward, that of the sensitive filaments from without inward. Immedi-
ately after the separation of the frog's leg from the body, irritation
of the nerve at any point produces muscular contraction in the
limb below. As time elapses, however, and the irritability of the
nerve diminishes, the galvanic current, in order to produce con-
traction, must be applied at a point nearer its termination. Subse-
quently, the irritability of the nerve is entirely lost in its upper
portions, but is retained in the parts situated lower down, from
which also, in turn, it afterward disappears ; receding in this man-
ner farther and farther toward the terminal distribution of the
nerve, where it finally disappears altogether.

On the other hand, sensibility disappears, at the time of death,
first in the extremities. From them the numbness gradually creeps
upward, invading successively the middle and upper portions of the
limbs, and the more distant portions of the trunk. The central
parts are the last to become insensible.

3. Each nervous filament acts inde2iendently of the rest throughout its
entire length, and does not communicate its irritation to those which are
i ' n proximity with it. It is evident that this is true with regard to
the nerves of sensation, from the fact that if the integument be
touched with the point of a needle, the sensation is referred to that
spot alone. Since the nervous filaments coming from it and the
adjacent parts are all bound together in parallel bundles, to form
the trunk of the nerve, if any irritation were communicated from
one sensitive filament to another, the sensation produced would be
indefinite and diffused, whereas it is really confined to the spot irri-
tated. If a frog's leg, furthermore, be prepared, with the sciatic
nerve attached, a few of the fibres separated laterally from the
nervous trunk for a portion of its length, and the poles of a galvanic
battery applied to the separated portion, the contractions which
follow in the leg will not be general, but will be confined to those
muscles in which the galvanized nervous fibres especially have
their distribution. There are also various instances, in the body,
of antagonistic muscles, which must act independently of each
other, but which are supplied with nerves from a common trunk.
The superior and inferior straight muscles of the eyeball, for
example, are both supplied by the motor oculi communis nerve.
Extensor and flexor muscles, as, for example, those of the fingers,
are often supplied by the same nerve, and yet act alternately with-
out mutual interference. It is easv to see that if this were not the

408 THE SPINAL CORD.

case, confusion would constantly arise, both in the perception of
sensations, and in the execution of movements.

4. There are certain sensations which are excited simultaneously
by the same causes, and which are termed associated sensations ; and
there are also certain movements which take place simultaneously,
and are called associated movements. In the former instance, one of
the associated sensations is called up immediately upon the percep-
tion of the other, without requiring any direct impulse of its own.
Thus, tickling the soles of the feet produces a peculiar sensation
at the epigastrium. Nausea is occasioned by certain disagreeable
odors, or by rapid rotation of the body, so that the landscape seems
to turn round. A striking example of associated movements, on
the other hand, may be found in the action of the muscles of the
eyeball. The eyeballs always accompany each other in their lateral
motions, turning to the right or the left side simultaneously. It is
evident, however, that in producing this correspondence of motion,
the left internal rectus muscle must contract and relax together
with the right external; while a similar harmony of action must
exist between the right internal and the left external. The explana-
tion of such singular correspondences cannot be found in the anato-
mical arrangement of the muscles themselves, nor in that of the
nervous filaments by which they are directly supplied, but must be
looked for in some special endowment of the nervous centres from
which they originate.

EEFLEX ACTION OF THE SPINAL CORD. — The spinal cord, as we
have thus far examined it, may be regarded simply as a great nerve ;
that is, as a bundle of motor and sensitive filaments, connecting
the muscles and integument below with the brain above, and
assisting, in this capacity, in the production of conscious sensation
and voluntary motion. Beside its nervous filaments, however, it
contains also a large quantity of gray matter, and is, therefore,
itself a ganglionic centre, and capable of independent action as
such. We shall now proceed to study it in its second capacity, as
a distinct nervous centre.

If a frog be decapitated, and the body allowed to remain at rest
for a few moments, so as to recover from the depressing effects of
shock upon the nervous system, it will be found that, although sen-
sation and consciousness are destroyed, the power of motion still
remains. If the skin of one of the feet be irritated by pinching it
with a pair of forceps, the leg is immediately drawn up toward the

REFLEX ACTION OF THE SPINAL CORP.

409

body, as if to escape the cause of irritation. If the irritation applied
to the foot be of slight intensity, the corresponding leg only will
move ; but if it be more severe in character, motions will often be
produced in the posterior extremity of the opposite side, and even
in the two fore legs, at the same time. These motions, it is import-
ant to observe, are never spontaneous. The decapitated frog remains
perfectly quiescent if left to himself. It is only when some cause
of irritation is applied externally, that movements occur as above
described.

It will be seen that the character of these phenomena indicates
the active operation of some part of the nervous system, and par-
ticularly of some ganglionic centre. The irritation is applied to
the skin of the foot, and the muscles of the leg contract in conse-
quence ; showing evidently the intermediate action of a nervous
connection between the two.

The effect in question is due to the activity of the spinal cord,
operating as a nervous centre. In order that the movements may
take place as above, it is essential that both the integument and the
muscles should be in communication with the spinal cord by nerv-
ous filaments, and that the cord itself be in a state of integrity. If
the sciatic nerve be divided in the upper part of the thigh, irritation
of the skin below is no longer followed by any muscular contrac-
tion. If either the anterior or posterior roots of the nerve be
divided, the same want of action results ; and finally, if, the nerve
and its roots remaining entire, the spinal cord itself be broken up
by a needle introduced into the spinal
canal, the integument may then be
irritated or mutilated to any extent,
without exciting the least muscular
contraction. It is evident, therefore,
that the spinal cord acts, in this case,
as a nervous centre, through which
the irritation applied to the skin is
communicated to the muscles. The
irritation first passes upward, as shown
in the accompanying diagram (Fig.
136), along the sensitive fibres of the
posterior root (a) to the gray matter
of the cord, and is then reflected back,
along the motor fibres of the anterior
root (b), until it finally reaches the muscles, and produces a contrac

Fig. 136.

Diagram of SPINAL COKD IN VKK-
TICAI, SECTION, showing reflex action.
— n. Posterior root of spinal nerve. 6.
Anterior root of spinal nerve.

410 THE SPINAL CORD.

tion. This action is known, accordingly, as the reflex action of the
spinal cord.

It will be remembered that this reflex action of the cord is not
accompanied by volition, nor even by any conscious sensation.

The function of the spinal cord as a nervous centre is simply to
convert an impression, received from the skin, into a motor, impulse
which is sent out again to the muscles. There is absolutely no
farther action than this ; no exercise of will, consciousness, or judg-
ment. This action will therefore take place perfectly well after
the brain has been removed, and after the entire sympathetic sys-
tem has also been taken away, provided only that the spinal cord
and its nerves remain in a state of integrity.

The existence of this reflex action after death is accordingly an
evidence of the continued activity of the spinal cord, just as con-
tractility is an evidence of the activity of the muscles, and irrita-
bility of that of the nerves. Like the two last-mentioned properties,
also, it continues for a longer time after death in cold-blooded than
in warm-blooded animals. It is for this reason that frogs and other
reptiles are the most useful subjects for the study of these pheno-
mena, as for that of most others belonging to the nervous system.

The irritability of the spinal cord, as manifested by its reflex
action, may be very much exaggerated by certain diseases, and by
the operation of poisonous substances. Tetanus and poisoning by
strychnine both act in this way, by heightening the irritability of
the spinal cord, and causing it to produce convulsive movements
on the application of external stimulus. It has been observed that
the convulsions in tetanus are rarely, if ever, spontaneous, but that
they always require to be excited by some external cause, such as
the accidental movement of the bedclothes, the shutting of a door,
or the sudden passage of a current of air. Such slight causes of
irritation, which would be entirely inadequate to excite involuntary
movements in the healthy condition, act upon the spinal cord, when
its irritability is heightened by disease, in such a manner as to pro-
duce violent convulsions.

Similar appearances are to be seen in animals poisoned by strych-
nine. This substance acts upon the spinal cord and increases its
irritability, without materially affecting the functions of the brain.
Its effects will show themselves, consequently, without essential
modification, after the head has been removed. If a decapitated
frog be poisoned with a moderate dose of strychnine, the body and
limbs will remain quiescent so long as there is no external source

EEFLEX ACTION OF THE SPINAL CORD. 411

of excitement ; but the limbs are at once thrown into convulsions
by the slightest irritation applied to the skin, as, for example, the
contact of a hair or a feather, or even the jarring of the table on
which the animal is placed. That the convulsions in cases of
poisoning by strychnine are always of a reflex character, and never
spontaneous, is shown by the following fact first noticed by Ber-
nard,1 viz., that if a frog be poisoned after division of the posterior
roots of all the spinal nerves, while the anterior roots are left un-
touched, death takes place as usual, but is not preceded by any con-
vulsions. In this instance the convulsions are absent simply
because, owing to the division of the posterior roots, external irri-
tations cannot be communicated to the cord.

The reflex action, above described, may be seen very distinctly
in the human subject, in certain cases of disease of the spinal cord.
If the upper portion of the cord be disintegrated by inflammatory
softening, so that its middle and lower portions lose their natural
connection with the brain, paralysis of voluntary motion and loss of
sensation ensue in all parts of the body below the seat of the ana-
tomical lesion. Under these conditions, the patient is incapable of
making any muscular exertion in the paralyzed parts, and is uncon-
scious of any injury done to the integument in the same region.
Notwithstanding this, if the soles of the feet be gently irritated
with a feather, or with the point of a needle, a convulsive twitch-
ing of the toes will often take place, and even retractile movements
of the leg and thigh, altogether without the patient's knowledge.
Such movements may frequently be excited by simply allowing
the cool air to come suddenly in contact with the lower extremities.
We have repeatedly witnessed these phenomena, in a case of dis-
ease of the spinal cord, where the paralysis and insensibility of the
lower extremities were complete. Many other similar instances
are reported by various authors.

The existence of this reflex action of the cord has enabled the
physiologist to ascertain several other important facts concerning
the mode of operation of the nervous system. M. Bernard has
demonstrated,2 by a series of extremely ingenious experiments on
the action of poisonous substances, 1st, that the irritability of the
muscles may be destroyed, while that of the nerves remains unal-

1 Lemons sur les effets des Substances toxiques et medicamenteuses, Paris, 1857,
p. 357.

2 Ibid., Chaps. 23 and 24.

412

THE SPINAL CORD.

Fig. 137.

tered ; and 2d, that the motor and sensitive nervous filaments may
be paralyzed independently of each other. The above facts are
shown by the three following experiments : —

1. In a living frog (Fig. 137), the sciatic nerve (N) is exposed in
the back part of the thigh, after which a ligature is passed under-
neath it and drawn tight around the bone and the remaining soft
parts. In this way the circulation is entirely cut off from the limb
(d), which remains in connection with the trunk only by means of
the sciatic nerve. A solution of sulphocyanide of potassium is then

introduced beneath the skin
of the back, at I, in sufficient
quantity to produce its speci-
fic effect. The poison is then
absorbed, and is carried by
the circulation throughout the
trunk and the three extremi-
ties a, b, c ; while it is pre-
vented from entering the limb
d, by the ligature which has
been placed about the thigh.
Sulphocyanide of potassium
produces paralysis, as we have
previously mentioned, by act-
ing directly upon the muscu-
lar tissue. Accordingly, a gal-
vanic discharge passed through
the limbs a, b, and c, produces
no contraction in them, while
the same stimulus, applied to
d, is followed by a strong and
healthy reaction, But at the
moment when the irritation
is applied to the poisoned
limbs a, b, and c, though no
visible effect is produced in
them, an active movement
takes place in the healthy
limb, d. This can only be
owing to a reflex action of the spinal cord, originating in the inte-
gument of a, b, and c, and transmitted, by sensitive and motor fila-
ments, through the cord to d. While the muscles of the poisoned

REFLEX ACTION OF THE SPINAL CORD. 413

limbs, therefore, have been directly paralyzed, the nerves of the same
parts have retained their irritability.

2. If a frog be poisoned with woorara by simply placing the
poison under the skin, no reflex action of the spinal cord can be
demonstrated after death. We have already shown, from experi-
ments detailed in Chapter II., that this substance destroys the irrita-
bility of the motor nerves, without affecting that of the muscles. In
the above instance, therefore, where the reflex action is abolished, its
loss may be owing to a paralysis of both motor and sensitive fila-
ments, or to that of the motor filaments alone. The following experi-
ment, however, shows that the motor filaments are the only ones
affected. If a frog be prepared as in Fig. 137, and poisoned by the
introduction of woorara at /, when the limb d is irritated its own
muscles react, while no movement takes place in a, b, or c ; but if
the irritation be applied to a, b, or c, reflex movements are imme-
diately produced in d. In the poisoned limbs, therefore, while the
motor nerves have been paralyzed, the sensitive filaments have retained
their irritability.

3. If a frog be poisoned with strychnine, introduced underneath
the skin in sufficient quantity, death takes place after general con-
vulsions, which are due, as we have seen above, to an unnatural
excitability of the reflex action. This is followed, however, by a
paralysis of sensibility, so that after death no reflex movements
can be produced by irritating the skin or even the posterior roots
of the spinal nerves. But if the anterior roots, or the motor nerves
themselves be galvanized, contractions immediately take place in
the corresponding muscles. In this case, therefore, the sensitive fila-
ments have been paralyzed, while the motor filaments and the muscles
have retained their irritability.

AVe now come to investigate the reflex action of the spinal cord,
as it takes place in a healthy condition during life. This action
readily escapes notice, unless our attention be particularly directed
to it, because the sensations which we are constantly receiving, and
the many voluntary movements which are continually executed,
serve naturally to mask those nervous phenomena which take place
without our immediate knowledge, and over which we exert no
voluntary control. Such phenomena, however, do constantly take
place, and are of extreme physiological importance. If the surface
of the skin, for example, be at any time unexpectedly brought in
contact with a heated body, the injured part is often withdrawn by
a rapid and convulsive movement, long before we feel the pain, or

41-i THE SPINAL CORD.

even fairly understand the cause of the involuntary act. If the
body by any accident suddenly and unexpectedly loses its balance,
the limbs are thrown into a position calculated to protect the ex-
posed parts, and to break the fall, by a similar involuntary and in-
stantaneous movement. The brain does not act in these cases, for
there is no intentional character in the movement, nor even any
complete consciousness of its object. Everything indicates that it
is the immediate result of a simple reflex action of the spinal cord.

The cord exerts also an important and constant influence upon
the sphincter muscles. The sphincter ani is habitually in a state of
contraction, so that the contents of the intestine are not allowed to
escape. When any external irritation is applied to the anus, or
whenever the feces present themselves internally, the sphincter
contracts involuntarily, and the discharge of the feces is prevented.
I This habitual closure of the sphincter depends on the reflex action
of the spinal cord. It is entirely an involuntary act, and will con*
tinue, in the healthy condition, during profound sleep, as complete
and efficient as in the waking state.

When the rectum, however, has become filled by the accumula-
tion of feces from above, the nervous action changes. Then the
impression produced on the mucous membrane of the distended
rectum, conveyed to the spinal cord, causes at the same time re-
laxation of the sphincter and contraction of the rectum itself; so
that a discharge of the feces consequently takes place.

Now all these actions are to some extent under the control of
sensation and volition. The distended state of the rectum is usually
accompanied by a distinct sensation, and the resistance of the
sphincter may be voluntarily prolonged for a certain period, just as
the respiratory movements, which are. usually involuntary, may be
intentionally hastened or retarded, or even temporarily suspended.
But this voluntary power over the sphincter and the rectum is
limited. After a time the involuntary impulse, growing more
urgent with the increased distension of the rectum, becomes irre-
sistible ; and the discharge finally takes place by the simple reflex
action of the spinal cord.

If the spinal cord be injured in its middle or upper portions, the
sensibility and voluntary action of the sphincter are lost, because its
connection with the brain has been destroyed. The evacuation
then takes place at once, by the ordinary mechanism, as soon as
the rectum is filled, but without any knowledge on the part of the

REFLEX ACTION OF THE SPINAL CORD. 415

patient. The discharges are then said to be " involuntary and un-
conscious."

If the irritability of the cord, on the other hand, be exaggerated
by disease, while its connection with the brain remains entire, the
distension of the rectum is announced by the usual sensation, but
the reflex impulse to evacuation is so urgent that it cannot be
controlled by the will, and the patient is compelled to allow it to
take place at once. The discharges are then said to be simply
" involuntary."

Finally, if the substance of the spinal cord be extensively de-
stroyed by accident or disease, the sphincter is permanently relaxed.
The feces are then evacuated almost continuously, without any
knowledge or control on the part of the patient, as fast as they
descend into the rectum from the upper portions of the intestine.

Injury of the spinal cord produces a somewhat different effect on
the urinary bladder. Its muscular fibres are directly paralyzed ;
and the organ, being partially protected by elastic fibres, both at
its own orifice and along the urethra, becomes gradually distended
by urine from the kidneys. The urine then overcomes the elas-
ticity of the protecting fibres, by simple force of accumulation, and
afterward dribbles away as fast as it is excreted by the kidneys.
Paralysis of the bladder, therefore, first causes a permanent disten-
sion of the organ, which is afterward followed by a continuous,
passive, and incomplete discharge of its contents.

Injury of the spinal cord produces also an important, though
probably an indirect effect on nutrition, secretion, animal heat, &c.,
in the paralyzed parts. Diseases of the cord which result in its
softening or disintegration, are notoriously accompanied by consti-
pation, often of an extremely obstinate character. In complete
paraplegia, also, the lower extremities become emaciated. The
texture and consistency of the muscles are altered, and the animal
temperature is considerably reduced. All such disturbances of
nutrition, however, which almost invariably follow upon local para-
lysis, are no doubt immediately owing to the inactive condition of
the muscles ; a condition which naturally induces debility of the
circulation, and consequently of all those functions which are de-
pendent upon it.

It is less easy to explain the connection between injury of the
spinal cord and ij>%mmatirm pf t.fre urinary passages. It is, how-
ever, a matter of common observation among pathologists, that
injury or disease of the cord, particularly in the dorsal and u

416 THE SPINAL CORD.

lumbar regions, is soon followed by catarrhal inflammation of the
urinary passages. This gives rise to an abundant production of
altered mucus, which in its turn, by causing an alkaline fermenta-
tion of the urine contained in the bladder, converts it into an irri-
tating and ammoniacal liquid, which reacts upon the mucous mem-
brane and aggravates the previous inflammation.

We find, therefore, that the spinal cord, in its character of a
nervous centre, exerts a general protective action over the whole
body. It presides over the involuntary movements of the limbs
and trunk ; it regulates the action of the sphincters, the rectum,
and the bladder ; while at the same time it exerts an indirect influ-
ence on the nutritive changes in those parts which it supplies with
nerves.

THE BRAIN. 417

CHAPTER IV.

THE BRAIN.

BY the brain, or encephalon, as it is sometimes called, we mean all
that portion of the nervous system which is situated within the
cavity of the cranium. It consists, as we have already shown, of
a series of different ganglia, connected with each other by transverse
and longitudinal commissures.

Since we have found the functions of sensation and motion, or
sensibility and excitability, so distinctly separated in the spinal
cord, we should expect to find the same distinction in the interior
of the brain. These two properties have indeed been found to be
distinct from each other, so far as they exist at all, in the encephalic
mass ; but it is a very remarkable fact that they are both confined
to very small portions of the brain, in comparison with its entire
bulk. According to the investigations of Longet, neither the
olfactory ganglia, the corpora striata, the optic thalami, the tuber-
cula quadrigemina, nor the white or gray substance of the cerebrum
or the cerebellum, are in the least degree excitable. Mechanical
irritation of these parts does not produce the slightest convulsive
movement in the muscles below. The application of caustic liquids
and the passage of galvanic currents are equally without effect.
The only portions of the brain in which irritation is followed by
convulsive movements are the anterior surface of the medulla ob-
longata, the tuber annulare, and the lower part of the crura cerebri ;
that is, the lower and central parts of the brain, containing continu-
ations of the anterior columns of the cord. On the other hand,
neither the olfactory ganglia, the corpora striata, the tubercula
quadrigemina, nor the white or gray substance of the cerebrum or
cerebellum, give rise, on being irritated, to any painful sensation.
The only sensitive parts are the posterior surface of the medulla
oblongata, the restiform bodies, the processus e cerebello ad testes,
and the upper part of the crura cerebri ; that is, those portions of
the base of the brain which contain prolongations of the posterior
columns of the cord.
27

418 THE BRAIN.

The most central portions of the nervous system, therefore, and
particularly the gray matter, are destitute of both excitability and
sensibility. It is only those portions which serve to conduct sen-
sations and nervous impulses that can be excited by mechanical
irritation ; not the ganglionic centres themselves, which receive and
originate the nervous impressions.

"We shall now ^tudy in succession the different ganglia of which
the brain is composed.

OLFACTORY GANGLIA. — These ganglia, which in some of the
lower animals are very large, corresponding in size with the ex-
tent of the olfactory membrane and the acuteness of the sense of
smell, are very small in the human subject. They are situated on
the cribriform plate of the ethmoid bone, on each side of the crista
galli, just beneath the anterior lobes of the cerebrum. They send
their nerves through the numerous perforations which exist in the
ethmoid bone at this part, and are connected with the base of the
brain by two longitudinal commissures. The olfactory ganglia
with their commissures are sometimes spoken of as the " olfactory
nerves." They are not nerves, however, but ganglia, since they are
mostly composed of gray matter ; and the term " olfactory nerves"
can be properly applied only to the filaments which originate from
them, and which are afterward spread out in the substance of the
olfactory membrane.

It has been found difficult to determine the function of these
ganglia by direct experiment on the lower animals. They may be
destroyed by means of a strong needle introduced through the bones
of the cranium ; but the signs of the presence or absence of the
sense of smell, after such an operation, are too indefinite to allow us
to draw from them a decided conclusion. The anatomical distribu-
tion of their nerves, however, and the evident correspondence which
exists, in different species of animals, between their degree of de-
velopment and that of the external olfactory organs, leaves no doubt
as to their true function. They are the ganglia of the special sense
of smell, and are not connected, in any appreciable degree, with
ordinary sensibility, nor with the pcoduction of voluntary move-
ments.

OPTIC THALAMI. — These bodies are jjot, as their name would
imply, the ganglia of vision. Longet has found that the power of
sight and the sensibility of the pupil both remain, in birds, after

CORPORA STRIATA. — HEMISPHERES. 419

the optic thalami have been thoroughly disorganized ; and that arti-
ficial irritation of the same ganglia has no effect in producing
either contraction or dilatation of the pupil. The optic thalami,
however, according to the same observer, have a peculiar crossed
action upon the voluntary movements. If both hemispheres and
both optic thalami be removed in the rabbit, the animal is still
capable of standing and of using his limbs in progression. But if
the right optic thalamus alone be removed, the animal falls at once
upon his left side ; and if the left thalamus be destroyed, a similar
debility is manifest on the right side of the body. In these in-
stances there is no absolute paralysis of the side upon which the
animal falls, but rather a simple want of balance between the two
opposite sides. The exact mechanism of this peculiar functional
disturbance is not well understood ; and but little light has yet
been thrown, either by direct experiment or by the facts of compa-
rative anatomy, on the real function of the optic thalami.

CORPORA STRIATA, — The function of these ganglia is equally
uncertain with that of the preceding. They are traversed, as we
have already seen, by fibres coming from the anterior columns of
the cord; and they are connected, by the continuation of these
fibres, with the gray substance of the hemispheres. They have
therefore, in all probability, like the optic thalami, some connection
with sensation and volition ; but the precise nature of this connec-
tion is at present altogether unknown.

HEMISPHERES. — The hemispheres, or the cerebral ganglia, con-
stitute in the human subject about nine-tenths of the whole mass
of the brain. Throughout their whole extent they are entirely
destitute, as we have already mentioned, of both sensibility and ex-
citability. Both the white and gray substance may be wounded,
burned, lacerated, crushed, or galvanized in the living animal, with-
out exciting any convulsive movement or any apparent sensation.
In the human subject a similar insensibility has been observed
when the substance of the hemispheres has been exposed by acci-
dental violence, or in the operation of trephining.

Yery severe mechanical injuries may also be inflicted upon the
hemispheres, even in the human subject, without producing any
directly fatal result. One of the most remarkable instances of this
fact is a case reported by Prof. William Detmold, of New York,1 in

1 Am. Journ. of Med. Sci., January, 1850.

420 THE BRAIN.

which an abscess in the anterior lobe of the brain was opened by an
incision passing through the cerebral substance, not only without
any immediate bad effect, but with great temporary relief to the
patient. This was the case of a laborer who was struck on the left
side of the forehead by a piece of falling timber, which produced a
compound fracture of the skull at this part. One or two pieces of
bone afterward became separated and were removed, and the wound
subsequently healed. Nine weeks after the accident, however,
headache and drowsiness came on ; and the latter symptom, becom-
ing rapidly aggravated, soon terminated in complete stupor. At
this time, the existence of an abscess being suspected, the cicatrix,
together with the adherent portion of the dura mater, was dissected
away, several pieces of fractured bone removed, and the surface of
the brain exposed. A knife was then passed into the cerebral sub-
stance, making a wound one inch in length and half an inch in
depth, when the abscess was reached and over two ounces of pus
discharged. The patient immediately aroused from his comatose
condition, so that he was able to speak ; and in a few days reco-
vered, to a very considerable extent, his cheerfulness, intelligence,
and appetite. Subsequently, however, the collection of pus re-
turned, accompanied by a renewal of the previous symptoms ; and
the patient finally died at the end of seven weeks from the time of
opening the abscess.

Another and still more striking instance of recovery from severe
injury of the brain is reported by Prof. H. J. Bigelow in the
American Journal of Medical Sciences for July, 1850. In this case, a
pointed iron bar, three feet and a half in length, and one inch and a
quarter in diameter, was driven through the patient's head by the
premature blasting of a rock. The bar entered the left side of the
face, just in front of the angle of the jaw, and passed obliquely
upward, inside the zygomatic arch and through the anterior part
of the cranial cavity, emerging from the top of the frontal bone on
the median line, just in front of the point of union of the coronal
and sagittal sutures. The patient was at first stunned, but soon
recovered himself so far as to be able to converse intelligently, rode
home in a common cart, and with a little assistance walked up stairs
to his room. He became delirious within two days after the acci-
dent, and subsequently remained partly delirious and partly coma-
tose for about three weeks. He then began to improve, and at the
end of rather more than two months from the date of the injury,
was able to walk about. At the end of sixteen months he was in

HEMISPHERES. 421

perfect health, with the wounds healed, and with the mental and
bodily functions entirely unimpaired, except that sight was perma-
nently lost in the eye of the injured side.

The hemispheres, furthermore, are not the seat of sensation or of
volition, nor are they immediately essential to the continuance of
life. In quadrupeds, the complete removal of the hemispheres is
attended with so much hemorrhage that the operation is generally
fatal from this cause within a few minutes. In birds, however, it
may be performed without any immediate danger to life. Longet
has removed the hemispheres in pigeons and fowls, and has kept
these animals afterward for several days, with most of the organic
functions unimpaired. We have frequently performed the same
experiment upon pigeons, with a similar favorable result.

The effect of this mutilation is simply to plunge the animal into
a state of profound stupor, in which he is almost entirely inatten-
tive to surrounding objects. The bird remains sitting motionless
upon his perch, or standing upon the ground, with the eyes closed,
and the head sunk between the shoulders. (Fig. 138.) The plu-

Fig. 138.

PIGEON, AFTER REMOVAL OF THE HEMISPHERES.

mage is smooth and glossy, but is uniformly expanded, by a kind
of erection of the feathers, so that the body appears somewhat
puffed out, and larger than natural. Occasionally the bird opens
his eyes with a vacant stare, stretches his neck, perhaps shakes his
bill once or twice, or smooths down the feathers upon his shoulders,
and then relapses into his former apathetic condition. This state
of immobility, however, is not accompanied by the loss of sight, of

422 THE BBAIIST.

hearing, or of ordinary sensibility. All these functions remain, as
well as that of voluntary motion. If a pistol be discharged behind
the back of the animal, he at once opens his eyes, moves his head
half round, and gives evident signs of having heard the report ; but
he immediately becomes quiet again, and pays no farther attention
to it. Sight is also retained, since the bird will sometimes fix its
eye on a particular object, and watch it for several seconds together.
Longet has even found that by moving a lighted candle before the
animal's eyes in a dark place, the head of the bird will often follow
the movements of the candle from side to side or in a circle, showing
that the impression of light is actually perceived by the sensorium.
Ordinary sensation also remains, after removal of the hemispheres,
together with voluntary motion. If the foot be pinched with a
pair of forceps, the bird becomes partially aroused, moves uneasily
once or twice from side to side, and is evidently annoyed at the
irritation.

The animal is still capable, therefore, after removal of the hemi-
spheres, of receiving sensations from external objects. But these
sensations appear to make upon him no lasting impression. He is
incapable of connecting with his perceptions any distinct succession
of ideas. He hears, for example, the report of a pistol, but he is not
alarmed by it ; for the sound, though distinctly enough perceived,
does not suggest any idea of danger or injury. There is accord-
ingly no power of forming mental associations, nor of perceiving
the relation between external objects. The memory, more particu-
larly, is altogether destroyed, and the recollection of sensation is
not retained from one moment to another. The limbs and muscles
are still under the control of the will ; but the will itself is inactive,
because apparently it lacks its usual mental stimulus and direction.
The powers which have been lost, therefore, by destruction of the
cerebral hemispheres, are altogether of a mental or intellectual
character ; that is, the power of comparing with each other different
ideas, and of perceiving the proper relation between them.

The same result is well known to follow, in the human subject,
from injury or disease of these parts. A disturbance of the mental
powers has long been recognized as the ordinary consequence of
lesions of the brain. In cases of impending apoplexy, for example,
or of softening of the cerebral substance, among the earliest and
most constant phenomena is a loss or impairment of the memory.
The patient forgets the names of particular objects or of particular
persons ; or he is unable to calculate numbers with his usual facility.

HEMISPHERES. 423

His mental derangement is often shown in the undue estimate which
he forms of passing events. He is no longer able to appreciate the
true relation between different objects and different phenomena.
Thus, he will show an exaggerated degree of solicitude about a
trivial occurrence, and will pay no attention to other matters of
real importance. As the difficulty increases, he becomes careless
of the directions and advice of his attendants, and must be watched
and managed like a child or an imbecile. After a certain period,
he no longer appreciates the lapse of time, and even loses the dis-
tinction between day and night. Finally, when the injury to the
hemispheres is complete, the senses may still remain active and
impressible, while the patient is completely deprived of intelligence,
memory, and judgment.

If we examine the comparative development of the hemispheres
in different species of animals, and in different races of men, we
shall find that the size of these ganglia corresponds very closely
with the degree of intelligence possessed by the individual. We
have already traced, in a preceding chapter, the gradual increase
in size of the hemispheres in fish, reptiles, birds, and quadrupeds :
four classes of animals which may be arranged, with regard to the
amount of intelligence possessed by each, in precisely the same
order of succession. Among quadrupeds, the elephant has much
the largest and most perfectly formed cerebrum, in proportion to
the size of the entire body ; and of all quadrupeds he is proverbially
the most intelligent and the most teachable. It is important to
observe in this connection, that the kind of intelligence which
characterizes the elephant and some other of the lower animals,
and which most nearly resembles that of man, is a teachable intelli-
gence ; a very different thing from the intelligence which depends
upon instinct, such as that of insects, for example, or birds of pas-
sage. Instinct is unvarying, and always does the same thing in the
same manner, with endless repetition ; but intelligence is a power
which adapts itself to new circumstances, and enables its possessor,
by comprehending and retaining new ideas, to profit by experience.
It is this quality which distinguishes the higher classes of animals
from the lower ; and which, in a very much greater degree, con-
stitutes the intellectual superiority of man himself. The size of
the cerebrum in man is accordingly very much greater, in propor-
tion to that of the entire body, than in any of the lower animals :
while other parts of the brain, on the contrary, such as the olfactory
ganglia or the optic tubercles, are frequently smaller in him than

424 THE BRAIN.

in them. For while man is superior in general intelligence to all
the lower animals, he is inferior to many of them in the acuteness
of the special senses.

As a general rule, also, the size of the cerebrum in different
races and in different individuals corresponds with the grade of
their intelligence. The size of the cranium, as compared with that
of the face, is smallest in the savage negro and Indian tribes ; larger
in the civilized or semi-civilized Chinese, Malay, Arab, and Japan-
ese ; while it is largest of all in the enlightened European races.
This difference in the development of the brain is not probably an
effect of long-continued civilization or otherwise ; but it is, on the
contrary, the superiority in cerebral development which makes
some races readily susceptible of civilization, while others are
either altogether incapable of it, or can only advance in it to a
certain limit. Although all races therefore may, perhaps, be said
to start from the same level of absolute ignorance, yet after the
lapse of a certain time one race will have advanced farther in
civilization than another, owing to a superior capacity for improve-
ment, dependent on original organization.

The same thing is true with regard to different individuals. At
birth, all men are equally ignorant ; and yet at the end of a certain
period one will have acquired a very much greater intellectual
power than another, even under similar conditions of training,
education, &c. He has been able to accumulate more information
from the same sources, and to use the same experience to better
advantage than his associates ; and the result of this is a certain
intellectual superiority, which becomes still greater by its own
exercise. This superiority, it will be observed, lies not so much
in the power of perceiving external objects and events, and of re-
cognizing the connection between them, as in that of drawing con-
clusions from one fact to another, and of adapting to new combina-
tions the knowledge which has already been acquired.

It is this particular kind of intellectual difference, existing in a
marked degree, between animals, races, and individuals, which cor-
responds with the difference in development of the cerebral hemi-
spheres. We have, therefore, evidence from three different sources
that the cerebral hemispheres are the seat of the reasoning powers,
or of the intellectual faculties proper. First, when these ganglia
are removed in the lower animals, the intellectual faculties are the
only ones which are lost. Secondly, injury to these ganglia, in the
human subject, is followed by a corresponding impairment of the

HEMISPHERES. 425

same faculties. Thirdly, in different species of animals, as well as
in different races of men and in different individuals, the develop-
ment of these faculties is in proportion to that of the cerebral
h

lat the hemispheres are the seat of the
mory, reason, judgment, and the like,
faculties are, strictly speaking, located
spheres, or that they belong directly to
mispheres are composed. The hemi-
y the instruments through which the
themselves, and which are accordingly
If these instruments be imperfect in
any manner by violence or disease, the
are affected in a corresponding degree.

J ;al faculties are the subject of physio-

logical research and experiment, they are necessarily connected
with the hemispherical ganglia; and the result of investigation
shows this connection to be extremely intimate and important in
its character.

There are, however, various circumstances which modify, in
particular cases, the general rule given above, viz., that the larger
the cerebrum the greater the intellectual superiority. The func-
tional activity of the brain is modified, no doubt, by its texture as
well as by its size ; and an increased excitability may compensate,
partially or wholly, for a deficiency in bulk. This fact is some-
times illustrated in the case of idiots. There are instances where
idiotic children with small brains are less imbecile and helpless
than others with a larger development, owing to a certain vivacity
and impressibility of organization which take the place, to a certain
extent, of the purely intellectual faculties.

This was the case, in a marked degree, with a pair of dwarfed
and idiotic Central American children, who were exhibited some
years ago in various parts of the United States, under the name of
the "Aztec children." They were a boy and a girl, aged respectively
about seven and five years. The boy was 2 feet 9} inches high, and
weighed a little over 20 pounds. The girl was 2 feet 5J inches
high, and weighed 17 pounds. Their bodies were tolerably well
proportioned, but the cranial cavities, as shown by the accompany-
ing portraits, were extremely small.

The antero-posterior diameter of the boy's head was only 4J
inches, the transverse diameter less than 4 inches. The antero-

426

THE BRAIN.

posterior diameter of the girl's head was 4J inches, the transverse
diameter only 3f inches. The habits of these children, so far as
regards feeding and taking care of themselves, were those of chil-

Fig. 139.

AZTEC CHILDREN. — Taken from life, at five and seven years of age.

dren two or three years of age. They were incapable of learning
to talk, and could only repeat a few isolated words. Notwithstand-
ing, however, the extremely limited range of their intellectual
powers, these children were remarkably vivacious and excitable.
While awake they were in almost constant motion, and any new
object or toy presented to them immediately attracted their atten-
tion, and evidently awakened a lively curiosity. They were ac-
cordingly easily influenced by proper management, and understood
readily the meaning of those who addressed them, so far as this
meaning could be conveyed by gesticulation and the tones of the
voice. Their expression and general appearance, though decidedly
idiotic, were not at all disagreeable or repulsive ; and they were
much less troublesome to the persons who had them in charge than
is often the case with idiots possessing a larger cerebral development.

It may also be observed that the purely intellectual or reasoning
powers are not the only element in the mental superiority of certain
races or of particular individuals over their associates. There is
also a certain rapidity of perception and strength of will which may
sometimes overbalance greater intellectual acquirements and more
cultivated reasoning powers. These, however, are different facul-
ties from the latter ; and occupy, as we shall hereafter see, different
parts of the encephalon.

A very remarkable physiological doctrine, dependent partly on
the foregoing facts, was brought forward some years ago by Gall

HEMISPHERES. 427

and Spurzheim, under the name of Phrenology. These observers
recognized the fact that the intellectual powers are undoubtedly
seated in the brain, and that the development of the brain is, as a
general rule, in correspondence with the activity of .these powers.
They noticed also that in other parts of the nervous system, different
functions occupy different situations ; and regarding the mind as
made up of many distinct mental faculties, they conceived the idea
that these different faculties might be seated in different parts of
the cerebral mass. If so, each separate portion of the brain would
undoubtedly be more or less developed in proportion to the activity
of the mental trait or faculty residing in it. The shape of the head
would then vary in different individuals, in accordance with their
mental peculiarities ; and the character and endowments of the in-
dividual might therefore be estimated from an examination of the
elevations and depressions on the surface of the cranium.

Accordingly, the authors of this doctrine endeavored, by examin-
ing the heads of various individuals whose character was already
known, to ascertain the location of the different mental faculties.
In this manner they finally succeeded, as they supposed, in accom-
plishing their object; after which they prepared a chart, in which
the surface of the cranium was mapped out into some thirty or forty
different regions, corresponding with as many different mental traits
or faculties. With the assistance of this chart it was thought that
phrenology might be practised as an art ; and that, by one skilled
in its application, the character of a stranger might be discovered
by simply examining the external conformation of his head.

We shall not expend much time in discussing the claims of phre-
nology to rank as a science or an art, since we believe that it has
of late years been almost wholly discarded by scientific men, owing
to the very evident deficiencies of the basis upon which it was
founded. Passing over, therefore, many minor details, we will
merely point out, as matters of physiological interest, the principal
defects which must always prevent the establishment of phrenology
as a science, and its application as an art.

First, though we have no reason for denying that different parts
of the brain may be occupied by different intellectual faculties,
there is no direct evidence which would show this to be the case.
Phrenologists include, in those parts of the brain which they em-
ploy for examination, both the cerebrum and cerebellum ; and they
justly regard the external parts of these bodies, viz., the layer of
gray matter which occupies their surface, as the ganglionic portion

428

THE BRATN.

in which must reside more especially the nervous functions which
they possess. But this layer of gray matter, in each principal por-
tion of the brain, is continuous throughout. There is no anatomical
division or limit between its different parts, like those between
the different ganglia in other portions of the nervous system ; and
consequently such divisions of the cerebrum and cerebellum must
be altogether arbitrary in character, and not dependent on any
anatomical basis.

Secondly, the only means of ascertaining the location of the
different mental traits, supposing them to occupy different parts of
the brain, would be that adopted by Gall and Spurzheim, viz., to
make an accurate comparison, in a sufficient number of cases, of the
form of the head in individuals of known character. But the prac-
tical difficulty of accomplishing this is very great. It requires a
long acquaintance and close observation to learn accurately the
character of a single person ; and it is in this kind of observation,
more than in any other, that we are proverbially liable to mistakes.
It is extremely improbable, therefore, that either Gall or Spurzheim
could, in a single lifetime, have accomplished this comparison in so
many instances as to furnish a reliable basis for the construction of
a phrenological chart.

A still more serious practical difficulty, however, is the following.
The different intellectual faculties being supposed to reside in the
layer of gray substance constituting the surfaces of the cerebrum

and cerebellum, they must of course be
distributed throughout this layer, where-
ever it exists. Gall and Spurzheim
located all the mental faculties in those
parts of the brain which are accessible
to external exploration. An examina-
tion of different sections of the brain
will show, however, that the greater por-
tion of the gray substance is so placed,
that its quantity cannot be estimated by
an external examination through the
skull. The only portions which are
exposed to such an examination are the

Diagram of the BRAIN r* .if*. 3 j fe j portions Qf tbe con.

shuwmg those portions which are ex- ^r

posed to examination. vcxities of the hemispheres, together

with the posterior edge and part of the
under surface of the cerebellum. (Fig. 140.) ^ A very extensive

Fig. 140.

HEMISPHERES.

429

portion of the cerebral surface, however, remains concealed in such
a manner that it cannot possibly be subjected to examination, viz.,
the entire base of the brain, with the under surface of the ante-
rior and middle lobes (i, 2); the upper surface of the cerebellum
(3) and the inferior surface of the posterior lobe of the cerebrum
which covers it (4) ; that portion of the cerebellum situated above the
medulla oblongata(o); and the two opposite convoluted surfaces in
the fissure of Sylvius (e, 7), where the anterior and middle lobes of
the cerebrum lie in contact with each other. The whole extent,
also, of the cerebral surfaces which are opposed to each other in the
great longitudinal fissure (Fig. 141), throughout its entire length,
are equally protected by their position, and
concealed from external examination. The
whole of the convoluted surface of the brain
must, however, be regarded as of equal im-
portance in the distribution of the mental
qualities; and yet it is evident that not
more than one-third or one-quarter of this
surface is so placed that it can be examined
by external manipulation. It must further-
more be recollected that the gray matter of
the cerebrum and cerebellum is everywhere
convoluted, and that the convolutions pene-
trate to various depths in the substance of
the brain. Even if we were able to feel, therefore, the external
surface of the brain itself, it would not be the entire convolutions,
but only their superficial edges, that we should really be able to
examine. And yet the amount of gray matter contained in a given
space depends quite as much upon the depth to which the convolu-
tions penetrate, as upon the prominence of their edges.

While phrenology, therefore, is partially founded upon acknow-
ledged physiological facts, there are yet essential deficiencies in its
scientific basis, as well as insurmountable difficulties in the way of
its practical application.

CEREBELLUM. — The cerebellum is the second ganglion of the
encephalon, in respect to size. If it be examined, moreover, in
regard to the form and disposition of its convolutions, it will be
seen that these are much more complicated and more numerous
than in the cerebrum, and penetra£3 much deeper into its substance.
Though the cerebellum therefore is smaller, as a whole, than the

Transverse section of B K A i x,
showing depth of great longi-
tudinal fissure, at a.

430 THE BRAIN.

cerebrum, it contains, in proportion to its size, a much larger quan-
tity of gray matter.

In examining the comparative development of the brain, also, in
different classes and species of animals, we find that the cerebellum
nearly always keeps pace, in this respect, with the cerebrum. These
facts would lead us to regard it as a ganglion hardly secondary in
importance to the cerebrum itself.

Physiologists, however, have thus far failed to demonstrate the
nature of its function with the same degree of precision as that of
many other parts of the brain. The opinion of Gall, which located
in the cerebellum the sexual impulse and instincts, is at the present
day generally abandoned ; for the reason that it has not been found
to be sufficiently supported by anatomical and experimental facts,
many of which are indeed directly opposed to it. The opinion
which has of late years been received with the most favor is that
first advocated by Flourens, which attributes to the cerebellum the
power of associating or "co-ordinating" the different voluntary
movements.

It is evident, indeed, that such a power does actually reside in
some part of the nervous system. No movements are effected by
the independent contraction of single muscles; but always by
several muscles acting in harmony with each other. The number
and complication of these associated movements vary in different
classes of animals. In fish, for example, progression is accom-
plished in the simplest possible manner, viz., by the lateral flexion
and extension of the vertebral column. In serpents it is much the
same. In frogs, lizards, and turtles, on the other hand, the four
jointed extremities come into play, and the movements are some-
what complicated. They are still more so in birds and quadrupeds;
and finally, in the human subject they become both varied and
complicated in the highest degree. Even in maintaining the ordi-
nary postures of standing and sitting, there are many different mus-
cles acting together, in each of which the degree of contraction, in
order to preserve the balance of the body, must be accurately pro-
portioned to that of the others. In the motions of walking and
running, or in the still more delicate movements of the hands and
fingers, this harmony of muscular action becomes still more evident,
and is seen also to be absolutely indispensable to the efficiency of
the muscular apparatus.

The opinion which locates the above harmonizing or associating
power in the cerebellum was first suggested by the effects observed

CEREBELLUM. 431

after experimentally injuring or destroying this part of the brain.
If the cerebellum be exposed in a living pigeon, and a portion of
its substance removed, the animal exhibits at once a peculiar un-
certainty in his gait, and in the movement of his wings. If the
injury be more extensive, he loses altogether the power of flight,
and can walk, or even stand, only with great difficulty. This is not
owing to any actual paralysis, for the movements of the limbs are
exceedingly rapid and energetic ; but is due to a peculiar want of
control over the muscular contractions, precisely similar to that
which is seen in a man in a state of intoxication. The movements
of the legs and wings, though forcible and rapid, are confused and
blundering ; so that the animal cannot direct his steps to any par-
ticular spot, nor support himself in the air by flight. He reels and
tumbles, but can neither walk nor fly.

Fig. 142.

PIGEON, AFTER REMOVAL OF THE CEREBELLUM.

The senses and intelligence at the same time are unimpaired. It
is extremely curious, as first remarked by Longet, to compare the
different phenomena produced by removal of the cerebrum and
that of the cerebellum. If we do these operations upon two dif-
ferent pigeons, and place the animals side by side, it will be seen
that the first pigeon, from whom the cerebrum only has been re-
moved, remains standing firmly upon his feet, in a condition of
complete repose ; and that when aroused and compelled to stir, he

432 THE BRAIN.

moves sluggishly and unwillingly, but otherwise acts in a perfectly
natural manner. The second pigeon, on the other hand, from
whom the cerebellum only has been taken away, is in a constant
state of agitation. He is easily terrified, and endeavors, frequently
with violent struggles, to escape the notice of those who are
watching him; but his movements are sprawling and unnatural,
and are evidently no longer under the effectual control of the will.
(Fig. 142.) If the entire cerebellum be destroyed, the animal is
no longer capable of assuming or retaining any natural posture.
His legs and wings are almost constantly agitated with ineffectual
struggles, which are evidently voluntary in character, but are at
the same time altogether irregular and confused. Death generally
takes place after this operation within twenty-four hours.

We have often performed the above operation, and always with
the same effect. Indeed there are few experiments that have been
tried upon the nervous system, which give results so uniform and
so constant as this. Taken by themselves, these results would
invariably sustain the theory of Flourens, which, indeed, is founded
entirely upon them.

But we have met with another very important fact, in this respect,
which has hitherto escaped notice. That is, that birds, which have
lost their power of muscular co-ordination from injury of the cere-
bellum, may recover this power in process of time, notwithstanding that
a large portion of the cerebellum has been permanently removed.
Usually such an operation upon the cerebellum, as we have men-
tioned above, is fatal within twenty-four hours, probably on account
of the close proximity of the medulla oblongata. But in some
instances, the pigeons upon which we have operated have survived,
and in these cases the co-ordinating power became re-established.

In the first of these instances, about two-thirds of the cerebellum
was taken away, by an opening in the posterior part of the cranium.
Immediately after the operation, the animal showed all the usual
effects of the operation, being incapable of flying, walking, or even
standing still, but reeled and sprawled about in a perfectly helpless
manner. In the course of five or six days, however, he had regained
a very considerable control over the voluntary movements, and at
the end of sixteen days his power of muscular co-ordination was
so nearly perfect, that its deficiency, if any existed, was impercep-
tible. He was then killed; and on examination, it was found that
his cerebellum remained in nearly the same condition as immediately
after the operation ; about two-thirds of its substance being deficient,

CEREBELLUM. 433

and no attempt having been made at regeneration of the lost parts.
The accompanying figures, 143 to 146, show the appearances, in
this case, as compared with the brain of a healthy pigeon.

We have also met with three other cases, similar to the above, in
which about one-half of the cerebellum was removed by operation.
The loss of co-ordinating power, immediately after the operation,
though less complete than in the instance above mentioned, was
perfectly well marked in character ; and in little more tha'n a fort-
Fig. 143. F,v. 144

BRAIN- OF HEALTHY PIOEO x— Profile BRAIK OP OPERATED PIGEON—

v.ew.— 1 Hemisphere. 2 Optic tubercle. 3. Profile view— showiajf the mutilation

Cerebellum. 4. Optic nerve. 5. Medulla ob- of cerebellum.

longata.

Fig. 145. Fie. 14*3.

BRAIN OF HEALTHY PIGEOX— Poste- BRAIN OF OPERATED PIGEON—

rior view. Posterior view — showing tLe mutila-

tion of cerebellum.

night the animals had nearly or quite recovered the natural control
of their motions.

These instances show, accordingly, that a large portion of the
cerebellum may be wanting without a corresponding deficiency of
the co-ordinating power. If the theory of Flourens be correct,
therefore, these cases can only be explained by supposing that
those parts of the cerebellum which remain gradually become en-
abled to supply the place of those which are removed. It is more
probable, however, that the loss of co-ordinating power, which is
immediately produced by taking away a considerable portion of
this nervous centre, is to be regarded rather as the effect of the
sudden injury to the cerebellum as a whole, than as due to the mere
removal of a portion of its mass.
28

434 THE BRAIN.

Morbid alterations of the cerebellum, furthermore, particularly
of a chronic nature, such as slow inflammations, abscesses, tumors,
&c., have often been observed in the human subject, without giving
rise to any marked disturbance of the voluntary movements.

On the other hand, many facts derived from comparative anatomy
seem to favor the opinion of Flourens. If we compare different
classes of animals with each other, as fish with reptiles, or birds
with quadrupeds, in which the development and activity of the
entire nervous system vary extremely, the results of the comparison
will be often contradictory. But if the comparison be made be-
tween different species in which the general structure and plan of
organization are similar, we often find the development of the cere-
bellum to correspond very closely with the perfection and variety
of the voluntary movements. The frog, for example, is an aquatic
reptile, provided with anterior and posterior extremities; but its
movements, though rapid and vigorous, are exceedingly simple in
character, consisting of little else than flexion and extension of the
posterior limbs. The cerebellum in this animal is exceedingly
small, as compared with the rest of the brain ; being nothing more
than a thin, narrow ribbon of nervous matter, stretched across the
upper part of the fourth ventricle. In the common turtle we have
another aquatic reptile, where the movements of swimming, diving,
progression, &c., are accomplished by the consentaneous action of
anterior and posterior extremities, and where the motions of the
head and neck are also much more varied than in the frog. In
this instance the cerebellum is very much more highly developed
than in the former. In the alligator, again, a reptile whose motions,
both of the head, limbs, and tail, approach very closely to those of
the quadrupeds, the cerebellum is still larger in proportion to the
remaining ganglia of the encephalon.

The complete function of the cerebellum, accordingly, as a nerv-
ous centre, cannot be regarded as positively ascertained ; but so far
as we may rely on the results of direct experiment, this organ has
evidently such an intimate and peculiar connection with the volun-
tary movements, that a sudden and extensive injury inflicted upon
its substance is always followed by an immediate, though tempo-
rary, disturbance of the co-ordinating power.

TUBERCULA QUADRIGEMINA. — These bodies, notwithstanding
their small size, are very important in regard to their function.
They give origin to the optic nerves, and preside, as ganglia, over

TUBERCULA QUADRIGEMIXA. 435

the sense of sight ; on which account they are also known by the
name of the " optic ganglia." Their development corresponds very
closely with that of the external organs of vision. Thus, they are
large in fish, reptiles, and birds, in which the eyeball is for the
most part very large in proportion to the entire head; and are small
in quadrupeds and in man, where the eyeball is, comparatively
speaking, of insignificant size. Direct experiment also shows the
close connection between the tubercula quadrigemina and the sense
of sight. Section of the optic nerve at any point between the
retina and the tubercles, produces complete blindness ; and destruc-
tion of the tubercles themselves has the same effect. But if the
division be made between the tubercles and the cerebrum, or if the
cerebrum itself be taken away while the tubercles are left un-
touched, vision, as we have already seen, still remains. It is the
tubercles, therefore, in which the impression of light is perceived.
So long as these ganglia are uninjured and retain their connection
with the eye, vision remains. As soon as this connection is cut
off) or the ganglia themselves are injured, the power of vision is
destroyed.

The tubercula quadrigemina not only serve as nervous centres
for the perception of light, but a reflex action also takes place
through them, by which the quantity of light admitted to the eye
is regulated to suit the sensibility of the pupil. In darkness and
in twilight, or wherever the light is obscure and feeble, the pupil
is enlarged by relaxation of its circular fibres, so as to admit as
large a quantity of light as possible. On first coming into a dark
room, accordingly, everything is nearly invisible ; but gradually,
as the pupil dilates and as more light is admitted, objects begin to
show themselves with greater distinctness, and at last we can see
tolerably well in a place where we were at first unable to perceive
a single object. On the other hand, when the eye is exposed to an
unusually brilliant light, the pupil contracts and shuts out so much
of it as would be injurious to the retina.

The above is a reflex action, in which the impression received by
the retina is transmitted along the optic nerve to the tubercula
quadrigemina. From the tubercles, a motor impulse is then sent
out through the motor nerves of the eye and the filaments dis-
tributed to the iris, and a contraction of the pupil takes place in
consequence. The optic nerves act here as sensitive fibres, which
convey the impression from the retina to the ganglion ; and if
they be irritated in any part of their course with the point of a

THE BRAIN.

needle, the result is a contraction of the pupil. This influence is
not communicated directly from the nerve to the iris, but is first
sent inward to the tubercles, to be afterward reflected outward by
the motor nerves. So long as the eyeball remains in connection
with the brain, mechanical irritation of the optic nerve, as we have
shown above, causes contraction of the pupil ; but if the nerve be
divided, and the extremity which remains in connection with the
eyeball be subjected to irritation, no effect upon the pupil is pro-
duced.

The anatomical arrangement of the optic nerves, and the connec-
tions of the optic tubercles, are modified in a remarkable degree in
different animals, to correspond with the position of the two eyes.
In fish, for example, the eyes are so placed, on opposite sides of the
head, that their axes cannot be brought into parallelism with each
other, and the two eyes can never be directed together at the same
object. In these animals, the optic nerves cross each other at the
base of the brain without any intermixture of their fibres ; that
from the right optic tubercle passing to the left eye, and that from
the left optic tubercle passing to the right eye. (Fig. 147.) The two

Fig. 147.

Fig. 148.

INFERIOR SURFACE OF BRAIN
OF COD.— 1. Right optic nerve. 2. Left
optic nerve. 3. Right optic tubercle. 4.
Left optic tubercle. 5, 6. Hemispheres.
7. Medulla oblongata.

INFERIOR SURFACE OF BRAIN OF
FOWL. — 1. Right optic nerve. 2 Left optic
nerve. 3. Right optic tubercle. 4. Left
optic tubercle. 5, 6. Hemispheres. 7. Me-
dulla oblougata.

nervous cords are here totally distinct from each other throughout
their entire length ; and are only connected, at the point of cross-

TUBERCULA QUADRIGEMIXA. 437

ing, by intervening areolar tissue. Impressions made on the right
eye must therefore be perceived on the left side of the brain ; while
those which enter the left eye are conveyed to the right side of the
brain.

In birds, also, the axes of the two eyes are so widely divergent
that an object cannot be distinctly in focus for both of them at the
same time. The optic nerves are here united, and apparently sol-
dered together, at their point of crossing ; but the decussation of
their fibres is nevertheless complete. (Fig. 148.) The nervous fila-
ments coming from the left side pass altogether over to the right ;
and those coming from the right side pass over to the left. The
result of direct experiment on the crossed action of the tubercles in
these animals corresponds with the anatomical arrangement of the
nervous fibres. If one of the optic tubercles be destroyed in the
pigeon, complete blindness is at once produced in the eye of the
opposite side ; but vision remains unimpaired in the eye of the side
on which the injury was inflicted.

Fitr. 149.

COTRSK OF OPTIC NERVES rx MAX.— 1, 2. Right and left eyeballs. 3. Dccu sation of optic
nerve<. 4, 4. Tubercnla qnadrigemina.

In the human subject, on the other hand, where the visual axes
are parallel, and where both eyes are simultaneously directed toward

438 THE BRAIN.

the same object, the optic nerves decussate with each other in such a
manner as to form a connection between the two opposite sides, as
well as between each tubercle and retina of the same side. (Fig.
149.) This decussation, which is somewhat complicated, takes place
in the following manner. From each optic tubercle three different
bundles or " tracts" of nervous fibres are given off. One set passes
across transversely at the point of decussation, and, turning back-
ward, terminates in the tubercle of the opposite side ; another, cross-
ing diagonally, continues onward to the opposite eyeball ; while a
third passes directly forward to the eyeball of the same side. A
fourth set of fibres, still, passes across in front of the decussation,
from the retina of one eye to that of the opposite side. We have,
therefore, by this arrangement, the two retina^ as well as the two
optic tubercles, connected with each other by commissural fibres ;
while each tubercle is, at the same time, connected both with its
own retina, and with that of the opposite side. It is undoubtedly
owing to these connections that when, in the human subject, the
eyes are directed in their proper axes, the two retinae, as well as
the two optic tubercles, act as a single organ. Yision is single,
therefore, though there are two images upon the retinas. Double,
vision occurs only when the eyeballs are turned out of their proper
direction, so that the parallelism of their axes is lost, and the image
no longer falls upon corresponding parts of the two retinae.

TUBER ANNULARE. — The collection of gray matter imbedded in
the deeper portions of the tuber annulare occupies a situation near
the central part of the brain, and lies directly in the course of the
ascending fibres of the anterior and posterior columns of the cord.
This ganglion is immediately connected with the functions of sensa-
tion and voluntary motion. We have already seen that these func-
tions are not destroyed by taking away the cerebrum, and that they
also remain after removal of the cerebellum. According to the ex-
periments of Longet, even after complete removal of the olfactory
ganglia, the cerebrum, cerebellum, optic tubercles, corpora striata
and optic thalami, and when nothing remains in the cavity of the
cranium but the tuber annulare and the medulla oblongata, the
animal is still sensitive to external impressions, and will still en-
deavor by voluntary movements to escape from a painful irritation.
The same observer has found, however, that as soon as the ganglion
of the tuber annulare is broken up, all manifestations of sensation
and volition cease, and even consciousness no longer appears to

MEDULLA OBLONGATA. 439

exist. The only movements which then follow external irritation
are the occasional convulsive motions which are due to reflex action
of the spinal cord, and which may be readily distinguished from
those of a voluntary character. The animal, under these circum-
stances, is to all appearance reduced to the condition of a dead
body, except for the movements of respiration and circulation,
which still go on for a certain time. The tuber annulare must
therefore be regarded as the ganglion by which impressions, con-
veyed inward through the nerves, are first converted into conscious
sensations; and in which the voluntary impulses originate, which
stimulate the muscles to contraction.

We must carefully distinguish, however, in this respect, a simple
sensation from the ideas to which it gives origin in the mind, and
the mere act of volition from the train of thought which leads to
it. Both these purely mental operations take place, as we have
seen, in the cerebrum; for mere sensation and volition may exist
independently of any intellectual action, as they may exist after
the cerebrum has been destroyed. A sensation may be felt for
example, without our having the power of thoroughly appreciating
it, or of referring it to its proper source. This condition is often
experienced in a state of deep sleep, .when, the body being exposed
to cold, or accidentally placed in a constrained position, we feel a
sense of suffering without being able to understand its cause. We
may even, under such circumstances, execute voluntary movements
to escape the cause of annoyance ; but these movements, not being
directed by any active intelligence, fail of accomplishing their ob-
ject. We therefore remain in a state of discomfort until, on awak-
ening, the activity of the reason and judgment is restored, when the
offending cause is at once removed.

We distinguish, then, between the simple power of sensation,
and the power of fully appreciating a sensitive impression and of
drawing a conclusion from it. We distinguish also between the
intellectual process which leads us to decide upon a voluntary
movement, and the act of volition itself. The former must precede,
the latter must follow. The former takes place, so far as experi-
ment can show, in the cerebral hemispheres ; the latter, in the gan-
glion of the tuber annulare.

MEDULLA OBLONG ATA. — The last remaining ganglion of the en-
cephalon is that of the medulla oblongata. This ganglion, it will
be remembered, is imbedded in the substance of the restiform bodv,

440 THE BRAIN.

occupying the lateral and posterior portions of the medulla, at the
point of origin of the pneumogastric nerves. This portion of the
brain has long been known to be particularly essential to the pre-
servation of life ; so that it has received the name of the " vital
point," or the " vital knot." All the other parts of the brain may
be injured or removed, as we have already seen, without the imme-
diate and necessary destruction of life ; but so soon as the medulla
oblongata is broken up, and its ganglion destroyed, respiration
ceases instantaneously, and the circulation also soon comes to an
end. Eemoval of the medulla oblongata produces, therefore, as its
immediate and direct result, a stoppage of respiration : and death
takes place principally as a consequence of this fact.

Flourens and Longet have determined, with considerable accu-
racy, the precise limits of this vital spot in the medulla oblongata.
Flourens ascertained that in rabbits it extended from just above
the origin of the pneumogastric nerve, to a level situated three lines
and a half below this origin. In larger animals, its extent is pro-
portionally increased. Longet ascertained, furthermore, that the
properties of the medulla were not the same throughout its entire
thickness ; but that its posterior and anterior parts might be de-
stroyed with comparative impunity, the peculiarly vital spot being
confined to the intermediate portions. This vital point accordingly
is situated in the layer of gray matter, imbedded in the thickness
of the restiform bodies, which has been previously spoken of as
giving origin to the pneumogastric nerves.

The precise nature of the connection between this ganglion and
the function of respiration may be described as follows. The
movements of respiration, which follow each other with incessant
regularity through the whole period of life, are not voluntary
movements. We may to a certain extent, hasten or retard them
at will, but our power over them, even in this respect, is extremely
limited ; and in point of fact they are performed, during the greater
part of the time, in a perfectly quiet and regular manner, without
our volition and even without our consciousness. They continue
uninterruptedly through the deepest slumber, and even in a con-
dition of insensibility from accident or disease.

These movements are the result of a reflex action taking place
through the medulla oblongata. The impression which gives rise
to them originates principally in the lungs, from the accumulation
of carbonic acid in the pulmonary vessels and air-cells, is trans-
mitted by the pneumogastric nerves to the medulla, and is thence

MEDULLA O3LONGATA. 441

reflected along the motor nerves to the respiratory muscles. These
muscles are then called into action, producing an expansion of
the chest. The impression so conveyed to the medulla is usually
unperceived by the consciousness. It is generally converted directly
into a motor impulse, without attracting our attention or giving
rise to any conscious sensation. Respiration, accordingly, goes on
perfectly well without our interference and without our knowledge.
The nervous impression, however, conveyed to the medulla, though
usually imperceptible, may be made evident at any time by volun-
tarily suspending the respiration. As the carbonic acid begins to
accumulate in the blood and in the lungs, a peculiar sensation makes
itself felt, which grows stronger and stronger with every moment,
and impels us to recommence the movements of inspiration. This
peculiar sensation, entirely different in character from any other, is
designated by the French under the name of " besoin de respirer."
It becomes more urgent and distressing, the longer respiration is
suspended, until finally the impulse to expand the chest can no
longer be resisted by any effort of the will.

During ordinary respiration, therefore, each inspiratory move-
ment is excited by the partial vitiation of the air contained in the
lungs. As soon as a new supply has been inhaled, the impulse to
respire is satisfied, the muscles relax, and the chest collapses. In
a few seconds the previous condition recurs and the same move-
ments are repeated, producing in this way a regular alternation of
inspirations and expirations.

Since the movements of respiration are performed partly by the
diaphragm and partly by the intercostal muscles, they will be
differently modified by injuries of the nervous system, according to
the spot at which the injury is inflicted. If the spinal cord, for
example, be divided or compressed in the lower part of the neck,
all the intercostal muscles will be necessarily paralyzed, and respi-
ration will then be performed entirely by the diaphragm. The
chest in these cases remaining motionless, and the abdomen alone
rising and falling with the movements of the diaphragm, such
respiration is called " abdominal" or " diaphragmatic" respiration.
It is a common symptom of fracture of the spine in the lower
cervical region. If the phrenic nerve, on the other hand, be
divided, the diaphragm will be paralyzed, and respiration will then
be performed altogether by the rising and falling of the ribs. It
is then called "thoracic" or "costal" respiration. If the injury
inflicted upon the spinal cord be above the origin of the second

442 THE BRAIN.

and third cervical nerves, both the phrenic and intercostal nerves
are at once paralyzed, and death necessarily takes place from suf-
focation. The attempt at respiration, however, still continues in
these cases, showing itself by ineffectual inspiratory movements of
the mouth and nostrils. Finally, if the medulla itself be broken up
by a steel instrument introduced through the foramen magnum, so
as to destroy the nervous centre in which the above reflex action
takes place, both the power and the desire to breathe are at once
taken away. No attempt is made at inspiration, there is no strug-
gle, and no appearance of suffering. The animal dies simply by
a want of aeration of the blood, which leads in a few moments to
an arrest of the circulation.

It is owing to the above action of the medulla oblongata that in-
juries of this part are so promptly and constantly fatal. When the
" neck is broken," as in hanging or by sudden falls upon the head,
a rupture takes place of the transverse ligament of the atlas ; the
head, together with the first cervical vertebra, is allowed to slide
forward, and the medulla is compressed between the odontoid pro-
cess of the axis in front and the posterior part of the arch of the
atlas behind. In cases of apoplexy, where any part of the hemi-
spheres, corpora striata, or optic thalarni, is the seat of the hemor-
rhage, the patient generally lives at least twelve hours ; but if the
hemorrhage takes place into the medulla itself, or at the base of the
brain in its immediate neighborhood, so as to compress its sub-
stance, death follows instantaneously, and by the same mechanism
as where the medulla is intentionally destroyed.

An irregularity or want of correspondence in the movements of
respiration is accordingly found to be one of the most threatening
of all symptoms in affections of the brain. A disturbance or sus-
pension of the intellectual powers does not indicate necessarily any
immediate danger to life. Even sensation and volition may be im-
paired without serious and direct injury to the organic functions.
These symptoms only indicate the threatening progress of the dis-
ease, and show that it is gradually approaching the vital centre. It
is common to see, however, as the medulla itself begins to be impli-
cated, a paralysis first showing itself in the respiratory movements
of the nostrils and lips, while those of the chest and abdomen still
go on as usual. The cheeks are then drawn in with every inspira-
tion and puffed out sluggishly with every expiration, the nostrils
themselves sometimes participating in these unnatural movements.
A still more threatening symptom, and one which frequently pre-

MEDULLA OBLOXGATA. 443

cedes death, is an irregular, hesitating respiration, which sometimes
attracts the attention of the physician, even before the remaining
cerebral functions are seriously impaired. These phenomena de-
pend on the connection between the respiratory movements and the
reflex action of the medulla oblongata.

We have now, in studying the functions of various parts of the
cerebro- spinal system, become familiar with three different kinds of
reflex action.

The first is that of the spinal cord. Here, there is no proper
sensation and no direct consciousness of the act which is performed.
It is simply a nervous impression, coming from the integument,
and transformed by the gray matter of the spinal cord into a motor
impulse destined for the muscles. This action will take place after
the removal of the hemispheres and the abolition of consciousness,
as well as in the ordinary condition. The respiratory action of the
medulla oblongata is of the same general character ; that is, it is
not necessarily connected with either volition or consciousness.
The only peculiarity in this instance is that the original nervous
impression is of a special character, and its influence is finally
exerted upon a special muscular apparatus. Actions of this nature
are termed, par excellence, reflex actions.

The second kind of reflex action takes place in the tuber annu-
lare. Here the nervous impression, which is conveyed inward
from the integument, instead of stopping at the spinal cord, passes
onward to the tuber annulare, where it first gives rise to a con-
scious sensation; and this sensation is immediately followed by a
voluntary act. Thus, if a crumb of bread fall into the larynx, the
sensation produced by it excites the movement of coughing. The
sensations of hunger and thirst excite a desire for food and drink.
The sexual impulse acts in precisely the same manner ; the percep-
tion of particular objects giving rise immediately to special desires
of a sexual character.

It will be observed, in these instances, that in the first place,
the nervous sensation must be actually perceived, in order to pro-
duce its effect; and in the second place that the action which
follows is wholly voluntary in character. But the most important
peculiarity, in this respect, is that the voluntary impulse follows
directly upon the receipt of the sensation. There is no intermediate
reasoning or intellectual process. We do not cough because we
know that this is the most effectual way to clear the larynx ; but
simply because we are impelled to do so by the sensation which is

444 THE BRAIN".

felt at the time. We do not take food or drink because we know
that they are necessary to support life, much less because we under-
stand the mode in which they accomplish this object ; but merely
because we desire them whenever we feel the sensation of hunger
and thirst.

All actions of this nature are termed instinctive. They are volun-
tary in character, but are performed blindly ; that is, without any
idea of the ultimate object to be accomplished by them, and simply
in consequence of the receipt of a1 particular sensation. Accord-
ingly experience, judgment, and adaptation have nothing to do with
these actions. Thus the bee builds his cell on the plan of a mathe-
matical figure, without performing any mathematical calculation.
The silkworm wraps himself in a cocoon of his own spinning,
certainly without knowing that it is to afford him shelter during
the period of his metamorphosis. The fowl incubates her eggs
and keeps them at the proper temperature for development, simply
because the sight of them creates in her a desire to do so. The
habits of these animals, it is true, are so arranged by nature, that
such instinctive actions are always calculated to accomplish an
ultimate object. But this calculation is not made by the animal
himself, and does not form any part of his mental operations.
There is consequently no improvement in the mode of performing
such actions, and but little deviation under a variety of circum-
stances.

The third kind of reflex action requires the co-operation of the
hemispheres. Here, the nervous impression is not only conveyed
to the tuber annulare and converted into a sensation, but, still
following upward the course of the fibres to the cerebrum, it there
gives rise to a special train of ideas. We understand then the
external source of the sensation, the manner in which it is calcu-
lated to affect us, and how by our actions we may turn it to our
advantage or otherwise. The action which follows, therefore, in
these cases, is not simply voluntary but reasonable. It does not
depend directly upon the external sensation, but upon an intellec-
tual process which intervenes between the sensation and the voli-
tion. These actions are distinguished, accordingly, by a character
of definite contrivance, and a conscious adaptation of means to
ends ; characteristics which do not belong to any other operations
of the nervous system.

The possession of this kind of intelligence and reasoning power
is not confined to the human species. We have already seen that

MEDULLA OBLOXGATA. 445

there are many purely instinctive actions in man, as well as in
animals. It is no less true that in the higher animals there is often
thg same exercise of reasoning power as in man. The degree of
this power is much less in them than in him, but its nature is the
same. Whenever, in an animal, we see any action performed with
the evident intention of accomplishing a particular object, to which
it is properly adapted, such an act is plainly the result of reason-
ing powers, not essentially different from our own. The establish-
ment of sentinels by gregarious animals, to warn the herd of the
approach of danger, the recollection of punishment inflicted for a
particular action, and the subsequent avoidance or concealment of
that action, the teachability of many animals, and their capacity of
forming new habits or of improving the old ones, are all instances
of the same kind of intellectual power, and are quite different from
instinct, strictly speaking. It is this faculty which especially pre-
dominates over the others in the higher classes of animals, and
which finally attains its maximum of development in the human
species.

446 THE CRANIAL NERVES.

CHAPTER V.

THE CRANIAL NERVES.

IN examining the cranial nerves, we shall find that although they
at first seem quite different in their distribution and properties
from the spinal nerves, yet they are in reality arranged for the
most part on the same plan, and may be studied in a similar
manner.

At the outset, however, we find that there are three of the cra-
nial nerves, commonly so called, which must be arranged in a class
by themselves ; since they have no character in common with the
other nerves originating either from the brain or the spinal cord.
These are the three nerves of special sense; viz., the Olfactory,
Optic, and Auditory. They are, properly speaking, not so much
nerves as commissures, connecting different parts of the encephalic
mass with each other. They are neither sensitive nor motor, in
the ordinary meaning of these terms ; but are capable of conveying
only the special sensation characteristic of the organ with which
they are connected.

OLFACTORY NERVES. — We have already described the so-called
olfactory nerves as being in reality commissures, connecting the
olfactory ganglia with the central parts of the brain. The masses
situated upon the cribriform plate of the ethmoid bone are com-
posed of gray matter; and even the filaments which they send
outward to be distributed in the Schneiderian mucous membrane,
are gray and gelatinous in their texture, and quite different from
the fibres of ordinary nerves. The olfactory nerves are not very
well adapted for direct experiment. It is, however, at least certain
with regard to them that they serve to convey the special sensation
of smell; that their mechanical irritation does not give rise to
either pain or convulsions; and finally that their destruction,
together with that of the olfactory ganglia, does not occasion any
paralysis nor loss of ordinary sensibility.

THE CRANIAL NERVES. 447

OPTIC NERVES. — We have already given some account of these
nerves and their decussations, in connection with the history of the
tubercula quadrigemina. They consist of rounded bundles of white
fibres, running between the tubercles and the retinae. As the reti-
nae themselves are membranous expansions consisting mostly of
vesicular or cellular nervous matter, the optic nerves, or " tracts,'1
must be regarded as commissures connecting the retinae with the
tubercles. We have also seen that they serve, by some of their
fibres, to connect the two retinae with each other, as well as the two
tubercles with each other.

The optic nerves convey only the special impression of light from
without inward, and give origin to the reflex action of the optic
tubercles, by which the pupil is made to contract. According to
Longet, the optic nerves are absolutely insensible to pain through-
out their entire length. When a galvanic current is passed through
the eyeball, or when the retina is touched in operations upon the
eye, the irritation has been found to produce the impression of lumi-
nous sparks and flashes, instead of an ordinary painful sensation.
The impression of colored rings or spots may be easily produced
by compressing the eye in particular directions; and a sudden
stroke upon the eyeball will often gi ve rise to an apparent discharge
of brilliant sparks. Division of the optic nerves produces complete
blindness, but does not destroy ordinary sensibility in any part of
the eye, nor occasion any muscular paralysis.

AUDITORY NERVES. — The nervous expansion in the cavity of
the internal ear contains, like the retina, vesicles or cells as well as
fibres; and the auditory nerves are therefore to be regarded, like
the optic and olfactory, as commissural in their character. They
are also, like the preceding, destitute of ordinary sensibility. Ac-
cording to Longet, they may be injured or destroyed without giving
rise to any sensation of pain. They serve to convey to the brain
the special sensation of sound, and seem incapable of transmitting
any other. Longet1 relates an experiment performed by Yolta, in
which, by passing a galvanic current through the ears, the observer
experienced the sensation of an interrupted hissing noise, so long
as the connection of the wires was maintained. Inflammations
within the ear, or in its neighborhood, are often accompanied by
the perception of various noises, like the ringing of bells, the

1 Traite de Physiologic, vol. ii. p 286.

448

THE CRANIAL NERVES.

washing of the waves, the humming of insects ; sounds which have
no external existence, but which are simulated by the morbid irri-
tation of the auditory nerve.

It is evident, from the facts detailed above, that the nerves of
special sense are neither motor or sensitive, properly speaking;
and that they are distinct in their nature from the ordinary spinal
nerves.

The remainder of the cranial nerves, however, present the
ordinary qualities belonging to the spinal nerves. Some of them
are exclusively motor in character, others exclusively sensitive;
while most of them exhibit the two properties, to a certain extent,
as mixed nerves. They may be conveniently arranged in three
pairs, according to the regions in which they are distributed, cor-
responding very closely with the motor and sensitive roots of the
spinal nerves. According to such a plan, the arrangement of the
cranial nerves would be as follows : —

CRANIAL NERVES.

Nerves of Special Sense.

1. Olfactory. 2. Optic. 3. Auditory.

1st PAIR. •

Motor nerves.
' Motor oculi com.
Patheticus
Motor oc. externus

Sensitive Nerves.

Distributed to

Small root of 5th pair
_ Facial
2d PAIR. Hypoglossal
3d PAIR. Spinal accessory

Large root of 5th pair. Face.
Glosso-pharyngeal. Tongue.

Pneumogastric.

Neck, &c.

The above arrangement of the cranial nerves is not absolutely
perfect in all its details. Thus, while the hypoglossal supplies the
muscles of the tongue alone, the glosso-pharyngeal sends part of
its sensitive fibres to the tongue and part to the pharynx ; and
while the large root of the 5th pair is mostly distributed in the
face, one of its branches, viz., the gustatory, is distributed to the
tongue. Notwithstanding these irregularities, however, the above
division of the cranial nerves is in the main correct, and will be
found extremely useful as an assistant in the study of their func-
tions.

There is no impropriety, moreover, in regarding all the motor
branches distributed upon the face as one nerve ; since even the
anterior roots of the spinal nerves originate from the spinal cord,
each by several distinct filaments, which are associated into a single

THE CRANIAL NERVES. 449

bundle only at a certain distance from their point of origin. The
mere fact that two nerves leave the cavity of the cranium by the
same foramen does not indicate that they have the same or even a
similar function. Thus the facial and auditory both escape from
the cavity of the cranium by the foramen auditorium intern um, and
yet we do not hesitate to regard them as entirely distinct in their
nature and functions. It is the ultimate distribution of a nerve,
and not its course through the bones of the skull, that indicates
its physiological character and position. For while the ultimate
distribution of any particular nerve is always the same, its arrange-
ment as to trunk and branches may vary, in different species
of animals, with the anatomical arrangement of the bones of the
skull. This is well illustrated by a fact first pointed out by Prof.
Jeffries Wyman1 in the anatomy of the nervous system of the
bullfrog. In this animal, both the facial nerve and motor oculi
externus, instead of arising as distinct nerves, are actually given
off as branches of the 5th pair ; while their ultimate distribution is
the same as in other animals. All the motor and sensitive nerves
distributed to the face are accordingly to be regarded as so many
different branches of the same trunk ; varying sometimes in their
course, but always the same in their ultimate distribution.

The motor nerves of the head are in all respects identical in their
properties with the anterior roots of the spinal nerves. For, in the
first place, they are distributed to muscles, and not to the integu-
ment or to mucous membranes; secondly, their division causes
muscular paralysis; and thirdly, mechanical irritation applied at
their origin produces muscular contraction in the parts to which
they are distributed, but does not give rise to a painful sensa-
tion. In several instances, nevertheless, the motor nerves, though
insensible at their origin, show a certain degree of sensibility when
irritated after their exit from the skull, owing to fibres of com-
munication which they receive from the purely sensitive nerves.
In this respect they resemble the spinal nerves, the motor and
sensitive filaments of which are at first distinct in the anterior
and posterior roots, but afterward mingle with each other, on
leaving the cavity of the spinal canal.

The three sensitive nerves originating from the brain are the

1 Nervous System of Rana pipiens ; published by the Smithsonian Institution.
Washington, 1853.
29

450 THE CRANIAL NERVES.

large root of the fifth pair, the glosso-pharyngeai, and the pneumo-
gastric. It will be observed that, in all their essential properties,
they correspond with the posterior roots of the spinal nerves. Like
them they are inexcitable, but extremely sensitive. Irritated at
their point of origin, they give rise to acutely painful sensations,
but to no convulsive movements. Secondly, if divided at the same
situation, the operation is followed by loss of sensibility in the
parts to which they are distributed, without any disturbance of the
motive power. Each of these nerves, furthermore, like the poste-
rior root of a spinal nerve, is provided with a ganglion through
which its fibres pass : the fifth pair, with the Casserian ganglion,
situated near the inner extremity of the petrous portion of the tem-
poral bone ; the glosso-pharyngeai, with the ganglion of Andersch,
situated in the jugular fossa; while the pneumogastric presents,
just before its passage through the jugular foramen, a ganglion
known as the ganglion of the pneumogastric nerve. Finally, the
sensitive fibres of all these nerves, beyond the situation of their gan-
glia, are intermingled with others of a motor origin. The large root
of the fifth pair, which is exclusively sensitive, is accompanied by
the fibres of the small root, which are exclusively motor. The
glosso-pharyngeai receives motor filaments from the facial and spi-
nal accessory, becoming consequently a mixed nerve outside the
cranial cavity ; while the pneumogastric is joined by fibres from the
spinal accessory and various other nerves of a motor character.
These nerves, accordingly, are exclusively sensitive only at their
point of origin. Though they afterward retain the predominating
character of sensitive nerves, they are yet found, if irritated in the
middle of their course, to be intermingled with motor fibres, and
to have consequently acquired, to a certain extent, the character of
mixed nerves.

The resemblance, therefore, between the cranial and spinal nerves
is complete.

MOTOR OCULI COMMUNIS. — This nerve, which is sometimes known
by the more convenient name of the oculo-motorius, originates from
the inner edge of the crus cerebri, passes into the cavity of the
orbit by the sphenoidal fissure, and is distributed to the lexator
palpebras superioris, and to all the muscles moving the eyeball,
except the external rectus and the superior oblique. Its irritation
accordingly produces convulsive movements in these parts, and

FIFTH PAIR. 451

its division has the effect of paralyzing the muscles to which it is
distributed. The superior eyelid falls down over the pupil, and
cannot be raised, owing to the inaction of its levator muscle, so
that the eye appears constantly half shut. This condition is known
by the name of " ptosis." The movements of the eyeball are also
nearly suspended, and permanent external strabismus takes place,
owing to the paralysis of the internal rectus muscle, while the ex-
ternal rectus, animated by a different nerve, preserves its activity.

PATHETIC as. — This nerve, which supplies the superior oblique
muscle of the eyeball, is similar in its general properties to the pre-
ceding. Its section causes paralysis of the above muscle, "without
any loss of sensibility.

MOTOR EXTERNUS. — This nerve, the sixth pair, according to the
usual anatomical arrangement, is distributed to the external rectus
muscle of the eyebalL Its division or injury by disease is followed
by internal strabismus, owing to the unopposed action of the internal
rectus muscle.

FIFTH PAIR. — This is one of the most important and remarkable
in its properties of all the cranial nerves. It is the great sensitive
nerve of the face, and of the adjoining mucous membranes. Its
larger root, after emerging from the outer and under surface of the
pons Varolii, passes forward over the inner extremity of the petrous
portion of the temporal bone. It there expands into a crescentic-
shaped swelling, containing a quantity of gray matter with which
its fibres are intermingled, and which is known as the Casserian
ganglion. The fibres of the smaller root, passing forward in com-
pany with the others, do not take any part in the formation of this
ganglion, but may be seen passing beneath it as a distinct bundle,
and continuing their course forward to the foramen ovale, through
which they emerge from the skull. In front of the anterior and
external border of the Casserian ganglion, the fifth nerve separates
into three principal divisions, viz., the ophthalmic, the superior
maxillary, and the inferior maxillary. The first of these divisions,
viz., the ophthalmic, is so called because it passes through the orbit
of the eye. It enters the sphenoidal fissure, and runs along the
upper portion of the orbit, sending branches to the ophthalmic gan-
glion of the sympathetic, to the lachrymal gland, the conjunctiva.

452

THE CRANIAL NERVES.

Fig. 150.

and the mucous membrane of the lachrymal sac. It also sends off
a small branch (nasal branch) which penetrates into the nasal pas-
sages and supplies the Schneiderian mucous membrane. It then
ernerges upon the face by the supra-orbital foramen, and is distri-
buted to the integument of the forehead and side of the head as far
back as the vertex.

The second division of this nerve, or the superior maxillary,
passes out by the foramen rotundum, and runs along the longitu-
dinal canal in the floor of the orbit, giving off branches during its
passage to the teeth of the upper jaw and to the mucous membrane
of the antrum maxillare. It finally emerges upon the middle of the
face by the infra -orbital foramen, and is distributed to the integu-
ment of the lower eyelid, nose, cheek, and upper lip.

The third, or inferior maxillary division of the fifth pair, which
is the largest of the three, leaves the cavity of the cranium by the

foramen ovale. It comprises a con-
siderable portion of the large root
of the nerve, and all the fibres of
the small root. This division is
therefore a mixed nerve, containing
both motor and sensitive fibres,
while the two former are exclu-
sively sensitive. It is distributed,
accordingly, both to muscles and
to the sensitive surfaces. Soon after
emerging from the foramen ovale
it sends branches to the temporal
muscle, to the masseter, the bucci-
nator, and to the internal and ex-
ternal pterygoids; that is, to the
muscles which are particularly con-
cerned in the movements of the
lower jaw. It also sends sensitive
filaments to the integument of the

temple, to that of a portion of the external ear and external audi-
tory meatus. The third division of the fifth pair, then passing
downward and forward, gives off a branch of considerable size, the
lingual branch, which is distributed to the mucous membrane of the
anterior two-thirds of the tongue, and which also sends filaments to
the arches of the palate and to the mucous membrane of the cheek.

DISTRIBUTION OF FIFTH NERVE
CPOW THE FACE.— a. Casserian ganglion.
1 Ophthalmic division. 2. Superior maxil-
lary division. 3. Inferior maxillary division.

FIFTH PAIR. 453

The remaining portion of the third division, after giving a few
branches to the mylo-hyoid muscle and to the anterior belly of the
digastric, then enters the inferior dental canal, sends filaments to
the teeth of the lower jaw, emerges at the mental foramen, and is
finally distributed to the integument of the chin, lower lip, and
inferior part of the face.

This nerve is accordingly distributed to the sensitive surfaces,
that is, the integument and mucous membranes about the face, and
to the muscles of mastication. A few of its fibres are sent also to
the superficial muscles of the face, such as the buccinator and the
orbicularis oris ; but these fibres are sensitive in their character,
and serve merely to impart to the muscles a certain degree of
sensibility. It has been ascertained by Longet that if the various
branches of this nerve be irritated by a galvanic current, no con-
vulsive movements whatever are produced in those superficial
muscles of the face, which it supplies with filaments; but if its
smaller or non-ganglionic root be irritated in the same way, con-
tractions instantly follow in the muscles of mastication.

The fifth pair is the most acutely sensitive nerve in the whole
body. Its irritation by mechanical means always causes intense
pain, and even though the animal be nearly unconscious from the
influence of ether, any severe injury to its large root is almost
invariably followed by cries which indicate the extreme sensibility
of its fibres.

If this nerve be completely divided, in the living animal, within
the cranium, at the situation of the Casserian ganglion, the operation
is followed by total loss of sensibility in the skin of the face and in
the adjacent mucous membranes. The conjunctiva, upon the affected
side, is then completely insensible, and may be touched with the
point of a needle or the blade of a knife, without exciting any un-
easiness, and even without the consciousness of the animal. Probes
and needles may be passed into the nostril, and the lips or the
cheek may be pinched, pierced or cut, without exciting the least
sign of sensibility. The animal is entirely indifferent to all me-
chanical injuries upon the affected side, though upon the opposite
side the parts retain their natural sensibility.

Owing to the paralysis of the lingual nerve, also, after this ope-
ration, the tongue, in its anterior two-thirds, becomes insensible to
ordinary irritations, and loses, beside, the power of taste.

Another peculiar effect of the division of the fifth pair depends

454 THE CRANIAL NERVES.

upon the paralysis of its motor fibres, which are distributed, as we
have seen, to the muscles of mastication. In many of the lower
animals, consequently, the movements of mastication become ex-
ceedingly enfeebled upon the affected side. In the cat, for example,
an animal in which mastication is usually very thoroughly per-
formed, this process becomes excessively laborious, so that the
animal after this operation cannot masticate solid meat, but requires
to be fed with that which has already been cut in pieces.

The fifth pair, beside supplying the sensibility of the integument
of the face, has a peculiar and important influence on the organs of
special sense. This influence appears to consist in some connection
between the action of the fifth pair and the processes of nutrition ;
so that when the former is injured, the latter very soon become
deranged. For the perfect action of any one of the organs of
special sense, two conditions are necessary : first, the sensibility of
the special nerve belonging to it, and secondly, the integrity of the
component parts of the organ itself. Now as the nutrition of the
organ is, to a certain extent, under the control of the fifth pair, any
serious injury to this nerve produces a derangement in the tissues
of the organ, and consequently interferes with the due performance
of its function.

The mucous membrane of the nasal passages, for example, is
supplied* by two different nerves; first, the olfactory, distributed
throughout its upper portion, by which it is endowed with the
special sense of smell ; and, secondly, the nasal branch of the fifth
pair, distributed throughout its middle and lower portions, by
which it is supplied with ordinary sensibility.

Since the fifth pair, accordingly, supplies general sensibility to
the nasal passages, this property will remain after the special sense
of smell has been destroyed. If, however, the fifth pair itself be
divided, not only is general sensibility destroyed in the Schneiderian
mucous membrane, but a disturbance begins to take place in the
nutrition of its tissue, by which it is gradually rendered unfit for
the performance of its special function, and the power of smell is
finally lost. The mucous membrane, under these circumstances,
becomes injected and swollen, and the nasal passage is obstructed
by an accumulation of puriform mucus. According to Longet, the
mucous membrane also assumes a fungous consistency, and is liable
to bleed at the slightest touch. The effect of this alteration is to
blunt or altogether destroy the sense of smell. It is owing to a
similar unnatural condition of the mucous membrane that the power

FIFTH PAIR. 455

of smell is always more or less impaired in cases of coryza and
influenza. The olfactory nerves become inactive in consequence
of the morbid alteration in their mucous membrane, and in the
secretions which cover it.

The influence of this nerve over the organ of vision is still more
remarkable. It has been known for many years that division of
the fifth pair within the cranium, or of its ophthalmic branch, is fol-
lowed by an inflammation of the corresponding eye, which usually
goes on to complete and permanent destruction of the organ.
Immediately after the operation, the pupil becomes contracted and
the conjunctiva loses its sensibility. At the end of twenty -four
hours, the cornea begins to become opaline, and by the second
day the conjunctiva is already inflamed and begins to discharge a
purulent secretion. The inflammation, after commencing in the
conjunctiva, increases in intensity and soon spreads to the iris,
which becomes covered with a layer of inflammatory exudation.
The cornea grows constantly more opaque, until it is at last
altogether impermeable to light, and vision is consequently sus-
pended. Blindness, therefore, does not result in these instances
from any direct affection of the optic nerve or of the retina, but is
owing simply to opacity of the cornea. Sometimes the diseased
action goes on until it results in ulceration of the cornea and dis-
charge of the humors of the eye ; sometimes, after the lapse of
several days, the inflammatory appearances subside, and the eye is
finally restored to its natural condition.

It has been observed, however, that although the above conse-
quences always follow division of the fifth pair, when performed at
the level of the Casserian ganglion, or between it and the eyeball,
they are either much diminished in intensity or altogether wanting
when the division is made at a point posterior to the ganglion.
This circumstance has led to the belief that the influence of the fifth
pair on the nutrition of the eyeball does not reside in its own proper
fibres, but in some filaments of the sympathetic nerve which join
the fifth pair at the level of the Casserian ganglion. If the section
accordingly be made at this point, or in front of it, the fibres of the
sympathetic will be divided with the others, and inflammation of
the eye will result ; but if the section be made behind the ganglion,
the fibres of the sympathetic will escape division, and the injurious
effects upon the eye will be wanting. Such is the explanation
usually given of the above-mentioned facts ; but the question has
not as yet been determined in a positive manner.

456 THE CRANIAL NERVES.

Division of the fifth pair destroys also the general sensibility of
the external auditory meatus, the lining membrane of which is
supplied by its filaments. Inflammation of this membrane and its
consequent alterations, it is well known, interfere seriously with
the sense of hearing. It is no uncommon occurrence for an accu-
mulation of cerumen to take place after inflammation of this part,
so as to block up the auditory canal and produce partial or com-
plete deafness. It has not been ascertained, however, whether
division of the fifth pair is usually followed by similar changes in
this part.

The lingual branch of the fifth pair supplies the anterior ex-
tremity and middle portion of the tongue both with general sensi-
bility and with the power of taste. The sensibility of the tongue
is accordingly provided for by two different nerves ; in its anterior
two-thirds, by the lingual branch of the fifth pair ; in its posterior
third, by the fibres of the glosso-pharyngeal.

The facial branches of the fifth pair are the ordinary seat of tic
douloureux. This affection is not unfrequently confined to either
the supra-orbital, the infra-orbital, or the mental branch ; and the
pain may be accurately traced in the direction of their diverging
fibres. It has already been mentioned that the painful sensations
sometimes also follow the course of the facial, owing to some sensi-
tive filaments which that nerve receives from the fifth pair.

FACIAL. — This nerve was known to the older anatomists as the
"portio dura of the seventh pair." It leaves the cavity of the
cranium by the internal auditory foramen, in company with the
auditory nerve ; and, as the latter is of a softer consistency than the
former, they have received the names respectively of the "portio
mollis" and " portio dura" of the seventh pair. There is, however,
no physiological connection between these two nerves ; for while
the auditory is spread out in the cavity of the internal ear, the facial
passes onward through the petrous portion of the temporal bone,
emerges at the stylo-mastoid foramen, bends round beneath the
external ear, and passes forward through the substance of the
parotid gland, forming a plexus called the " pes anserinus," by the
abundant inosculation of its different branches. It then sends its
filaments forward in a diverging course, and is finally distributed
to the muscles of the external ear, to the frontalis and superciliaris
muscles, to the orbicularis oculi, the compressors and dilators of
the nares, the orbicularis oris. and to the elevators and depressors

FACIAL XERVE. 457

of the lips ; that is, to the superficial muscles of the face, which are
concerned in the production of expression. (Fig. 151.)

The facial, consequently, is the Fi 151

motor nerve of the face. It has
nothing to do with transmitting
sensitive impressions, since it has
been frequently shown that after
section of the fifth pair, the facial
remaining entire, the sensibility of
the face is completely lost ; so that
the integument may be cut, pricked,
pierced, or lacerated, without any
sign of pain being exhibited by the
animal. The facial, therefore, does
not transmit sensation from these
parts ; and its division, which was
formerly resorted to in cases of
tic douloureux, is accordingly alto-
gether incapable of relieving neuralgic pains.

This nerve, however, is directly connected with muscular action,
since mechanical or galvanic irritation of its fibres produces con-
vulsive twitching in the ears, nostrils, lips, and cheeks.

If the facial nerve be divided in one of the lower animals, as, for
example, in the cat, immediately after its emergence from the
stylo-mastoid foramen, it will be found that complete muscular
paralysis has occurred in all those parts to which the nerve is dis-
tributed, while the power of sensation remains unimpaired. The
animal is incapable of moving the ear, which remains constantly in
the same position. There is also incapacity of closing the eyelids,
owing to paralysis of the orbicularis oculi, and the eye accordingly
remains constantly open, even when the opposite eye is closed ;
as during sleep, or in the act of winking. If the conjunctiva be
touched, the animal feels the irritation, and endeavors to escape
from it ; but the eyeball is only drawn partially backward into the
socket by the action of the recti muscles, and the third eyelid
pushed partly across the cornea. The complete closure of the eye
is impossible. It will be observed, accordingly, that precisely oppo-
site effects are produced upon the eyelids by paralysis of the oculo-
motorius nerve, and by that of the facial. In the former instance,
owing to the paralysis of the levator palpebras superioris, the eye
is always partially closed ; in the latter, owing to paralysis of the

458 THE CRANIAL NERVES.

orbicularis, it is always partially open. The movements of the
aares are also suspended on the side of the injury, and if the angle
of the mouth be examined on that side, it will be found to hang
down lower than on the opposite side, and to be constantly partly
open, owing to the paralysis of the orbicularis oris and the eleva-
tors of the angle of the mouth.

These are the only inconveniences which follow the division of
the facial nerve in the cat, but in some other of the lower animals,
where various muscular organs in this region are particularly de-
veloped, the consequences are more troublesome. Thus, in the rabbit,
the ear, upon the affected side, falls down, and cannot be raised or
pointed in different directions ; and as the movements of the ear
are important in these animals, as aids to the hearing, the per-
fection of this sense must be considerably impaired by paralysis of
the facial nerve. In the horse, it has been noticed by Bernard,1
that division of the facial on both sides is fatal by suffocation. For
this animal breathes exclusively through the nostrils, which open
widely at the time of inspiration, to allow the admission of air. If
these movements be suspended, by paralysis of the facial nerve, the
nostrils immediately collapse, and the animal dies by suffocation.

In the human subject, the facial nerve is occasionally paralyzed
upon one side, sometimes from sympathetic irritation, sometimes
from organic disease in the petrous portion of the temporal bone,
or within the cranial cavity near the origin of the nerve. In either
case, an extremely well-marked affection is the result, known as
"facial paralysis." This condition is chiefly characterized by an
entire absence of expression on the affected side of the face. The
lower eyelid sinks downward, from paralysis of the orbicularis
muscle, and cannot be closed.

The corner of the mouth also falls downward, and the whole
lower part of the face is drawn over to the opposite side, by the
force of the antagonistic muscles. The lips are unable to retain
the fluids of the mouth ; and the saliva dribbles away from between
them, giving to the face a remarkably vacant and helpless appear-
ance.

The principal inconvenience, however, suffered by the human
subject in facial paralysis, depends upon the want of action of the
muscles about the lips and cheek. In drinking, the fluids escape

1 Lemons sur la Physiologie et la Pathologie du Systetne Nerveux, Paris, 1858,
vol. ii. p. 38.

GLOSSO-PHARYNGEAL NERVE. 459

by the corner of the mouth, and in mastication the food has partly
a tendency to escape by the same opening, and partly accumulates,
on the affected side, between the gums and the cheek, owing to the
paralysis of the buccinator muscle, which receives its motor fila-
ments from the facial nerve. Thus, the action of all the superficial
facial muscles is suspended, the expression of the face is destroyed,
and the movements of the lips and the prehension of the food
seriously interfered with.

Though the facial, however, be essentially a motor nerve, yet its
principal branches distributed to the face have a certain degree of
sensibility ; that is, when these branches are irritated in the middle
of their course, the animal immediately gives evidence of a painful
sensation. Longet has shown, by an extremely ingenious mode
of experiment,1 that this sensibility of the branches of the facial
does not depend on any sensitive fibres of their own, but upon
those which they derive from inosculation with the fifth pair. He
exposes, for example, the facial nerve in the dog, and, irritating its
principal branches one after the other, at each application of the
irritant there are evident signs of pain. He then divides the facial
nerve at its point of exit from the stylo-mastoid foramen, and
finds that, after this operation, the sensibility of its branches still
remains. The fibres, accordingly, upon which this sensibility
depends, do not pass out with the trunk of the nerve, but are
derived from some other source. The experimenter, then, upon
another animal, divides the fifth pair within the skull, leaving the
facial untouched; and afterward, on irritating as before the ex-
posed branches of the latter nerve, he finds that its sensibility has
entirely disappeared. It is by filaments, accordingly, derived from
the fifth pair, that a certain degree of sensibility is communicated
to the branches of the facial.

These facts account for the peculiar circumstance that, in cases
of tic douloureux, the spasmodic pain sometimes follows exactly
the course of the facial nerve, viz : from behind the ear forward
upon the side of the face ; and yet the section of this nerve does not
put an end to the neuralgia, but only causes paralysis of the facial
muscles.

GLOSSO-PHARYNGEAL. — This nerve originates from the lateral
portion of the medulla oblongata, passes outward, and enters the

1 Traite de Physiologie, vol. ii. pp. 354-357.

460 THE CRANIAL NERVES.

posterior foramen lacerum in company with the pneumogastric and
spinal accessory. While in the jugular fossa it presents a gangliform
enlargement, called the ganglion of Andersch, below the level of
which it receives branches of communication from the facial and
the spinal accessory. It then runs downward and forward, and is
distributed to the mucous membrane of the base of the tongue,
pillars of the fauces, soft palate, middle ear, and upper part of the
pharynx. It also sends some branches to the constrictors of the
pharynx and the neighboring muscles. Longet has found this
nerve at its origin to be exclusively sensitive ; but below the level
of its ganglion it has been found by him, as well as by various
other observers, to be both sensitive and motor, owing to the fibres
of communication received from the motor nerves mentioned above.
Its final distribution is, however, as we have seen, principally to
sensitive surfaces. The principal office of this nerve is to impart
the sense of taste to the posterior third of the tongue, to which it is
distributed. It also presides over the general sensibility of this
part of the tongue, as well as that of the fauces and pharynx.

Dr. John Reid,1 who has performed a great variety of experiments
upon this nerve, comes to the following conclusions in regard to it.
First, that it is essentially a sensitive nerve, since there are unequi-
vocal signs of pain when it is pricked, pinched, or cut. Second,
that irritation of this nerve produces convulsive movements of the
throat and lower part of the face ; but that these movements are, in
great measure, not direct, but reflex in their character, since they
will take place equally well after the glosso-pharyngeal has been
divided, if the irritation be applied to its cranial extremity. Third,
that this nerve supplies the special sensibility of taste to a portion
of the tongue ; but that it is not the exclusive nerve of this sense,
since the power of taste remains, after it has been divided on both
sides.

There are certain reflex actions, furthermore, which take place
through the medium of the glosso-pharyngeal nerve. After the
food has been thoroughly masticated, it is carried, by the move-
ments of the tongue and sides of the mouth, through the fauces,
and brought in contact with the mucous membrane of the pharynx.
This produces an impression which, conveyed to the medulla
oblongata by the filaments of the glosso-pharyngeal, excites the

1 In Todd's Cyclopaedia of Anatomy and Physiology, article Glosso-pharynyeal
Nerve.

PNEUMOGASTRIC NERVE. 461

muscles of the fauces and pharynx by reflex action. The food is
consequently grasped by these muscles, without the concurrence of
the will, and the process of deglutition is commenced. This action
is not only involuntary, but it will frequently take place even in
opposition to the will. The food, once past the isthmus of the fauces,
is beyond the control of volition, and cannot be returned except by
convulsive action, equally involuntary in its character.

Natural stimulants, therefore, applied to the mucous membrane
of the pharynx, excite deglutition; unnatural stimulants, applied
to the same part, excite vomiting. If the finger be introduced into
the fauces and pharynx, or if the mucous membrane of these part?
be irritated by prolonged tickling with the end of a feather, the
sensation of nausea, conveyed through the glosso-pharyngeal nerve,
is sometimes so great as to produce immediate and copious vomit-
ing. This method may often be successfully employed in cases of
poisoning, when it is desirable to excite vomiting rapidly, and when
emetic medicines are not at hand.

PXEUMOGASTRIC. — Owing to the numerous connections of the
pneumogastric with other nerves, its varied and extensive distribu-
tion, and the important character of its functions, this is properly
regarded as one of the most remarkable nerves in the whole body.
Owing to the wandering course of its fibres, which are distributed
to no less than four different vital organs, viz., the heart, lungs,
stomach and liver, as well as to several other parts of secondary
importance, it has been often known by the name of the par vagum.
The pneumogastric arises, by a number of separate filaments, from
the lateral portion of the medulla oblongata, in the groove between
the olivary and restiform bodies. These filaments unite into a
single trunk, which emerges from the cranium by the jugular fora-
men, where it is provided with a longitudinal ganglionic swelling,
the " ganglion of the pneumogastric nerve." Immediately below
the level of this ganglion the nerve receives an important branch
of communication from the spinal accessory, and afterward from
the facial, the hypoglossal, and the anterior branches of the first
and second cervicals.

At its origin, the pneumogastric is exclusively a sensitive nerve.
Irritated above the situation of its ganglion, it has been found to
convey painful sensations alone ; but if the irritation be applied at
a lower level, it causes at the same time muscular contractions,
owing to the filaments which it has received from the above-men-

462

THE CRANIAL NERVES.

Fig. 152.

tioned motor nerves. It becomes, consequently, after emerging
from the cranial cavity, a mixed nerve ; and has, accordingly, in
nearly all its branches, a double distribution, viz., to the mucous
membranes and the muscular coat of the organs to which it belongs.

The ordinary sensibility of the pneu-
mogastric nerve, however, as all experi-
menters have observed, is exceedingly
dull, in comparison with that of the other
sensitive cranial nerves. We have often
divided this nerve in the middle of the
neck, without any distinct manifestation
of pain being given by the animal ; and
though Bernard has found that at some
times its sensibility is well marked, while
at others it is very indistinct, he is not
able to say upon what special physio-
logical conditions this difference depends.
While the pneumogastric, however, is
decidedly deficient, as a general rule, in
ordinary sensibility, it possesses, as we
shall see hereafter, a sensibility of a pecu-
liar kind, which is exceedingly important
for the maintenance of the vital func-
tions.

In passing down the neck, this nerve
sends branches to the mucous membrane
and muscular coat of the pharynx, oeso-
phagus, and respiratory passages. Among
the most important of these branches are
the two laryngeal nerves, viz., the supe-
rior and inferior. The superior laryngeal
nerve, which is given off from the trunk
of the pneumogastric just after it has
emerged from the cavity of the skull,
passes downward and forward, penetrates
the larynx by an opening in the side of
the thyro-hyoid membrane, and is distributed to the mucous mem-:
brane of the larynx and glottis, and also to a single laryngeal mus-
cle, viz., the crico-thyroid. This branch is therefore partly mus-
cular, but mostly sensitive in its distribution. The inferior laryngeal
branch is given off just after the pneumogastric has entered the

Diagram of PNEUMOGASTRIC
NERVE, with its principalbrauclies.
— 1. Pharynireal branch. 2. Supe-
rior lary n^eal. 3. Inferior laryu-
freal. 4. Pulmonary branches. 6.
Stomach. 6. Liver.

PXEUMOGASTBIC NERVE. 463

cavity of the chest. It curves round the subclavian artery on the
right side and the arch of the aorta on the left, and ascends in the
groove between the trachea and oesophagus, to the larynx. It
then enters the larynx between the cricoid cartilage and the pos-
terior edge of the thyroid, and is distributed to all the muscles of
the larynx, with the exception of the crico- thyroid. This brand i
is, therefore, exclusively muscular in its distribution.

The trunk of the pneumogastric, after supplying the above
branches, as well as sending numerous filaments to the trachea
and oesophagus in the neck, gives off in the chest its pulmonary
branches, which follow the bronchial tubes in the lungs to their
minutest ramifications. It then passes into the abdomen and sup-
plies the muscular and mucous layers of the stomach, ramifying
over both the anterior and posterior surfaces of the organ ; after
which its fibres spread out and are distributed to the liver, spleen,
pancreas, and gall-bladder.

The functions of the pneumogastric will now be successively
studied in the various organs to which it is distributed.

Pharynx and (Esophagus. — The reflex action of deglutition, which
has already been described as commencing in the upper part of the
pharynx, by means of the glosso-pharyngeal, is continued in the
lower portion of the pharynx and throughout the oesophagus by
the aid of the pneumogastric. As the food is compressed by the
superior constrictor muscle of the pharynx and forced downward,
it excites the mucous membrane with which it is brought in contact
and gives rise to another contraction of the middle constrictor. The
lower constrictor is then brought into action in its turn in a similar
manner ; and a wave-like or peristaltic contraction is thence pro-
pagated throughout the entire length of the oesophagus, by which
the food is carried rapidly from above downward, and conducted at
last to the stomach. Each successive portion of the mucous mem-
brane, in this instance, receives in turn the stimulus of the food,
and excites instantly its own muscles to contraction ; so that the
food passes rapidly from one end of the oesophagus to the other, by
an action which is wholly reflex in character and entirely withdrawn
from the control of the will. Section of the pneumogastric, or of
its pharyngeal and cesophageal branches, destroys therefore at the
same time the sensibility and the motive power of these parts. The
food is no longer conveyed readily to the stomach, but accumulates
in the paralyzed oesophagus, into which it is forced by the voluntary

464 THE CRANIAL NERVES.

movements of the mouth and fauces, and by the continued action
of the upper part of the pharynx.

It must be remembered that the general sensibility of the oeso-
phagus is very slight, as compared with that of the integument, or
even of the mucous membranes near the exterior. It is a general
rule, in fact, that the sensibility of the mucous membranes is most
acute at the external orifices of their canals ; as, for example, at the
lips, anterior nares, anus, orifice of the urethra, &c. It diminishes
constantly from without inward, and disappears altogether at a
certain distance from the surface. The sensibility of the pharynx
is less acute than that of the mouth, but is still sufficient to enable
us to perceive the contact of ordinary substances; while in the
oesophagus we are not usually sensible of the impression of the food
us it passes from above downward. The reflex action takes place
here without any assistance from the consciousness ; and it is only
when substances of an unusually pungent or irritating nature are
mingled with the food, that its passage through the oesophagus pro-
duces a distinct sensation.

Larynx. — We have already described the course and distribution
of the two laryngeal branches of the pneumogastric. The superior
laryngeal nerve is principally the sensitive nerve of the larynx.
Its division destroys sensibility in the mucous membrane of this
organ, but paralyzes only one of its muscles, viz : the crico-thyrpid.
Galvanization of this nerve has also been found to induce con-
tractions in the crico-thyroid, but in none of the other muscles
belonging to the larynx. The inferior laryngeal, on the other
hand, is a motor nerve. Its division paralyzes all the muscles of
the larynx except the crico-thyroid ; and irritation of its divided
extremity produces contraction in the same muscles. The muscles
and mucous membrane of the larynx are therefore supplied by two
different branches of the same trunk, viz., the superior laryngeal
nerve for the mucous membrane, and the inferior laryngeal nerve
for the muscles.

The larynx, in man and in all the higher animals, performs a
double function ; one part of which is connected with the voice, the
other with respiration.

The formation of the voice in the larynx takes place as follows.
If the glottis be exposed in the living animal, by opening the
pharynx and oesophagus on one side, and turning the larynx for-
ward, it will be seen that so long as the vocal chords preserve
their usual relaxed condition during expiration, no sound is heard,

PNEUMOGASTRIC NERVE. 465

except the ordinary faint whisper of the air passing gently through
the cavity of the larynx. When a vocal sound, however, is to be
produced, the chords are suddenly made tense and applied closely
to each other, so as to diminish very considerably the size of the
orifice; and the air, driven by an unusually forcible expiration
through the narrow opening of the glottis, in passing between the
vibrating vocal chords, is itself thrown into vibrations which pro-
duce the sound required. The tone, pitch, and intensity of this
sound, vary with the conformation of the larynx, the degree of ten-
sion and approximation of the vocal chords, and the force of the
expiratory effort. The narrower the opening of the glottis, and the
greater the tension of the chords, under ordinary circumstances, the
more acute the sound ; while a wider opening and a less degree of
tension produce a graver note. The quality of the sound is also
modified by the length of the column of air included between the
glottis and the mouth, the tense or relaxed condition of the walls
of the pharynx and fauces, and the state of dryness or moisture of
the mucous membrane lining the aerial passages.

Articulation, on the other hand, or the division of the vocal sound
into vowels and consonants, is accomplished entirely by the lips,
tongue, teeth, and fauces. These organs, however, are under the
control of other nerves, and the mechanism of their action need not
occupy us here.

Since the production of a vocal sound, therefore, depends upon
the tension and position of the vocal chords, as determined by the
action of the laryngeal muscles, it is not surprising that division of
the inferior laryngeal nerves, by paralyzing these muscles, should
produce a loss of voice. It has been sometimes found that in very
young animals the crico-thyroid muscles, which are the only ones
not affected by division of the inferior laryngeal nerves, are still
sufficient to give some degree of tension to the vocal chords, and
to produce in this way an imperfect sound ; but usually the voice
is entirely lost after such an operation.

It is a very remarkable fact, however, in this connection, that all
the motor filaments of the pneumogastric, which are concerned in
the formation of the voice, are derived from a single source. It
will be remembered that the pneumogastric, itself originally a
sensitive nerve, receives motor filaments, on leaving the cranial
cavity, from no less than five different nerves. Of these filaments,
however, those coming from the spinal accessory are the only ones
necessary to the production of vocal sounds. For it has been found
30

466 THE CRANIAL NERVES.

by Bischoff and by Bernard1 that if all the roots of the spinal acces-
sory be divided at their origin, or if the nerve itself be torn away
at its exit from the skull, all the other cranial nerves remaining
untouched, the voice is lost as completely as if the inferior laryn-
geal itself had been destroyed. All the motor fibres of the pneu-
mogastric, therefore, which act in the formation of the voice are
derived, by inosculation, from the spinal accessory nerve.

In respiration, again, the larynx performs another and still more
important function. In the first place, it stands as a sort of guard,
or sentinel, at the entrance of the respiratory passages, to prevent
the intrusion of foreign substances. If a crumb of bread accidentally
fall within the aryteno-epiglottidean folds, or upon the edges of the
vocal chords, or upon the posterior surface of the epiglottis, the
sensibility of these parts immediately excites a violent expulsive
cough, by which the foreign body is dislodged. The impression
received and conveyed inward by the sensitive fibres of the superior
laryngeal nerve, is reflected back upon the expiratory muscles
of the chest and abdomen, by which the instinctive movements of
coughing are accomplished. Touching the above parts with the
point of a needle, or pinching them with the blades of a forceps,
will produce the same effect. This reaction is essentially dependent
on the sensibility of the laryngeal mucous membrane ; and it can
no longer be produced after section of the pneumogastric nerve, or
of its superior laryngeal branch.

In the second place, the respiratory movements of the glottis, already
described in a previous chapter, are of the greatest importance to
the preservation of life. We have seen that at the moment of
inspiration the vocal chords are separated from each other, and the
glottis opened, by the action of the posterior crico-arytenoid muscles ;
and that in expiration the muscles and the vocal chords are both
relaxed, and the air allowed to pass out readily through the glottis.
The opening of the glottis in inspiration, therefore, is an active
movement, while its partial closure or collapse in expiration is a
passive one. Furthermore, the opening of the glottis in inspiration
is necessary in order to afford a sufficiently wide passage for the
air, in its way to the trachea, bronchi, and pulmonary vesicles.

Now we have found, as Budge and Longet had previously no-
ticed, that if the inferior laryngeal nerve on the right side be
divided while the glottis is exposed as above, the respiratory move-

1 Recherches Experimentales sur les fonetions dn nerf spinal. Paris, 1851.

PNEUMOGASTRIC NERVE. 467

ments of the right vocal chord instantly cease, owing to the para-
lysis of the posterior crico-arytenoid muscle on that side. If the
inferior laryngeal nerve on the left side be also divided, the para-
lysis of the glottis is then complete, and its respiratory movements
cease altogether. A serious difficulty in respiration is the imme-
diate consequence of this operation. For the vocal chords, being
no longer stretched and separated from each other at the moment
of inspiration, but remaining lax and flexible, act as a double valve,
and are pressed inward by the column of inspired air ; thus par-
tially blocking up the passage and impeding the access of air to
the lungs. If the pneumogastrics be divided in the middle of the
neck, the larynx is of course paralyzed precisely as after section
of the inferior laryngeal nerves, since these nerves are given off
only after the main trunks have entered the cavity of the chest.
The immediate effect of either of these operations is to produce
a difficulty of inspiration, accompanied by a peculiar wheezing or
sucking noise, evidently produced in the larynx and dependent on
the falling together of the vocal chords. In very young animals,
as, for example, in pups a few days old, in whom the glottis is
smaller and the larynx less rigid than in adult dogs, this difficulty
is much more strongly marked. Legallois1 has even seen a pup
two days old almost instantly suffocated after section of the two
inferior laryngeal nerves. We have found that, in pups two
weeks old, division of the inferior laryngeals is followed by death
at the end of from thirty to forty hours, evidently from impeded
respiration.

The importance, therefore, of these movements of the glottis in
respiration becomes very evident. They are, in fact, part and
parcel of the general respiratory movements, and are necessary to
a due performance of the function. It has been found, moreover,
that the motor filaments concerned in this action are not derived,
like those of the voice, from a single source. While the vocal
movements of the larynx are arrested, as mentioned above, by
division of the spinal accessory alone, those of respiration still go
on ; and in order to put a stop to the latter, either the pneumo-
gastrics themselves must be divided, or all five of the motor nerves
from which their accessory filaments are derived. This fact has
been noticed by Longet as showing that nature multiplies the safe-
guards of a function in proportion to its importance ; for while the

1 In Longet's Traite de Phvsiologie, vol. ii. p. 324.

468 THE CRANIAL NERVES.

spinal accessory, or any other one of the above-mentioned nerves,
might be affected by local accident or disease, it would be very
improbable that any single injury should paralyze simultaneously
the spinal accessory, the facial, the hypoglossal, and the first and
second cervicals. The respiratory movements of the larynx are
consequently much more thoroughly protected than those which
are merely concerned in the formation of the voice.

Lungs. — The influence of the pneumogastric upon the function
of the lungs is exceedingly important. The nerve acts here, as in
most other organs to which it is distributed, in a double or mixed
capacity ; but it is principally as the sensitive nerve of the lungs
that it has thus far received attention. It is this nerve which
conveys from the lungs to the medulla oblongata that peculiar
impression, termed besoin de respirer, which excites by reflex action
the diaphragm and intercostal muscles, and keeps up the play of
the respiratory movements. As we have already shown, this action
is an involuntary one, and will even take place when consciousness
is entirely suspended. It may indeed be arrested for a time by an
effort of the will ; but the impression conveyed to the medulla soon
becomes so strong, and the stimulus to inspiration so urgent, that
they can no longer be resisted, and the muscles contract in spite of
our attempts to restrain them.

A very remarkable effect is accordingly produced on respiration
by simultaneous division of both pneumogastric nerves. This
experiment is best performed on adult dogs, which may be ether-
ized, and the nerves exposed while the animal is in a condition of
insensibility, avoiding, in this way, the disturbance of respiration,
which would follow if the dissection were performed while the ani-
mal was conscious and sensible to pain. After the effects of the
etherization have entirely passed off, and respiration and circulation
have both returned to a quiescent condition, the two nerves, which
have been previously exposed and secured by a loose ligature, may
be instantaneously divided, and the effects of the operation readily
appreciated.

Immediately after the division of the nerves, when performed in
the above manner, the respiration is hurried and difficult, owing to
the sudden paralysis of the larynx and partial closure of the glottis
by the vocal chords, as already described. This condition, how-
ever, is of short continuance. In a few moments, the difficulty of
breathing and the general agitation subside, the animal becomes
perfectly quiet, and the only remaining visible effect of the opera-

PNEUMOGASTRIC NERVE. 469

tion is a diminished frequency in the movements of respiration. This
diminution is frequently strongly marked from the first, the number
of respirations falling at once to ten or fifteen per minute, and be-
coming, in an hour or two, still farther reduced. The respirations
are performed easily and quietly ; and the animal, if left undisturbed,
remains usually crouched in a corner, without giving any special
signs of discomfort. If he be aroused and compelled to move
about, the frequency of the respiration is temporarily augmented ;
but as soon as he is again quiet, it returns to its former standard.
By the second or third day, the number of respirations is often
reduced to five, four, or even three per minute ; when this is the
case, the animal usually appears very sluggish, and is roused with
difficulty from his inactive condition. At this time the respiration
is not only diminished in frequency, but is also performed in a
peculiar manner. The movement of inspiration is slow, easy, and
silent, occupying several seconds in its accomplishment ; expiration,
on the contrary, is sudden and audible, and is accompanied by a well
marked expulsive effort, which has the appearance of being, to a
certain extent, voluntary in character. The intercostal spaces also
sink inward during the lifting of the ribs ; and the whole movement
of respiration has an appearance of insufficiency, as if the lungs
were not thoroughly filled with air. This insufficiency of respira-
tion is undoubtedly owing to a peculiar alteration in the pulmonary
texture, which has by this time already commenced.

Death takes place at a period varying from one to six days after
the operation, according to the age and strength of the animal.
The only symptoms accompanying it are a steady failure of the
respiration, with increased sluggishness and indisposition to be
aroused. There are no convulsions, nor any evidences of pain.
After death the lungs are found in a peculiar state of solidification,
which is almost exclusively a consequence of this operation, and
which is entirely different from ordinary inflammatory hepatization.
They are not swollen, but rather smaller than natural. They are
of a dark purple color, leathery and resisting to the feel, destitute
of crepitation, and infiltrated with blood. Pieces of the lung cut
out sink in water. The pleural surfaces, at the same time, are bright
and polished, and their cavity contains no effusion or exudation.
The lungs, in a word, are simply engorged with blood and empty
of air ; their tissue having undergone no other alteration.

These changes are not generally uniform over both lungs. The
organs are usually mottled on their exterior ; the variations in color

470 THE CRANIAL NERVES.

corresponding with the different degrees of alteration exhibited by
different parts.

The explanation usually adopted of the above consequences fol-
lowing division of the pneumogastrics is as follows : The nerves
being divided, the impression which originates in the lungs from
the accumulation of carbonic acid, and which is destined to excite
the respiratory movements by reflex action, can no longer be trans-
mitted to the medulla oblongata. The natural stimulus to respira-
tion being wanting, it is, accordingly, less perfectly performed. The
respiratory movements diminish in frequency, and, growing con-
tinually slower and slower, finally cease altogether, and death is
the result.

The above explanation, however, is not altogether sufficient. It
accounts very well for the diminished frequency of respiration, but
not for its partial continuance. For if the pneumogastric nerves
be really the channel through which the stimulus to respiration is
conveyed to the medulla, the difficulty is not to understand why
respiration should be retarded after division of these nerves, but
why it should continue at all. In point of fact, the respiratory
movements, though diminished in frequency, continue often for
some days after this operation. This cannot be owing to force of
habit, or to any remains of nervous influence, as has been some-
times suggested, since, when the medulla itself is destroyed, respira-
tion, as we know, stops instantaneously, and no attempt at move-
ment is made after the action of the nervous centre is suspended.

It is evident, therefore, that the pneumogastric nerve, though the
chief agent by which the respiratory stimulus is conveyed to the
medulla, is not the only one. The lungs are undoubtedly the
organs which are most sensitive to an accumulation of carbonic
acid, and an imperfect arterialization of the blood ; and the sensa-
tion which results from such an accumulation is accordingly first
felt in them. There is reason to believe, however, that all the vas-
cular organs are more or less capable of originating this impression,
and that all the sensitive nerves are capable, to some extent, of trans-
mitting it. Although the first disagreeable sensation, on holding
the breath, makes itself felt in the lungs, yet, if we persist in sus-
pending the respiration, we soon become conscious that the feeling
of discomfort spreads to other parts : and at last, when the accu-
mulation of carbonic acid and the impurity of the blood have
become excessive, all parts of the body suffer alike, and are per-
vaded by a general feeling of derangement and distress. It is easy;

PNEL'MOGASTKIC NERVE. 471

therefore, to understand why respiration should be retarded, after
section of the pneumogastrics, since the chief source of the stimulus
to respiration is cut off; bat the movements still go on. though more
slowly than before, because the other sensitive nerves, which con-
tinue to act, are also capable, in an imperfect manner, of conveying
the same impression.

The immediate cause of death, after this operation, is no doubt
the altered condition of the lungs. These organs are evidently
very^ imperfectly filled with air, for some time previous to death ;
and their condition, as shown in post-mortem examination, is evi-
dently incompatible with a due performance of the respiratory
function. It is not at all certain, however, that these alterations
in the pulmonary tissue are directly dependent on division of the
pneumogastric nerves. It must be recollected that when the sec-
tion of the pneumogastrics is performed in the middle of the neck,
the filaments of the inferior laryngeal nerves are also divided, and
the narrowing of the glottis, produced by their paralysis, must
necessarily interfere with the free admission of air into the chest.
This difficulty, either alone or combined with the diminished fre-
quency of respiration, must have a very considerable effect in im-
peding the pulmonary circulation, and bringing the lungs into such
a condition as unfits them for maintaining life.

In order to ascertain the comparative influence upon the lungs
of division of the inferior laryngeals and that of the other filaments
of the pneumogastrics, we have resorted to the following experi-
ment.

Two pups were taken, belonging to the same litter and of the
same size and vigor, about two weeks old. In one of them (No. 1)
the pneumogastrics were divided in the middle of the neck ; and
in the other (No. 2) a section was made at the same time of the
inferior laryngeals, the trunk of the pneumogastrics being left un-
touched. For the first few seconds after the operation, there was
but little difference in the condition of the two animals. There was
the same obstruction of the breath (owing to closure of the glottis),
the same gasping and sucking inspiration, and the same frothing at
the mouth. Very soon, however, in pup No. 1, the respiratory
movements became quiescent, and at the same time much reduced
in frequency, falling to ten, eight, and five respirations per minute,
as usual after section of the pneumogastrics ; while in No. 2 the
respiration continued frequent as well as laborious, and the general
signs of agitation and discomfort were kept up for one or two hours.

472 THE CRANIAL NERVES.

The animal, however, after that time became exhausted, cool, and
partially insensible, like the other. They both died, between thirty
and forty hours after the operation. On post-mortem inspection it
was found that the peculiar congestion and solidification of the
lungs, considered as characteristic of division of the pneumogastrics,
existed to a similar extent in each instance ; and the only appre-
ciable difference between the two bodies was that in No. 1 the blood
was coagulated, and the abdominal organs natural, while in No. 2
the blood was fluid and the abdominal organs congested. We are
led, accordingly, to the following conclusions with regard to the
effect produced by division of this nerve.

1. After section of the pneumogastrics, death takes place by a pecu-
liar congestion of the lungs.

2. This congestion is not directly produced by division of the
nerves, but is caused by the imperfect admission of air into the
chest.

In adult dogs, the closure of the glottis from paralysis of the
laryngeal muscles is less complete than in pups; but it is still
sufficient to exert a very decided influence on respiration, and to
take an active part in the production of the subsequent morbid
phenomena.

We therefore regard the death which takes place after division
of both pneumogastric nerves, as produced in the following man-
ner: —

The glottis is first narrowed by paralysis of the laryngeal mus-
cles, and an imperfect supply of air is consequently admitted, by
each inspiration, into the trachea. Next, the stimulus to respiration
being very much diminished, the respiratory movements take place
less frequently than usual. From these two causes combined, the
blood is imperfectly arterialized. But the usual consequence of
such a condition, viz., an increased rapidity of the respiratory
movements, does not follow. The imperfect arterialization of
the blood does not excite the respiratory muscles to increased
activity as it would do in health, owing to the division of the pneu-
mogastrics. At the same time, the accumulation of carbonic acid
in the blood and in the tissues begins to exert a narcotic effect,
diminishing the sensibility of the nervous centres, and tending to
retard still more the movements of respiration. Thus all these
causes react upon and aggravate each other ; because the connec-
tion, naturally existing between imperfectly tirterialized blood and
the stimulus to respiration, is now destroyed. The narcotism and

PNEUMOGASTRIC NERVE. 473

pulmonary engorgement, therefore, continue to increase, until the
lungs are so seriously altered and engorged that they are no longer
capable of transmitting the blood, and circulation and respiration
come to an end at the same time.

It must be remembered, also, that the pneumogastric nerve has
other important distributions, beside those to the larynx and the
lungs; and the effect produced by its division upon these other
organs has no doubt a certain share in producing the results which
follow. Bearing in mind the very extensive distribution of the
pneumogastric nerve and the complicated character of its func-
tions, we may conclude that after section of this nerve death takes
place from a combination of various causes; the most active of
which is a peculiar engorgement of the lungs and imperfect per-
formance of the respiratory function.

Stomach, and Digestive Function. — After division of the pneumo-
gastric nerves, the sensations of hunger and thirst remain, and the
secretion of gastric juice continues. Nevertheless the digestive
function is disturbed in various ways, though not altogether abo-
lished. The appetite is more or less diminished, as it would be
after any serious operation, but it remains sufficiently active to
show that its existence is not directly dependent on the integrity of
the pneumogastric nerve. Digestion, however, very seldom takes
place, to any considerable extent, owing to the following circum-
stances : The animal is frequently seen to take food and drink with
considerable avidity ; but in a few moments afterward the food and
drink are suddenly rejected by a peculiar kind of regurgitation.
This regurgitation does not resemble the act of vomiting, but the
substances swallowed are again discharged so easily and instan-
taneously as to lead to the belief that they had never passed into
the stomach. Such, indeed, is actually the case, as any one may
convince himself by watching the process, which is often repeated
by the animal at short intervals. The food and drink, taken volun-
tarily, pass down into the oasophagus, but owing to the paralysis of
the muscular fibres of this canal, are not conveyed into the stomach.
They accumulate consequently in the lower and middle part of the
oesophagus ; and in a few moments are rejected by a sudden anti-
staltic action of the parts, excited, apparently, through the influence
of the great sympathetic.

The muscular coat of the stomach is also paralyzed to a con-
siderable extent by section of this nerve. Longet has shown, by
introducing food artificially into the stomach, that gastric juice

47-i THE CRANIAL NERVES.

may be secreted and the food be actually digested and disappear,
when introduced in small quantity. But when introduced in large
quantity, it remains undigested, and is found after death, with the
exterior of the mass softened and permeated by gastric juice, while
the central portions are unaltered, and do not even seem to have
come in contact with the digestive fluid. This is undoubtedly
owing both to the diminished sensibility of the mucous membrane
of the stomach, and to the paralysis of its muscular fibres. The
peristaltic action of the organ is very important in digestion, in
order to bring successive portions of the food in contact with its
mucous membrane, and to carry away such as are already softened
or as are not capable of being digested in the stomach. This
constant movement and agitation of the food is probably also one
great stimulus to the continued secretion of the gastric juice. The
digestive fluid will therefore be deficient in quantity after division
of the pneumogastric nerve, at the same time that the peristaltic
movements of the stomach are suspended. Under these circum-
stances, the secretion of gastric juice may be sufficient to permeate
and digest small quantities of food, while a larger mass may resist
its action, and remain undigested. The effect produced by division
of these nerves on the digestive, as on the respiratory organs, is
therefore of a complicated character, and results from the combined
action of several different causes, which influence and modify each
other.

The effect produced upon the liver by section of the pneumo-
gastrics, as well as the influence usually exerted by these nerves
upon the hepatic functions, has been so little studied that nothing
definite has been ascertained in regard to it. We shall therefore
pass over this portion of the subject in silence.

SPINAL ACCESSORY. — This nerve originates, by many filaments,
from the side of the medulla oblongata, below the level of the
pneumogastric, and also from the lateral portions of the spinal cord,
between the anterior and posterior roots of the upper five or six
cervical nerves. These fibres of spinal origin pass upward, uniting
into a slender rounded filament, which enters the cavity of the
cranium by the foramen magnum, and is then joined by the fibres
which originate from the medulla oblongata. The spinal accessory
nerve, thus constituted, passes out from the cavity of the skull by
the posterior foramen lacerum, in company with the glosso-pharyn-
geal and pneumogastric nerves. Immediately afterward it divides

SPINAL ACCESSORY. 475

into two principal branches: First the internal or anastomotic
branch, which joins the pneumogastric nerve, and becomes mingled
with its fibres; and, secondly, the external or muscular branch,
which passes downward and outward/and is distributed to the
sterno-mastoid and trapezius muscles.

The spinal accessory is essentially a motor nerve. It has been
found, both by Bernard and Longet, to be insensible at its origin,
like the anterior roots of the spinal nerves ; but if irritated after
its exit from the skull, it gives signs of sensibility. This sensibi-
lity it acquires from the filaments of inosculation which it receives
from the anterior branches of the first and second cervical nerves.
Though its external branch, accordingly, is exclusively distributed
to muscles, as we have already seen, this branch contains some sensi-
tive fibres, which have the same destination. The reason for this
anatomical fact, viz., that motor nerves are supplied during their
course with sensitive fibres, becomes evident when we reflect that the
muscles themselves possess a certain degree of sensibility, though
less acute than that which belongs to the skin. The sensibility of
the muscles is undoubtedly essential to the perfect performance of
their function ; and as the motor nerves are incapable, by them-
selves, of transmitting sensitive impressions, they are joined, soon
after their origin, by other filaments which communicate to them
this necessary power.

The most important result which has been obtained by experi-
ment upon the spinal accessory nerve, is that its internal or anasto-
motic branch is directly connected with the vocal movements of the
glottis. It has been found by Bischoff, by Longet, and by Bernard,
that if the spinal accessory nerves on both sides, or their branches
of inosculation with the pneumogastric, be divided or lacerated,
the pneumogastric nerves themselves being left entire, the voice is
instantly lost, and the animal becomes incapable of making a vocal
sound. We have also found this result to follow, in the cat, after
the spinal accessory nerves have been torn out by their roots,
through the jugular foramen. The animal, after this operation, can
no longer make an audible sound. At the same time the respira-
tory movements of the glottis go on undisturbed, and most of the
other animal functions remain unaffected.

The fibres of communication, therefore, derived from the spinal
accessory, pass to the pneumogastric nerve and become entangled
with its other filaments, so that they can no longer be traced by
anatomical dissection. They pass downward, however, and become

476 THE CRANIAL NERVES.

a part of the motor fibres of the inferior laryngeal or recurrent
branches of the pneumogastric ; being finally distributed to the
muscles of the larynx, which they supply with those nervous influ-
ences which are required for the formation of the voice.

The special function of the external or muscular branch of the
spinal accessory is not so fully understood. This branch, as we
have seen, is distributed to the sterno-mastoid and trapezius mus-
cles. But these muscles also receive filaments from the cervical
spinal nerves ; and, accordingly, they still retain the power of mo-
tion, to a certain degree, after the external branches of the spinal
accessory have been divided on both sides.

The spinal accessory is, accordingly, a nerve of very peculiar
distribution. For it partly supplies motor fibres to the pneumo-
gastric nerve, and is partly distributed to two muscles, both of
which also receive motor nerves from another source. Sir Charles
Bell, noticing the close connection between this nerve and the
pneumogastric, regarded the two as associated also in their func-
tion, as nerves of respiration. He considered, therefore, the exter-
nal branch of the spinal accessory as destined to assist in the
movements of respiration, when these movements become unusu-
ally laborious, by bringing into play the sterno-mastoid and trape-
zius muscles, in aid of the action of the intercostals. He therefore
called this nerve the " superior respiratory nerve."

But the most satisfactory explanation of this peculiarity is that
proposed by M. Bernard. According to this explanation, whenever
a muscle, or set of muscles, derive their nervous influence from two
different sources, this is not for the purpose of assisting them in the
performance of the same function, but of enabling them to perform
two different functions. We have seen this already exemplified in
the muscles of the larynx. For these muscles perform certain
movements of respiration for which they receive indirectly filaments
from the facial hypoglossal, and cervical nerves. But they also
perform the movements necessary to the formation of the voice, the
nervous stimulus for which is derived altogether from the spinal
accessory.

The internal branch of the spinal accessory, accordingly, excites,
in the parts to which it is distributed a function which is incompa-
tible with respiration. For the movements of respiration cannot
go on while the voice is sounded; and a necessary preliminary
to the production of a vocal sound, is the temporary stoppage of
respiration. The movements of respiration, therefore, and the

HYPOGLOSSAL. 477

movements of the voice alternate with each other, but are never
simultaneous ; so that the internal branch of the spinal accessory is
antagonistic to the motor fibres of the larynx de^'Wl from other
nerves.

It is thought by M. Bernard, that the fibres of the external
branch of the spinal accessory have also a function which is anta-
gonistic to respiration. For respiration is naturally suspended in
all steady and prolonged muscular efforts. In these efforts, such as
those of straining, lifting, and the like, the movements of respira-
tion cease, the spinal column is made rigid by the contraction of
its muscles, and the head and neck are placed in a fixed position,
principally by the contraction of the sterno-mastoid and trapezius
muscles. The function of the spinal accessory, in both its branches,
is therefore regarded as destined to excite movements which are
incompatible with those of respiration ; and which accordingly come
into play only when the ordinary movements of respiration have
been temporarily suspended.

HYPOGLOSSAL. — The hypoglossal nerve originates from the ante-
rior and lateral portions of the medulla oblongata, and passing out
by the anterior condyloid foramen, is distributed exclusively to the
muscles of the tongue. Irritation of its fibres in any part of their
course produces convulsive twitching in this organ. Its section
paralyzes completely the movements of the tongue, without affect-
ing directly the sensibility of its mucous membrane. This nerve,
accordingly, is the motor nerve of the tongue. If irritated at its
origin, the hypoglossal nerve, according to the experiments of
Longet, is entirely insensible ; but if the irritation be applied in the
middle of its course, signs of pain are immediately manifested. Its
sensibility, like that of the facial, is consequently derived from its
inosculation with other sensitive nerves, after its emergence from
the skull.

4:78 THE SPECIAL SENSES.

CHAPTER VI.

\

THE SPECIAL SENSES.

GENEKAL AND SPECIAL SENSIBILITY. — We have already seen
that there exists, in the general integument, a power of sensation, by
which we are made acquainted with surrounding objects and some
of their most important physical qualities. By this power we feel
the sensations of heat and cold, and are enabled to distinguish
between hard and soft substances, rough bodies and smooth, solids
and liquids. This kind of power is termed General Sensibility,
because it resides in the general integument, and because by its
aid we obtain information with regard to the simplest and most
material properties of external objects.

The general sensibility, thus existing in the integument, is an
endowment of the sensitive nerves derived from the cerebro-spinal
system. These nerves ramify in the substance of the skin, and by
subsequent inosculation form a minute plexus in the superficial
portions of the tissue of the corium. From this plexus, the ulti-
mate filaments, reduced to an exceedingly minute size, pass up-
ward into the conical papilla with which the free surface of the
corium is covered. In the papilla the nervous filaments terminate,
sometimes by loops returning upon themselves, and sometimes ap-
parently by free extremities. The papillse are also supplied with
looped capillary bloodvessels, and are capable of receiving an
abundant vascular injection.

These papillae appear to be the most essential organs of general
sensation, since the sensibility of the skin is most acute where they
are most abundant and most highly developed, as, for example, on
the palm of the hand and the tips of the fingers.

The best method of measuring accurately the sensibility of dif-
ferent regions is that adopted by Professors Weber and Valentin.
They applied the rounded points of a pair of compasses to the
integument of different parts, and found that if they were held
very near together they could no longer be distinguished as sepa-

GENERAL AND SPECIAL SENSIBILITY. 479

rate points, but the two sensations were confounded into one. The
distance, however, at which the two points failed to be distinguished
from each other, was much shorter for some parts of the body
than for others. Prof. Valentin's measurements,1 which are the
most varied and complete, give the following as the limits of dis-
tinct perception in various parts : —

PARIS LINE.

At the tip of tongue .483

" palmar surface of tips of fingers .... .723

" " " of second phalanges . . . 1.558

" " " of first phalanges .... 1.650

" dorsum of tongue 2.500

" dorsal surface of fingers 3.900

" cheek 4.541

" back of hand 6.966

" skin of throat 8.292

" dorsum of foot 12.525

" skin over sternum 15.875

" middle of back 24.208

This method cannot, of course, give the absolute measure of the
acuteness of sensibility in the different regions, since the two points
might be less easily distinguished from each other in any one re-
gion, and yet the absolute amount of sensation produced might be
as great as in the surrounding parts ; still it is undoubtedly a very
accurate measure of the delicacy of tactile sensation, by which we
are enabled to distinguish slight inequalities in the surface of solid
bodies. AVe find, furthermore, that certain parts of the body are
particularly well adapted to exercise the function of general sen-
sation, not only on account of the acute sensibility of their integu-
ment, but also owing to their peculiar formation. Thus, in man,
the hands are especially well formed in this respect, owing to the
articulation and mobility of the fingers, by which they may be
adapted to the surface of solid bodies, and brought successively
in contact with all their irregularities and depressions. The hands
are therefore more especially used as organs of touch, and we are
thus enabled to obtain by their aid the most delicate and precise
information as to the texture, consistency, configuration, &c., of
foreign bodies.

But the hands are not the exclusive organs of touch, even in the
human subject, and in some of the lower animals, the same func-

1 In ToHd's Cyclopaedia of Anatomy and Physiology, vol. iv., article on Touch,
by Dr. Carpenter.

480 THE SPECIAL SENSES.

tion is fully performed by various other parts of the body. Thus
in the cat and in the seal, the long bristles seated upon the lips are
used for this purpose, each bristle being connected at its base with
a highly developed nervous papilla : in some of the monkeys the
extremity of the prehensile tail, and in the elephant the end of the
nose, which is developed into a flexible and sensitive proboscis, is
employed as an organ of touch. This function, therefore, may be
performed by either one part of the body or another, provided the
accessory organs be developed in a favorable manner.

About the head and face, the sensibility of the skin is dependent
mainly upon branches of the fifth pair. In the neck, trunk, and
extremities it is due to the sensitive fibres of the cervical, dorsal,
and lumbar spinal nerves. It exists also, to a considerable extent,
in the mucous membranes of the mouth and nose, and of the pas-
sages leading from them to the interior of the body. In these
situations, it depends upon the sensitive filaments of certain of the
cranial nerves, viz., the fifth pair, the glosso-pharyngeal, and the
pneumogastric. The sensibility of the mucous membranes is most
acute in those parts supplied by branches of the fifth pair, viz., the
conjunctiva, anterior part of the nares, inside of the lips and cheeks,
and the anterior two-thirds of the tongue. At the base of the
tongue and in the fauces, where the mucous membrane is supplied
by filaments of the glosso-pharyngeal nerve, the general sensibility
is less perfect; and finally it diminishes rapidly from the upper
part of the oesophagus and the glottis toward the stomach and the
lungs. Thus, we can appreciate the temperature and consistency
of a foreign substance very readily in the mouth and fauces, but
these qualities are less distinctly perceived in the oesophagus, and
not at all in the stomach, unless the foreign body happen to be
excessively hot or cold, or unusually hard and angular in shape.
The general sensibility, which is resident in the skin and in a certain
portion of the mucous membranes, diminishes in degree from with-
out inward, and disappears altogether in those organs which are
not supplied with nerves from the cerebro-spinal system.

It is particularly to be observed, however, that while the general
sensibility of the skin, and of the mucous membranes above men-
tioned, varies in acuteness in different parts of the body, it is every-
where the same in kind. The tactile sensations, produced by the
contact of a foreign body, are of precisely the same nature whether
they be felt by the tips of the fingers, the dorsal or palmar surfaces
of the hands, the lips, cheeks, or any other part of the integument.

TASTE. 481

The only difference in the sensibility of these parts lies in the de-
gree of its development.

But there are certain other sensations which are different in kind
from those perceived by the general integument, and which, owing
to their peculiar and special character, are termed special sensations.
Such are, for example, the sensation of light, the sensation of sound,
the sensation of savor, and the sensation of odors. The special
sensibility which enables us to feel the impressions derived from
these sources is not distributed over the body, like ordinary sensi-
bility, but is localized in distinct organs, each of which is so con-
stituted as to receive the special sensation peculiar to it, and no
other.

Thus we have, beside the general sensibility of the skin and
mucous membranes, certain peculiar faculties or special senses, as
they are called, which enable us to derive information from ex-
ternal objects, which we could not possibly obtain by any other
means. Thus light, however intense, produces no perceptible sen-
sation when allowed to fall upon the skin, but only when admitted
to the eye. The sensation of sound is perceptible only by the
ear, and that of odors only by the olfactory membrane. These
different sensations, therefore, are not merely exaggerations of
ordinary sensibility, but are each distinct and peculiar in their
nature, and are in relation with distinct properties of external
objects.

In examining the organs of special sense, we shall find that they
each consist — First, of a nerve, endowed with the special sensibility
required for the exercise of its peculiar function ; and, Secondly, of
certain accessory parts, forming an apparatus more or less compli-
cated, which is intended to assist in its performance and render it
more delicate and complete. We shall take up the consideration
of the special senses in the following order. First, the sense of
Taste ; second, that of Smell ; third, that of Sight ; and fourth, that
of Hearing.

TASTE. — We begin the study of the special senses with that of
Taste, because this sense is less peculiar than any of the others, and
differs less, both in its nature and its conditions, from the ordinary
sensibility of the skin. In the first place, the organ of taste is no
other than a portion of the mucous membrane, beset with vascular
and nervous papillae, similar to those of the general integument.
31

482 THE SPECIAL SENSES.

Secondly, it gives us impressions of such substances only as are
actually in contact with sensitive surfaces, and can establish no
communication with objects at a distance. Thirdly, the surfaces
which exercise the sense of taste are also endowed with general sen-
sibility; and Fourthly, there is no one special and distinct nerve
of taste, but this property resides in portions of two different
nerves, viz., the fifth pair and the glosso-pharyngeal ; nerves which
also supply general sensibility to the mouth and surrounding parts.
The sense of taste is localized in the mucous membrane of the
tongue, the soft palate, and the fauces. The tongue, which is more
particularly the seat of this sense, is a flattened, leaf-like, muscular
organ, attached to the inner surface of the symphysis of the lower
jaw in front, and to the os hyoides behind. It has a vertical sheet
or lamina of fibrous tissue in the median line, which serves as a
framework, and is provided with an abundance of longitudinal
transverse and radiating muscular fibres, by which it can be elon-
gated, retracted, and moved about in every direction.

The mucous membrane of the fauces and posterior third of the
tongue, like that lining the cavity of the mouth, is covered with
minute vascular papillae, similar to those of the skin, which are,
however, imbedded and concealed in the smooth layer of epithe-
lium forming the surface of the organ. But about the junction of
its posterior and middle thirds, there is, upon the dorsum of the
tongue, a double row of rounded eminences, arranged in a V-shaped
figure, running forward and outward, on each side, from the situa-
tion of the foramen caecum ; and, from this point forward, the upper
surface of the organ is everywhere covered with an abundance of
thickly-set, highly developed papillae, projecting from its surface,
and readily visible to the naked eye.

These lingual papillae are naturally divided into three different
sets or kinds. First, the filiform papillse, which are the most nume-
rous, and which cover most uniformly the upper surface of the
organ. They are long and slender, and are covered with a some-
what horny epithelium, usually prolonged at their free extremity
into a filamentous tuft. At the edges of the tongue these papillae
are often united into parallel ranges or ridges of the mucous mem-
brane. Secondly, the fungiform papillae. These are thicker and
larger than the others, of a rounded club-shaped figure, and covered
with soft, permeable epithelium. They are most abundant at the
tip of the tongue, but may be seen elsewhere on the surface of the
organ, scattered among the filiform papillae. Thirdly, the circum-

TASTE. 483

va llate pa-pill se. These are the rounded eminences which form the
V-shaped figure near the situation of the foramen caecum. They
are eight or ten in number. Each one of them is surrounded by
a circular wall, or circumvallation, of mucous membrane, which
gives to them their distinguishing appellation. The circumvalla-
tion, as well as the central eminence, has a structure similar to that
of the fimgiform papillae.

The sensitive nerves of the tongue, as we have already seen, are
two in number, viz., the lingual branch of the fifth pair, and the
lingual portion of the glosso-pharyngeal. The lingual branch of
the fifth pair enters the tongue at the anterior border of the hyo-
glossus muscle, and its fibres then run through the muscular tissue
of the organ, from below upward and from behind forward, with-
out any ultimate distribution, until they reach the mucous mem-
brane. The nervous filaments then penetrate into the lingual
papillae, where they finally terminate. The exact mode of their
termination is not positively known. According to Kolliker, they
sometimes seem to end in loops, and sometimes by free extremities.

The lingual portion of the glosso-pharyngeal nerve passes into
the tongue below the posterior border of the hyo-glossus muscle.
It then divides into various branches, which pass through the mus-
cular tissue, and are finally distributed to the mucous membrane of
the base and sides of the organ.

Fig. 153.

DIAGRAM OF To NOUE, with its sensitive nerves and papillae.— 1. Lingual branch of fifth pair,
2. Glosso-pharyngeal nerve.

The mucous membrane of the base of the tongue, of its edges,
and its under surface near the tip, as well as the mucous membrane
of the mouth and fauces generally, is also supplied with mucous
follicles, which furnish a viscid secretion by which the free surface
of the parts is lubricated.

484 THE SPECIAL SENSES.

Finally, the muscles of the tongue, it will be remembered, are
animated exclusively by the filaments of the hypoglossal nerve.

The exact seat of the sense of taste has been determined by
placing in contact with different parts of the mucous membrane a
small sponge, moistened with a solution of some sweet or bitter
substance. The experiments of Verniere, Longet and others have
shown that the sense of taste resides in the whole superior surface,
the point and edges of the tongue, the soft palate, fauces, and part
of the pharynx. The base, tip, and edges of the tongue seem to
possess the most acute sensibility to savors, the middle portion of
its dorsum less of this sensibility, and its inferior surfaces little or
none. Now as the whole anterior part of the organ is supplied by
the lingual branch of the fifth pair alone, and the whole of its
posterior portion by the glosso-pharyngeal, it follows that the sense
of taste, in these different parts, is derived from these two different
nerves.

Furthermore, the tongue is supplied, at the same time and by the
same nerves, with- general sensibility and with the special sensibility of
taste. The general sensibility of the anterior portion of the tongue,
and that of the branch of the fifth pair with which it is supplied,
are sufficiently well known. Section of the fifth pair destroys the
sensibility of this part of the tongue as well as that of the rest of
the face. Longet has found that after the lingual branch of this
nerve has been divided, the mucous membrane of the anterior two-
thirds of the tongue may be cauterized with a hot iron or with
caustic potassa, in the living animal, without producing any sign of
pain. Dr. John Keid, on the other hand, together with other experi-
menters, has determined that ordinary sensibility exists in a marked
degree in the glosso-pharyngeal, and is supplied by it to the parts
to which this nerve is distributed.

Accordingly we must distinguish, in the impressions produced
by foreign substances taken into the mouth, between the special
impressions derived from their sapid qualities, and the general sensa-
tions produced by their ordinary physical properties. As the tongue is
exceedingly sensitive to ordinary impressions, and as the same body
is often capable of exciting both the tactile and gustatory functions,
these two properties are sometimes liable to be confounded with
each other by careless observation. The truly sapid qualities,
however, the only ones, properly speaking, which we perceive by
the sense of taste, are such savors as we designate by the term
sweet, bitter, salt, sour, alkaline, and the like. But there are many

TASTE. 485

other properties, belonging to various articles of food, which belong
really to the class of ordinary physical qualities and are appre-
ciated by the ordinary sensibility of the tongue, though we usually
speak of them as being perceived by the taste. Thus a starchy,
viscid, watery, or oleaginous taste is merely a certain variety of con-
sistency in the substance tasted, which may exist either alone or in
connection with real savors, but which is exclusively perceived by
means of the general sensibility. So also with a pungent or burning
taste, such as that of red pepper or any other irritating powder.
The quality of piquancy in the preparation of artificial kinds of
food is alwa}^s communicated to them by the addition of some such
irritating substance. The styptic taste seems to be a combination of
an ordinary irritant or astringent effect with a peculiar taste, which
we always associate with the former quality in astringent sub-
stances.

There is also sometimes a liability to confound the real taste of
certain substances with their odorous properties, or flavors. Thus
in most aromatic articles of food, such as tea and coffee, and in
various kinds of wine, a great part of what we call the taste is in
reality due to the aroma, or smell which reaches the nares during
the act of swallowing. Even in many solid kinds of food, such as
freshly cooked meats, the odor produces a very important part of
their effect on the senses. We can easily convince ourselves of this
by holding the nose while swallowing such substances, or by recol-
lecting how much a common catarrh interferes with our perception
of their taste.

The most important conditions of the sense of taste are the fol-
lowing : —

In the first place, the sapid substance, in order that its taste may
be perceived, must be brought in contact with the mucous mem-
brane of the mouth in a, state of solution. So long as it remains
solid, however marked a savor it may possess, it gives no other
impression than that of any foreign body in contact with the sensi-
tive surfaces. But if it be applied in a liquid form, it is then spread
over the surface of the mucous membrane, and its taste is imme-
diately perceived. Thus it is only the liquid and soluble portions
of our food which are tasted, such as the animal and vegetable
juices and the soluble salts. Saline substances which are insoluble,
such as calomel or carbonate of lead, when applied to the tongue,
produce no gustatory sensation whatever.

The mechanism of the sense of taste is, therefore, in all proba-

486 THE SPECIAL SENSES.

bility, a direct and simple one. The sapid substances in solution
penetrate the lingual papillae by endosmosis, and, coming in actual
contact with the terminal nervous filaments, excite their sensibility
by uniting with their substance. We have already seen that the
rapidity with which endosmosis will take place under certain con-
ditions is sufficiently great to account for the almost instantaneous
perception of the taste of sapid substances when introduced into the
mouth.

It is on this account that a free secretion of the salivary fluids is
so essential to the full performance of the gustatory function. If
the mouth be dry and parched, our food seems to have lost its taste :
but when the saliva is freely secreted, it is readily mixed with the
food in mastication, and assists in the solution of its sapid ingredi-
ents ; and the fluids of the mouth, thus impregnated with the savory
substances, are absorbed by the mucous membrane, and excite the
gustatory nerves. An important part, also, is taken in this process
by the movements of the tongue ; for by these movements the food
is carried from one part of the mouth to another, pressed against
the hard palate, the gums, and the cheeks, its solution assisted, and
the penetration of the fluids into the substance of the papillae more
rapidly accomplished. If a little powdered sugar, or some vege-
table extract be simply placed upon the dorsum of the tongue, but
little effect is produced ; but as soon as it is pressed by the tongue
against the roof of the mouth, as naturally happens in eating or
drinking, its taste is immediately perceived. This effect is easily
explained ; since we know how readily movement over a free sur-
face, combined with slight friction, will facilitate the imbibition of
liquid substances. The nervous papillae of the tongue may there-
fore be regarded as the essential organs of the sense of taste, and
the lingual muscles as its accessory organs.

The full effect of sapid substances is not obtained until they are actu-
ally swallowed. During the preliminary process of mastication a
sufficient degree of impression is produced to enable us to perceive
the presence of any disagreeable or injurious ingredient in the food,
and to get rid of it, if we desire. But it is only when the food is
carried backward into the fauces and pharynx, and is compressed
by the constrictor muscles of these parts, that we obtain a complete
perception of its sapid qualities. For at that time the food is spread
out by the compression of the muscles, and brought at once in
contact with the entire extent of the mucous membrane possessing
gustative sensibility. Then, it is no longer under the control of the

TASTE. 487

will, and is carried by the reflex actions of the pharynx and oeso-
phagus downward to the stomach.

The impressions of taste made upon the tongue remain for a cer-
tain time afterward. When a very sweet or very bitter substance
is taken into the mouth, we retain the taste of its sapid qualities
for several seconds after it has been ejected or swallowed. Conse-
quently, if several different savors be presented to the tongue in
rapid succession, we soon become unable to distinguish them, and
they produce only a confused impression, made up of the union of
various different sensations ; for the taste of the first, remaining in
the mouth, is mingled with that of the second, the taste of these
two with that of the third, and so on, until so many savors become
confounded together that we are no longer able to recognize either
of them. Thus it is notoriously impossible to recognize two or
three different kinds of wine with the eyes closed, if they be repeat-
edly tasted in quick succession.

If the substance first tasted have a particularly marked savor,
its taste will preponderate over that of the others, and perhaps pre-
vent our recognizing them at all. This effect is still more readily
produced by substances which excite the general sensibility of the
tongue, such as acrid or stimulating powders. In the same manner
as a painful sensation, excited in the skin, prevents the nerves, for
the time, from perceiving delicate tactile impressions, so any pungent
or irritating substance, which excites unduly the general sensibility
of the tongue, blunts for a time its special sensibility of taste. This
effect is produced, however, in the greatest degree, by substances
which are at the same time sapid, pungent and aromatic, like sweet-
meats flavored with peppermint. Advantage is sometimes taken
of this in the administration of disagreeable medicines. By first
taking into the mouth some highly flavored and pungent substance,
nauseous drugs may be swallowed immediately afterward with but
little perception of their disagreeable qualities.

A very singular fact, in connection with the sense of taste, is that
it is sometimes affected in a marked degree by paralysis of the facial
nerve. No less than six cases of this kind, occurring in the human
subject, have been collected by M. Bernard, and we have also met
with a similar instance in which the peculiar phenomena were well
marked. M. Bernard has furthermore seen a similar effect upon
the taste produced in animals by division of the facial nerve within
the cranium. The result of these experiments and observations is
as follows : When the facial nerve is divided or seriously injured

4SS THE SPECIAL SENSES.

by organic disease, before its emergence from the stylo-mastoid
foramen, not only is there a paralysis of the superficial muscles of
the face, but the sense of taste is diminished on the corresponding
side of the tongue. If the tongue be protruded, and salt, citric acid
or sulphate of quinine be placed upon its surface on the two sides
of the median line, the taste of these substances is perceived on the
affected side more slowly and obscurely than on the other. It is
not, therefore, a destruction, but only a diminution of the sense of
taste, which follows paralysis of the facial in these instances. At
the same time the general tactile sensibility of the tongue is unal-
tered, retaining its natural acuteness on both sides of the tongue.

The exact mechanism of this peculiar influence of the facial nerve
upon the sense of taste is not perfectly understood. It may be
considered as certain, however, that it is derived through the
medium of that branch of the facial nerve known as the chorda
tympani. This filament leaves the facial at the intumescentia
gangliformis, in the^interior of the aqueduct of Fallopius, enters the
cavity of the tympanum, passes across the membrane of the tym-
panum, and then, emerging from the cranium, runs downward and
forward and joins the lingual branch of the fifth pair. It then ac-
companies this nerve as far as the posterior extremity of the sub-
maxillary gland. Here it divides into two portions ; one of which
passes to the subm axillary ganglion, and, through it, to the sub-
stance of the submaxillary gland, while the other continues onward,
still in connection with the lingual branch of the fifth pair, and, in
company with the filaments of this nerve, is distributed to the tongue.

The chorda tympani thus forms the only anatomical connection
between the facial nerve and the anterior part of the tongue. When
the facial, accordingly, is divided or injured after its emergence
from the stylo-mastoid foramen, no effect is produced upon the
sense of taste; but when it is injured during its course through the
aqueduct of Fallopius, and before it has given off the chorda tym-
pani, this nerve suffers at the same time, and the sense of taste is
diminished in activity, as above described. It is probable that this
affect is produced in an indirect way, by a diminution in the activity
of secretion in the lingual follicles, or by some alteration in the
vascularity of the parts.

SMELL. — The main peculiarity of the sense of smell consists in
the fact that it gives us intelligence of the physical character of
bodies in a gaseous or vaporous condition. Thus we are enabled to

SMELL.

489

perceive the existence of an odorous substance at a distance, and
when it is altogether concealed from sight. The minute quantity
of volatile material emanating from it, and thus pervading the
atmosphere, comes in contact with the mucous membrane of the
nose, and produces a peculiar and special sensation.

The apparatus of this sense consists, first, of the olfactory mem-
brane, supplied by the filaments of the olfactory nerve, as its
special organ ; and secondly, of the nasal passages, with the tur-
binated bones and the muscles of the anterior and posterior nares,
as its accessory organs. At the upper part of the nasal fossae,
the mucous membrane is very thick, soft, spongy and vascular,
and is supplied with mucous follicles which exude a secretion, by
which its surface is protected and kept in a moist and sensitive
condition.

It is only this portion of the mucous membrane of the nares
which is supplied by filaments of the olfactory nerve, and which is
capable of receiving the impressions of smell ; it is therefore called
the Olfactory membrane. Elsewhere, the nasal passages are lined
with a mucous membrane which is less vascular and spongy in
structure, and which is called the Schneiderian membrane.

The filaments derived from the olfactory ganglia, and which
penetrate through the cribri-
form plate of the ethmoid
bone, are distributed to the
mucous membrane of the su-
perior and middle turbinated
bones, and to that of the upper
part of the septum nasi. The
exact mode in which these
filaments terminate in the ol-
factory membrane has not
been definitely ascertained.
They are of a soft consistency
and gray color, and, after di-
viding and ramifying freely
in the membrane, appear to
become lost in its substance.
It is these nerves which exer-
cise the special function of
smell. They are, to all appearnnce, incapable of receiving ordinary
impressions, and must be regarded as entirely peculiar in their

DISTRIBUTION OF XEKVE s IN THE NASAI.
FASSJAUES. — 1. Olfactory ganglion, w'thits nerves
2. Nasal branch of fifth pair. 3. Spheuo-palatiue
ganglion.

490 THE SPECIAL SENSES.

nature and endowments. The nasal passages, however, are supplied
with other nerves beside the olfactory. The nasal branch of the
ophthalmic division of the fifth pair, after entering the anterior part
of the cavity of the nares, just in advance of the cribriform plate of
the ethmoid bone, is distributed to the mucous membrane of the in-
ferior turbinated bone and the inferior meatus. Thus the organ
of smell is provided with sensitive nerves from two different sources,
viz., at its upper part, with the olfactory nerves proper, derived
from the olfactory ganglion (Fig. 154, i), which are nerves of special
sensation ; and secondly, at its lower part, with the nasal branch of
the fifth pair (2), a nerve of general sensation. Beside which, the
spheno-palatine ganglion of the great sympathetic (a) sends fila-
ments to the mucous membrane of the whole posterior part of the
nasal passages, and to the levator palati and azygos uvula3 muscles.
Finally, the muscles of the anterior nares are supplied by filaments
of the facial nerve.

The conditions of the sense of smell are much more special in
their nature than those of taste. For, in the first place, this sense is
excited, not by actual contact with the foreign body, but only with
its vaporous emanations; and the quantity of these emanations,
sufficient to excite the smell, is often so minute as to be altogether
inappreciable by other means. We cannot measure the loss of
weight in an odorous body, though it may affect the atmosphere
of an entire house, and the senses of all its inhabitants, for days
and weeks together. Secondly, in the olfactory organ, the special
sensibility of smell and the general sensibility of the mucous mem-
brane are separated from each other and provided for by different
nerves, not mingled together and exercised by the same nerves, as
is the case in the tongue.

In order to produce an olfactory impression, the emanations of
the odorous body must be drawn freely through the nasal passages.
As the sense of smell, also, is situated only in the upper part of these
passages, whenever an unusually faint or delicate odor is to be per-
ceived, the air is forcibly directed upward, toward the superior
turbinated bones, by a peculiar inspiratory movement of the nos-
trils. This movement is very marked in many of the lower animals.
As the odoriferous vapors arrive in the upper part of the nasal
passages, they are undoubtedly dissolved in the secretions of the
olfactory membrane, and thus brought into relation with its nerves.
Inflammatory disorders, therefore, interfere with the sense of smell,
both by checking or altering the secretions of the part, and by

SMELL. 491

producing an unnatural tumefaction of the mucous membrane,
which prevents the free passage of the air through the nasal fossae.

As in the case of the tongue, also, we must distinguish here
between the perception of true odors, and the excitement of the
general sensibility of the Schneiderian mucous membrane by irri-
tating substances. Some of the true odors are similar in their nature
to impressions perceived by the sense of taste. Thus we have
sweet and sour smells, though none corresponding to the alkaline
or the bitter tastes. Most of the odors, however, are of a very
peculiar nature and are difficult to describe ; but they are always
distinct from the simply irritating properties which may belong to
vapors as well as to liquids. Thus, pure alcohol has little or no
odor, and is only irritating to the mucous membrane ; while the
odor of wines, of cologne water, &e., is communicated to them by
the presence of other ingredients of a vegetable origin. In the
same way, pure acetic acid is simply irritating; while vinegar has
a peculiar odor in addition, derived from its vegetable impurities.
Ammonia, also, is an irritating vapor, but contains in itself no
odoriferous principle.

The sensations of smell, like those of taste, remain for a certain timt
after they have been produced, and modify in this way other less
strongly marked odors which are presented afterward. As a
general thing, the longer we are exposed to a particular odor, the
longer its effect upon our senses continues ; and in some cases it
may be perceived many hours after the odoriferous substance has
been removed. Odors, however, are particularly apt to remain
after the removal or destruction of the source from which they
were derived, owing to their vaporous character, and the facility
with which they are entangled and retained by porous substances,
such as plastered walls, woollen carpets, and hangings, and woollen
clothes. It is supposed to be in this way that the odor of a post-
mortem examination will sometimes remain so as to be perceptible
for several hours or even an entire day afterward. But this alone
does not fully explain the fact. For if it depended simply on the
retention of the odor by porous substances, it would afterward be
perceived constantly, until it gradually and continuously wore off;
while in point of fact, the physician who has made an autopsy of
this kind does not afterward perceive its odor constantly, but only
occasionally, and by sudden and temporary fits.

The explanation is probably this. As the odor remains con-
stantly by us, we soon become insensible to its presence, as in the

492 THE SPECIAL SENSES.

case of all other continuous and unvarying impressions. Our at-
tention is only called to it when we meet suddenly with another
and familiar odor. This second odor, we find, does not produce its
usual impression, because it is mingled with and modified by the
other, which is more persistent and powerful. Thus we are again
made aware of the former one, to which we had become insensible
by reason of its constant presence.

The sense of smell is comparatively feeble in the human species,
but is excessively acute in some of the lower animals. Thus, the
dog will not only distinguish different kinds of game in the forest
by this sense, and follow them by their tracks, but will readily dis-
tinguish particular individuals by their odor, and will recognize
articles of dress belonging to them by the minute quantity of odor-
iferous vapors adhering to their substance.

SIGHT. — The sight undoubtedly occupies the first rank in the
list of special nervous endowments. It is the most peculiar in its
operation, and the most immaterial in its nature, of all the senses,
and it is through it that we receive the most varied and valuable
impressions. The physical agent, also, to which the organ of sight
is adapted, and by which its sensibility is excited, is more subtle
and peculiar than any of those which act upon our other senses.
For the senses of touch, taste, and smell require, for their exercise,
the actual contact of a foreign body, either in a solid, liquid, or
aeriform condition; and even the hearing depends upon the me-
chanical vibrations of the atmosphere, or some other sonorous
medium. But the eye does not need to be in contact with the
luminous body. It will receive the impressions of light with per-
fect distinctness, even when they are transmitted from an immea-
surable distance, as in the case of the fixed stars ; ancj the light
itself is not only immaterial in its nature, so far as we can ascertain,
but is also capable of being transmitted through space without the
intervention of any material conducting medium, yet discoverable.

Finally, the apparatus of vision is more complicated in its struc-
ture than that of any other of the special senses. This apparatus
consists, first, of the retina, as a special sensitive nervous membrane ;
and secondly, of the vitreous body, crystalline lens, choroid, scle-
rotic, iris and cornea, together with the muscles moving the eye-
ball and eyelids, lachrymal gland, &c., as accessory organs. The
arrangement of the parts, constituting the globe of the eye, is shown
in the following figure. (Fig. 155.)

SIGHT. 493

The filaments of the optic nerve, after running forward and pene-
trating the posterior part of the eyeball, spread out into the sub-
stance of the retina (a), thus forming a delicate and vascular nerv-

Vertical Section of the EYE BALI, .—1. Sclerotic. 2 Choroid. 3. Ketina. 4. Lens. 5. Hyaloid
membraue. 6. Cornea. 7. Iris. 8. Ciliary muscle and processes.

ous expansion, in the form of a spheroidal bag or sac, with a wide
opening in front, where the retina terminates at the posterior mar-
gin of the ciliary body. This expansion of the retina is the essen-
tial nervous apparatus of the eye. It is endowed with the special
sensibility which renders it capable of receiving luminous impres-
sions ; and, so far as we have been able to ascertain, it is incapable of
perceiving any other. On the outside, the retina is covered by the
choroid coat (2), a vascular membrane, which is rendered opaque by
the presence of an abundant layer of blackish-brown pigment-cells,
and which thus absorbs the light which has once passed through
the retina, and prevents its being reflected in such a way as to
confuse and dazzle the sight. Inside the retina is the vitreous body,
a transparent spheroidal mass of a gelatinous consistency, which is
surrounded and retained in- position by a thin, structureless mem-
brane, called the hyaloid membrance (5), lying immediately in
contact with the internal surface of the retina. The lens (4) is
placed in front of the vitreous body, in the central axis of the eye-
ball, enveloped in its capsule, which is continuous with the hyaloid
membrane. Just at the edge of the lens, the hyaloid membrane
divides into two laminae, which separate from each other, leaving
between them a triangular canal, the canal of Petit, which can be
seen in the above figure. In front of the lens is the iris (7), a nearly

494 THE SPECIAL SENSES.

vertical muscular curtain, formed of radiating and concentric fibres,
pierced at its centre with a circular opening, the pupil, through
which the light is admitted, and covered on its posterior surface
with a continuation of the choroidal pigment, which excludes the
passage of any other rays than those which pass through the pupil.
At the same time, the whole globe is inclosed and protected by a
thick, fibrous, laminated tunic, which in its posterior and middle
portions is opaque, forming the sclerotic (i), and in its anterior por-
tion is transparent, forming the cornea (s). The muscles of the eye-
ball are attached to the external surface of the sclerotic in such a
way that the cornea may be readily turned in various directions ;
while the eyelids, which may be opened and closed at will, protect
the eye from injury, and, with the aid of the lachrymal secretion,
keep its anterior surfaces moist, and preserve the transparency of
the cornea.

The organ of vision is supplied with nerves of ordinary sensi-
bility by the ophthalmic branch of the fifth pair. The filaments
of this nerve which terminate about the eye are distributed mostly
to the conjunctiva, lachrymal gland, and skin of the eyelids; while
a very few of them run forward in company with the ciliary nerves
proper, and are distributed to the ciliary circle and iris. All these
parts, therefore, but more particularly the conjunctiva and skin of
the eyelids, possess ordinary sensibility, which appears to be totally
wanting in the deeper parts of the eye. The ophthalmic ganglion
gives off the ciliary nerves, which are distributed to the iris and
ciliary muscle. Finally, the muscles moving the eyeball and eye-
lids are supplied with motor nerves from the third, fourth, sixth
and seventh pairs.

Of all the properties and functions belonging to the different
structures of the eyeball, the most peculiar and characteristic is the
special sensibility of the retina. This sensibility is such that the
retina appreciates both the intensity and the quality of the light —
that is to say, its color and the different shades which this color
may present. On account of the form, also, in which the retina is
constructed, viz., that of a spheroidal membranous bag, with an
opening in front, it becomes capable of appreciating the direction
from which the rays of light have come, and, of course, the situation
of the luminous body and of its different parts. For the rays which
enter through the pupil from below can reach the retina only at its
upper part, while those which come in from above, can reach it
only at its lower part ; so that in both instances the rays strike the

SIGHT. 495

sensitive surface perpendicularly, and thus convey the impression
of their direction from above or below.

But beside the sensibility of the retina, the perfection and value
of the sense of sight depend very much on the arrangement of the
accessory organs, the most important of which is the crystalline lens.

The function of the crystalline lens is to produce distinct perception
of form and outline. For if the eye consisted merely of a sensitive
retina, covered with transparent integument, though the impressions
of light would be received by such a retina they could not give
any idea of the form of particular objects, but could only produce
the sensation of a confused luminosity. This condition is illus-
trated in Fig. 156, where the arrow, a, b, represents the luminous
object, and the vertical dotted line, at the right of the diagram,
represents the retina. Rays, of course, will diverge from every
point of the object in ever}7 direction, and will thus reach every
part of the retina. The different parts of the retina, consequently,
1, 2, 3, 4, will each receive rays coming both from the point of the
arrow, a, and from its butt, b. There will therefore be no distinc-
tion, upon the retina, between the different parts of the object, and no

Fig. 156. Fig. 157.

definite perception of its outline. But if, between the object and the
retina, there be inserted a double convex refracting lens, with the
proper curvatures and density, as in Fig. 157, the effect will be dif-
ferent. For then all the rays emanating from a will be concentrated
at x, and all those emanating from b will be concentrated at y.
Thus the retina will receive the impression of the point of the
arrow separate from that of the butt ; and all parts of the object,
in like manner, will be distinctly and accurately perceived.

This convergence of the rays of light is accomplished to a certain
extent by the other transparent and refracting parts of the eyeball ;
but the lens is the most important of all in this respect, owing to
its superior density and the double convexity of its figure. The
distinctness of vision, therefore, depends upon the action of the

496 THE SPECIAL SENSES.

lens in converging all the rays of light, emanating from a given
point, to an accurate focus, at the surface of the retina. To accomplish
this, the density of the lens, the curvature of its surfaces, and its
distance from the retina, must all be accurately adapted to each
other. For if the lens be too convex, and its refractive power con-
sequently too great, the rays will be converged to a focus too soon,
and will not reach the retina until after they have crossed each
other and become partially dispersed, as in Fig. 158. The visual
impression, therefore, coming from any particular point in the
object is not concentrated and distinct, but diffused and dim, from
being dispersed more or less over the retina, and interfering with
the impressions coming from other parts. This is the condition
which is present in myopia, or near-sightedness. On the other hand,

Fig. 158. Fig. 159.

MYOPIA. PRESBYOPIA.

if the lens be too flat, and its convergent power too feeble, as in
Fig. 159, the rays will fail to come together at all, and will strike
the retina separately, producing a confused image, as before. This
is the defect which exists in presbyopia, or long-sightedness. In
both cases, the immediate cause of the confusion of sight is the
same, viz., the rays coming from the same point of the object
striking the retina at different points ; but in the first instance, this
is because the rays have actually converged, and then crossed ; in
the second, it is because they have only approached each other, but
have never converged to a focus.

Another important particular in regard to the action of the lens
is the accommodation of the eye to distinct vision at different distances.
It is evident that the same arrangement of the refractive parts, in
the eye, will not produce distinct vision when the distance of the
object from the eye is changed. If this arrangement be such that
the object is seen distinctly at a certain distance, as in Fig. 160,
and the object be then removed to a remoter point, as in Fig. 161,
the image will become confused ; for the rays will then be con-

SIGHT.

497

verged to a focus at a point in front of the retina ; because, being
less divergent, when they strike the lens, the same amount of re-
fraction will bring them together sooner than before. On the other
hand, if the object be moved to a point nearer the eye, the rays,
becoming more divergent as they strike the lens, will be converged
less rapidly to a focus, and vision will again" become indistinct.

This may easily be seen by the aid of a very simple experiment.
If two needles be placed upright, at different distances from the eye,
one for example at eight and
the other at eighteen inches, but
nearly in the same linear range,
and if then, closing one eye, we
look at them alternately, we shall
find that we cannot see both dis-
tinctly at the same time. For
when we look at the one near-
Fig. 161.

Fig. 160.

est the eye, so as to perceive its form distinctly, the image of the
more remote one becomes confused ; and when we see the more re-
mote object in perfection, that which is nearer loses its sharpness of
outline. This shows, in the first place, that the same condition of
the eye will not allow us to see two objects at different distances
with distinctness at the same time ; and secondly that, on looking
from one to the other, there is a change of some kind in the focus of
the eye, by which it is adapted to different distances. Indeed we
are conscious of a certain effort at the time when the point of vision
is transferred from one object to the other, by which, the eye is
adapted to the new distance ; and this alteration is not quite instan-
taneous, but requires a certain interval of time for its completion.
This accommodation of the eye to different distances is un-
doubtedly effected by an antero-posterior movement of the lens
within the eyeball. It will at once be perceived, on referring to
Fig. 161, that if the lens were moved a little backward toward the
32

498 THE SPECIAL SENSES.

retina, at the same time that the object is removed to a greater dis-
tance from the eye, the focus of the convergent rays would still fall
upon the retina, and the image would still be distinct. In the op-
t posite case, where the object is brought nearer the eye, a similar
movement of the lens forward would again secure perfect vision.
Thus, when we look at near objects, the lens moves forward
toward the pupil ; when we look at remote objects, it moves back-
ward toward the retina.

This movement of the lens is apparently accomplished by the
action of the ciliary muscle. This muscle (Fig. 155, e) arises, in
front, from the conjunction of the sclerotic and the cornea, and run-
ning backward and outward, is inserted into the anterior part of
the choroid, about the situation at which the hyaloid membrane
passes off, to become the suspensory ligament of the lens. As
already mentioned, this muscle is supplied with nervous filaments
from the ophthalmic ganglion. Its action is to draw the lens for-
ward, by means of its attachment to the hyaloid membrane and
choroid coat; and, in the human subject, the retreat or retrogres-
sion of the lens toward the retina, after the ciliary muscle is relaxed,
seems to be due to the elastic resiliency of the remaining tissues of
the eyeball.

But in order to allow of such a backward and forward movement
of the lens, since the liquids of the eyeball are incompressible, there
must be a corresponding displacement of other parts, both before
and behind. This is undoubtedly provided for by the vascularity
of the choroid coat. This membrane is supplied with an exceedingly
abundant vascular plexus over its whole posterior portion ; and in
front it is thrown into a circle of prominent converging folds, or
processes, the ciliary processes, which are nothing more than erectile
congeries of bloodvessels, covered with the pigment of the choroid.
A portion of the ciliary processes projects in front of the lens, and
their vascular network is continued over a great part of the pos-
terior surface of the iris. Thus there is, both behind and in front
of the lens, an erectile system of bloodvessels ; and as these blood-
vessels become alternately empty or turgid, they will allow of the
displacement of the lens in an anterior or posterior direction.

Accordingly there is a certain accommodation of the eye neces-
sary to the distinct sight of objects at different distances. But the
range of this accommodation is limited, and the same eye cannot be
made to see distinctly at all distances. For all ordinary eyes, the
accommodation fails, and vision becomes imperfect, when the object

SIGHT. 499

is placed at less than six inches distance from the eye. But from
that point outward, the eye can adapt itself to any distance at which
light is perceptible, even to the immeasurable distances of the fixed
stars. A much greater accommodating power, however, is re-
quired for near distances than for remote, since the difference in
divergence between rays, entering the pupil from a distance of one
inch and from that of six inches, is greater than the difference be-
tween six inches and a yard, or even distances which are immea-
surably remote. Accordingly, near-sighted persons can see objects
distinctly when placed very near the eye ; since, as their lens con-
verges the rays of light more powerfully than usual, they can be
brought to a focus upon the retina, even when excessively diverg-
ent at the time they enter the eye. But distant objects become,
indistinct, since, however far backward the lens is moved, the rays
are still brought to a focus and cross each other, before reaching
the retina, as in Fig. 161. Near-sighted persons, therefore, have a
limited range of accommodation, like all others, only it is confined
within short distances, owing to the excessive refracting power of
the lens.

On the other hand, long-sighted persons can see remote objects
without trouble, since a very little movement of the lens will be
sufficient to adapt it for long distances ; but within short distances,
the divergence of the rays becomes too great, and they cannot be
brought to a focus.

Circle of Vision. — Since the opening of the pupil will admit rays
of light coming from various directions, there is in front of the eye
a circle, or space, within which luminous objects are perceived, and
beyond which nothing can be seen, because the rays, coming from
the side or from behind, cannot enter the pupil. This space, within
which external objects can be perceived, is called the " circle of
vision." But, for short distances, there is only a single point, in the
centre of the circle of vision, at which objects can be seen distinctly.
Thus, if we place ourselves in front of a row of vertical stakes or
palisades, we can see those directly in front of the eye with perfect
distinctness, but those at a little distance on each side are only per-
ceived in a confused and uncertain manner. On looking at the
middle of a printed page, in the direct range of vision, we see the
distinct outlines of the letters ; while at successive distances from
this point, the eye remaining fixed, we can distinguish first only
the separate letters with confused outlines, then only the words, and
lastly only the lines and spaces.

500 THE SPECIAL SENSES.

This is because rays of light coming into the eye very obliquely,
in a lateral or vertical direction, are not brought to their proper focus.
Thus, in Fig. 162, the rays diverging from the point a, directly in
front of the eye, fall upon the lens in such a way that they are all
brought together at x, at the surface of the retina ; but those coming
from b fall upon the lens so obliquely that, for rays having an equal
divergence with those coming from a, there is more difference in their
angles of incidence, and of course more difference in the amount
of their refraction. They are consequently brought together more
rapidly, and on reaching the retina are dispersed over the space y, z.

Fig. 162.

The perfection of the eye, as a visual apparatus, is very much
increased by the action of the iris. This organ, as we have already
mentioned, is a nearly vertical muscular curtain, placed in front of
the lens, attached by its external margin to the junction of the
cornea and sclerotic, and pierced about its centre by the circular
opening of the pupil. It consists, according to most anatomists, of
two sets of muscular fibres — viz., the circular and the radiating.
The circular fibres, which are much the most abundant, are arranged
in concentric lines about the inner edge of the irjs, near the pupil ;
the others are said to radiate in a scattered manner, from its central
parts to its outer margin. The action of these two sets of fibres is
to contract and enlarge the orifice of the pupil. The circular fibres,
in contracting, draw together the edges of the pupil, and so diminisli
its opening; and when these are relaxed, the radiating fibres come
into play, and by drawing apart the edges of the orifice, enlarge

SIGHT. 501

the pupillary opening. The action of the circular fibres, at the
same time, is much the most marked and important of the two.
For when the whole muscular apparatus of the eye is paralyzed
by the action of belladonna, or by the division of the third pair of
nerves, or in the general relaxation of the muscular system at the
moment of death, the pupil is invariably dilated, probably by the
passive elasticity of its tissues.

During life, however, these different conditions of the pupil cor-
respond with the different degrees of light to which the eye is ex-
posed. In a strong light, the pupil contracts and shuts out the
superfluous rays; in a feeble light, it dilates, in order to collect
into the eye all the light which can be received from the object.
This contractile and expansive movement of the pupil is a reflex
action. It is not produced by the direct impression of the light
upon the iris itself, but upon the retina; since, if the retina be
affected with complete amaurosis, or if the light be entirely shut out
from it by an opacity of the lens, no such effect is produced, though
the iris itself be exposed to the direct glare of day. From the
retina the impression is transmitted, through the optic nerve, to the
optic tubercles and the brain, thence reflected outward by the oculo-
motorius nerve to the ophthalmic ganglion, and so through the
ciliary nerves to the iris.

The pupil is subject, however, to various other nervous influences
beside the impressions of light received by the retina. Thus in
poisoning by opium, it is contracted ; in coma from compression of
the brain, it is dilated ; in natural sleep it is contracted, and the eye-
ball rolled upward and inward. In various mental conditions, the
pupil is also enlarged or diminished, and thus modifies the expres-
sion of the eye; and in viewing remote objects, it is generally
enlarged, while, in looking at near objects, it is comparatively con-
tracted. But still, the most constant and important function be-
longing to the iris is the admission or exclusion of the rays, accord-
ing to the intensity of the light.

Our impressions of distance and solidity, in viewing external
objects, are produced mainly by the combined action of the two eyes.
For, as the eyes are seated a certain distance apart from each other
in the head, when they are both directed toward the same object,
their axes meet at the point of sight, and form a certain angle with
each other ; and this angle varies with the distance of the object.
Thus, when the object is within a short distance, the axes of the
two eyes will necessarily be very convergent, and the angle which

602

THE SPECIAL SENSES.

they form with each other a large one ; but for remote objects, the
visual axes will become more nearly parallel, and their angle con-
sequently smaller. It is on this account that we can always dis-
tinguish whether any person at a short distance is looking at us,
or at some other object in our direction ; since we instinctively
appreciate, from the appearance of the eyes, whether their visual
axes meet at the level of our own face.

In looking at a landscape, accordingly, we do not see the whole
of it distinctly at the same moment, but only those parts to which
out attention is immediately directed. This is because, in the first
place, the focus of distinct vision varies, in each eye, for different
distances, as we have seen in a former paragraph, and secondly,
because both eyes can only be directed together, at one time, to
objects at a certain distance. Thus, when we see the foreground
or the middle ground distinctly, the distance is vague and uncer-
tain, and when we direct our eyes more particularly to the horizon,
objects in the foreground become indistinct. In this way we ap-
preciate the difference in distance between the various portions of
the landscape, as a whole. In the case of particular objects, we are
assisted also by the alteration in their individual characters ; for
distance produces a diminution, both in apparent size and in in-
tensity of color.

The combined action of the two eyes is also very valuable, for
near objects, in giving us an idea of solidity or projection. For
within a certain distance, the visual axes when directed together

Fig. 163.

Fig. 164.

AS SEKN BY THK LEFT EYE.

AS SEEN BY THE KlGHT EYE.

fit a solid object, are so convenient that the two eyes do not receive
the same image. As in Figs. 163 and 164, which represent a skull

SIGHT. 503

as seen by the two eyes, when placed exactly in front of the ob-
server at the distance of eighteen inches or two feet, the right eye
will see the object partly on one side, and the left eye partly on the
other. And by the union or combination of these two images by
the visual organs, the impression of solidity is produced.

By the employment of double pictures, so drawn as to represent
the appearances presented to the two eyes by the same object, and
so arranged that each shall be seen only by the corresponding eye,
a deceptive resemblance may be produced to the actual appearance
of solid objects. This is accomplished in the contrivance known
as the Stereoscope. Thus, if two pictures similar to those in Figs.
163 and 164 be so placed that one shall be seen only with the right
eye and the other only with the left, the combination of the two
figures will take place as if they came from the real object, and
all the natural projections will come out in relief.

But this effect is produced only in the case of objects situated
within a moderately short distance. For very remote objects, we
lose the impression of solidity, since the difference in the images on
the two eyes becomes so slight as to be inappreciable, and we see
only a plane expanse of surface, with sharp outlines and various
shades of color, but no actual projections or depressions.

The sensibility of the retina is such that it cannot distinguish
luminous points which are received upon its surface at a very
minute distance from each other. In this particular, the sensibility
of the retina resembles that of the skin, since we have already
found that the integument cannot distinguish the impressions
made by the points of two needles placed a very short distance
apart. The delicacy of this discriminating power, in the retina, is
immeasurably superior to that of the skin ; and yet it has its
limits, even in the nervous expansion of the eye. For if we look
at an object which is excessively minute, or which is so remote
that its apparent size is very much diminished, we lose the power
of distinguishing its different parts, and can no longer perceive
its real outline. This is a very different condition from that in
which the confusion of vision arises from defect of focusing in the
eye, as, for example, in long or short-sightedness, or where the
object is placed too near the eye or too much on one side. For
when the difficulty depends simply on its minute size or its remote-
ness, the rays coming from the top of the object and those coming
from the bottom, are all brought to their proper focus at distinct
points on the retina — only these points are too near each other for the

504 THE SPECIAL SENSES.

retina to distinguish them apart. Consequently we can no longer
appreciate the form of the object.

For the same reason, when we mix together minute grains of a
different hue, we produce an intermediate color. If yellow and
blue be mingled in this way, we no longer perceive the separate
blue and yellow grains, but only a uniform tinge of green; and
white and black granules, mixed together, produce, at a short dis-
tance, the appearance of a continuous shade of gray.

Impressions, once produced upon the retina, remain for a short time
afterward. Usually these impressions are so evanescent after the*
removal of their immediate cause, and are so soon followed by
others which are more vivid, that we do not notice their existence.
They may very readily be demonstrated, however, by swinging
rapidly in a circle before the eyes, in a dark room, a stick lighted
at one end. As soon as the motion has attained a certain degree of
velocity, the impression produced on the retina, when the lighted
end of the stick arrives at any particular spot, remains until it has
completed its revolution and has again reached the same point ;
so that the effect thus produced upon the eye is that of a continu-
ous circle of light. The same fact has been illustrated by the
optical contrivance, known as the Thaumatrope, in which successive
pictures of similar figures in different positions are made to revolve
rapidly before the eye, and thus to produce the apparent effect of a
single figure in rapid motion ; — since the eye fails to perceive the
intervals between the different pictures.

The sense of vision, therefore, through the impressions of light,
gives us ideas of form, size, color, position, distance, and movement.
But these ideas may also be excited by impressions derived from
an internal source, as well as those produced by rays coming from
without. And it is one of the most striking peculiarities of the
sense of sight that these ideal or internal impressions which are
excited in it by various causes, are much more vivid and powerful
than those of any other of the senses. Thus, in a dream, we often see
external objects, with all their visible peculiarities of light, color
form, «fec., nearly or quite as distinctly as when we are awake ; but
the imaginary impressions of sound, in this condition, are always
comparatively faint, and those of taste, smell, and touch, almost
entirely imperceptible. Even in a reverie, in the waking condi-
tion, when the absorption of the mind in its own thoughts is com-
plete, and we are withdrawn altogether from outward influences,
we see objects which have no present existence as if they were

HEARING. 505

actually before us. It is this sense also which becomes most easily
and thoroughly excited in certain nervous disorders ; as, for exam-
ple, in delirium tremens, where the patient often sees passing before
his eyes extensive and magnificent landscapes, crowds of human
faces and figures, and series of towns and cities, which seem to be
depicted upon the imagination with a force and distinctness, much
superior to that of other delirious impressions. Since the sense of
sight, therefore, depends less directly than the other senses upon
the actual contact of material objects, it is also more easily thrown
into activity when withdrawn from their influence.

HEARING. — The sense of hearing depends upon the vibrations
excited in the atmosphere by sonorous bodies, which are themselves
first thrown into vibration by various causes, and which then com-
municate similar undulations to the surrounding air. These sono-
rous vibrations are of such a character that they cannot be directly
appreciated by ordinary sensibility, but the result of numerous and
well-directed physical experiments on this subject leaves no doubt
whatever of their existence ; and when such vibrations are commu-
nicated to the auditory apparatus, they produce in it the sensation
of sound.

In the case of the aquatic animals, which pass their entire exist-
ence beneath the surface of the water, the water itself, which is
capable of vibrating in the same way, communicates the sonorous
impressions to the organ of hearing; but in terrestrial animals,
and particularly in man, it is the atmosphere which always serves
as the medium of transmission.

The auditory apparatus, in man and in the quadrupeds, consists,
first, of a somewhat expanded and trumpet-shaped mouth, or ex-
ternal ear, destined to receive and collect the sonorous impulses
coming from various quarters. This external ear is constructed
of a cartilaginous framework, covered with integument, loosely
attached to the bones of the head, and more or less movable by
means of various muscles, which by their contraction turn its
expanded orifice in different directions. In man, the movements
of the external ear are almost always inappreciable, though the mus-
cles may be easily demonstrated ; but in many of the lower animals
these movements are exceedingly varied and extensive, and play a
very important part in the working of the auditory apparatus.

At the bottom of the external ear, its orifice is prolonged into a
tube or canal, the external auditory meatus, partly cartilaginous and

506 THE SPECIAL SENSES.

partly bony; which penetrates the lateral part of the temporal bone
in a nearly horizontal and transverse direction. In the human
subject, this canal is a little over one inch in length, and is lined
by a continuation of the external integument. The integument
toward its outer portion is beset with small hairs, and provided
with ceruminous glands which supply a secretion of a waxy or
resinous consistency. By these means the passage is protected
from the accidental ingress of various foreign bodies.

Secondly, at the bottom of the external meatus the auditory pas-
sage is closed by a thin fibrous membrane, stretched across its cavity,
called the membrana tympani. Upon this membrane are received the
sonorous vibrations which have been collected by the external ear
and conducted inward by the external auditory meatus. Behind
the membrana tympani is the cavity of the middle ear, or the cavity
of the tympanum. This cavity communicates posteriorly with the
mastoid cells, and anteriorly with the pharynx, by a narrow passage,
lined with ciliated epithelium, and running downward, forward and
inward, called the Eustachian tube. A chain of small bones, the
malleus, incus, and stapes, is stretched across the cavity of the
tympanum, and forms a communication between the membrana
tympani on the outside, and the membrane closing the foramen
ovale in the petrous portion of the temporal bone. All the vibra-
tions, accordingly, which are received by the membrana tympani,
are transmitted by the chain of bones to the membrane of the
foramen ovale. The tension of the membranes is regulated by two
small muscles, the tensor tympani and stapedius muscles, which arise
from the bony parts in the neighborhood, and are inserted respect-
ively into the neck of the malleus and the head of the stapes, and
which draw these bones forward and backward upon their articu-
lations.

Thirdly, behind the membrane of the foramen ovale lies the
labyrinth, or internal ear. This consists of a complicated cavity,
excavated in the petrous portion of the temporal bone, and com-
prising an ovoid central portion, the vestibule, a double spiral canal,
the cochlea, and three semicircular canals, all communicating by
means of the common vestibule. All parts of this cavity contain
a watery fluid termed the perilymph. The vestibule and semi-
circular canals also contain closed membranous sacs, suspended in
the fluid of the perilymph, which reproduce exactly the form of
the bony cavities themselves, and communicate with each other in
a similar way. These sacs are filled with another watery fluid,

HEARING. 507

the endolymph ; and the terminal filaments of the auditory nerve
are distributed upon the membranous sac of the vestibule and upon
the ampullae, or membranous dilatations, at the commencement of
the three semicircular canals. The remaining portion of the audi-
tory nerve is distributed upon the septum between the two spiral
canals of the cochlea.

Thus, the essential or fundamental portion of the auditory appa-
ratus is evidently the internal ear, a cavity, partly membranous and
partly bony, in which is distributed a nerve of special sense, the
auditory nerve, capable of appreciating sonorous impressions. The
accessory parts, on the other hand, are the chain of bones and the
membrane of the tympanum, which communicate the sonorous
vibrations directly to the internal ear ; and the meatus and external
ear, which collect them from the atmosphere. The reception of

Fig. 165.

HTM AX AUDITORY APPARATUS, showing external auditory meat us, tympanum, and laby-
rinth.

sonorous impulses is therefore accomplished in a very indirect way.
For the sonorous body first communicates its vibrations to the
atmosphere. By the atmosphere these vibrations are communicated
to the membrana tympani. From the membrana tympani, they are
transmitted, through the chain of bones, to the membrane of the
foramen ovale ; thence to the perilymph, or fluid of the labyrinthic
cavity, and from the perilymph to the membranous parts of the
labyrinth and the nerves which are distributed upon them.

The arrangement of the different parts composing the tympanum
is of the greatest importance for the perfect enjoyment of the sense

503 THE SPECIAL SENSES.

of hearing. For the air on the two sides of the membrane of the
tympanum should be in the same condition of elasticity in order to
allow of the proper vibration of the membrane; and this equilibrium
would be liable to disturbance if the air within the tympanum were
completely confined, while that outside is subjected to variations
of barometric pressure. By means of the Eustachian tube, how-
ever, a communication is established between the cavity of the
tympanum and the exterior, and the free vibration of the membrane
is thus secured.

The exact tension of the membrana tympani itself is also provided
for, as we have already observed, by the action of the two muscles
inserted into the malleus and the stapes. By the contraction of
the internal muscle of the malleus, or tensor tympani, the membrane
of the tympanum is drawn inward and rendered more tense than
usual. The action of the stapedius muscle is by some thought to
relax the membrana tympani, by others to assist in the tension
both of this membrane and that of the foramen ovale, to which
the stapes is attached. But there is no doubt that both these mus-
cles, by their combined or alternate action, can regulate the tension
of the tympanic membrane, to an extraordinary degree of nicety,
and thus increase the ease and delicacy with which various sounds
are distinguished. For if the membrane be so put upon the stretch
that its fundamental note shall be the same with that of the sound
which is to be heard, it will vibrate more readily in consonance
with the undulations of the atmosphere, and the sound will be
more distinctly heard. On the contrary, if the membrane be too
highly stretched, very grave sounds may not be heard at all, until
its tension is diminished to the requisite degree.

Contrary to what is sometimes asserted, the communication of
sonorous impulses to the internal ear is accomplished altogether by
means of the tympanum and chain of bones. It has been thought that
sounds were transmitted, in many instances, directly to the internal
ear by the medium of the cranial bones. This was inferred from
such facts as the following. If a tuning-fork, in vibration, be taken
between the teeth, its sound will appear very much louder than
if it were simply held near the external ear; and if, while it is so
held, one of the ears be closed, the sound will appear very much
louder on that side than on the other. The sound will also be heard
if the tuning-fork be applied to the upper part of the cranium or
the mastoid process, with a similar increase of resonance on closing
the ears. Finally our own voices are heard, though the ears be

HEARING. 509

both closed, and the sound is much louder with the ears closed
than open.

These are the facts which have led to the belief that, in such
instances, the sound was communicated directly through the bones
of the head, vibrating in consonance with the sounding body. But
a little examination will show that such is not the case. When we
hold the end of a vibrating tuning-fork between the teeth, we no
longer hear the sound in the vibrating extremity of the instrument
or its neighborhood, but in the mouth and the nasal fossce. It is the
vibration of the air in these passages which produces the sound;
and this vibration is communicated to the cavity of the tympanum
through the Eustachian tube. The apparent increase of sound, also,
on closing the ears, which could not be explained on the supposition
that it was conducted directly through the bones of the cranium,
is due to the same cause. For it can easily be seen, on trying the
experiment, either with a tuning-fork held between the teeth or
simply with our own voices, that this apparent increase of sound
takes place only when the ears are closed by gentle pressure. If the
pressure be excessive, so that the integument is forced inward into
the meatus and the air in the meatus subjected to undue compres-
sion, the sound no longer appears louder in the corresponding ear,
and may even be lost altogether.

The apparent increase of sound, therefore, in such cases, when
the ear is gently closed, is due to the fact that the meatus is thus
converted into a reverberatory cavity, by which the vibrations of
the tympanum are increased in intensity. But if the air in the
meatus be too much compressed by forcible closure, the vibrations
of the tympanum are then interfered with and the sound is dimi-
nished or destroyed.

In all cases, then, it is the sonorous vibrations of the air which
produce the sound, and these vibrations are received invariably by
the membrane of the tvmpanum, and thence transmitted to the
internal ear by the chain of bones. The cranial bones are incapable
of communicating these vibrations to the labyrinth and its contents,
except very faintly and imperfectly. For common experience shows
that even the loudest and sharpest sounds, coming from without,
are almost entirely lost on closing the external ears; and our own
respiratory and cardiac sounds, which are so easily heard as soon
as the chest is connected with the ear by a flexible stethoscope, are
entirely inaudible to us in the usual condition.

The exact function of the different parts of the internal ear is

510 THE SPECIAL SENSES.

not well understood. It has been thought to be the office of the
semicircular canals to determine the direction from which the sono-
rous impulses are propagated. This opinion was based upon the
curious fact that these canals, always three in number, are placed
in such positions as to correspond with the three different directions
of vertical height, lateral extension, and longitudinal extension;
for one of them is nearly vertical and transverse, another vertical
and longitudinal, and the third horizontal in position. The sono-
rous impulses, therefore, coming in either of these directions, would
be received by only one of the semicircular canals (by direct con-
duction through the bones of the head) perpendicularly to its own
plane; and an intermediate direction, it was thought, might be
appreciated by the combined effect of the impulse upon two adja-
cent canals.

Enough has already been said, however, in regard to the com-
munication of sound directly through the bones of the head to the
internal ear, to show that this cannot be the way in which the direc-
tion of sound is ascertained. Indeed,, when we hear any loud and
well-marked sound coming from a particular region, such as the
music of a military band or the whistle of a locomotive, we have only
to close the external ears to lose our perception both of the sound
and its direction. The direction of sonorous impressions is appre-
ciated in a different way. In the first place, we feel that the sound
comes from one side or the other, by its making a more distinct
impression on one ear than the opposite; and by inclining the
head slightly in various directions, we easily ascertain whether the
sound becomes more or less acute, and so judge of its actual source.
Many of the lower animals, whose ears are very large and movable,
use this method to great extent. A horse, for example, when upon
the road, often keeps his ears in constant motion, feeling, as it were,
in the distance, for the origin of the various sounds which excite
his attention.

Beside the above, we are further assisted in our judgment of the
direction of sounds by our previous knowledge of the localities,
the direction of the wind, and the manner in which the sound is
reflected by surrounding objects. When these sources of informa-
tion fail us, we are often at a loss. It is notoriously difficult, for
example, to judge of the place of the chirping of a cricket in a
perfectly closed room, or of the direction of a bell heard on the
water in a thick fog.

The sense of hearing has a much closer analogy with ordinary

ON THE SENSES IN GENEBAL. 511

sensibility than that of sight. Thus, in the first place, hearing is
accomplished by the direct intervention and contact of a material
body — the atmosphere ; for sonorous impulses cannot be produced
in a vacuum, and we hear no sound from a bell rung under an
exhausted receiver. Secondly, the nature of the impressions pro-
duced by sound is such that we can often describe them by the
same terms which are applied to ordinary sensations. Thus, we
speak of sounds as sharp and dull, piercing, smooth, or rough ; and
we feel the impulse of a sudden and violent explosive sound, like
that of a blow upon the tympanum.

By this sense, therefore, we distinguish the quality, intensity,
pitch, duration, and direction of sonorous impulses. The delicacy
with which these distinctions are appreciated varies considerably
in different individuals ; and in different kinds of animals there is
reason to believe that the diversity is much greater, some of them
being almost insensible to sounds which are readily perceived by
others. In man, the number and variety of tones which can usually
be discriminated is very great ; and this sense, accordingly, in the
complication and finish of its apparatus, and the perfection and deli-
cacy of its action, must be regarded as second only to that of vision.

ON THE SENSES IN GENERAL. — There are several facts connected
with the operation of the senses, both general and special, which
are common to all of them, and which still remain to be considered.
In the first place, an impression of any kind, made upon a sensi-
tive organ, remains for a time after the removal of its exciting cause.
We have already noticed this in regard to the senses of taste, smell,
and sight, but it is equally true of the hearing and the touch.
Thus, if the skin be touched with a piece of ice, the acute sensa-
tion remains for a few seconds, whether the ice be removed or not.
For the higher order of the special senses, the time during which
this secondary impression remains is a shorter one. In the case of
hearing, however, it has been measured with a tolerable approach
to accuracy ; for it has been found that, if the sonorous undulations
follow each other with a greater rapidity than sixteen times per
second, they become fused together into a continuous sound, pro-
ducing upon the ear the impression of a musical note. The varying
pitch of the note depends upon the rapidity with which the vibra-
tions succeed each other. When the succession of vibrations is
very rapid, a high note is the result, and when comparatively slow,
a low note is produced ; but when the number of impulses falls

512 THE SPECIAL SENSES.

below sixteen per second, we then begin to perceive the distinct
vibrations, and so lose the impression of a continuous note.

All the senses, in the second place, become accustomed to a con-
tinued impression, so that they no longer perceive its existence.
Thus, if a perfectly uniform pressure be exerted upon any part of
the body, the compressing substance after a time fails to excite any
sensation in the skin, and we remain unconscious of its existence.
In order to attract our notice, it is then necessary to increase or
diminish the pressure ; while, so long as this remains uniform, no
effect is perceived. But if, after the skin has thus become accus-
tomed to its presence, the foreign body be suddenly removed, our
attention is then immediately excited, and we notice the absence of
an impression, in the same way as if it were a positive sensation.

We all know how rapidly we become habituated to odors, whether
agreeable or disagreeable in their nature, in the confined air of a
close apartment; although, on first entering from without our
attention may have been attracted by them in a very decided
manner. A continuous and "uniform sound, also, like the steady
rumbling of carriages, or the monotonous hissing of boiling water,
becomes after a time inaudible to us; but as soon as the sound
ceases, we notice the alteration, and our attention is at once excited.
The senses, accordingly, receive their stimulus more from the varia-
tions and contrasts of external impressions, than from these impres-
sions themselves.

Another important particular, in regard to the senses, is their
capacity for education. The proofs of this are too common and too
apparent to need more than a simple allusion. The touch may be
so trained that the blind may read words and sentences by its aid,
in raised letters, where an ordinary observer would hardly detect
anything more than a barely distinguishable inequality of surface.
The educated eye of the artist, or the naturalist, will distinguish
variations of color, size, and outline, altogether inappreciable to
ordinary vision ; and the senses of taste and smell, in those who are
in the habit of examining wines and perfumes, acquire a similar
superiority of discriminating power.

In these instances, however, it is not probable that the organ of
sense itself becomes any more perfect in organization, or more
susceptible to sensitive impressions. The increased functional
power, developed by cultivation, depends rather upon the greater
delicacy of the perceptive and discriminative faculties. It is a mental
and not a physical superiority which gives the painter or the

ON TIIE SENSES IN GENERAL. 513

naturalist a greater power of distinguishing colors and outlines,
and which enables the physician to detect nice variations of quality
in the sounds of the heart or the respiratory murmur of the lungs.
The impressions of external objects, therefore, in order to produce
their complete effect, must first be received by a sensitive appa-
ratus, which is perfect in organization and functional activity;
and, secondly, these impressions must be subjected to the action of
an intelligent perception, by which their nature, source and rela-
tions may be fully appreciated.

That part of the nervous system which we have hitherto
studied, viz., the cerebro-spinal system, consists of an apparatus of
nerves and ganglia, destined to bring the individual into relation
with the external world. By means of the special senses, he is
made cognizant of sights, sounds, taste, and odors, by which he
is attracted or repelled, and which guide him in the pursuit and
choice of food. By the general sensations of touch and the volun-
tary movements, he is enabled to alter at will his position and
location, and to adapt them to the varying conditions under which
he may be placed. The great passages of entrance into the body,
and of exit from it, are guarded by the same portion of the nerv-
ous system. The introduction of food into the mouth, and its
passage through the oesophagus to the stomach, are regulated by
the same nervous apparatus ; and even the passage of air through
the larynx, and its penetration into the lungs, are equally under
the guidance of sensitive and motor nerves belonging to the
cerebro-spinal system.

It will be observed that the above functions relate altogether
either to external phenomena or to the simple introduction into the
body of food and air, which are destined to undergo nutritive
changes in the interior of the frame.

If we examine, however, the deeper regions of the body, we find
located in them a series of internal phenomena, relating only to
the substances and materials which have already penetrated into
the frame, and which form or are forming a part of its structure.
These are the purely vegetative functions, as they are called ; or
those of growth, nutrition, secretion, excretion, and reproduction.
These functions, and the organs to which they belong, are not
under the direct influence of the cerebro-spinal nerves, but are
regulated by another portion of the nervous system, viz., the
" ganglionic system ;" or, as it is more commonly called, the " sys-
tem of the great sympathetic."
33

514 SYSTEM OF THE GREAT SYMPATHETIC.

CHAPTER VII.

•

SYSTEM OF THE GREAT SYMPATHETIC.

THE sympathetic system consists of a double chain of nervous
ganglia, running from the anterior to the posterior extremity of the
body, along the front and sides of the spinal column, and connected
with each other by slender longitudinal filaments. Each ganglion
is reinforced by a motor and sensitive filament derived from the
cerebro- spinal system, and thus the organs under its influence are
brought indirectly into communication with external objects and
phenomena. The nerves of the great sympathetic are distributed
to organs over which the consciousness and the will have no imme-
diate control, as the intestine, kidneys, heart, liver, &c.

The first sympathetic ganglion in the head is the ophthalmic gan-
glion. This ganglion is situated within the orbit of the eye, on the
outer aspect of the optic nerve. It communicates by slender fila-
ments with the carotid plexus, which forms the continuation of the
sympathetic system from below ; and receives a motor root from
the oculo-motorius nerve, and a sensitive root from the ophthalmic
branch of the fifth pair. Its filaments of distribution, known as the
" ciliary nerves," pass forward upon the eyeball, pierce the sclerotic,
and finally terminate in the iris.

The next division of the great sympathetic in the head is the
spheno -palatine ganglion, situated in the spheno-maxillary fossa. It
communicates, like the preceding, with the carotid plexus, and
receives a motor root from the facial nerve, and a sensitive root
from the superior maxillary branch of the fifth pair. Its filaments
are distributed to the levator palati and azygos uvulas muscles, and
to the mucous membrane about the posterior nares.

The third sympathetic ganglion in the head is the submaxillary,
situated upon the submaxillary gland. It communicates with the
superior cervical ganglion of the sympathetic by filaments which
accompany the facial and external carotid arteries. It derives its
sensitive filaments from the lingual branch of the fifth pair, and its

SYSTEM OF THE GREAT SYMPATHETIC.

515

Fig. 166.

motor filaments from the facial nerve, by means of the chorda
tympani. Its branches of distribution pass to the sides of the tongue
and to the submaxillary and sublingual glands.

The last sympathetic ganglion in the head is the otic ganglion.
It is situated just beneath the
base of the skull, on the inner
side of the third division of
the fifth pair. It sends fila-
ments of communication to
the carotid plexus; and re-
ceives a motor root from the
facial nerve, and a sensitive
root from the inferior maxil-
lary division of the fifth pair.
Its branches are sent to the
internal muscle of the mal-
leus in the middle ear (tensor
tympani), and to the mucous
membrane of the tympanum
and Eustachian tube.

The continuation of the
sympathetic nerve in the neck
consists of two and some-
times three ganglia, the su-
perior, middle, and inferior.
These ganglia communicate
with each other, and also
with the anterior branches
of the cervical spinal nerves.
Their filaments follow the
course of the carotid artery
and its branches, covering
them with a network of inter-
lacing fibres, and are finally
distributed to the substance of
the thyroid gland, and to the

,, „ , ,

walls of the larynx, trachea,

pharynx, and oesophagus.

By the superior, middle, and inferior cardiac nerves, they also supply

sympathetic fibres to the cardiac plexuses and to the substance of

the heart.

Conrse and distributi n of the GREAT STMPA-

516 SYSTEM OF THE GUEAT bYMPATHETIO.

In the chest, the ganglia of the sympathetic nerve are situated on
each side the spinal column, just over the heads of the ribs, with
which they accordingly correspond in number. Their communi-
cations with the intercostal nerves are double ; each sympathetic
ganglion receiving two filaments from the intercostal nerve next
above it. The filaments originating from the thoracic ganglia are
distributed upon the thoracic aorta, and to the lungs and oesophagus.

In the abdomen, the continuation of the sympathetic system con-
sists principally of the aggregation of ganglionic enlargements
situated upon the coeliac artery, known as the semilunar or ccdiac
ganglion. From this ganglion a multitude of radiating and inoscu-
lating branches are sent out, which, from their diverging course and
their common origin from a central mass, are termed the " solar
plexus." From this, other diverging plexuses originate, which
accompany the abdominal aorta and its branches, and are distri-
buted to the stomach, small and large intestine, spleen, pancreas,
liver, kidneys, supra-renal capsules, and internal organs of gene-
ration.

Beside the above ganglia there are in the abdomen four other
pairs, situated in front of the lumbar vertebrae, and having similar
connections with those occupying the cavity of the chest. Their
filaments join the plexuses radiating from the semilunar ganglion.

In the pelvis, the sympathetic system is continued by four or five
pairs of ganglia, situated on the anterior aspect of the sacrum, and
terminating, at the lower extremity of the spinal column, in a single
ganglion, the " ganglion impar," which is probably to be regarded
as a fusion of two separate ganglia.

The entire sympathetic series is in this way composed of nume-
rous small ganglia which are connected throughout, first, with each
other ; secondly, with the cerebro-spinal system ; and thirdly, with
the internal viscera of the body.

The properties and functions of the great sympathetic have been
less successfully studied than those of the cerebro-spinal system,
owing to the anatomical difficulties in the way of reaching and
operating upon this nerve for purposes of experiment. The cerebro-
spinal axis and its nerves are easily exposed and subjected to exami-
nation. It is also easy to isolate particular portions of this system,
and to appreciate the disturbances of sensation and motion conse-
quent upon local lesions or irritations. The phenomena, further-
more, which result from experiments upon this part of the nervous
apparatus, are promptly produced, are well-marked in character,

SYSTEM OF THE GREAT SYMPATHETIC. 517

and are, as a general rule, readily understood by the experimenter.
On the other hand, the principal part of the sympathetic system is
situated in the interior of the chest and abdomen ; and the mere
operation of opening these cavities, so as to reach the ganglionic
centres, causes such a disturbance in the functions of vital organs,
and such a shock to the system at large, that the results of these
experiments have been always more or less confused and unsatis-
factory. Furthermore, the connections of the sympathetic ganglia
with each other and with the cerebro-spinal axis are so numerous
and so scattered, that these ganglia cannot be completely isolated
without resorting to an operation still more mutilating and injuri-
ous in its character. And finally, the sensible phenomena which
are obtained by experimenting on the great sympathetic are, in
the majority of cases, slow in making their appearance, and not
particularly striking or characteristic in their nature.

Notwithstanding these difficulties, however, some facts have been
ascertained with regard to this part of the nervous system, which
give us a certain degree of insight into its character and functions.

The great sympathetic is endowed both with sensibility and the
power of exciting motion; but these properties are less active
here than in the cerebro-spinal system, and are exercised in a dif-
ferent manner. If we irritate, for example, a sensitive nerve in
one of the extremities, or apply the galvanic current to the poste-
rior root of a spinal nerve, the evidences of pain or of reflex
action are acute and instantaneous. There is no appreciable inter-
val between the application of the stimulus and the sensations
which result from it. On the other hand, experimenters who have
operated upon the sympathetic ganglia and nerves of the chest and
abdomen find that evidences of sensibility are distinctly manifested
here also, but much less acutely, and only after somewhat prolonged
application of the irritating cause. These results correspond very
closely with what we know of the vital properties of the organs
which are supplied either principally or exclusively by the sym-
pathetic; as the liver, intestine, kidneys, &c. These organs are
insensible, or nearly so, to ordinary impressions. We are not con-
scious of the changes and operations going on in them, so long as
these changes and operations retain their normal character. But
they are still capable of perceiving unusual or excessive irritations,
and may even become exceedingly painful when in a state of in-
flammation.

There is the same peculiar character in the action of the motor

518 SYSTEM OF THE GREAT SYMPATHETIC.

nerves belonging to the sympathetic system. If the facial or hypo-
glossal, or the anterior root of a spinal nerve be irritated, the con-
vulsive movement which follows is instantaneous, violent, and only
momentary in its duration. But if the semilunar ganglion or its
nerves be subjected to a similar experiment, no immediate effect is
produced. It is only after a few seconds that a slow, vermicular,
progressive contraction takes place in the corresponding part of the
intestine, which continues for some time after the exciting cause
has been removed.

Morbid changes taking place in organs supplied by the sympa-
thetic present a similar peculiarity in the mode of their produc-
tion. If the body be exposed to cold and dampness, for example,
congestion of the kidneys shows itself perhaps on the following
day. Inflammation of any of the internal organs is very rarely
established within twelve or twenty -four hours after the application
of the exciting cause. The internal processes of nutrition, together
with their derangements, which are regarded as especially under
the control of the great sympathetic, always require a longer time
to be influenced by incidental causes, than those which are regulated
by the nerves and ganglia of the cerebro-spinal system.

In the head, the sympathetic has a close and important connec-
tion with the exercise of the special senses. This is illustrated
more particularly in the case of the eye, by its influence over the
alternate expansion and contraction of the pupil. The ophthalmic
ganglion sends off a number of ciliary nerves, which are distributed
to the iris. It is connected, as we have seen, with the remaining
sympathetic ganglia in the head, and receives, beside, a sensitive
root from the ophthalmic branch of the fifth pair, and a motor root
from the oculo-motorius. The reflex action by which the pupil
contracts under a strong light falling upon the retina, and expands
under a diminution of light, takes place, accordingly, through this
ganglion. The impression conveyed by the optic nerve to the
tubercula quadrigemina, and reflected outward by the fibres of
the oculo-motorius, is not transmitted directly by the last named
nerve to the iris ; but passes first to the ophthalmic ganglion, and
is thence conveyed to its destination by the ciliary nerves.

The reflex movements of the iris exhibit consequently a some-
what sluggish character, which indicates the intervention of a part
of the sympathetic system. The changes in the size of the pupil
do not take place instantaneously, with the variation in the amount
of light, but always require an appreciable interval of time. If

SYSTEM OF THE GREAT SYMPATHETIC. 519

we pass suddenly from a brilliantly lighted apartment into a dark
room, we are unable to distinguish surrounding objects until a
certain time has elapsed, and the expansion of the pupil has taken
place ; and vision even continues to grow more and more distinct
for a considerable period afterward, as the expansion of the pupil
becomes more complete. Again, if we cover the eyes of another
person with the hand or a folded cloth, and then suddenly expose
them to the light, we shall find that the pupil, which is at first
dilated, contracts somewhat rapidly to a certain extent, and after-
ward continues to diminish in size during several seconds, until the
proper equilibrium is fairly established. Furthermore, if we pass
suddenly from a dark room into the bright sunshine, we are imme-
diately conscious of a painful sensation in the eye, which lasts for
a considerable time ; and which results from the inability of the
pupil to contract with sufficient rapidity to shut out the excessive
amount of light. All such exposures should be made gradually,
so that the movements of the iris may keep pace with the varying
quantity of stimulus, and so protect the eye from injurious impres-
sions.

The reflex movements of the iris, however, thpugh accomplished
through the medium of the ophthalmic ganglion, derive their
original stimulus, through the motor root of this ganglion, from
the oculo-motorius nerve. For it has been found that if the oculo-
motorius nerve be divided between the brain and the eyeball, the
pupil becomes immediately dilated, and will no longer contract
under the influence of light. The motive power originally derived
from the brain is, therefore, in the case of the iris, modified by
passing through one of the sympathetic ganglia before it reaches
its final destination.

An extremely interesting fact in this connection is the following.
Of the three organs of special sense in the head, viz., the eye, the
nose, and the ear, each one is provided with two sets of muscles,
superficial and deep, which together regulate the quantity of stimu-
lus admitted to the organ, and the mode in which it is received.
The superficial set of these muscles is animated by branches of the
facial nerve ; the deep-seated or internal set, by filaments from a
sympathetic ganglion.

Thus, the front of the eyeball is protected by the orbicularis and
levator palpebrae superioris muscles, which open or close the eye-
lids at will, and allow a larger or smaller quantity of light to reach
the cornea. These muscles are supplied by the oculo-motorius and

520 SYSTEM OP THE GREAT SYMPATHETIC.

facial nerves, and are for the most part voluntary in their action.
The iris, on the other hand, is a more deeply-seated muscular
curtain, which regulates the quantity of light admitted through the
pupil. There is also the ciliary muscle, which regulates the position
of the crystalline lens, and secures a correct focusing of the light,
at different distances. Both these muscles are supplied, as we have
seen, by filaments from the ophthalmic ganglion, and their move-
ments are involuntary in character.

In the olfactory apparatus, the anterior or superficial set of
muscles are the compressors and elevators of the alae nasi, which
are animated by filaments of the facial nerve. By their action,
odoriferous vapors, when faint and delicate in their character, are
snuffed up and directed into the upper part of the nasal passage?,
where they come in contact with the most sensitive portions of the
olfactory membrane; or, if too pungent or disagreeable in flavor,
are excluded from entrance. These muscles are not very im-
portant or active in the human subject; but in many of the lower
animals with a more active and powerful sense of smell, as, for
example, the carnivora, they may be seen to play a very important
part in the mechanism of olfaction. Furthermore, the levators and
depressors of the velum palati, which are more deeply situated,
serve to open or close the orifice of the posterior nares, and accom-
plish a similar office with the muscles already named in front. The
levator palati and azygos uvulas muscles, which, by their action,
tend to close the posterior nares, are supplied by filaments from the
spheno-palatine ganglion, and are involuntary in their character.

The ear has two similar sets of muscles, similarly supplied. The
first, or superficial set, are those moving the external ear, viz., the
anterior, superior, and posterior auriculares. Like the muscles of
the anterior nares, they are comparatively inactive in man, but in
many of the lower animals are well developed and important. In
the horse, the deer, the sheep, &c., they turn the ear in various
directions so as to catch more distinctly faint and distant sounds, or
to exclude those which are harsh and disagreeable. These muscles
are supplied by filaments of the facial nerve, and are voluntary in
their action.

The deep-seated set are the muscles of the middle ear. In order
to understand their action, we must recollect that sounds are trans-
mitted from the external to the middle ear through the membrane
of the tympanum, which vibrates, like the head of a drum, on
receiving sonorous impulses from without.

SYSTEM OF THE GREAT SYMPATHETIC. 521

The membrane of the tympanum, accordingly, which is an elastic
sheet, stretched across the passage to the internal ear, may be made
more or less sensitive to sonorous impressions by varying its con-
dition of tension or relaxation. This condition is regulated, as we
have already seen, by the combined action of the two muscles of
the middle ear, viz., the tensor tympani and the stapedius. The
first named muscle, the action of which is perfectly well understood,
is supplied with nervous filaments from the otic ganglion of the
sympathetic. By its contraction, the handle of the malleus is drawn
inward, bringing the membrana tympani with it, and putting this
membrane upon the stretch. On the relaxation of the muscle, the
chain of bones returns to its ordinary position, by the elasticity of
the neighboring parts, and the previous condition of the tympanic
membrane is restored. This action, so far as we can judge, is purely
involuntary. But the stapedius muscle is separately supplied by a
minute branch of the facial nerve. It is probable that this arrange-
ment enables us to make also a certain degree of voluntary exer-
tion, in listening intently for faint or distant sounds.

In all these instances, the reflex action taking place in the
deeper seated muscles, originates from a sensation which is con-
veyed inward to the cerebro-spinal centres, and is then transmitted
outward to its final destination through the medium of one of the
sympathetic ganglia.

Another very striking fact, concerning the sympathetic, relates to
the changes produced by its division, in the nutritive processes of
the parts supplied by it. One of the most important and remark-
able of these changes is an elevation of temperature in the affected
parts. If the sympathetic nerve be divided on one side of the neck,
in the rabbit, cat, or dog, an elevation of temperature begins to be
perceptible on the corresponding side of the head in a very short
time. In the cat, we have found a very sensible difference in
temperature between the two sides at the end of ten minutes :
and in the rabbit, at the end of half an hour. A vascular conges-
tion of the parts also takes place, which may be seen to great
advantage in the ear of the rabbit, when held up between the eye
and the light. The elevation of temperature, in these cases, is very
perceptible to the touch, and may also be measured by the thermo-
meter. Bernard1 has found it to reach 8° or 9° F. The elevation
of temperature and congested state of the parts are sometimes found
to be diminished by the next day, and afterward disappear rapidly.

1 Recherches Experimentales sur le Grand Sympathique. Paris, 1854.

522 SYSTEM OF THE GREAT SYMPATHETIC.

Occasionally, however, they last for a long time. Bernard (op. tit.)
has seen the unnatural temperature of the affected parts remain, in
the rabbit, from fifteen to eighteen days, and in the dog for two
months. Where the superior cervical ganglion has been extirpated,
he has even found the above appearances to continue, in the dog, for
a year and a half. They may also, according to the same authority,
be reproduced several times in the same animal, by repeated divi-
sions of the sympathetic nerve.

The above effect is due to a peculiar modification in the nutri-
tion of the affected parts, which has some analogy with inflamma-
tion. The unnatural heat, the congestion, and the increased sensi-
bility which are present, all serve to indicate a certain resemblance
between the two conditions. None of the more serious consequences
of inflammation, however, such as oedema, exudation, sloughing or
ulceration, have ever been known to follow from this operation ;
and the term inflammation, accordingly, cannot properly be applied
to its results.

Division of the sympathetic nerve in the middle of the neck
has also a very singular and instantaneous effect on the muscular
apparatus of the eye. Within a very few seconds after the above
operation has been performed upon the cat, the pupil of the cor-
responding eye becomes strongly contracted, and remains in that
condition. At the same time the third eyelid, or " nictitating mem-
brane," with which these animals
167> are provided, is drawn partially

over the cornea, and the upper
and lower eyelids also approxi-
mate very considerably to each
other; so that all the apertures
guarding the eyeball are very
perceptibly narrowed, and the ex-
pression of the face on that side is
altered in a corresponding degree.
This effect upon the pupil has
been explained by supposing the

CAT,aftei section of the right sympathetic. circular fibres of the iris, Or the

constrictors of the pupil, to be

animated exclusively by nervous filaments derived from the oculo-
motorius ; and the radiating fibres, or the dilators, to be supplied
by the sympathetic. Accordingly, while division of the oculo-
motorius would produce dilatation of the pupil, by paralysis of

SYSTEM OF THE GREAT SYMPATHETIC. 523

the circular fibres only, division of the sympathetic would be
followed by exclusive paralysis of the dilators, and a permanent
contraction of the pupil would consequently take place. The
above explanation, however, is not a satisfactory one; since, in
the first place, division of the oculo-motorius, as the experiments of
Bernard have shown,1 does not by itself produce complete dilata-
tion of the pupil ; and, secondly, after division of the sympathetic
nerve in the cat, as we have already shown, not only is the pupil
contracted, but both the upper and lower eyelids and the nictitating
membrane are also partially drawn over the cornea, and assist in
excluding the light. The last-named effect cannot be owing to any
direct paralysis, from division of the fibres of the sympathetic. It
is more probable that the section of this nerve operates simply by
exaggerating for a time the sensibility of the retina, as it does that
of the integument ; and that the partial closure of the eyelids and
pupil is a secondary consequence of that condition.

It will be remembered that in describing the inflammation of the
eyeball, consequent upon section of the fifth pair of nerves, we
found that there were reasons for believing this effect to be due
to injury of certain sympathetic fibres which accompany the fifth
pair. If the fifth pair in fact be divided at the level of the Cas-
serian ganglion, where it is joined by sympathetic fibres from the
carotid plexus, or between this ganglion and the eyeball, a destruc-
tive inflammation of the organ follows. But if the section be made
behind the ganglion, so as to avoid the filaments of communication
with the sympathetic, no inflammatory change takes place. If this
fact be really owing to the presence of sympathetic fibres which
accompany the fifth pair, it indicates a remarkable difference in the
effects of dividing the sympathetic near the eyeball and at a dis-
tance from it; since no real inflammation of the eyeball or its
appendages is ever produced by division of this nerve in the middle
of the neck, but only the elevation of temperature and increase of
sensibility which have been already described.

The influence of the sympathetic nerve and the consequences
of its division upon the thoracic and abdominal viscera have been
only very imperfectly investigated by experimental methods. It
undoubtedly serves as a medium of reflex action between the sensi-
tive and motor portions of the digestive, excretory, and generative

1 Lemons sur la Physiologie et U Pathologie du Sy?teoie Nerveux, Paris, 1858,
vol. ii p. 203.

524 SYSTEM OF THE GREAT SYMPATHETIC.

apparatuses ; and it is certain that it also takes part in reflex actions
in which the cerebro-spinal system is at the same time interested.
There are accordingly three different kinds of reflex action, taking
place wholly or partially through the sympathetic system, which
may be observed to occur in the living body.

1st. Reflex actions talcing place from the internal organs, through
the sympathetic and cerebro-spinal systems, to the voluntary muscles and
sensitive surfaces. — The convulsions of young children are often
owing to the irritation of undigested food in the intestinal canal.
Attacks of indigestion are also known to produce temporary amau-
rosis, double vision, strabismus, and even hemiplegia. Nausea, and
a diminished or capricious appetite, are often prominent symptoms
of early pregnancy, induced by the peculiar condition of the uterine
mucous membrane.

2d. Reflex actions taking place from the sensitive surfaces, through
the cerebro-spinal and sympathetic systems, to the involuntary muscles
and secreting organs. — Imprudent exposure of the integument to
cold and wet, will often bring on a diarrhoea. Mental and moral
impressions, conveyed through the special senses, will affect the
motions of the heart, and disturb the processes of digestion and
secretion. Terror, or an absorbing interest of any kind, will pro-
duce a dilatation of the pupil, and communicate in this way a pecu-
liarly wild and unusual expression to the eye. Disagreeable sights
or odors, or even unpleasant occurrences, are capable of hastening
or arresting the menstrual discharge, or of inducing premature
delivery.

3d. Reflex actions taking place through the sympathetic system from
one part of the internal organs to another. — The contact of food with
the mucous membrane of the small intestine excites a peristaltic
movement in the muscular coat. The mutual action of the diges-
tive, urinary and internal generative organs upon each other takes
place through the medium of the sympathetic ganglia and their
nerves. The variations of the capillary circulation in different
abdominal viscera, corresponding with the state of activity or re-
pose of their associated organs, are to be referred to a similar nerv-
ous influence. These phenomena are not accompanied by any
consciousness on the part of the individual, nor by any apparent
intervention of the cerebro-spinal system.

SECTION III.
REPRODUCTION.

CHAPTER I.

ON THE NATURE OF REPRODUCTION, AND THE
ORIGIN OF PLANTS AND ANIMALS.

THE process of reproduction is the most characteristic, and in
many respects the most interesting, of all the phenomena presented
by organized bodies. It includes the whole history of the changes
taking place in the organs and functions of the individual at suc-
cessive periods of life, as well as the production, growth, and de-
velopment of the new germs which make their appearance by
generation.

For all organized bodies pass through certain well-defined epochs
or phases of development, by which their structure and functions
undergo successive alterations. We have already seen that the
living animal or plant is distinguished from inanimate substances
by the incessant changes of nutrition and growth which take place
in its tissues. The muscles and the mucous membranes, the osse-
ous and cartilaginous tissues, the secreting and circulatory organs,
all incessantly absorb oxygen and nutritious material from with-
out, and assimilate their molecules ; while new substances, produced
by a retrogressive alteration and decomposition, are at the same
time excreted and discharged. These nutritive changes correspond
in rapidity with the activity of the other vital phenomena ; since
the production of these phenomena, and the very existence of the
vital functions, depend upon the regular and normal continuance
of the nutritive process. Thus the organs and tissues, which are
always the seat of this double change of renovation and decay,

(525 )

526 NATURE OF REPRODUCTION.

retain nevertheless their original constitution, and continue to be
capable of exhibiting the vital phenomena.

The above changes, however, are not in reality the only ones
which take place. For although the structure of the body and the
composition of its constituent parts appear to be maintained in an
unaltered condition, by the nutritive process, from one moment to
another, or from day to day, yet a comparative examination of
them at greater intervals of time will show that this is not pre-
cisely the case ; but that the changes of nutrition are, in point of
fact, progressive as well as momentary. The composition and pro-
perties of the skeleton, for example, are not the same at the age of
twenty-five that they were at fifteen. At the later period it con-
tains more calcareous and less organic matter than before ; and its
solidity is accordingly increased, while its elasticity is diminished.
Even the anatomy of the bones alters in an equally gradual manner ;
the medullary cavities enlarging with the progress of growth, and
the cancellated tissue becoming more open and spongy in texture.
We have already noticed the difference in the quantity of oxygen
and carbonic acid inspired and exhaled at different ages. The
muscles, also, if examined after the lapse of some years, are found
to be less irritable than formerly, owing to a slow, but steady and
permanent deviation in their intimate constitution.

The vital properties of the organs, therefore, change with their
varying structure ; and a time comes at last when they are per-
ceptibly less capable of performing their original functions than
before. This alteration, being dependent on the varying activity
of the nutritive process, continues necessarily to increase. The very
exercise of the vital powers is inseparably connected with the sub-
sequent alteration of the organs employed in them ; and the func-
tions of life, therefore, instead of remaining indefinitely the same,
pass through a series of successive changes, which finally terminate
in their complete cessation.

The history of a living animal or plant is, therefore, a history of
successive epochs or phases of existence, in each of which the struc-
ture and functions of the body differ more or less from those in
every other. Every living being has a definite term of life, through
which it passes by the operation of an invariable law, and which,
at some regularly appointed time, comes to an end. The plant
germinates, grows, blossoms, bears fruit, withers, and decays. The
animal is born, nourished, and brought to maturity, after which he
retrogrades and dies. The very commencement of existence, by

NATURE OF REPRODUCTION. 527

leading through its successive intermediate stages, conducts at last
necessarily to its own termination.

But while individual organisms are thus constantly perishing and
disappearing from the stage, the particular kind, or species, remains
in existence, apparently without any important change in the cha-
racter or appearance of the organized forms belonging to it. The
horse and the ox, the oak and the pine, the different kinds of wild
and domesticated animals, even the different races of man himself,
have remained without any essential alteration ever since the earliest
historical epochs. Yet during this period innumerable individuals,
belonging to each species or race, must have lived through their
natural term and successively passed out of existence. A species
may therefore be regarded as a type or class of organized beings, in
which the particular forms or structures composing it die off con-
stantly and disappear, but which nevertheless repeats itself from
year to year, and maintains its ranks constantly full by the regular
accession of new individuals. This process, by which new organ-
isms make their appearance, to take the place of those which are
destroyed, is known as the process of reproduction or generation. Let
us now see in what manner it is accomplished.

It has always been known that, as a general rule in the process
of generation, the young animals or plants are produced directly
from the bodies of the elder. The relation between the two is that
of parents and progeny ; and the new organisms, thus generated,
become in turn the parents of others who succeed them. For this
reason wherever such plants or animals exist, they indicate the
previous existence of others belonging to the same species ; and if
by any accident the whole species should be destroyed in any par-
ticular locality, no new individuals could be produced there, unless
by the previous importation of others of the same kind.

The commonest observation shows this to be true in regard to
those animals and plants with whose history we are more familiarly
acquainted. An opinion, however, has sometimes been maintained
that there are exceptions to this rule ; and that living beings may,
under certain circumstances, be produced from inanimate substances,
without any similar plants or animals having preceded them ; pre-
senting, accordingly, the singular phenomenon of a progeny without
parents. Such a production of organized bodies is known by the
name of spontaneous generation. It is believed by the large majority
of physiologists at the present day that no such spontaneous gene-
ration ever takes place; but that plants and animals are always

528 NATURE OF REPRODUCTION.

derived, by direct reproduction, from previously existing parents
of the same species. As this, however, is a question of some im-
portance, and one which has been frequently discussed in works on
physiology, we shall proceed to pass in review the facts which have
been adduced in favor of the occurrence of spontaneous generation,
as well as those which would lead to its disproval and rejection.

It is evident, in the first place, that many apparent instances of
spontaneous generation are found to be of a very different character
as soon as they are subjected to a critical examination. Thus grass-
hoppers and beetles, earthworms and crayfish/ the swarms of minute
insects that fill the air over the surface of stagnant pools, and even
frogs, moles, and lizards, have been supposed in former times to be
generated directly from the earth or the atmosphere ; and it was
only by investigating carefully the natural history of these animals
that they were ascertained to be produced in the ordinary manner
by generation from parents, and were found to continue the repro-
duction of their species in the same way. A still more striking
instance is furnished by the production of maggots in putrefying
meat, vegetables, flour paste, fermenting dung, &c. If a piece of
meat be exposed, for example, and allowed to undergo the process
of putrefaction, at the end of a few days it will be found to contain
a multitude of living maggots which feed upon the decomposing
flesh. Now these maggots are always produced under the same
conditions of warmth, moisture and exposure, and at the same stage
of the putrefactive process. They are never to be found in fresh
meat, nor, in fact, in any other situation than the one just mentioned.
They appear, consequently, without any similar individuals having
existed in the same locality ; and considering the regularity of their
appearance under the given conditions, and their absence elsewhere,
it has been believed that they were spontaneously generated, under
the influence of warmth, moisture, and the atmosphere, from the
decaying organic substances.

A little examination, however, discovers a very simple solution
of the foregoing difficulty. On watching the exposed animal or
vegetable substances during the earlier periods of their decompo-
sition, it is found that certain species of flies, attracted by the odor
of the decaying material, hover round it and deposit their eggs
upon its surface or in its interior. These eggs, hatched by the
warmth to which they are exposed, produce the maggots ; which
are simply the young of the winged insects, and which after a time
become transformed, by the natural progress of development, into

INFUSORIAL ANIMALCULES. 529

perfect insects similar to their parents. The difficulty of account-
ing for the presence of the maggots by generation, therefore, de-
pends simply on the fact that they are different in appearance from
the parents that produce them. This difference, however, is merely
a temporary one, corresponding with the difference in age, and dis-
appears when the development of the animal is complete; just as
the young chicken, when recently hatched, has a different form and
plumage from those which it presents in its adult condition.

Nearly all the causes of error, in fact, which have suggested at
various times the doctrine of spontaneous generation, have been
derived from these two sources. First, the ready transportation of
eggs or germs, and their rapid hatching under favorable circum-
stances ; and secondly, the different appearances presented by the
same animal at different ages, in consequence of which the youthful
animal may be mistaken, by an ignorant observer, for an entirely
different species. These sources of error are, however, so readily
detected, as a general rule, by scientific investigation, that it is
hardly necessary to point out the particular instances in which they
exist. In fact, whenever a rare or comparatively unknown animal
or plant has been at any time supposed to be produced by sponta-
neous generation, it has only been necessary, for the most part, to
investigate thoroughly its habits and functions, to discover its secret
methods of propagation, and to show that they correspond, in all
essential particulars, with the ordinary laws of reproduction. The
limits, therefore, within which the doctrine of spontaneous genera-
tion can be applied, have been narrowed in precisely the same
degree that the study of natural history and comparative physiology
has advanced. At present, indeed, there remain but two classes
of phenomena which are ever supposed to lend any support to the
above doctrine ; viz., the existence and production, 1st, of infuso-
rial animalcules, and 2d, of animal and vegetable parasites. We
shall now proceed to examine these two parts of the subject in
succession.

INFUSORIAL ANIMALCULES. — If water, holding in solution or-
ganic substances, be exposed to the contact of the atmosphere at
ordinary temperatures, it is found after a short time to be filled
with swarms of minute living organisms, which are visible only by
the microscope. The forms of these microscopic animalcules are
exceedingly varied ; owing either to the great number of species
in existence, or to their rapid alteration during the successive pe-
34

530

NATURE OF REPRODUCTION.

Fig. 168.

Different kinds of INFUSOKI A.

riods of their growth. Ehrenberg has described more than 300
different varieties of them. They are generally provided with cilia
attached to the exterior of their bodies, and are, for the most part,
in constant and rapid motion in the fluid which they inhabit.

Owing to their presence in
animal and vegetable watery
infusions, they have received
the name of "infusoria," or
" infusorial animalcules."

Now these infusoria are
always produced under the
conditions which we have de-
scribed above. The animal
or vegetable substance used
for the infusion may be pre-
viously baked or boiled, so
as to destroy all living germs
which it might accidentally
contain; the water in which
it is infused may be carefully
distilled, and thus freed from all similar contamination; and yet the
infusorial animalcules will make their appearance at the usual time
and in the usual abundance. It is only requisite that the infusion
be exposed to a moderately elevated temperature, and to the access
of atmospheric air; conditions which are equally necessary for
maintaining the life of all animal and vegetable organisms, what-
ever be the source from which they are derived. Under the above
circumstances, therefore, either the animalcules must have been
produced by spontaneous generation in the watery infusion, or their
germs must have been introduced into it through the medium of
the atmosphere. No such introduction has ever been directly de-
monstrated, nor have even any eggs or germs belonging to the
infusoria ever been detected.

Nevertheless, there is every probability that the infusoria are
produced from germs, and not by spontaneous generation. Since
the infusoria themselves are microscopic in size, it is not surprising
that their eggs, which must be smaller still, should have escaped
observation. We know, too, that in many instances the minute
germs of animals or plants may be wafted about in a dry state by
the atmosphere, until, by accidentally coming in contact with warmth
and moisture, they become developed and bring forth living organ-

INFUSOBIAL ANIMALCULES. 531

isms. The eggs of the infusoria, accordingly, may be easily raised
and held suspended in the atmosphere, under the form of minute
dust-like particles, ready to germinate and become developed when-
ever they are caught by the surface of a stagnant pool, or of any
artificially prepared infusion. In point of fact, the atmosphere
does really contain an abundance of such dust-like particles, even
when it appears to be most transparent and free from impurities.
This may be readily demonstrated by admitting a single beam of
sunshine into a darkened apartment, when the shining particles sus-
pended in the atmosphere become immediately visible in the track
of the sunbeam. Again, if a perfectly clean and polished mirror
be placed with its face upward in a securely closed room, and left
undisturbed for several days, its surface at the end of that time will
be found to be dimmed by the settling upon it of minute dust,
deposited from the atmosphere. There is no reason, therefore, for
disbelieving that the air may always contain a sufficient number of
organic germs for the production of infusorial animalcules.

There is some difficulty, however, in obtaining direct proof that it
is through the medium of the atmosphere that organic germs pene-
trate into the watery infusions. It is true that if such an infusion
be prepared from baked meat or vegetables and distilled water, and
afterward hermetically sealed, no infusoria are developed in it ; but
this only shows, as we have already intimated, that the free access
of air is necessary to the development of all organic life, just as it is
to the support of animals and plants under ordinary conditions of
growth and reproduction. Such a result, therefore, proves nothing
with regard to the external origin of the infusoria. In order to be
conclusive, such an experiment should be so contrived that the
watery infusion, previously freed from all foreign contamination,
should be supplied with a free access of atmospheric air, while the
introduction of living germs by this channel should at the same time
be rendered impossible. An experiment of this kind has in reality
been contrived and successfully carried out by Schultze, of Berlin.1

This observer prepared an infusion containing organic substances
in solution, and inclosed it in a glass flask (Fig. 169, a) of such a
size, that the infusion filled about one-half the entire capacity of the
vessel. The mouth of the flask was fitted with an air-tight stopper
provided with two holes, through which were passed narrow glass
tubes bent at right angles. To each of these tubes was attached a

1 Edinburgh New Philosophical Journal, Oct. 1637.

532

NATURE OF REPRODUCTION.

Fig. 169.

Schultze's experiment on SPONTA-
NEOUS GE NEK AT ION. — a. Flask con-
taining watery infusion, b. Potash-ap-
paratus containing sulphuric acid c.
Potash-apparatus containing caustic po-
tassa.

potash-apparatus (b, c), similar to those used for condensing carbonic
acid in organic analyses. One of these (b) was filled with concen-
trated sulphuric acid, the other (c) with a solution of caustic potassa.

The flask with the organic infusion
having been subjected to a boiling
temperature, in order to destroy any
living germs which it might con-
tain, the stopper was inserted, and
the whole apparatus exposed to the
light, at the ordinary summer tempera-
ture. The connections of the apparatus
being perfectly tight, no air could pene-
trate into the flask, except by passing
through either the sulphuric acid or
the potassa; either of which would
retain and destroy any organic germs
which might be suspended in it. Every
day a fresh supply of air was introduced
into the flask by drawing it through

the tubes b, c ; and in this way the atmospheric air above the infu-
sion was constantly renewed, while at the same time the introduction
of living germs from without was effectually prevented.

Schultze kept this apparatus under his observation, as above, from
the last of May till the first of August ; frequently examining the
edges of the fluid with a lens, through the sides of the glass jar,
but without ever detecting in it any traces of living organisms. At
the end of that period the flask was opened, and the fluid which it
contained subjected to direct examination, equally without result.
It was then exposed, in the same vessel and in the same situation
as before, to the free access of the atmosphere, and at the end of
two or three days it was found to be swarming with infusoria.

It is plain, therefore, that the infusoria cannot be regarded as
produced by spontaneous generation, but must be considered as
originating in the usual manner from germs; since they do not
make their appearance in the watery infusion, when the accidental
introduction of germs from without has been effectually prevented.

ANIMAL AND VEGETABLE PARASITES. — This very remarkable
group of organized bodies is distinguished by the fact that they
live either upon the surface or in the interior of other animal or
vegetable organisms. Thus, the mistletoe fixes itself on the branches

ANIMAL AND VEGETABLE PARASITES. 533

of aged trees ; the Oidium albicans vegetates upon the mucous sur-
faces of the mouth and pharynx ; the Botrytis Bassiana attacks the
body of the silkworm, and plants itself in its tissues ; while many
species of trematoid worms live attached to the gills of fish and of
water-lizards.

These parasites are usually nourished by the fluids of the animal
whose body they inhabit. Each particular species of parasite is
found to inhabit the body of a particular species of animal, and is
not found elsewhere. They are met with, moreover, as a general
rule, only in particular organs, or even in particular parts of a
single organ. Thus the Tricocephalus dispar is found only in the
caecum ; the Strongylus gigas in the kidney ; the Distoma hepati-
cum in the biliary passages. The Distoma variegatum is found
only in the lungs of the green frog, the Distoma cylindraceum in
those of the brown. The Taenia solium is found in the intestine of
the human subject in certain parts of Europe, while the Taenia lata
occurs exclusively in others. It appears, therefore, as though some
local combination of conditions were necessary to the production
of these parasites; and they have been supposed, accordingly, to
originate by spontaneous generation in the localities where they
are exclusively known to exist.

A little consideration will show, however, that the above condi-
tions are not, properly speaking, necessary or sufficient for the
production, but only for the development of these parasites. All the
parasites mentioned above reproduce their species by generation.
They have male and female organs, and produce fertile eggs, often
in great abundance. The eggs contained in a single female Ascaris
are to be counted by thousands ; and in a tapeworm, it is said, even
by millions. Now these eggs, in order that they may be hatched
and produce new individuals, require certain special conditions
which are favorable for their development; in the same manner
as the seeds of plants require, for their germination and growth, a
certain kind of soil and a certain supply of warmth and moisture.
It is accordingly no more surprising that the Ascaris vermicularis
should inhabit the rectum, and the Ascaris lumbricoides the ileum,
than that the Lobelia inflata should grow only in dry pastures, and
the Lobelia cardinalis by the side of running brooks. The lichens
flourish on the exposed surfaces of rocks and stone walls ; while
the fungi vegetate in darkness and moisture, on the decaying trunks
of dead trees. Yet no one imagines these vegetables to be spon-
taneously generated from the soil which they inhabit. The truth

534 NATURE OF REPRODUCTION.

is simply this, that if the animal or vegetable germ be deposited in
a locality which affords the requisite conditions for its development,
it becomes developed ; otherwise not. Each female Ascaris pro-
duces, as we have stated above, many thousands of ova. Now,
though the chances are very great against any particular one of
these ova being accidentally transported into the intestinal canal of
another individual, it is easy to see that there are many causes in
operation by which some of them might be so transported. By far
the greater number undoubtedly perish, from not meeting with the
conditions necessary for their development. One in a thousand, or
perhaps one in a million, is accidentally introduced into the body
of another individual, and consequently becomes developed there
into a perfect Ascaris.

The circumstance, therefore, that particular parasites are confined
to particular localities, presents no greater difficulty as to their
mode of reproduction, than the same fact regarding other animal
and vegetable organisms.

Neither is there any difficulty in accounting for the introduction
of parasitic germs into the interior of the body. The air and the
food offer a ready means of entrance into the respiratory and
digestive passages ; and, a parasite once introduced into the intes-
tine, there is no difficulty in accounting for its presence in any of
the ducts leading from or opening into the alimentary canal. Some
parasites are known to insinuate themselves directly underneath
the surface of the skin ; as the Pulex penetrans or " chiggo" of
South America, and the Ixodes Americanus or " tick." Others,
like the (Estrus bovis, penetrate the integument for the purpose of
depositing their eggs in the subcutaneous areolar tissue. Some
may even gain an entrance into the bloodvessels, and circulate in
this way all over the body. Thus the Filaria rubella is found alive
in the bloodvessels of the frog, the Distoma hsematobium in those
of the human subject, and a species of Spiroptera in those of the
dog. It is easy to see, therefore, how, by such means, parasitic
germs may be conveyed to any part of the body ; and may even be
deposited, by accidental arrest of the circulation, in the substance
of the solid organs.

The most serious difficulty, however, in the way of accounting
for the production of parasitic organisms, was that presented by the
existence of a class known as the encysted or sexless entozoa. These
parasites for the most part occupy the interior of the solid organs
and tissues, into which they could not have gained access by the

ANIMAL AXD VEGETABLE PARASITES. 535

mucous canals. Thus the Coenurus cerebralis is found imbedded
in the substance of the brain, the Trichina spiralis between the
fibres of the voluntary muscles, and the Cysticercus cellulosse in the
areolar tissue of various parts of the body. They are also distin-
guished from all other parasites by two peculiar characters. First,
they are inclosed in a distinct cyst, with which they have no organic
connection and from which they may be readily separated ; and se-
condly, they have no genera-
tive organs, nor is there any Fjg- no.

apparent difference between
the sexes. The Trichina spi-
ralis, for example (Fig. 170),
is inclosed in an ovoid or
spindle-shaped cyst, swollen
in the middle and tapering at
each extremity, with a round-

•f* TKICHIX A SPIRAMS: from rictus femoris uius-

ed Cavity in itS Central por- cle uf human subject. Maguified 57 diameters.

tion, in which the worm lies

coiled up in a spiral form. The worm itself has neither testicles

nor ovaries, nor does it present any trace of a sexual organization.

Now we have seen that it is easy to account for the conveyance
of these or any other parasites into the interior of vascular organs
and tissues; the eggs from which they are produced being trans-
ported by the bloodvessels to any part of the body, and there
retained by a local arrest of the capillary circulation. In the case
of the encysted entozoa, however, we have a much greater diffi-
culty ; since these parasites are entirely without sexual organs or
generative apparatus of any sort, nor have they ever been dis-
covered in the act of producing eggs, or of developing in any
manner a progeny similar to themselves. It appears, accordingly,
difficult to understand how animals, which are without a sexual
apparatus, should have been produced by sexual generation. As
it is certain that they can have no progeny, it would seem equally
evident that they must have been produced without a parentage.

This difficulty, however, serious as it at first appears, is susceptible
of a very simple explanation. The case is in many respects analogous
to that of the maggots, hatched from the eggs of flies in putrefying
meat. These maggots are also without sexual organs ; for they
are still imperfectly developed, and in a kind of embryonic condi-
tion. It is only after their metamorphosis into perfect insects, that
generative organs are developed and a distinction between the

536

NATURE OF REPRODUCTION.

Fig. 171.

sexes manifests itself. This is, indeed, more or less the case with
all animals and with all vegetables. The blossom, which is the
sexual apparatus of the plant, does not appear, as a general rule,
until the growth of the vegetable has continued for a certain time,
and it has acquired a certain age and strength. Even in the human
subject the sexual organs, though present at birth, are still very
imperfectly developed as to size, and altogether inactive in func-
tion. It is only later that these organs acquire their full growth,
and the sexual characters become complete. In very many of the
lower animals the sexual organs are entirely
absent at birth, and appear only at a later
period of development.

Now the encysted or sexless entozoa are
simply the undeveloped young of other para-
sites which propagate by sexual generation;
the membrane in which they are inclosed
being either an embryonic envelope, or else
an adventitious cyst formed round the para-
sitic embryo. These embryos have come, in
the natural course of their migrations, into
a situation which is not suitable for their com-
plete development. Their development is
accordingly arrested before it arrives at matu-
rity ; and the parasite never reaches the adult
condition, until removed from the situation in
which it has been placed, and transported to a
more favorable locality.

The above explanation has been demon-
strated to be the true one, more particularly
with regard to the Tsenia, or tapeworm, and
several varieties of Cysticercus. The Tsenia
(Fig. 171) is a parasite of which different species
are found in the intestine of the human subject,
the dog, cat, fox, and other of the lower animals.
Its upper extremity, termed the " head," con-
sists of a nearly globular mass, presenting upon
its lateral surfaces a set of four muscular disks, or " suckers," and
terminating anteriorly in a conical projection which is provided
with a crown of curved processes or hooks, by which the parasite
attaches itself to the intestinal mucous membrane. To this " head"
succeeds a slender ribbon-shaped neck, which is at first smooth, but

AXIMAL AND VEGETABLE PARASITES. 537

which soon becomes transversely wrinkled, and afterward divided
into distinct rectangular pieces or " articulations." These articula-
tions multiply by a process of successive growth or budding, from
the wrinkled portion of the neck ; and are constantly removed farther
and farther from their point of origin by new ones formed behind
them. As they gradually descend, by the process of growth,
farther down the body of the tapeworm, they become larger and
begin to exhibit a sexual apparatus, developed in their interior.
In each fully formed articulation there are contained both male
and female organs of generation ; and the mature eggs, which are
produced in great numbers, are thrown off together with the articu-
lation itself from the lower extremity of the tapeworm. Since the
articulations are successively produced, as we have mentioned above,
by budding from the neck and the back part of the head, the para-
site cannot be effectually dislodged by taking away any portion of
the body, however large ; since it is subsequently reproduced from
the head, and continues its growth as before. But if the head itself
be removed from the intestine, no further reproduction of the articu-
lations can take place.

The Cysticercus is an encysted parasite, different varieties of which
are found in the liver, the peritoneum, and the meshes of the areolar
tissue in various parts of the body. It consists (Fig. 172) first, of
a globular sac, or cyst (a), which is not adherent to the tissues of
the organ in which the parasite is found, but may be easily sepa-

Fig. 172. Fig. 173.

CYSTICERCCS. — a. External cyst, ft In-
ternal we, containing fluid, c. Narrow c.v ;il,
formed hy involution of walls of sac. at the
bottom of which in the head of the tzenia.

CTBT1CKBC08, nnfoldeJ.

rated from them. In its interior is found another sac (k), lying
loose in the cavity of the former, and filled with a serous fluid.
This second sac presents, at one point upon its surface, a puckered
depression, leading into a long, narrow canal (c). This canal, which

533 NATURE OF REPRODUCTION.

is formed by an involution of the walls of the second sac, presents
at its bottom a small globular mass, like the head of the Tsenia,
provided with suckers and hooks, and supported upon a short
slender neck. If the outer investing sac be removed, the narrow
canal just described may be everted by careful manipulation, and
the parasite will then appear as in Fig. 173, with the head and neck
resembling those of a Taenia, but terminating behind in a dropsical
sac-like swelling, instead of the chain of articulations which are
characteristic of the fully formed tapeworm.

Now it has been shown, by the experiments of Kuchenmeister,
Siebold, and others, that the Cysticercus is only the imperfectly
developed embryo, or young, of the Ta3nia. When the mature
articulation of the tapeworm is thrown off', as already mentioned,
from its posterior extremity, the eggs which it incloses have already
passed through a certain period of development, so that each one
contains an imperfectly formed embryo. The articulation, contain-
ing the eggs and embryos, is then taken, with the food, into the
stomach of another animal; the substance of the articulation, to-
gether with the external covering of the eggs, is destroyed by di-
gestion, and the embryos are thus set free. They then penetrate
through the walls of the stomach, into the neighboring organs or
the areolar tissue, and becoming encysted in these situations, are
there developed into cysticerci, as represented in Fig. 172. After-
ward, the tissues in which they are contained being devoured by
a third animal, the cysticercus passes into the intestine, fixes itself
to the mucous membrane, and, by a process of budding, produces
the long tape-like series of articulations, by which it is finally con-
verted into the full-grown Tsenia.

Prof. Siebold found the head of the Cysticercus fasciolaris, met
with in the liver of rats and mice, presenting so close a resem-
blance to the Taenia crassicollis, inhabiting the intestine of the cat,
that he was led to believe the two parasites to be identical. This
identity was, in fact, proved by the experiments of Kuchenmeister ;
and Siebold afterward demonstrated1 the same relation to exist
between the Cysticercus pisiformis, found in the peritoneum of rab-
bits, and the Taenia serrata, from the intestine of the clog. This
experimenter succeeded in administering to dogs a quantity of the
cysticerci, fresh from the body of the rabbit, mixed with milk ; and

' In Buffalo Medical Jonrml, Feb. 1853 ; also in Siebold on Tape and Cystic
Worms, Sydenham translation: London, 1857, p. 59.

ANIMAL AND VEGETABLE PARASITES. 539

on killing the dogs, at various periods after the meal, from three
hours to eight weeks, he found the cysticerci in various stages of
development in the intestine, and finally converted into the full
grown Taenia, with complete articulations and mature eggs.

Dr. Kuchenraeister1 has also performed the same experiment, with
success, on the human subject. A number of cysticerci were ad-
ministered to a criminal, at different periods before his execution,
varying from 12 to 72 hours ; and upon post-mortem examination
of the body, no less than ten young ta3nia3 were found in the
intestine, four of which could be distinctly recognized as specimens
of Taenia solium.

Finally, both Leuckart and Kuchenmeister* have shown, on the
other hand, that the eggs of Ta3nia solium, introduced into the body
of the pig, will give rise to the development of Cysticercus cellulose ;
thus demonstrating that the two kinds of parasites are identical in
their nature, and differ only in the manner and degree of their
development.

There remains, accordingly, no good reason for believing that
even the encysted parasites are produced by spontaneous genera-
tion. Whatever obscurity may hang round the origin or reproduc-
tion of any class or species of animals, the direct investigations of
the physiologist always tend to show that they do not, in reality,
form any exception to the general law in this respect ; and the only
opinion which is admissible, from the facts at present within our
knowledge, is that organizedleings, animal and vegetable, wherever they
may be found, are always the progeny of previously existing parents.

1 On Animal ard Vegetable Parasites, Svdeiih.aiu transition : L^rdon, 1857,
p. 115.

2 Up. cit., p. 120.

540

SEXUAL GENERATION.

CHAPTER II.

Fig. 174.

ON SEXUAL GENERATION, AND THE MODE OF ITS
ACCOMPLISHMENT.

THE function of generation is performed by means of two sets of
organs, each of which gives origin to a peculiar product, capable
of uniting with the other so as to produce a new individual. These

two sets of organs, belonging to the
two different sexes, are called the male
and female organs of generation. The
female organs produce a globular body
called the germ, or egg, which is capable
of being developed into the body of
the young animal or plant ; the male
organs produce a substance which is
necessary to fecundate the germ, and
enable it to go through with its natural
growth and development.

Such are the only essential and uni-
versal characters of the organs of gene-
ration. These organs, however, exhibit
various additions and modifications in
different classes of organized beings,
while they show throughout the same
fundamental and essential characters.
In the flowering plants, for example,
the blossom, which is the generative
apparatus (Fig. 17-i), consists first of a
female organ containing the germ (a), situated usually upon the
highest part of the leaf-bearing stalk. This is surmounted by a
nearly straight column, termed the pistil (5), dilated at its summit
into a globular expansion, and occupying the centre of the flower.
Around it are arranged several slender filaments, or stamens, bear-
ing upon their extremities the male organs, or anthers (c, c). The

BLOSSOM OF CUN
PCRPITKEUS. (Morning glory.)— a.
Germ. b. Pistil, c. c. Stamens, with
anthers, d. Corolla, e. Calyx.

SEXUAL GENERATION.

541

Fig. 175.

whole is surrounded by a circle or crown of delicate and brilliantly
colored leaves, termed the corolla (d), which is frequently provided
with a smaller sheath of green leaves outside, called the calyx (e).
The anthers, when arrived at maturity, discharge a fine organic
dust, called the pollen, the granules of which are caught upon the
extremity of the pistil, and then penetrate downward through its
tissues, until they reach its lower extremity and come in contact
with the germ. The germ thus fecundated, the process of genera-
tion is accomplished. The pistil, anthers, and corolla wither and
fall off, while the germ increases rapidly in size, and changes in
form and texture, until it ripens into the mature fruit or seed. It
is then ready to be separated from the parent stem ; and, if placed
in the proper soil, will germinate and at last produce a new plant
similar to the old.

In the above instance, the male and female organs are both
situated upon the same flower ; as in the lily, the violet, the con-
volvulus, &c. In other cases, there are separate male and female
flowers upon the same plant, of which the male flowers produce
only the pollen, the female, the
germ and fruit. In others still,
the male and female flowers are
situated upon different plants,
which otherwise resemble each
other, as in the willow, poplar,
and hemp.

In animals, the female organs
of generation are called ovaries,
since it is in them that the egg,
or "ovum," is produced. The
male organs are the testicles,
which give origin to the fecun-
dating product, or "seminal
fluid," by which the egg is fer-
tilized. We have already men-
tioned above that in the articula-
tions of the tapeworm the ovaries
and testicles are developed to-
gether. (Fig. 175.) The ovary
(a, a, a) is a series of branching follicles terminating in rounded
extremities, and communicating with each other by a central canal.
The testicle (b) is a narrow, convoluted tube, very much folded

SlXflLB A R T I C tr I. A T I O * OF

CK ASS iroLMs, from small intestine of cat —
n, a, a. Ovary filled with eggs. b. Testicle, c.
Genital orifice.

5-42 SEXUAL GENERATION.

upon itself, which opens by an external orifice (c) upon the lateral
border of the articulation, about midway between its two ex-
tremities. The spermatic fluid produced in the testicle is intro-
duced into the female generative passage, which opens at the same
spot, and, penetrating deeply into the interior, comes in contact
with the eggs, which are thereby fecundated and rendered fertile.
The fertile eggs are afterward set free by the rupture or decay of
the articulation, and a vast number of young are produced by their
development.

In snails, also, and in some other of the lower animals, the ovaries
and testicles are both present in the same individual ; so that these
animals are sometimes said to be " hermaphrodite," or of double
sex. In reality, however, it appears that the male and female
organs do not come to maturity at the same time ; but the ovaries
are first developed and perform their function, after which the tes-
ticles come into activity in their turn. The same individual, there-
fore, is not both male and female at any one time; but is first
female and afterward male, exercising the two generative functions
at different ages.

In all the higher animals, however, the two sets of generative
organs are located in separate individuals; and the species is
consequently divided into two sexes, male and female. All that
is absolutely requisite to constitute the two sexes is the existence
of testicles in the one, and of ovaries in the other. Beside these,
however, there are, in most instances, certain secondary or acces-
sory organs of generation, which assist more or less in the accom-
plishment of the process, and which occasion a greater difference in
the anatomy of the two sexes. Such are the uterus and mammary
glands of the female, the vesiculaa seminales and prostate gland
of the male. The female naturally having the immediate care of
the young after birth, and the male being occupied in providing
food and protection for both, there are also corresponding differ-
ences in the general structure of the body, which affect the whole
external appearance of the two sexes, and which even show them-
selves in their mental and moral, as well as in their physical
characteristics. In some cases this difference is so excessive that
the male and female would never be recognized as belonging to the
same species, unless they were seen in company with each other.
Not to mention some extreme instances of this among insects and
other invertebrate animals, it will be sufficient to refer to the well-
known examples of the cock and the hen, the lion and lioness, the

SEXUAL GENERATION. 543

buck and the doe. In the human species, also, the distinction
between the sexes shows itself in the mental constitution, the dis-
position, habits, and pursuits, as well as in the general conforma-
tion of the body, and the peculiarities of external appearance.

We shall now study more fully the character of the male and
female organs of generation, together with their products, and the
manner in which these are discharged from the body, and brought
into relation with each other.

EGG AND FEMALE ORGAX3 OF GENEBATION.

ON THE EGG,

CHAPTER III.

AND THE FEMALE
GENERATION.

ORGANS OF

Fig. 176.

THE egg is a globular body which varies considerably in size in
different classes of animals, according to the peculiar conditions
under which its development is to take place. In the frog it mea-
sures T'5 of an inch in diameter, in the lamprey o1^, in quadrupeds
and in the human species T.J0. It consists, first, of a membranous
external sac or envelope, the vitelline membrane ; and secondly, of a
spherical mass inclosed in its interior, called the vitellus.

The vitelline membrane in birds and reptiles is very thin, measur-
ing often not more than T^<ytr °f an incn in thickness, and is at the

same time of a somewhat fibrous texture.
In man and the higher animals, on the
contrary, it is perfectly smooth, structure-
less and transparent, and is about T gVzr of
an inch in thickness. Notwithstanding
its delicate and transparent appearance, it
has a considerable degree of resistance
and elasticity. The egg of the human
subject, for example, may be perceptibly
flattened out under the microscope by
pressing with the point of a needle upon
the slip of glass which covers it; but it
still remains unbroken, and when the

pressure is removed, readily resumes its globular form. When the
egg is somewhat flattened under the microscope in this way, by
pressure of the glass slip, the apparent thickness of the vitelline
membrane is increased, and it then appears (Fig. 176) as a rather
wide, colorless, and pellucid border or zone, surrounding the granu-
lar and opaque vitellus. Owing to this appearance, it has some-
times received the name of the " zona pellucida." The name of

HUMAN OVUM, magnified 85
diameters, a. Vitelline membrane,
ft Vitellus. c. Germinative vesicle.
d. Germinative spot.

EGG AND FEMALE ORGANS OF GENERATION. 545

vitelline membrane, however, is the one more generally adopted,
and is also the more appropriate of the two.

The vitellus (b) is a globular, semi-solid mass, contained within
the vitelline membrane. It consists of a colorless albuminoid sub-
stance, with an abundance of minute molecules and oleaginous
granules scattered through it. These minute oleaginous masses
give to the vitellus a partially opaque and granular aspect under
the microscope. Imbedded in the vitellus, usually near its surface
and almost immediately beneath the vitelline membrane, there is a
clear, colorless, transparent vesicle (c) of a rounded form, known
as the germinative vesicle. In the egg of the human subject and of
the quadrupeds, this vesicle measures gj^ to 5^ of an inch in
diameter. It presents upon its surface a
dark spot, like a nucleus ((/), which is known ^l* 177'

by the name of the germinative spot. The
germinative vesicle, with its nucleus-like
spot, is often partially concealed by the
granules of the vitellus by which it is sur-
rounded, but it may always be discovered
by careful examination.

If the egg be ruptured by excessive pres- HTMAX ov™, ruptured by
sure under the microscope, the vitellus is Pressare; 8howi°« the vitellu*

partially expelled, the germiua-

seen to have a gelatinous consistency. It tive vesicle at«, and the *mooti,
is gradually expelled from the vitelline CM of the vitelline mPra-

cavity, but still retains the granules and oil

globules entangled in its substance. (Fig. 177.) The edges of the
fractured vitelline membrane, under these circumstances, present a
smooth and nearly straight outline, without any appearance of
laceration or of a fibrous structure. The membrane is, to all ap-
pearance, perfectly homogeneous.

The most essential constituent of the egg is the vitellus. It is
from the vitellus that the body of the embryo will afterward be
formed, and the organs of the new individual developed. The
vitelline membrane is merely a protective inclosure, intended to
secure the vitellus from injury, and enable it to retain its figure
during the early periods of development.

The egg, as above described, consists therefore of a simple
vitellus of minute size, and a vitelline membrane inclosing it. It
is such an egg which is found in the human subject, the quadru-
peds, most aquatic reptiles, very many fish, and some invertebrate
animals. In nearly all those species, in fact, where the fecundated
35

546 EGG AND FEMALE ORGANS OF GENERATION.

eggs are deposited and hatched in the water, as well as those in
which they are retained in the body of the female until the develop-
ment of the young is completed, such an egg as above described is
sufficient for the formation of the embryo ; since during its develop-
ment it can absorb freely, either from the water in which it floats,
or from the mucous membrane of the female generative organs, the
requisite supply of nutritious fluids. But in birds and in the
terrestrial reptiles, such as lizards, tortoises, &c., where the eggs
are expelled from the body of the female at an early period, and
incubated on land, there is no external source of nutrition, to pro-
vide for the support of the young animal during its development.
In these instances accordingly the vitellus, or "yolk," as it is called,
is of very large size ; and the bulk of the egg is still further in-
creased by the addition, within the female generative passages, of
layers of albumen and various external fibrous and calcareous
envelopes. The essential constituents of the egg, however, still
remain the same in character, and the process of embryonic deve-
lopment follows the same general laws as in other cases.

The eggs are produced in the interior of certain organs, situated
in the abdominal cavity, called the ovaries. These organs consist
of a number of globular sacs, or follicles, known as the " Graafian
follicles," each one of which contains a single egg. The follicles
are connected with each other by a quantity of vascular areolar
tissue, which binds them together into a well-defined and consistent
mass, covered upon its exterior by a layer of peritoneum. The
egg has sometimes been spoken of as a " product," or even as a
" secretion" of the ovary. Nothing can be more inappropriate,
however, than to compare the egg with a secretion, or to regard the
ovary as in any respect resembling a glandular organ. The egg is
simply an organized body, growing in the ovary like a tooth in its
follicle, and forming a constituent part of the body of the female.
It is destined to be finally separated from its attachments and
thrown off; but until that time, it is, properly speaking, a part of
the ovarian texture, and is nourished like any other portion of the
female organism.

The ovaries, accordingly, since they are directly concerned in
the production of the eggs, are to be regarded as the essential
parts of the female generative apparatus. Beside them, however,
there are usually present certain other organs, which play a secon-
dary or accessory part in the process of generation. The most
important of these accessory organs are two symmetrical tube?, or

EGG AND FEMALE ORGANS OF GENERATION.

547

Fig. 178.

oviducts, which are destined to receive the eggs at their internal
extremity and convey them to the external generative orifice. The
mucous membrane lining the oviducts is also intended to supply
certain secretions during the passage of the egg, which are requi-
site either to complete its structure, or to provide for the nutrition
of the embryo.

In the frog, for example, the oviduct commences at the upper
part of the abdomen, by a rather wide orifice, which communicates
directly with the peritoneal cavity. It
soon after contracts to a narrow tube,
and pursues a zigzag course down the
side of the abdomen (Fig. 178), folded
upon itself in convolutions, like the
small intestine, until it opens, near its
fellow of the opposite side, into the
" cloaca" or lower part of the intestinal
canal. The oviducts present the same
general characters with those described
above, in nearly all species of reptiles
and birds ; though there are some modi-
fications, in particular instances, which
do not require any special notice.

The ovaries, as well as the eggs which
they contain, undergo at particular sea-
sons a periodical development or increase

r

in growth. If we examine the female
frog in the latter part of summer or the
fall, we shall find the ovaries presenting

the appearance of small clusters of minute and nearly colorless
eggs, the smaller of which are perfectly transparent and not over
T|^ of an inch in diameter. But in the early spring, when the
season of reproduction approaches, the ovaries will be found in-
creased to four or five times their former size, and forming large
lobulated masses, crowded with dark-colored opaque eggs, measur-
ing J2 of an inch in diameter. At the approach of the generative
season, in all the lower animals, a certain number of the eggs, which
were previously in an imperfect and inactive condition, begin to
increase in size and become somewhat altered in structure. The
vitellus more especially, which was before colorless and transparent.
becomes granular in texture as well as increased in volume ; and
assumes at the same time, in many species of animals, a black.

F K M A T< E G E * E R A T I r E ° R"

GAUS OF FROG.— a, a. Ovaries.

&, 6. oviducts. c, c. Their internal

548 EGG AND FEMALE ORGANS OF GENERATION.

brown, yellow, or orange color. In the human subject, however,
the change consists only in an increase of size and granulation,
without any remarkable alteration of color.

The eggs, as they ripen in this way, becoming enlarged and
changed in texture, gradually distend the Graafian follicles and
project from the surface of the ovary. At last, when fully ripe,
they are discharged by a rupture of the walls of the follicles, and,
passing into the oviducts, are conveyed by them to the external
generative orifice, and there expelled. In this way, as successive
seasons come round, successive crops of eggs enlarge, ripen, leave
the ovaries, and are discharged. Those which are to be expelled
at the next generative epoch may always be recognized by their
greater degree of development ; and in this way, in many animals,
the eggs of no less than three different crops may be recongized in
the ovary at once, viz., 1st, those which are perfectly mature and
ready to be discharged ; 2d, those which are to ripen in the follow-
ing season; and 3d, those which are as yet altogether inactive and
undeveloped. In most fish and reptiles, as well as in birds, this
regular process of maturation and discharge of eggs takes place
but once a year. In different species of quadrupeds it may take
place annually, semi-annually, bi-monthly, or even monthly; but
in every instance it recurs at regular intervals, and exhibits accord-
ingly, in a marked degree, the periodic character which we have
seen to belong to most of the other vital phenomena.

Action of the Oviducts and Female Generative Passages. — In frogs
and lizards, the ripening and discharge of the eggs take place, as
above mentioned in the early spring. At the time of leaving the

ovary, the eggs consist simply of the
'S-1'9- dark-colored and granular vitellus,

inclosed in the vitelline membrane.

They are then received by the inner
<* A r«M extremity of the oviducts, and carried

I®

downward by the peristaltic move-
ment of these canals, aided by the
FROGS' Eoos—rr. while more powerful contraction of the

still in the ovary. 1. After passing v j i -\ -TV • j.1

through th« oviduct. abdominal muscles. During the pas-

sage of the eggs, moreover, the mucous

membrane of the oviduct secretes a colorless, viscid, albuminoid
substance, which is deposited in successive layers round each egg,
forming a thick and tenacious coating or envelope. (Fig. 179.)
When the eggs are finally discharged, this albuminoid matter

EGG AND FEMALE ORGANS OF GENERATION. 549

absorbs the water in which the spawn is deposited, and swells up
into a transparent gelatinous mass, in which the eggs are separately
imbedded. This substance supplies, by its subsequent liquefaction
and absorption, a certain amount of nutritious material, during the
development and early growth of the embryo.

In the terrestrial reptiles and in birds, the oviducts perform a
still more important secretory function. In the common fowl, the
ovary consists, as in the frog, of a large number of follicles, loosely
connected by areolar tissue, in which the eggs can be seen in different
stages of development. (Fig. 180, a.) As the egg which is approach-
ing maturity enlarges, it distends the cavity of its follicle, and pro-
jects farther from the general surface of the ovary ; so that it hangs
at last into the peritoneal cavity, retained only by the attenuated
wall of the follicle, and a slender pedicle through which run the
bloodvessels by which its circulation is supplied. A rupture of the
follicle then occurs, at its most prominent part, and the egg is dis-
charged from the lacerated opening.

At the time of its leaving the ovary, the egg of the fowl consists
of a large, globular, orange-colored vitellus, or "yolk," inclosed in
a thin and transparent vitelline membrane. Immediately under-
neath the vitelline membrane, at one point upon the surface of the
vitellus, is a round white spot, consisting of a layer of minute
granules, termed the " cicatricula." It is in the central part of the
cicatricula that the germinative vesicle is found imbedded, at an
early stage of the development of the egg. At the time of its
discharge from the ovary, the germinative vesicle has usually dis-
appeared ; but the cicatricula is still a very striking and important
part of the vitellus, as it is from this spot that the body of the chick
begins afterward to be developed.

At the same time that the egg protrudes from the surface of the
ovary, it projects into the inner orifice of the oviduct ; so that, when
discharged from its follicle, it is immediately embraced by the upper
or fringed extremity of this tube, and commences its passage down-
ward. In the fowl, the muscular coat of the oviduct is highly deve-
loped, and its peristaltic contractions gently urge the egg from above
downward, precisely as the oesophagus or the intestines transport
the food in a similar direction. While passing through the first
two or three inches of the oviduct (c, d), where the mucous mem-
brane is smooth and transparent, the yolk merely absorbs a certain
quantity of -fluid, so as to become more flexible and yielding in con-
sistency. It then passes into a second division of the generative

550 EGG AND FEMALE ORGANS OF GENERATION.

canal, in which the mucous membrane is thick and glandular in
texture, and is also thrown into numerous longitudinal folds, which
project into the cavity of the oviduct. This portion of the oviduct
(d, e), extends over about nine inches of its entire length. In its
upper part, the mucous membrane secretes a viscid material, by
which the yolk is encased, and which soon consolidates into a gela-
tinous* membranous deposit ; thus forming a second homogeneous
layer, outside the vitelline membrane.

Now the peristaltic movements of this part of the oviduct are
such as to give a rotary, as well as a progressive motion to the
egg ; and the two extremities of the membranous layer described
above become, accordingly, twisted in opposite directions into two
fine cords, which run backward and forward from the opposite poles
of the egg. These cords are termed the " chalazas," and the mem-
brane with which they are connected, the " chalaziferous membrane."

Throughout the remainder of the second division of the oviduct,
the mucous membrane exudes an abundant, gelatinous, albuminoid
substance, which is deposited in successive layers round the yolk,
inclosing at the same time the chalaziferous membrane and the
chalazae. This substance, which forms the so-called albumen, or
" white of egg," is semi-solid in consistency, nearly transparent, and
of a faint amber color. It is deposited in greater abundance in front
of the advancing egg than behind it, and forms accordingly a
pointed or conical projection in front, while behind, its outline is
rounded off, parallel with the spherical surface of the yolk. In this
way, the egg acquires, when covered with its albumen, an ovoid
form, of which one end is round, the other pointed; the pointed
extremity being always directed downward, as the egg descends
along the oviduct.

In the third division of the oviduct (/), which is about three and
a half inches in length, the mucous membrane is arranged in longi-
tudinal folds, which are narrower and more closely packed than in
the preceding portion. The material secreted in this part, and de-
posited upon the egg, condenses into a firm fibrous covering, com-
posed of three different layers which closely embrace the surface
of the albuminous mass, forming a tough, flexible, semi-opaque
envelope for the whole. These layers are known as the external,
middle, and internal fibrous membranes of the egg.

Finally the egg passes into the fourth division of the oviduct (g),
which is wider than the rest of the canal, but only a little over two
inches in length. Here the mucous membrane, which is arranged

EGG AND FEMALE ORGANS OF GENERATION.

551

Fig. 180.

in abundant, projecting, leaf-like villosities, exudes a fluid very rich
in calcareous salts. The most external of the three membranes
just described is permeated by this fluid, and very soon the calcare-
ous matter begins to crystallize in
the interstices of its fibres. This
deposit of calcareous matter goes
on, growing constantly thicker and
more condensed, until the entire
external membrane is converted into
a white, opaque, brittle, calcareous
shell, which incloses the remaining
portions and protects them from ex-
ternal injury. The egg is then driven
outward by the contraction of the
muscular coat through a narrow por-
tion of the oviduct (h), and, gradually
dilating the passages by its conical
extremity, is finally discharged from
the external orifice.

The egg of the fowl, after it has
been discharged from the body, con-
sists, accordingly, of various parts;
some of which, as the yolk and the
vitelline membrane, entered into its
original formation, while the remain-
der have been deposited round it dur-
ing its passage through the oviduct.
On examining such an egg (Fig. 181),
we find externally the calcareous
shell (h), while immediately beneath
it are situated the middle and internal
fibrous shell-membranes (e,f).

Soon after the expulsion of the egg
there is a partial evaporation of its
watery ingredients, which are replaced
by air penetrating through the pores

F -MALE 'GENERATIVE ORGANS OF FOWL. — ft. Ovary. &. Graafian follicle, from which the
egg has just been discharged, c. Yolk, entering upper extremity of oviduct. d,e. Second division
of oviduct, in which chalaziferous membran*, chalazse, and albumen are formed. /. Third portion,
in which the fibrous shell membranes are produced, g. Fourth portion laid open, showing egg
comp'etely formed, with calcareous shell, h. Narrow canal through which the egg is discharged.

552 EGG AND FEMALE ORGANS OP GENERATION.

of the shell at its rounded extremity. The air thus introduced
accumulates between the middle and internal fibrous membranes
at this spot, separating them from each other, and forming a cavity
or air-chamber (g), which is always found between the two fibrous
membranes at the rounded end of the egg. Next we come to the
albumen or " white" of the egg (d) ; next to the chalaziferous mem-
brane and chalazs9 (c) ; and finally to the vitelline membrane (b)

Fig. 181.

Diagram of Fowi.'s EGG. — a. Yolk. ft. Vitelline membrane, c. Chalaziferotis membrane, d.
Albumen, e, f. Middle and internal shell membranes, g. Air-chamber, h. Calcareous shell.

inclosing the yolk (a). After the expulsion of the egg, the external
layers of the albumen liquefy ; and the vitellus, being specifically
lighter than the albumen, owing to the large proportion of oleagin-
ous matter which it contains, rises toward the surface of the egg,
with the cicatricula uppermost. This part, therefore, presents
itself almost immediately on breaking open the egg upon its lateral
surface, and is placed in the most favorable position for the action
of warmth and atmospheric air in the development of the chick.

The vitellus, therefore, is still the essential and constituent portion
of the egg ; while all the other parts consist either of nutritious mate-
rial, like the albumen, provided for the support of the embryo, or
of protective envelopes, like the shell and the fibrous membranes.

In the quadrupeds, another and still more important modification
of the oviducts takes place. In these animals, the egg, which is
originally very minute in size, is destined to be retained within the
generative passages of the female during the development of the
embryo. While the upper part of the oviduct, therefore, is quite
narrow, and intended merely to transmit the egg from the ovary,

EGG AND FEMALE ORGANS OF GENERATION.

553

and to supply it with, a little albuminous secretion, its lower por-
tions are very much increased in size, and are lined, moreover, with
a mucous membrane, so constructed as to provide for the protection
and nourishment of the embryo, during the entire period of gesta-
tion. The upper and narrower portions of the oviduct are known
as the " Fallopian tubes" (Fig. 182) ; while the lower and more

Fig. 182.

UTERCP A\D OVARIES OF THE Sow. -«,«-•. Ovarie*. l.J . Fallopian tubes, c, c. Horns of
nierux. d. Body of uterus, e. Vagina.

highly developed portions constitute the uterus. These lower por-
tions unite with each other upon the median line near their infe-
rior termination, so as to form a central organ, termed the " body"
of the uterus; while the remaining ununited parts are known as
its "cornua" or "horns."

In the human subject, the female generative apparatus presents
the following peculiarities. The ovaries consist of Graafian follicles,
which are imbedded in a somewhat dense areolar tissue, supplied
with an abundance of bloodvessels. The entire mass is covered
with a thick, opaque, yellowish white layer of fibrous tissue called
the " albugineous tunic." Over the whole is a layer of peritoneum,
which is reflected upon the vessels which supply the ovary, and is
continuous with the broad ligaments of the uterus.

The oviducts commence by a wide expansion, provided with
fringed edges, called the " fimbriated extremity of the Fallopian
tube." The Fallopian tubes themselves are very narrow and con-
voluted, and terminate on each side in the upper part of the body
of the uterus. In the human subject, the body of the uterus is so
much developed at the expense of the cornua, that the latter hardly
appear to have an existence ; and in fact no trace of them is visible
externally. But on opening the body of the uterus its cavity is

554

EGG AND FEMALE ORGANS OF GENERATION.

seen to be nearly triangular in 'shape, its two superior angles run-
ning out on each side to join the lower extremities of the Fallopian
tubes. This portion evidently consists of the cornua, which have
been consolidated with the body of the uterus, and enveloped in
its thickened layer of muscular fibres.

Fig. 183.

GENERATIVE OROAXS OF HITMAN FEMALE. — n, a. Ovaries. I, b. Fallopian tubes,
c. B-jdy of uterus, d. Cervix, e. Vagiua.

The cavity of the body of the uterus terminates below by a con-
stricted portion termed the os internum, by which it is separated
from the cavity of the cervix. These two cavities are not only
different from each other in shape, but differ also in the structure
of their mucous membrane and the functions which it is destined
to perform.

The mucous membrane of the body of the uterus in its usual
condition is smooth and rosy in color, and closely adherent to the
subjacent muscular tissue. It consists of minute tubular follicles
somewhat similar to those of the gastric mucous membrane, ranged
side by side, and opening by distinct orifices upon its free surface.
The secretion of these follicles is destined for the nutrition of the
embryo during the earlier periods of its formation.

The internal surface of the neck of the uterus, on the other hand,
is raised in prominent ridges which are arranged usually in two
lateral sets, diverging from a central longitudinal ridge ; presenting
the appearance known as the " arbor vitas uterina." The follicles
of this part of the uterine mucous membrane are different in struc-
ture from those of the foregoing. They are of a globular or sac-

EGG AND FEMALE ORGANS OF GENERATION. 555

like form, and secrete a very firm, adhesive, transparent mucus,
which is destined to block up the cavity of the cervix during ges-
tation, and guard against the accidental displacement of the egg.
Some of these follicles are frequently distended with their secretion,
and project, as small, hard, rounded eminences, from the surface
of the mucous membrane. In this condition they are sometimes
designated by the name of " ovula Nabothi," owing to their having
been formerly mistaken for eggs, or ovules.

The cavity of the cervix uteri is terminated below by a second
constriction, the "os externum." Below this comes the vagina,
which constitutes the last division of the female generative pas-
sages.

The accessory female organs of generation consist therefore of
ducts or tubes, by means of which the egg is conveyed from within
outward. These ducts vary in the degree and complication of
their development, according to the importance of the task assigned
to them. In the lower orders, they serve merely to convey the egg
rapidly to the exterior, and to supply it more or less abundantly
with an albuminous secretion. In the higher classes and in the
human subject, they are adapted to the more important function of
retaining the egg during the period of gestation, and of providing
during the same time for the nourishment of the young embryo.

556 MALE ORGANS OF GENERATION.

CHAPTER IV.

ON THE SPERMATIC FLUID, AND THE MALE
ORGANS OF GENERATION.

THE mature egg is not by itself capable of being developed into
the embryo. If simply discharged from the ovary and carried
through the oviducts toward the exterior, it soon dies and is de-
composed, like any other portion of the body separated from its
natural connections. It is only when fecundated by the spermatic
fluid of the male, that it is stimulated to continued development,
and becomes capable of a more complete organization.

The product of the male generative organs consists of a colorless,
somewhat viscid, and albuminous fluid, containing an innumerable
quantity of minute filamentous bodies, termed spermatozoa. The
name spermatozoa has been given to these bodies, on account of
their exhibiting under the microscope a very active and continu-
ous movement, bearing some resemblance to that of certain animal-
cules.

The spermatozoa of the human subject (Fig. 184, a) are about
eitf of an inch in length, according to the measurements of Kol-
liker. Their anterior extremity presents a somewhat flattened,
triangular-shaped enlargement, termed the " head." The head con-
stitutes about one-tenth part the entire length of the spermato-
zoon. The remaining portion is a very slender filamentous pro-
longation, termed the "tail," which tapers gradually backward,
becoming so exceedingly delicate towards its extremity, that it is
difficult to be seen except when in motion. There is no further
organization or internal structure to be detected in any part of the
spermatozoon ; and the whole appears to consist, so far as can be
seen by the microscope, of a completely homogeneous, tolerably
firm, albuminoid substance. The terms head and tail, therefore,
as justly remarked by Bergmann and Leuckart,1 are not used,
when describing the different parts of the spermatozoon, in the
same sense as that in which they would be applied to the corre-

1 Vergleicheride Physiologie. Stuttgart, 1852.

MALE ORGANS OF GENERATION.

557

spending parts of an animal, but simply for the sake of conveni-
ence ; just as one might speak of the head of an arrow, or the tail
of a comet.

In the lower animals, the spermatozoa have usually the same
general form as in the human subject; that is, they are slender
filamentous bodies, with the anterior extremity more or less en-
larged. In the rabbit they have a head which is roundish and
flattened in shape, somewhat resembling the globules of the blood.
In the rat (Fig. 184, b) they are much larger than in man, measur-
ing nearly TA5 of an inch in length. The head is conical in shape,

Fig. 184.

SPERMATOZOA. —o. Human. 5. Of Rat. e. Of Menobranchus. Magnified 4SO times.

about one-twentieth the whole length of the filament, and often
slightly curved at its anterior extremity. In the frog and in rep-
tiles generally, the spermatozoa are longer than in quadrupeds.
In the Menobranchus. or great American water-lizard, they are of
very unusual size (Fig. 184, c), measuring not less than ?'? of an
inch in length, about one-third of which is occupied by the head,
or enlarged portion of the filament.

The most remarkable peculiarity of the spermatozoa is their

553 MALE ORGANS OF GENERATION.

very singular and active movement, to which we have already
alluded. If a drop of fresh seminal fluid be placed under the
microscope, the numberless minute filaments with which it is
crowded are seen to be in a state of incessant and agitated motion.
This movement of the spermatozoa, in many species of animals,
strongly resembles that of the tadpole; particularly when, as in the
human subject, the rabbit, &c., the spermatozoa consist of a short
and well defined head, followed by a long and slender tail. Here
the tail-like filament keeps up a constant lateral or vibratory move-
ment, by which the spermatozoon is driven from place to place in
the spermatic fluid, just as the fish or the tadpole is propelled
through the water. In other instances, as for example in the water-
lizard, and in some parasitic animals, the spermatozoa have a con-
tinuous writhing or spiral-like movement, which presents a very
peculiar and elegant appearance when large numbers of them are
viewed together.

It is the existence of this movement which first suggested the
name of spermatozoa to designate the animated filaments of the
spermatic fluid ; and which has led some writers to attribute to
them an independent animal nature. This is, however, a very
erroneous mode of regarding them ; since they cannot properly be
considered as animals, notwithstanding the active character of their
movement, and the striking resemblance which it sometimes pre-
sents to a voluntary act. The spermatozoa are organic forms,
which are produced in the testicles, and constitute a part of their
tissue; just as the eggs, which are produced in the ovaries, natu-
rally form a part of the texture of these organs. Like the egg,
also, the spermatozoon is destined to be discharged from the organ
where it grew, and to retain, for a certain length of time afterward,
its vital properties. One of the most peculiar of these properties
is its power of keeping in constant motion ; which does not, how-
ever, mark it as a distinct animal, but only distinguishes it as a
peculiar structure belonging to the parent organism. The motion
of a spermatozoon is precisely analogous to that of a ciliated epi-
thelium cell. The movement of the latter will continue for some
hours after it has been separated from its mucous membrane, pro-
vided its texture be not injured, nor the process of decomposition
allowed to commence. In the same manner, the movement of the
spermatozoa is a characteristic property belonging to them, which
continues for a certain time, even after they have been separated
from the rest of the body.

MALE OKGANS OF GENERATION. 559

In order to preserve their vitality, the spermatozoa must be
kept at the ordinary temperature of the body, and preserved
from the contact of the air or other unnatural fluids. In this way,
they may be kept without difficulty many hours for purposes of
examination. But if the fluid in which they are kept be allowed
to dry, or if it be diluted by the addition of water, in the case of
birds and quadrupeds, or if it be subjected to extremes of heat or
cold, the motion ceases; and the spermatozoa themselves soon begin
to disintegrate.

The spermatozoa are produced in certain glandular-looking
organs, the testicles, which are characteristic of the male, as the ova-
ries are characteristic of the female. In man and all the higher
animals, the testicles are solid, ovoid-shaped bodies, composed
principally of numerous long, narrow, and convoluted tubes, the
" seminiferous tubes," somewhat similar in their general anatomical
characters to the tubuli uriniferi of the kidneys. These tubes lie
for the most part closely in contact with each other, so that nothing
intervenes between them except capillary bloodvessels and a little
areolar tissue. They commence, by blind, rounded extremities, near
the external surface of the testicle, and pursue an intricately con-
voluted course toward its central and posterior part. They are not
strongly adherent to each other, but may be readily unravelled by
manipulation, and separated from each other.

The formation of the spermatozoa, as it takes place in the
substance of the testicle, has been fully investigated by Kolliker.
According to his observations, as the age of puberty approaches,
beside the ordinary pavement epithelium lining the seminiferous
tubes, other cells or vesicles of larger size make their appearance
in these tubes, each containing from one to fifteen or twenty nuclei,
with nucleoli. It is in the interior of these vesicles that the sper-
matozoa are formed ; their number corresponding usually with that
of the nuclei just mentioned. They are at first developed in bundles
of ten to twenty, held together by the thin membranous substance
which surrounds them, but are afterward set free by the liquefac-
tion of the vesicle, and then fill nearly the entire cavity of the
seminiferous ducts, mingled only with a very minute quantity of
transparent fluid.

In the seminiferous tubes themselves, the spermatozoa are al-
ways inclosed in the interior of their parent vesicles; they are libe-
rated, and mingled promiscuously together, only after entering the
rete testis and the head of the epididymis.

560 MALE ORGANS OF GENERATION.

Beside the testicles, which are, as above stated, the primary and
essential parts of the male generative apparatus, there are certain
secondary or accessory organs, by means of which the spermatic
fluid is conveyed to the exterior, and mingled with various secre-
tions which assist in the accomplishment of its functions.

As the sperm leaves the testicle, it consists, as above mentioned,
almost entirely of the spermatozoa, crowded together in an opaque,
white, semi-fluid mass, which fills up the vasa efferentia, and com-
pletely distends their cavities. It then enters the single duct
which forms the body and lower extremity of the epididymis,
following the long and tortuous course of this tube, until it
reaches the vas deferens; through which it is still conveyed
onward to the point where this canal opens into the urethra.
Throughout this course, it is mingled with a glairy, mucus-like
fluid, secreted by the walls of the epididymis and vas deferens, in
which the spermatozoa are enveloped. The mixture is then depo-
sited in the vesiculae serninales, where it accumulates, as fresh quan-
tities are produced in the testicle and conveyed downward by the
spermatic duct. It is probable that a second secretion is supplied
also by the internal surface of the vesiculas semimiles, and that the
sperm, while retained in their cavities, is not only stored up for
subsequent use, but is at the same time modified in its properties
by the admixture of another fluid.

At the time when the evacuation of the sperm takes place, it is
driven out from the seminal vesicles by the muscular contraction
of the surrounding parts, and meets in the urethra with the secre-
tions of the prostate gland, the glands of Cowper, and the mucous
follicles opening into the urethral passage. All these organs are at
that time excited to an unusual activity of secretion, and pour out
their different fluids in great abundance.

The sperm, therefore, as it is discharged from the urethra, is an
exceedingly mixed fluid, consisting of the spermatozoa derived
from the testicles, together with the secretions of the epididymis
and vas deferens, the prostate, Cowper's glands, and the mucous fol-
licles of the urethra. Of all these ingredients, it is the spermatozoa
which constitute the essential part of the seminal fluid. They are
the true fecundating element of the sperm, while all the others are
secondary in importance, and perform only accessory functions.

Spallanzani found that if frog's semen be passed through a suc-
cession of filters, so as to separate the spermatozoa from the liquid
portions, the filtered fluid is destitute of any fecundating properties ;

MALE ORGANS OF GENERATION. 561

while the spermatozoa remaining entangled in the filter, if mixed
with a sufficient quantity of fluid of the requisite density for dilu-
tion, may still be successfully used for the impregnation of eggs.
It is well known, also, that animals or men from whom both testi-
cles have been removed, are incapable of impregnating the female
or her eggs ; while a removal or imperfection of any of the other
generative organs does not necessarily prevent the accomplishment
of the function.

In most of the lower orders of animals there is a periodical
development of the testicles in the male, corresponding in time with
that of the ovaries in the female. As the ovaries enlarge and the
eggs ripen in the one sex, so in the other the testicles increase in
size, as the season of reproduction approaches, and become turgid
with spermatozoa. The accessory organs of generation, at the
same time, share the unusual activity of the testicles, and become
increased in vascularity and ready to perform their part in the
reproductive function.

In the fish, for example, where the testicles occupy the same
position in the abdomen as the ovaries in the opposite sex, these
bodies enlarge, become distended with their contents, and project
into the peritoneal cavity. Each of the two sexes is then at the
same time under the influence of a corresponding excitement. The
unusual development of the generative organs reacts upon the entire
system, and produces a state of peculiar activity and excitability,
known as the condition of " erethism." The female, distended with
eggs, feels the impulse which leads to their expulsion ; while the
male, bearing the weight of the enlarged testicles and the accumu-
lation of newly-developed spermatozoa, is impelled by a similar
sensation to the discharge of the spermatic fluid. The two sexes,
accordingly, are led by instinct at this season to frequent the same
situations. The female deposits her eggs in- some spot favorable
to the protection and development of the young ; after which the
male, apparently attracted and" stimulated by the sight of the new-
laid eggs, discharges the spermatic fluid upon them, and their
impregnation is accomplished.

In such instances as the above, where the male and female gene-
rative products are discharged separately by the two sexes, the
subsequent contact of the eggs with the spermatic fluid would seem
to be altogether dependent on the occurrence of fortuitous circum-
stances, and their impregnation, therefore, often liable to fail. In
point of fact, however, the simultaneous functional excitement of
36

562 MALE ORGANS OF GENERATION.

the two sexes and the operation of corresponding instincts, leading
them to ascend the same rivers and to frequent the same spots,
provide with sufficient certainty for the impregnation of the eggs.
In these animals, also, the number of eggs produced by the female
is very large, the ovaries being often so distended as to fill nearly
the whole of the abdominal cavity ; so that, although many of the
eggs may be accidentally lost, a sufficient number will still be im-
pregnated and developed, to provide for the continuation of* the
species.

In other instances, an actual contact takes place between the
sexes at the time of reproduction. In the frog, for example, the
male fastens himself upon the back of the female by the anterior
extremities, which seem to retain their hold by a kind of spasmodic
contraction. This continues for one or two days, during which
time the mature eggs, which have been discharged from the ovary,
are passing downward through the oviducts. At last they are ex-
pelled from the anus, while at the same time the seminal fluid of
the male is discharged upon them, and impregnation takes place.

In the higher classes of animals, however, and in man, where the
egg is to be retained in the body of the female parent during its
development, the spermatic fluid is introduced into the female
generative passages by sexual congress, and meets the egg at or
soon after its discharge from the ovary. The same correspondence,
however, between the periods of sexual excitement in the male and
female, is visible in many of these animals, as well as in fish and
reptiles. This is the case in most species which produce young but
once a year, and at a fixed period, as the deer and the wild hog. In
other species, on the contrary, such as the dog, as well as the rabbit,
the guinea pig, &c., where several broods of young are produced
during the year, or where, as in the human subject, the generative
epochs of the female recur at short intervals, so that the particular
period of impregnation is comparatively indefinite, the generative
apparatus of the male is almost constantly in a state of full deve-
lopment ; and is excited to action at particular periods, apparently
by some influence derived from the condition of the female.

In the quadrupeds, accordingly, and in the human species, the
contact of the sperm with the egg and the fecundation of the latter
take place in the generative passages of the female ; either in the
uterus, the Fallopian tubes, or even upon the surface of the ovary ;
in each of which situations the spermatozoa have been found, after
the accomplishment of sexual intercourse.

PEB10DICAL OVULATION. 563

CHAPTER V.

OX PERIODICAL OYULATION, AND THE FUNCTION
OF MENSTRUATIO

I. PERIODICAL OVULATION.

WE have already spoken in general terms of the periodical ripen-
ing of the eggs and their discharge from the generative organs of
the female. This function is known by the name of " ovulation,"
and may be considered as the primary and most important act in
the process of reproduction. We shall, therefore, enter more fully
into the consideration of certain particulars in regard to it, by
which its nature and conditions may be more clearly understood.

1st. Eggs exist originally in the ovaries of all animals, as part of
their natural structure. In describing the ovaries of fish and reptiles
we have said that they consist of nothing more than Graafian vesi-
cles, each vesicle containing an egg, and united with the others by
loose areolar tissue and a peritoneal investment. In the higher
animals and in the human subject, the essential constitution of the
ovary is the same ; only its fibrous tissue is more abundant, so that
the texture of the entire organ is more dense, and its figure more
compact. In all classes, however, without exception, the interior
of each Graafian vesicle is occupied by an egg ; and it is from this
egg that the young offspring is afterward produced.

The process of reproduction was formerly regarded as essentially
different in the oviparous and the viviparous animals. In the ovipa-
rous classes, such as most fish, and all reptiles and birds, the young
animal was well known to be formed from an egg produced by the
female ; while in the viviparous animals, or those which bring
forth their young alive, such as the quadrupeds and the human
species, the embryo was supposed to originate in the body of the
female, by some altogether peculiar and mysterious process, in
consequence of sexual intercourse. As soon, however, as the
microscope began to be used in the examination of the tissues,

564 OVULATION AND FUNCTION OF MENSTRUATION.

the ovaries of quadrupeds were also found to contain eggs. These
eggs had previously escaped observation on account of their simple
structure and minute size; but they were nevertheless found to
possess all the most essential characters belonging to the larger
eggs of the oviparous animals.

The true difference in the process of reproduction, between the
two classes, is therefore merely an apparent, not a fundamental one.
In fish; reptiles, and birds, the egg is discharged by the female
before or immediately after impregnation, and the embryo is subse-
quently developed and hatched externally. In the quadrupeds and
the human species, on the other hand, the egg is retained within
the body of the female until the embryo is developed ; when the
membranes are ruptured and the young expelled at the same time.
In all classes, however, viviparous as well as oviparous, the young
is produced equally from an egg ; and in all classes the egg, some-
times larger and sometimes smaller, but always consisting essentially
of a vitellus and a vitelline membrane, is contained originally in
the interior of an ovarian follicle.

The egg is accordingly, as we have already intimated, an integral
part of the ovarian tissue. It may be found there long before the
generative function is established, and during the earliest periods
of life. It may be found without difficulty in the newly born
female infant, and may even be detected in the foetus before birth.
Its growth and nutrition, also, are provided for in the same man-
ner with that of other portions of the bodily structure.

2d. These eggs become' more fully developed at a certain age, when
tJie generative function is about to be established. During the early
periods of life, the ovaries and their contents, like many other
organs, are imperfectly developed. They exist, but they are as
yet inactive, and incapable of performing any function. In the
young chick, for example, the ovary is of small size ; and the eggs,
instead of presenting the voluminous, yellow, opaque vitellus which
they afterward exhibit, are minute, transparent, and colorless. In
the young quadrupeds, and in the human female during infancy
and childhood, the ovaries are equally inactive. They are small,
friable, and of a nearly homogeneous appearance to the naked eye ;
presenting none of the enlarged follicles, filled with transparent
fluid, which are afterward so readily distinguished. At this time,
accordingly, the female is incapable of bearing young, because the
ovaries are inactive, and the eggs which they contain immature.

At a certain period, however, which varies in the time of its

PERIODICAL OVULATION. 565

occurrence for different species of animals, the sexual apparatus
begins to enter upon a state of activity. The ovaries increase in
size, and their circulation becomes more active. The eggs, also,
instead of remaining quiescent, take on a rapid growth, and the
structure of the vitellus is completed by the abundant deposit of
oleaginous granules in its interior. Arrived at this state, the eggs
are ready for impregnation, and the female becomes capable of
bearing young. She is then said to have arrived at the state of
"puberty," or that condition in which the generative organs are
fully developed. This condition is accompanied by a visible
alteration in the system at large, which indicates the complete
development of the entire organism. In many birds, for example,
the plumage assumes at this period more varied and brilliant
colors; and in the common fowl the comb, or " crest," enlarges
and becomes red and vascular. In the American deer (Cervus
virginianus), the coat, which during the first year is mottled with
white, becomes in the second year of a uniform tawny or reddish
tinge. In nearly all species, the limbs become more compact and
the body more rounded ; and the whole external appearance is so
altered, as to indicate that the animal has arrived at the period of
puberty, and is capable of reproduction.

3d. Successive crops of eggs, in the adult female, ripen and are
discharged independently of sexual intercourse. It was formerly sup-
posed, as we have mentioned above, that in the viviparous animals
the germ was formed in the body of the female only as a conse-
quence of sexual intercourse. Even after the important fact
became known that eggs exist originally in the ovaries of these
animals, and are only fecundated by the influence of the sperm-
atic fluid, the opinion still prevailed that the occurrence of sexual
intercourse was the cause of their being discharged from the ovary,
and that the rupture of a Graafian vesicle in this organ was a
certain indication that coitus had taken place.

This opinion, however, was altogether unfounded. We already
know that in fish and reptiles the mature eggs not only leave the
ovary, but are actually discharged from the body of the female
while still unimpregnated, and only subsequently come in contact
with the spermatic fluid. In fowls, also, it is a matter of common
observation that the hen will continue to lay fully-formed eggs, if
well supplied with nourishment, without the presence of the cock :
only these eggs, being unimpregnated, are incapable of producing

566 OVULAT1ON AND FUNCTION OF MENSTRUATION.

chicks. In oviparous animals, therefore, the discharge of the egg,
as well as its formation, is independent of sexual intercourse.

Continued observation shows this to be the case, also, in the
viviparous quadrupeds. The researches of Bischoff, Pouchet, and
Coste have demonstated that in the sheep, the pig, the bitch, the
rabbit, £c., if the female be carefully kept from the male until after
the period of puberty is established, and then killed, examination
of the ovaries will show that Graafian vesicles have matured, rup-
tured, and discharged their eggs, in the same manner as though
sexual intercourse had taken place. Sometimes the vesicles are
found distended and prominent upon the surface of the ovary;
sometimes recently ruptured and collapsed ; and sometimes in vari-
ous stages of cicatrization and atrophy. Bischoff,1 in several in-
stances of this kind, actually found the unimpregnated eggs in the
oviduct, on their way to the cavity of the uterus. In those animals
in which the ripening of the eggs takes place at short intervals, as,
for example, the sheep, the pig, and the cow, it is very rare to exa-
mine the ovaries in any instance where traces of a more or less
recent rupture of the Graafian follicles are not distinctly visible.

One of the most important facts, derived from the examination
of such cases as the above, is that the ovarian eggs become deve-
loped and are discharged in successive crops, which follow each
other regularly at periodical intervals. If we examine the ovary
of the fowl; for example (Fig. 180), we see at a glance how the eggs
grow and ripen, one after the other, like fruit upon a vine. In this
instance, the process of evolution is very rapid ; and it is easy to
distinguish, at the same time, eggs which are almost microscopic in
size, colorless, and transparent; those which are larger, firmer,
somewhat opaline, and yellowish in hue ; and finally those which
are fully developed, opaque, of a deep orange color, and just ready
to leave the ovary.

It will be observed that in this instance the difference between
the undeveloped and the mature eggs consists principally in the
size of the vitellus, which is furthermore, for reasons previously
given (Chap. III.), very much larger than in the quadrupeds. It
is also seen that it is the increased size of the vitellus alone, by
which the ovarian follicle is distended and ruptured, and the egg
finally discharged.

1 Memoire sur la clinte periodique de 1'oeuf, &c , Annales des Sciences Naturelles,
A out— Septembre, 1844.

PERIODICAL OVULATION. 567

In the human species and the quadrupeds, on the other hand,
the microscopic egg never becomes large enough to distend the
follicle by its own size. The rupture of the follicle and the libera-
tion of the egg are accordingly provided for, in these instances, by
a totally different mechanism.

In the earlier periods of life, in man and the higher animals, the
egg is contained in a Graafian follicle which closely embraces its
exterior, and is consequently hardly larger than the egg itself. As
puberty approaches, those follicles which are situated near the free
surface of the ovary become enlarged by the accumulation of a
colorless serous fluid in their cavity. We then find that the ovary,
when cut open, shows a considerable number of globular, transpa-
rent vesicles, readily perceptible by the eye, the smaller of which
are deep seated, but which increase in size as they approach the
free surface of the organ. These vesicles are the Graafian follicles,
which, in consequence of the advancing maturity of the eggs con-
tained in them, gradually enlarge as the period of generation ap-
proaches.

The Graafian follicle at this time consists of a closed globular
sac or vesicle, the external wall of which, though quite translucent,
has a fibrous texture under the microscope and is well supplied
with bloodvessels. This fibrous and vascular wall is distinguished
by the name of the "membrane of the vesicle." It is not very
firm in texture, and if roughly handled is easily ruptured.

The membrane of the vesicle is lined throughout by a thin layer
of minute granular cells, which form for it a kind of epithelium,
similar to the epithelium of the pleura, pericardium, and other
serous membranes. This layer is termed the membrana granulosa.
It adheres but slightly to the membrane of the vesicle, and may
easily be detached by careless manipulation before the vesicle is
opened, being then mingled, in the form of light flakes and shreds,
with the serous fluid contained in the vesicle.

At the most superficial part of the Graafian follicle, or that
which is nearest the surface of the ovary, the membrana granulosa
is thicker than elsewhere. Its cells are here accumulated, in a
kind of mound or "heap," which has received the name of the
cumulus proligerus. It is sometimes called the discus proligerus,
because the thickened mass, when viewed from above, has a some-
what circular or disk-like form. In the centre of this thickened
portion of the membrana granulosa the egg is imbedded. It is

568 OVULATION AND FUNCTION OF MENSTRUATION.

accordingly always situated at the most superficial portion of the
follicle, and advances in this way toward the surface of the ovary.
As the period approaches at which the egg is destined to be dis-
charged, the Graafian follicle becomes more vascular, and enlarges
by an increased exudation of serum into its cavity. It then begins

Fig. 185.

Fig. 186.

GRAAFIAX FOLLICLE, near the period of rupture —n. Mernbraneof the vesicle. 1> Membrnna
granulosa. c. Cavity of follicle, d. Egg. e. Peritoneum. /. Tunica albugiuea. y, y. Tissue of
the ovary.

to project from the surface of the ovary, still covered by the albu-
gineous tunic and the peritoneum. (Fig. 185.) The constant accu-
mulation of fluid, however, in the follicle, exerts such a steady and
increasing pressure from within outward, that the albugineous tunic
and the peritoneum successively yield before it ; until the Graafian
follicle protrudes from the ovary as a tense, rounded, translucent

vesicle, in which the sense of
fluctuation can be readily per-
ceived on applying the fingers
to its surface. Finally, the pro-
cess of effusion and distension
still going on, the wall of the
vesicle yields at its most promi-
nent portion, the contained fluid
is driven out with a gush, by the
reaction and elasticity of the
neighboring ovarian tissues, car-
rying with it the egg, still en-
OVARY WITH GRAAFIAN FOLLICLE tangled in the cells of the pro-

RTPTURED: at a, egg just discharged with a -i- Y \r

portion of membraua granulosa. llgerOUS Q1SK.

The rupture of the Graafian
vesicle is accompanied, in some instances, by an abundant hemor-

PERIODICAL OVULATION. 569

rhage, which takes place from the internal surface of the congested
follicle, and by which its cavity is filled with blood. This occurs
in the human subject and in the pig, and to a certain extent, also, in
other of the lower animals. Sometimes, as in the cow, where no
hemorrhage takes place, the Graafian vesicle when ruptured
simply collapses ; after which a slight exudation, more or less tinged
with blood, is poured out during the course of a few hours.

Notwithstanding, however, these slight variations, the expulsion
of the egg takes place, in the higher animals, always in the manner
above described, viz., by the accumulation of serous fluid in the
cavity of the Graafian follicle, by which its walls are gradually dis-
tended and finally ruptured.

This process takes place in one or more Graafian follicles at a
time, according to the number of young which the animal produces
at a birth. In the bitch and the sow, where each litter consists of
from six to twenty young ones, a similar number of eggs ripen and
are discharged at each period. In the mare, in the cow, and in the
human female, where there is usually but one foetus at a birth, the
eggs are matured singly, and the Graafian vesicles ruptured, one
after another, at successive periods of ovulation.

4th. The ripening and discharge of the egg are accompanied by a
peculiar condition of the entire system, known as the "rutting" condi-
tion, or " cestruation" The peculiar congestion and functional
activity of the ovaries at each period of ovulation, act by sympathy
upon the other generative organs and produce in them a greater or
less degree of excitement, according to the particular species of ani-
mal. Almost always there is a certain amount of congestion of the
entire generative apparatus; Fallopian tubes, uterus, vagina, and
external organs. The secretions of the vagina and neighboring
parts are more particularly affected, being usually increased in quan-
tity and at the same time altered in quality. In the bitch, the
vaginal mucous membrane becomes red and tumefied, and pours
out an abundant secretion which is often more or less tinged with
blood. The secretions acquire also at this time a peculiar odor,
which appears to attract the male, and to excite in him the sexual
impulse. An unusual tumefaction and redness of the vagina and
vulva are also very perceptible in the rabbit ; and in some species
of apes it has been observed that these periods are accompanied
not only by a bloody discharge from the vulva, but also by an en-
gorgement and infiltration of the neighboring parts, extending even

570 OVULATION AND FUNCTION OF MENSTRUATION.

to the skin of the buttocks, the thighs, and the under part of the
tail.1

The system at large is also visibly affected by the process going
on in the ovary. In the cow, for example, the approach of an
oestrual period is marked by an unusual restlessness and agitation,
easily recognized by an ordinary observer. The animal partially
loses her appetite. She frequently stops browsing, looks about un-
easily, perhaps runs from one side of the field to the other, and then
recommences feeding, to be disturbed again in a similar manner
after a short interval. Her motions are rapid and nervous, and her
hide often rough and disordered ; and the whole aspect of the ani-
mal indicates the presence of some unusual excitement. After this
condition is fully established, the vaginal secretions show them-
selves in unusual abundance, and so continue for one or two days ;
after which the symptoms, both local and general, subside sponta-
neously, and the animal returns to her usual condition.

It is a remarkable fact, in this connection, that the female of
these animals will allow the approaches of the male only during and
immediately after the oestrual period ; that is, just when the egg is
recently discharged, and ready for impregnation. At other times,
when sexual intercourse would be necessarily fruitless, the instinct
of the animal leads her to avoid it ; and the concourse of the sexes
is accordingly made to correspond in time with the maturity of the
egg and its aptitude for fecundation.

II. MENSTRUATION.

In the human female, the return of the period of ovulation is
marked by a peculiar group of phenomena which are known as
menstruation, and which are of sufficient importance to be described
by themselves.

During infancy and childhood the sexual system, as we have
mentioned above, is inactive. No discharge of eggs takes place
from the ovaries, and no external phenomena show themselves,
connected with the reproductive function.

At the age of fourteen or fifteen years, however, a change begins
to manifest itself. The limbs become rounder, the breasts increase
in size, and the entire aspect undergoes a peculiar alteration, which
indicates the approaching condition of maturity. At the same
time a discharge of blood takes place from the generative passages,

1 Ponchet, Theorie positive de 1'ovulation, &c. Paris. 1847, p. 230.

MENSTRUATION". 571

accompanied by some disturbance of the general system, and the
female is then known to have arrived at the period of puberty.

Afterward, the bloody discharge just spoken of returns at regular
intervals of four weeks ; and, on account of this recurrence corres-
ponding with the passage of successive lunar months, its phenomena
are designated by the name of the "menses" or the "menstrual
periods." The menses return with regularity, from the time of
their first appearance, until the age of about forty- five years.
During this period, the female is capable of bearing children, and
sexual intercourse is liable to be followed by pregnancy. After
the forty-fifth year, the periods first become irregular, and then
cease altogether ; and their final disappearance is an indication that
the woman is no longer fertile, and that pregnancy cannot again
take place.

Even during the period above referred to, from the age of fifteen
to forty-five, the regularity and completeness of the menstrual
periods indicate to a great extent the aptitude of individual females
for impregnation. It is well known that all those causes of ill
health which derange menstruation are apt at the same time to
interfere with pregnancy ; so that women whose menses are habi-
tually regular and natural are much more likely to become preg-
nant, after sexual intercourse, than those in whom the periods are
absent or irregular.

If pregnancy happen to take place, however, at any time during
the child-bearing period, the menses are suspended during the con-
tinuance of gestation, and usually remain absent, after delivery, as
long as the woman continues to nurse her child. They then re-
commence, and subsequently continue to appear as before.

The menstrual discharge consists of an abundant secretion of
mucus mingled with blood. When the expected period is about
to come on, the female is affected with a certain degree of discomfort
and lassitude, a sense of weight in the pelvis, and more or less dis-
inclination to society. These symptoms are in some instances
slightly pronounced, in others more troublesome. An unusual
discharge of vaginal mucus then begins to take place, which soon
becomes yellowish or rusty brown in color, from the admixture of
a certain proportion of blood ; and by the second or third day the
discharge has the appearance of nearly pure blood. The unpleasant
sensations which were at first manifest then usually subside; and
the discharge, after continuing for a certain period, begins to grow
.more scanty. Its color changes from a pure red to a brownish or

572 OVULATION AND FUNCTION OF MENSTRUATION.

rusty tinge, until it finally disappears altogether, and the female
returns to her ordinary condition.

The menstrual epochs of the human female correspond with the
periods of oestruation in the lower animals. Their general resem-
blance to these periods is too evident to require demonstration.
Like them, they are absent in the immature female; and begin
to take place only at the period of puberty, when the aptitude for
impregnation commences. Like them, they recur during the child-
bearing period at regular intervals; and are liable to the same
interruption by pregnancy and lactation. Finally, their disappear-
ance corresponds with the cessation of fertility.

The periods of cestruation, furthermore, in many of the lower
animals, are accompanied, as we have already seen, with an unusual
discharge from the generative passages ; and this discharge is fre-
quently more or less tinged with blood. In the human female the
bloody discharge is more abundant than in other instances, but it
is evidently a phenomenon differing only in degree from that which
shows itself in many species of animals.

The most complete evidence, however, that the period of men-
struation is in reality that of ovulation, is derived from the results
of direct observation. A sufficient number of instances have now
been observed to show that at the menstrual epoch a Graafian
vesicle becomes enlarged, ruptures, and discharges its egg. Cruik-
shank1 noticed such a case so long ago as 1797. Negrier2 relates
two instances, communicated to him by Dr. Ollivier d'Angers, in
which, after sudden death during menstruation, a bloody and rup-
tured Graafian vesicle was found in the ovary. Bischoff3 speaks of
four similar cases in his own observation, in three of which the
vesicle was just ruptured, and in the fourth distended, prominent,
and ready to burst. Coste4 has met with several of the same kind.
Dr. Michel5 found a vesicle ruptured and filled with blood in a
woman who was executed for murder while the menses were pre-
sent. We have also" met with the same appearances in a case of
death from acute disease, on the second day of menstruation.

1 London Philosophical Transactions, 1797, p. 135.

2 Recherches sur les Ovaires, Paris, 1840, p. 78.

3 Aunales des Sciences Naturelles, August, 1844.

4 Histoire du Developpement des Corps Organises, Paris, 1847, vol. i. p. 221.

5 Am. Journ. Med. Sci., July, 1848.

6 Corpus Luteum of Menstruation and Pregnancy, in Transactions of American
Medical Association, Philadelphia, 1851.

MENSTRUATION. 573

The process of ovulation, accordingly, in the human female,
accompanies and forms a part of that of menstruation. As the
menstrual period comes on, a congestion takes place in nearly the
whole of the generative apparatus ; in the Fallopian tubes and the
uterus, as well as in the ovaries and their contents. One of the
Graafian follicles is more especially the seat of an unusual vascular
excitement. It becomes distended by the fluid which accumulates
in its cavity, projects from the surface of the ovary, and is finally
ruptured in the same manner as we have already described this
process taking place in the lower animals.

It is not quite certain at what particular period of the menstrual
flow the rupture of the vesicle and discharge of the egg take place.
It is the opinion of Bischoff, Pouchet, and Kaciborski, that the
regular time for this rupture and discharge is not at the commence-
ment, but towards the termination of the period. Coste1 has ascer-
tained, from his observations, that the vesicle ruptures sometimes
in the early part of the menstrual epoch, and sometimes later. . So
far as we can learn, therefore, the precise period of the discharge
of the egg is not invariable. Like the menses themselves, it may
apparently take place a little earlier, or a little later, accoi'ding to
various accidental circumstances ; but it always occurs at some
time in connection with the menstrual flow, and constitutes the
most essential and important part of the catamenial process.

The egg, when discharged from the ovary, enters the fimbriated
extremity of the Fallopian tube, and commences its passage toward
the uterus. The mechanism by which it finds its way into and
through the Fallopian tube is different, in the quadrupeds and the
human species, and in birds and reptiles. In the latter, the bulk
of the egg or mass of eggs discharged is so great as to fill entirely
the wide extremity of the oviduct, and they are afterward conveyed
downward by the peristaltic action of the muscular coat of this
canal. In the higher classes, on the contrary, the egg is micro-
scopic in size, and would be liable to be lost, were there not some
further provision for its safety. The wide extremity of the Fallo-
pian tube, accordingly, which is here directed toward the ovary, is
lined with ciliated epithelium; and the movement of the cilia,
which is directed from the ovary toward the uterus, produces a
kind of converging stream, or vortex, by which the egg is neces-
sarily drawn toward the narrow portion of the tube, and subse-
quently conducted to the cavity of the uterus.

1 Loc cit.

574 OVULATION AND FUNCTION OF MENSTRUATION.

Accidental causes, however, sometimes disturb this regular course
or passage of the egg. The egg may be arrested, for example,
at the surface of the ovary, and so fail to enter the tube at all.
If fecundated in this situation, it will then give rise to " ovarian
pregnancy." It may escape from the fimbriated extremity into the
peritoneal cavity, and form attachments to some one of the neigh-
boring organs, causing "abdominal pregnancy;" or finally, it may
stop at any part of the Fallopian tube, and so give origin to " tubal
pregnancy."

The egg, immediately upon its discharge from the ovary, is ready
for impregnation. If sexual intercourse happen to take place about
that time, the egg and the spermatic fluid meet in some part of the
female generative passages, and fecundation is accomplished. It
appears from various observations of Bischoff, Coste, and others,
that this contact may take place between the egg and the sperm,
either in the uterus or any part of the Fallopian tubes, or even
upon the surface of the ovary. If, on the other hand, coitus do not
take place, the egg passes down to the uterus unimpreguated, loses
its vitality after a short time, and is finally carried away with the
uterine secretions.

It is easily understood, therefore, why sexual intercourse should
be more liable to be followed by pregnancy when it occurs about
the menstrual epoch than at other times. This fact, which was long
since established as a matter of observation by practical obstetri-
cians, depends simply upon the coincidence in time between men-
struation and the discharge of the egg. Before its discharge, the
egg is immature, and unprepared for impregnation ; and after the
menstrual period has passed, it gradually loses its freshness and
vitality. The exact length of time, however, preceding and follow-
ing the menses, during which impregnation is still possible, has not
been ascertained. The spermatic fluid, on the one hand, retains its
vitality for an unknown period after coition, and the egg for an
unknown period after its discharge. Both these occurrences may,
therefore, either precede or follow each other within certain limits,
and impregnation be still possible ; but the precise extent of these
limits is still uncertain, and is probably more or less variable in
different individuals.

The above facts indicate also the true explanation of certain
exceptional cases, which have sometimes been observed, in which
fertility exists without menstruation. Various authors (Churchill,
Reid, Velpeau, &c.) have related instances of fruitful women in whom

MENSTRUATION. 575

the menses were very scanty and irregular, or even entirely absent.
The menstrual flow is, in fact, only the external sign and accompa-
niment of a more important process taking place within. It is
habitually scanty in some individuals, and abundant in others.
Such variations depend upon the condition of vascular activity of
the system at large, or of the uterine organs in particular; and
though the bloody discharge is usually an index of the general
aptitude of these organs for successful impregnation, it is not an
absolute or necessary requisite. Provided a mature egg be dis-
charged from the ovary at the appointed period, menstruation pro-
perly speaking exists, and pregnancy is possible.

The blood which escapes during the menstrual flow is supplied
by the uterine mucous membrane. If the cavity of the uterus be
examined after death during menstruation, its internal surface is
seen to be smeared with a thickish bloody fluid, which may be
traced through the uterine cervix and into the vagina. The Fallo-
pian tubes themselves are sometimes found excessively congested,
and filled with a similar bloody discharge. The menstrual blood
has also been seen to exude from the uterine orifice in cases of pro-
cidentia uteri, as well as in the natural condition by examination
with the vaginal speculum. It is discharged by a kind of capillary
hemorrhage, similar to that which takes place from the lungs in
cases of haemoptysis, only less sudden and violent. The blood does
not form any visible coagulum, owing to its being gradually exuded
from many minute points, and mingled with a large quantity of
mucus. When poured out, however, more rapidly or in larger
quantity than usual, as in cases of menorrhagia, the menstrual blood
coagulates in the same manner as if derived from any other source.
The hemorrhage which supplies it comes from the whole extent of
the mucous membrane of the body of the uterus, and is, at the same
time, the consequence and the natural termination of the periodical
congestion of the parts.

576 MENSTRUATION AND PREGNANCY.

CHAPTER VI.

ON THE COEPUS LUTEUM OF MENSTRUATION
AND PREGNANCY.

AFTER the rupture of the Graafian follicle at the menstrual
period, a bloody cavity is left in the ovary, which is subsequently
obliterated by a kind of granulating process, somewhat similar in
character to the healing of an abscess. For the Graafian follicle
is intended simply for the formation and growth of the egg.
After the egg therefore has arrived at maturity and has been dis-
charged, the Graafian follicle has no longer any function to per-
form. It then only remains for it to pass through a process of
obliteration and atrophy, as an organ which has become useless
and obsolete. While undergoing this process, the Graafian follicle
is at one time converted into a peculiar, solid, globular body, which
is called the corpus luteum ; a name given to it on account of the
yellow color which it acquires at a certain period of its formation.

We shall proceed to describe the corpus luteum in the human
species; first, as it follows the ordinary course of development
after menstruation ; and secondly, as it is modified in its growth
and appearance during the existence of pregnancy.

I. CORPUS LUTEUM OF MENSTRUATION.

We have already described, in the preceding chapter, the man-
ner in which a Graafian follicle, at each menstrual epoch, swells,
protrudes from the surface of the ovary, and at last ruptures and
discharges its egg. At the moment of rupture, or immediately
after it, an abundant hemorrhage takes place in the human sub-
ject from the vessels of the follicle, by which its cavity is filled
with blood. This blood coagulates soon after its exudation, as
it would do if extravasated in any other part of the body, and
the coagulum is retained in the interior of the Graafian follicle.

, CORPUS LUTEUM OF MENSTRUATION.

577

Fig. 187.

The opening by which the egg makes its escape is usually not an
extensive laceration, but a minute rounded perforation, often not
more than half a line in diameter. A small probe, introduced
through this opening, passes directly into the
cavity of the follicle. If the Graafian follicle
be opened at this time by a longitudinal inci-
sion (Fig. 187), it will be seen to form a globu-
lar cavity, one-half to three-quarters of an
inch in diameter, containing a soft, recent,
dark-colored coagulum. This coagulum has
no organic connection with the walls of the
follicle, but lies loose in its cavity and may be
easily turned out with the handle of a knife.
There is sometimes a slight mechanical adhe-
sion of the clot to the edges of the lacerated
opening, just as the coagulum in a recently J^'-iuS™-*
ligatured artery is entangled by the divided menstruation, aud aned
edges of the internal and middle coats; but ^hown^^^ng'ituZaUl1^c-
there is no continuity of substance between tion •— «• Ti8«ue °f the

, . , , .. ,.. ovary, b. Membrane of the

them, and the clot may be everywhere readily vesic]e. c. Point of rupture,
separated by careful manipulation. The mem-
brane of the vesicle presents at this time a smooth, transparent, and
vascular internal surface, without any alteration of color, consistency,
or texture.

An important change, however, soon begins to take place, both
in the central coagulum and in the membrane of the vesicle.

The clot, which is at first large, soft, and gelatinous, like any
other mass of coagulated blood, begins to contract ; and the serum
separates from the coagulum proper. The serum, as fast as it
separates from the coagulum, is absorbed by the neighboring parts ;
and the clot, accordingly, grows every day smaller and denser than
before. At the same time the coloring matter of the blood under-
goes the changes which usually take place in it after extravasation,
and is partially reabsorbed together with the serum. This second
change is somewhat less rapid than the former, but still a diminu-
tion of color is very perceptible in the clot, at the expiration of
two weeks.

The membrane of the vesicle during this time is beginning to
undergo a process of hypertrophy or development, by which it
becomes thickened and convoluted, and tends partially to fill up
37

578

MENSTRUATION AND PKEGNANCY.

the cavity of the follicle. This hypertrophy and convolution of
the membrane just named commences and proceeds most rapidly
at the deeper part of the follicle, directly opposite the situation of
the superficial rupture. From this point the membrane gradually
becomes thinner and less convoluted as it approaches the surface
of the ovary and the edges of the ruptured orifice.

At the end of three weeks, this hypertrophy of the membrane of
the vesicle has reached its maximum. The ruptured Graafian fol-
licle has now become so completely solidified by the new growth
above described, and by the condensation of its clot, that it receives
the name of the corpus luteum. It forms a perceptible prominence
on the surface of the ovary, and may be felt between the fingers
as a well-defined rounded tumor, which is nearly always somewhat
flattened from side to side. It measures about three-quarters of an

inch in length and half an inch in
depth. On its surface may be seen a
minute cicatrix of the peritoneum,
occupying the spot of the original
rupture.

On cutting it open at this time (Fig.
188), the corpus luteum is seen to con-
sist, as above described, of a central
coagulum and a convoluted wall.
The coagulurn is semi-transparent, of
a gray or light greenish color, more
or less mottled with red. The con-
voluted wall is about one- eighth of

. 188.

>pen

corpus

OVAllY CUt

luteum divided longitndinniiy ; three an inch thick at its deepest part, and

weeks aftt-r menstruation. From a girl
dead of haemoptysis.

of an indefinite yellowish or rosy
hue, not very different in tinge from

the rest of the ovarian tissue. The convoluted wall and the con-
tained clot lie simply in contact with each other, as at first, without
any intervening membrane or other organic connection ; and they
may still be readily separated from each other by the handle of a
knife or the flattened end of a probe. The corpus luteum at this
time may also be stripped out, or enucleated entire, from the ovarian
tissue, just as might have been done with the Graafian follicle pre-
viously to its rupture. When enucleated in this way, the corpus
luteum presents itself under the form of a solid globular or flat-
tened tumor, with convolutions upon it somewhat similar in ap-
pearance to those of the brain, and covered with the remains of

CORPUS LUTEUM OF MENSTRUATION.

579

Fig. 189.

OVART, showing corpus
luteum four weeks after men-
struation ; from a woman dead
of apoplexy.

the areolar tissue, bj which it was previously connected with the
substance of the ovary.

After the third week from the close of menstruation, the corpus
luteum passes into a retrograde condition. It diminishes percep-
tibly in size, and the central coagulum con-
tinues to be absorbed and loses still farther
its coloring matter. The whole body under-
goes a process of partial atrophy; and at
the end of the fourth week it is not more
than three-eighths of an inch in its longest
diameter. (Fig. 189.) The external cicatrix
may still usually be seen, as well as the
point where the central coagulum comes
in contact with the peritoneum. There is
still no organic connection between the
central coagulum and the convoluted wall ;
but the partial condensation of the clot and
the continued folding of the wall prevent the
separation of the two being so easily accom-
plished as before, though it may still be

effected by careful management. The entire corpus luteum may
also still be extracted from its bed in the ovarian tissue.

The color of the convoluted wall, during the early part of this
retrograde stage, instead of fading, like that of the fibrinous coagu-
lum, becomes more strongly marked. From having a dull yellowish
or rosy hue, as at first, it gradually as-
sumes a brighter and more decided yellow.
This change of color in the convoluted
wall is produced in consequence of a
kind of fatty degeneration which takes
place in its texture ; a large quantity of oil-
globules being deposited in it at this time,
as may be readily recognized under the
microscope. At the end of the fourth
week, this alteration in hue is complete ;
and the outer wall of the corpus luteum
is then of a clear chrome-yellow color, by
which it is readily distinguished from all
the neighboring tissues.

After this period, the process of atrophy
and degeneration goes on rapidly. The clot becomes constantly

Fig. 190.

OVART, phowinir corpus In-
teum. nine week* after menstrua-
tion ; from a pi rl dead of tuber-
cular meningitis.

580 MENSTRUATION AND PREGNANCY.

more dense and shrivelled, and is soon converted into a minute,
stellate, white, or reddish-white cicatrix. The yellow wall becomes
softer and more friable, as is the case with all tissues undergoing
fatty degeneration, and shows less distinctly the marking of its
convolutions. At the same time its surfaces become confounded
with the central coagulum on the one hand, and with the neigh-
boring tissues on the other, so that it is no longer possible to separate
them fairly from each other. At the end of eight or nine weeks
(Fig. 190) the whole body is reduced to the condition of an insignifi-
cant, yellowish, cicatrix-like spot, measuring less than a quarter of
an inch in its longest diameter, in which the original texture of the
corpus luteum can be recognized only by the peculiar folding and
coloring of its constituent parts. Subsequently its atrophy goes on
in a less active manner, and a period of seven or eight months some-
times elapses before its final and complete disappearance.

The corpus luteum, accordingly, is a formation which results
from the filling up and obliteration of a ruptured Graafian follicle.
Under ordinary conditions, a corpus luteum is produced at every
menstrual period ; and notwithstanding the rapidity with which it
retrogrades and becomes atrophied, a new one is always formed
before its predecessor has completely disappeared.

"When, therefore, we examine the ovaries of a healthy female, in
whom the menses have recurred with regularity for some time
previous to death, several corpora lutea will be met with, in different
stages of formation and atrophy. Thus we have found, under such
circumstances, four, five, six, and even eight corpora lutea in the
ovaries at the same time, perfectly distinguishable by their texture,
but very small, and most of them evidently in a state of advanced
retrogression. They finally disappear altogether, and the number
of those present in the ovary, therefore, no longer corresponds with
that of the Graafian follicles which have been ruptured.

II. CORPUS LUTEUM OP PREGNANCV.

Since the process above described takes place at every menstrual
period, it is independent of impregnation and even of sexual inter-
course. The mere presence of a corpus luteum, therefore, is no
indication that pregnancy has existed, but only that a Graafian
follicle has been ruptured and its contents discharged. We find,
nevertheless, that when pregnancy takes place, the appearance of
the corpus luteum becomes so much altered as to be readily dis-

CORPUS LUTEUM OF PREGNANCY. 581

tinguished from that which simply follows the ordinary menstrual
process. It is proper, therefore, to speak of two kinds of corpora
lutea ; one belonging to menstruation, the other to pregnancy.

The difference between these two kinds of corpora lutea is not
an essential or fundamental difference ; since they both originate in
the same way, and are composed of the same structures. It is,
properly speaking, only a difference in the degree and rapidity of
their development. For while the corpus luteum of menstruation
passes rapidly through its different stages, and is very soon reduced
to a condition of atrophy, that of pregnancy continues its develop-
ment for a long time, attains a larger size and firmer organization,
and disappears finally only at a much later period.

This variation in the development and history of the corpus
luteum depends upon the unusually active condition of the pregnant
uterus. This organ exerts a powerful sympathetic action, during
pregnancy, upon many other parts of the system. The stomach
becomes irritable, the appetite is capricious, and even the mental
faculties and the moral disposition are frequently more or less
affected. The ovaries, however, feel the disturbing influence of
gestation more certainly and decidedly than the other organs, since
they are more closely connected with the uterus in the ordinary
performance of their function. The moment that pregnancy takes
place, the process of menstruation is arrested. No more eggs come
to maturity, and no more Graafian follicles are ruptured, during the
whole period of gestation. It is not at all singular, therefore, that
the growth of the corpus luteum should also be modified, by an
influence which affects so profoundly the system at large, as well
as the ovaries in particular.

During the first three weeks of its formation, the growth of the
corpus luteum is the same in the impregnated as in the unimpreg-
nated condition. After that time, however, a difference becomes
manifest. Instead of commencing a retrograde course during the
fourth week, the corpus luteum of pregnancy continues its deve-
lopment. The external wall grows thicker, and its convolutions
more abundant. Its color alters in the same way as previously
described, and becomes a bright yellow by the deposit of fatty
matter in microscopic globules and granules.

By the end of the second month, the whole corpus luteum has
increased in size to such an extent as to measure seven-eighths of
an inch in length by half an inch in depth. (Fig. 191.) The central
coagulum has by this time become almost entirely decolorized, so as

582

MENSTRUATION AND PREGNANCY.

CORPTS LTTETM of pregnancy, at end of second
m>mth ; from a woman dead from induced abortion.

to present the appearance of a purely fibrinous deposit. Sometimes
we find that a part of the serum, during its separation from the clot,
has. accumulated in the centre of the mass, as in Fig. 191, forming a

little cavity containing a few

Fig- 191. drops of clear fluid and in-

closed by a whitish, fibrinous
layer, the remains of the solid
portion of the clot. It is
this fibrinous layer which has
sometimes been mistaken for
a distinct organized mem-
brane, lining the internal sur-
face of the convoluted wall,
and which has thus led to
the belief that the yellow

matter of the corpus luteum is normally deposited outside the mem-
brane of the Graafian follicle. Such, however, is not its real struc-
ture. The convoluted wall of the corpus luteurn is the membrane
of the follicle itself, partially altered by hypertrophy, as may be
readily seen by examination in the earlier stages of its growth ; and

the fibrinous layer, situated
internally, is the original
bloody coagulum, decolorized
and condensed by continued
absorption. The existence of
a central cavity containing
serous fluid, is merely an oc-
casional, not a constant pheno-
menon. More frequently, the
fibrinous clot is solid through
out, the serum being gradually
absorbed, as it separates spon-
taneously from the coagulum.
During the third and fourth
months, the enlargement of the corpus luteum continues ; so that at
the end of that time it may measure seven-eighths of an inch in
length by three-quarters of an inch in depth. (Fig. 192.) The con-
voluted wall is still thicker and more highly developed than before,
having a thickness, at its deepest part, of three-sixteenths of an inch.
Its color, however, has already begun to fade, and is now of a dull
yellow, instead of the bright, clear tinge which it previously ex-

Fig. 192.

CORPUS LUTEUM of pregnancy, at end of fourth
month ; from a woman dead by poisou.

CORPUS LUTEUM OF PREGNANCY.

533

Fie. 193.

hibited. The central coagulum, perfectly colorless and fibrinous
in appearance, is often so much flattened by the lateral compres-
sion of its mass, that it has hardly a line in thickness. The other
relations of the different parts of the corpus luteum remain the
same.

The corpus luteum has now attained its maximum of develop-
ment, and remains without any very perceptible alteration during
the fifth and sixth months. It then begins to retrograde, diminish-
ing constantly in size during the seventh and eighth months. Its
external wall fades still more perceptibly in color, becoming of a
faint yellowish white, not unlike that which it presented at the end
of the third week. Its texture is thick, soft, and elastic, and it is
still strongly convoluted. An abundance of fine red vessels can be
seen penetrating from the exterior into the
interstices of its convolutions. The central
coagulum is reduced by this time to the
condition of a whitish, radiated cicatrix.

The atrophy of the organ continues dur-
ing the ninth month. At the termination of
pregnancy, it is reduced to the size of half
an inch in length and three-eighths of an
inch in depth. (Fig. 193.) It is then of a
faint indefinite hue, but little contrasted
with the remaining tissues of the ovary.
The central cicatrix has become very small,
and appears only as a thin whitish lamina,
with radiating processes which run in be-
tween the interstices of the convolutions.
The whole mass, however, is still quite firm
and resisting to the touch, and is readily
distinguishable, both from its size and tex

ture, as a prominent feature in the ovarian tissue, and a reliable
indication of pregnancy. The convoluted structure of its external
wall is very perceptible, and the point of rupture, with its external
peritoneal cicatrix, distinctly visible.

After delivery, the corpus luteum retrogrades rapidly. At the
end of eight or nine weeks, it has become so much altered that its
color is no longer distinguishable, and only faint traces of its con-
voluted structure are to be discovered by close examination. These
traces may remain, however, for a long time afterward, more or less

CORPUS LUTETM of preg-
nancy, at term ; from a woman
dead in delivery from rupture
of the uterus.

584 MENSTKUATION AND PREGNANCY.

concealed in the ovarian tissue. "We have distinguished them so
late as nine and a half months after delivery. They finally disap-
pear entirely, together with the external cicatrix which previously
marked their situation.

During the existence of gestation, the process of menstruation
being suspended, no new follicles are ruptured, and no new corpora
lutea are produced ; and as the old ones, formed before the period of
conception, gradually fade and disappear, the corpus luteum which
marks the occurrence of pregnancy after a short time exists alone
in the ovary, and is not accompanied by any others of older date.
In twin pregnancies, we of course find two corpora lutea in the
ovaries ; but these are precisely similar to each other, and, being
evidently of the same date, will not give rise to any confusion.
Where there is but a single foetus in the uterus, and the ovaries
contain two corpora lutea of similar appearance, one of them
belongs to an embryo which has been blighted by some accident
in the early part of pregnancy. The remains of the blighted em-
bryo may often be discovered, in such cases, in some part of the
Fallopian tubes, where it has been arrested in its descent toward
the uterus.

After the process of lactation comes to an end, the ovaries again
resume their ordinary function. The Graafian follicles mature and
rupture in succession, as before, and new corpora lutea follow each
other in alternate development and disappearance.

We find, then, that the corpus luteum of menstruation differs from
that of pregnancy in the extent of its development and the dura-
tion of its existence. While the former passes through all the im-
portant phases of its growth and decline in the period of two
months, the latter lasts from nine to ten months, and presents,
during a great portion of the time, a larger size and a more solid
organization. It will be observed that, even with the corpus
luteum of pregnancy, the bright yellow color, which is so import-
ant a characteristic, is only temporary in its duration ; not making
its appearance till about the end of the fourth week, and again
disappearing after the sixth month.

The following table contains, in a brief form, the characters of
the corpus luteum, as belonging to the two different conditions of
menstruation and pregnancy, corresponding with different periods
of its development.

CORPUS LiJTEUM OF PREGNANCY.

585

CORPUS LUTBUM OF MENSTRUATION. CORPUS LUTEUM OF PREGNANCY.
At the end of Three-quarters of an inch in diameter ; central clot reddish ; con-

rhree weeks voluted wall pale.
One month Smaller ; convoluted wall bright

yellow ; clot still reddish.

Two months ' Reduced to the condition of an
insignificant cicatrix.

Six months Absent.

Nine mon.hs Absent,

Larger; convoluted wall bright
yellow ; clot still reddish.

Seven-eighths of an inch in dia-
meter; convoluted wall bright
yellow ; clot perfectly decolor-
ized.

Still as large as at end of second
month ; clot fibrinous ; convo-
luted wall paler.

One-half an inch in diameter ;
central clot converted into a
radiating cicatrix; the external
wall tolerably thick and convo-
luted, but without any bright
yellow color.

586 DEVELOPMENT OF THE IMPREGNATED EGG.

CHAPTER VII.

ON THE DEVELOPMENT OF THE IMPREGNATED
EGG— SEGMENTATION OF THE VITELLUS — BLAS-
TODERM1C MEMBRANE — FORMATION OF ORGANS
IN THE FROG.

WE have seen, in the foregoing chapters, how the egg, produced
in the ovarian follicle, becomes gradually developed and ripened,
until it is ready to be discharged. The egg, accordingly, passes
through several successive stages of formation, even while still con-
tained within the ovary ; and its vitellus becomes gradually com-
pleted, by the formation of albuminous material and the deposit of
molecular granulations. The last change which the egg undergoes,
in this situation, and that which marks its complete maturity, is the
disappearance of the germinative vesicle. This vesicle, which is, in
general, a prominent feature of the ovarian egg, disappears but a
short time previous to its discharge, or eyen just at the period of
its leaving the Graafian follicle.

The egg, therefore, consisting simply of the mature vitellus and
the vitelline membrane, comes in contact, after leaving the ovary,
and while passing through the Fallopian tube, with the spermatic
fluid, and is thereby fecundated. By the influence of fecundation,
a new stimulus is imparted to its growth ; and while the vitality
of the unimpregnated germ, arrived at this point, would have
reached its termination, the fecundated egg, on the contrary,
starts upon a new and more extensive course of development, by
which it is finally converted into the body of the young animal.

The egg, in the first place, as it passes down the Fallopian tube,
becomes covered with an albuminous secretion. In the birds, as we
have seen, this secretion is very abundant, and is deposited in suc-
cessive layers around the vitellus. In the reptiles, it is also poured
out in considerable quantity, and serves for the nourishment of the
egg during its early growth. In quadrupeds, the albuminous matter
is supplied in the same way, though in smaller quantity, by the

SEGMENTATION OF THE VITELLUS.

537

Fig. 194.

mucous membrane of the Fallopian tubes, and envelopes the egg
in a layer of nutritious material.

A very remarkable change now takes place in the impregnated egg,
which is known as the spontaneous division, or segmentation, of the
vitellus. A furrow first shows itself,
running round the globular mass of the
vitellus in a vertical direction, which
gradually deepens until it has divided
the vitellus into two separate halves or
hemispheres. (Fig. 19-i, a.) Almost at
the same time another furrow, run-
ning at right angles with the first,
penetrates also the substance of the
vitellus and cuts it in a transverse
direction. The vitellus is thus divided
into four equal portions (Fig. 194, b),
the edges and angles of which are
rounded off, and which are still con-
tained in the cavity of the vitelline
membrane. The spaces between
them and the internal surface of the
vitelline membrane are occupied by
a transparent fluid.

The process thus commenced goes
on by a successive formation of fur-
rows and sections, in various direc-
tions. The four vitelline segments
already produced are thus subdivided
into sixteen, the sixteen into sixty-
four, and so on ; until the whole vi-
tellus is converted into a mulberry-
shaped mass, composed of minute,
nearly spherical bodies, which are
called the "vitelline spheres." (Fig.
194, c.) These vitelline spheres have
a somewhat firmer consistency than
the original substance of the vitellus ;
and this consistency appears to in-
crease, as they successively multiply in numbers and diminish in
size. At last they have become so abundant as to be closely
crowded together, compressed into polygonal forms, and flattened

SEGMENTATION OF THE VITELLL-S.

588 DEVELOPMENT OF THE IMPREGNATED EGG.

against the internal surface of the vitelline membrane. (Fig 194, d.)
They have by this time been converted into true animal cells; and
these cells, adhering to each other by their adjacent edges, form a
continuous organized membrane, which is termed the Blastodermic
membrane.

During the formation of this membrane, moreover, the egg, while
passing through the Fallopian tubes into the uterus, has increased
in size. The albuminous matter with which it was enveloped has
liquefied ; and, being absorbed by endosmosis through the vitelline
membrane, has furnished the materials for the more solid and ex-
tensive growth of the newly-formed structures. It may also be
seen that a large quantity of this fluid has accumulated in the
central cavity of the egg, inclosed accordingly by the blastodermic
membrane, with the original vitelline membrane still forming an
external envelope round the whole.

The next change which takes place consists in the division or
splitting of the blastodermic membrane into two layers, which are
known as the external and internal layers of the blastodermic membrane.
They are both still composed exclusively of cells ; but those of the
external layer are usually smaller and more compact, while those
of the internal are rather larger and looser in texture. The egg
then presents the appearance of a globular sac, the walls of which
consist of three concentric layers, lying in contact with and inclos-
ing each other, viz., 1st, the structureless vitelline membrane on the
outside ; 2d, the external layer of the blastodermic membrane, com-
posed of cells ; and 3d, the internal layer of the blastodermic mem-
brane, also -composed of cells. The cavity of the egg is occupied
by a transparent fluid, as above mentioned.

This entire process of the segmentation of the vitellus and the
formation of the blastodermic membrane is one of the most re-
markable and important of all the changes which take place during
the development of the egg. It is by this process that the simple
globular mass of the vitellus, composed of an albuminous matter
and oily granules, is converted into an organized structure. For
the blastodermic membrane, though consisting only of cells nearly
uniform in size and shape, is nevertheless a truly organized mem-
brane, made up of fully formed anatomical elements. It is, more-
over, the first sign of distinct organization which makes its appear-
ance in the egg ; and as soon as it is completed, the body of the
new foetus is formed. The blastodermic membrane is, in fact, the
body of the foetus. It is at this time, it is true, exceedingly simple

BLASTODERMIC MEMBRANE. 589

in texture ; but we shall see hereafter that all the future organs
of the body, however varied and complicated in structure, arise out
of it, by modification and development of its different parts.

The segmentation of the vitellus, moreover, and the formation
of the blastoderm ic membrane, take place in essentially the same
manner in all classes of animals. It is always in this way that
the egg commences its development, whether it be destined to
form afterward a fish or a reptile, a bird, a quadruped, or a man.
The peculiarities belonging to different species show themselves
afterward, by variations in the manner and extent of the develop-
ment of different parts. In the higher animals and in the human
subject the development of the egg becomes an exceedingly com-
plicated process, owing to the formation of various accessory
organs, which are made requisite by the peculiar conditions under
which the development of the embryo takes place. It is, in fact,
impossible to describe or understand properly the complex embry-
ology of the quadrupeds, and more particularly that of the human
subject, without first tracing the development of those species in
which the process is more simple. We shall commence our descrip-
tion, therefore, with the development of the egg of the frog, which
is for many reasons particularly appropriate for our purpose.

The egg of the frog, when discharged from the body of the female
and fecundated by the spermatic fluid of the male, is deposited in
the water, enveloped in a soft elastic cushion of albuminous sub-
stance. It is therefore in a situation where it is freely exposed to
the light, the air, and the moderate warmth of the sun's rays, and
where it can absorb directly an abundance of moisture and appro-
priate nutritious material. We find accordingly that under these
circumstances the development of the egg is distinguished by a
character of great simplicity; since the whole of the vitellus is
directly converted into the body of the embryo. There are no acces-
sory organs required, and consequently no complication of the
formative process.

The two layers of the blastodermic membrane, above described,
represent together the commencement of all the organs of the foetus.
They are intended, however, for the production of two different
systems ; and the entire process of their development may be ex-
pressed as follows : TJie external layer of the blastodermic membrane
produces the spinal column and all the organs of animal life; while the
internal layer produces the intestinal canal, and all the organs of vege-
tative life.

590 DEVELOPMENT OF THE IMPREGNATED EGG.

The first sign of advancing organization in the external layer of
the blastodermic membrane shows itself in a thickening and con-
densation of its structure. This thickened portion has the form of an
elongated oval-shaped spot, termed the " embryonic spot" (Fig. 195),

the wide edges of which are somewhat
Fig- 195- more opaque than the rest of the blasto-

dermic membrane. Inclosed within
these opaque edges is a narrower color-
less and transparent space, the "area
pellucida," and in its centre is a delicate
line, or furrow, running longitudinally
from front to rear, which is called the
" primitive trace."

On each side of the primitive trace.
Boa, *uhTT in the area pellucida, the substance of
mencement of formation of embryo: the blastodermic membrane rises up in

showing embryonic spot, area pellu- . -,

cida, and primitive truce. such a manner as to form two nearly

parallel vertical plates or ridges, which

approach each other over the dorsal aspect of the foetus and are
therefore called the '''dorsal plates." They at last meet on the
median line, so as to inclose the furrow above described and con-
vert it into a canal. This afterward becomes the spinal canal, and
in its cavity is formed the spinal cord, by a deposit of nervous
matter upon its internal surface. At the anterior extremity of this
canal, its cavity is large and rounded, to accommodate the brain
and medulla oblongata ; at its posterior extremity it is narrow and
pointed, and contains the extremity of the spinal cord.

In a transverse section of the egg at this stage (Fig. 196), the
dorsal plates may be seen approaching each other above, on each
side of the primitive furrow or "trace." At a more advanced
period (Fig. 197) they may be seen fairly united with each other,
so as to inclose the cavity of the spinal canal. At the same time,
the edges of the thickened portion of the blastodermic membrane
grow outward and downward, so as to spread out more and more
over the lateral portions of the vitelline mass. These are called
the " abdominal plates ;" and as they increase in extent they tend
to unite with each other below and inclose the abdominal cavity,
just as the dorsal plates unite above, and inclose the spinal canal.
At last the abdominal plates actually do unite with each other on
the median line (at i, Fig. 197), embracing of course the whole
internal layer of the blastodermic membrane (5), which incloses in

FORMATION OF ORGANS.

its turn the remains of the original vitellus and the albuminous
fluid which has accumulated in its cavity.

Fig. 196.

Fig. 197.

Transverse section of EGO in an early
stage of development. — 1. External layer
of blastodermic membrane. 2, 2. Dorsal
plates. 3. Internal layer of blastodermic
membrane.

IMPREOX ATED ERG, at a somewhat
more advanced period.— 1. Umbilicus, or
point of union between abdominal plates.
2, 2. Dorsal plates united with each other
on the median line and inclosing the spinal
canal. 3. 3. Abdominal plates. 4. Sec-
tion of spinal column, with lamine and
ribs. f>. Internal layer of blastodermic
membrane.

During this time, there is formed, in the thickness of the external
blastodermic layer, immediately beneath the spinal canal, a longitu-
dinal cartilaginous cord, called the " chorda dorsalis." Around the
chorda dorsalis are afterward developed the bodies of the vertebrae
(Fig. 197, 4), forming the chain of the vertebral column; and the
oblique processes of the vertebrae run upward from this point into
the dorsal plates ; while the transverse processes, and ribs, run out-
ward and downward in the abdominal plates, to encircle more or
less completely the corresponding portion of the body.

If we now examine the egg in longitudinal section, while this
process is going on, the thickened portion of the external blasto-
dermic layer may be seen in profile, as at i , Fig. 198. The anterior
portion (*), which will form the head, is thicker than the posterior
(3), which will form the tail of the young animal. As the whole
mass grows rapidly, both in the anterior and the posterior direc-
tion, the head becomes very thick and voluminous, while the tail also
begins to project backward, and the whole egg assumes a distinctly
elongated form. (Fig. 199.) The abdominal plates at the same time

592

DEVELOPMENT OF THE IMPREGNATED EGG.

meet upon its under surface, and the point at which they finally
unite forms the abdominal cicatrix or umbilicus. The internal blas-
todermic layer is seen, of course, in the longitudinal section of the

Fig. 198.

Tig. 199.

Diagram of FROG'S EGG, in an earl.v Eoo OF FBOQ, in process of develop-

stage of development ; longitudinal sec- meat,

tion. — 1. Thickened portion of external
blastodermic layer, forminv body of fetus.
2. Anterior extremity of foetus 3 Poste-
rior extremity. 4. Internal layer of blas-
todermic membrane. 5. Cavity of vitellus.

egg, as well as in the transverse, embraced by the abdominal plates,
and inclosing, as before, the remains of the vitellus.

As the development of the above parts goes on (Fig. 200), the
head becomes sill larger, and soon shows traces of the formation

Fig. 200.

EGO OF FROG, farther advanced.

of organs of special sense. The tail also increases in size, and pro-
jects farther from the posterior extremity of the embryo. The
spinal cord runs in a longitudinal direction from front to rear, and
its anterior extremity enlarges, so as to form the brain and medulla
oblongata. In the mean time, the internal blastodermic layer, which
is subsequently to be converted into the intestinal canal, has been
shut in by the abdominal walls, and still forms a perfectly closed
sac, of a slightly elongated figure, without either inlet or outlet.
Afterward, the mouth is formed by a process of atrophy and perfo-
ration, which takes place through both external and internal layers,

FORMATION OF ORGANS. 503

at the anterior extremity, while a similar perforation, at the poste-
rior extremity, results in the formation of the anus.

All these parts, however, are as yet imperfect ; and, being merely
in the course of formation, are incapable of performing any active
function.

By a continuation of the same process, the different portions of
the external blastodermic layer are further developed, so as to re-
sult in the complete formation of the various parts of the skeleton,
the integument, the organs of special sense, and the voluntary
nerves and muscles. The tail at the same time acquires sufficient
size and strength to be capable of acting as an organ of locomo-
tion. (Fig. 201.) The intestinal canal, which has been formed from

Fig. 201.

TADPOLE fully developed.

the internal blastodermic layer, is at first a short, wide, and nearly
straight tube, running directly from the mouth to the anus. It
soon, however, begins to grow faster than the abdominal cavity
which incloses it, becoming longer and narrower, and is at the
same time thrown into numerous convolutions. It thus presents
a larger internal surface for the performance of the digestive
process.

Arrived at this period, the young tadpole ruptures the vitelline
membrane, by which he has heretofore been inclosed, and leaves the
cavity of the egg. He at first fastens himself upon the remains of
the albuminous matter deposited round the egg, and feeds upon it for
a short period. He soon, however, acquires sufficient strength and
activity to swim about freely in search of other food, propelling
himself by means of his large, membranous, and muscular tail.
The alimentary canal increases very rapidly in length and becomes
spirally coiled up in the abdominal cavity, so as to attain a length
from seven to eight times greater than that of the entire body.

After a time, a change takes place in the external form of the
young animal. The posterior extremities or limbs begin to show
38

DEVELOPMENT OF THE IMPREGNATED EGG.

themselves, by budding or sprouting from the sides of the body,
just at the base of the tail. (Fig. 202.) The anterior extremities also
grow at this time, but are at first concealed underneath the integu-
ment. They afterward, however, become liberated, and show them-
selves externally. At first both the fore and h;nd legs are very
small, imperfect in structure, and altogether useless for purposes of
locomotion. They soon, however, increase in size and strength;
and while they keep pace with the increasing development of the
whole body, the tail on the contrary ceases to grow, and becomes
shrivelled and atrophied. The limbs, in fact, are destined finally
to replace the tail as organs of locomotion ; and a time at last
arrives (Fig. 203) when the tail has altogether disappeared, while

Fig. 202.

Fig. 203.

TADPOLE, with limbs beginning to be formed.

Perfect FROG

the legs have become fully developed, muscular and powerful.
Then the animal, which was before confined to an aquatic mode
of life, becomes capable of living also upon land, and a trans-
formation is thus effected from the tadpole into the perfect frog.

During the same time, other changes of an equally important
character have taken place in the internal organs. The tadpole at
first breathes by gills; but these organs subsequently become
atrophied and disappear, being finally replaced by well developed
lungs. The structure of the mouth, also, of the integument, and
of the circulatory system, is altered to correspond with the varying
conditions and wants of the growing animal ; and all these changes
taking place in part successively and in part simultaneously,
bring the animal at last to a state of complete formation.

FORMATION OF ORGANS IN THE FROG. 595

The process of development may then be briefly recapitulated as
follows : —

1. The blastodermic membrane, produced by the segmentation
of the vitellus, consists of two cellular layers, viz., an external and
an internal blastodermic layer.

2. The external layer of the blastodermic membrane incloses by
its dorsal plates the cerebro-spinal canal, and by its abdominal
plates the abdominal or visceral cavity.

3. The internal layer of the blastodermic membrane forms the
intestinal canal, which becomes lengthened and convoluted, and
communicates with the exterior by a mouth and anus of secondary
formation.

4. Finally the cerebro-spinal axis and its nerves, the skeleton,
the organs of special sense, the integument, and the muscles, are
developed from the external blastodermic layer ; while the anterior
and posterior extremities are formed from the same layer by a pro-
cess of sprouting, or continuous growth.

596 THE UMBILICAL VESICLE.

CHAPTER VIII.

THE UMBILICAL VESICLE.

IN the frog, as we have seen, the abdominal plates, closing
together in front and underneath the body of the animal, shut in
directly the whole of the vitellus, and join each other upon the
median line, at the umbilicus. The whole remains of the vitellus
are then inclosed in the abdomen of the animal, and in the intestinal
sac formed by the internal blastodermic layer.

In many instances, however, as, for example, in several kinds of
fish, and in all the birds and quadrupeds, the abdominal plates do

not immediately embrace the whole of
Fig. 204. the vitelline mass, but tend to close

together about its middle; so that the
vitellus is constricted, in this way, and
divided into two portions: one internal,
and one external. (Fig. 204.) As the
process of development proceeds, the body
of the foetus increases in size, out of pro-
portion to the vitelline sac, and the con-

EGG OF FISH, showing forma- r

tiou of umbilical vesicle. striction just mentioned becomes at the

same time more strongly marked ; so that

the separation between the internal and external portions of the
vitelline sac is nearly complete. (Fig. 205.) The internal layer of
the blastodermic membrane is by the same means divided into
two portions, one of which forms the intestinal canal, while the
other, remaining outside, forms a sac-like appendage to the abdo-
men, which is known by the name of the umbilical vesicle.

The umbilical vesicle is accordingly lined by a portion of the
internal blastodermic layer, continuous with the mucous membrane
of the intestinal canal ; while it is covered on the outside by a por-
tion of the external blastodermic layer, continuous with the integu-
ment of the abdomen.

THE UMBILICAL VESICLE.

597

After the young animal leaves the egg, the umbilical vesicle
in some species becomes withered and atrophied by the absorption
of its contents; while in others, the abdominal walls gradually

Fig. 205.

Young FISH with umbilical vesicle.

extend over it, and crowd it back into the abdomen ; the nutritious
matter which it contained passing from the cavity of the vesicle
into that of the intestine by the narrow passage or canal which
remains open between them.

In the human subject, however, as well as in the quadrupeds, the
umbilical vesicle becomes more completely separated from the abdo-
men than in the cases just mentioned. There is at first a wide com-
munication between the cavity of the umbilical vesicle and that of
the intestine ; and this communication, as in other instances, becomes
gradually narrowed by the increasing constriction of the abdominal
walls. Here, however, the constriction proceeds so far that the
opposite surfaces of the canal come in contact with each other, and
adhere ; so that the narrow passage previously
existing, between the cavity of the intestine
and that of the umbilical vesicle, is obliterated,
and the vesicle is then connected with the
abdomen only by an impervious cord. This
cord afterward elongates, and becomes con-
verted into a slender, thread-like pedicle (Fig.
206), passing out from the abdomen of the
foetus, and connected by its farther extremity
with the umbilical vesicle, which is filled with
a transparent, colorless fluid. The umbilical
vesicle is very distinctly visible in the human
foetus so late as the end of the third month.
After that period it diminishes in size, and is gradually lost in the
advancing development of the neighboring parts.

In the formation of the umbilical vesicle, we have the first varia-

Fig. 206.

HCMAX EMBRYO, with
nmtiilical vesicle ; about the
fifth week.

593 THE UMBILICAL VESICLE.

tion from the simple plan of development described in the preceding
chapter. Here, the whole of the vitellus is not directly converted
into the body of the embryo ; but while a part of it is taken, as
usual, into the abdominal cavity, and used immediately for the
purposes of nutrition, a part is left outside the abdomen, in the
umbilical vesicle, a kind of secondary organ or appendage of the
foetus. The contents of the umbilical vesicle, however, are after-
ward absorbed, and so appropriated, finally, to the nourishment of
the newly-formed tissues.

^ AND ALLANTOIS. 599

CHAPTER IX.

AMNION AND ALL ANTOIS.— DE VELOPME NT OF
THE CHICK.

WE shall now proceed to the description of two other accessory
organs, which are formed, during the development of the fecundated
egg, in all the higher classes of animals. These are the amnion and
the allantois ; two organs which are always found in company with
each other, since the object of the first is to provide for the forma-
tion of the second. The amnion is formed from the external layer
of the blastodermic membrane, the allantois from the internal layer.

In the frog and in fish, as we have seen, the egg is abundantly
supplied with moisture, air, and nourishment, by the water with
which it is surrounded. It can absorb directly all the gaseous and
liquid substances, which it requires for the purposes of nutrition
and growth. The absorption of oxygen, the exhalation of carbonic
acid, and the imbibition of albuminous and other liquids, can all
take place without difficulty through the simple membranes of the
egg; particularly as the time required for the formation of the
embryo is very short, and as a great part of the process of develop-
ment remains to be accomplished after the young animal leaves
the egg.

But in birds and quadrupeds, the time required for the develop-
ment of the foetus is longer. The young animal also acquires a
much more perfect organization during the time that it remains
inclosed within the egg ; and the processes of absorption and exha-
lation necessary for its growth, being increased in activity to a
corresponding degree, require a special organ for their accomplish-
ment. This special organ, destined to bring the blood of the fcetus
into relation with the atmosphere and external sources of nutrition,
is the allantois.

In the frog and the fish, the internal blastodermic layer, forming
the intestinal mucous membrane, is inclosed everywhere, as above
described, by the external layer, forming the integument; and

600 AMNION AND ALLANTOIS.

consequently it can nowhere come in contact with the investing
membrane of the egg. But in the higher animals, the internal
blastodermic layer, which is the seat of the greatest vascularity>
and which is destined to produce the allantois, is made to come in
contact with the external membrane of the egg for purposes of
exhalation and absorption ; and this can only be accomplished by
opening a passage for it through the external germinative layer.
This is done in the following manner, by the formation of the
amnion.

Soon after the body of the foetus has begun to be formed by the
thickening of the external layer of the blastodermic membrane,
a double fold of this external layer rises up on all sides about
the edges of the newly-formed embryo ; so that the body of the
foetus appears as if sunk in a kind of depression, and surrounded
with a membranous ridge or embankment, as in
Fig. 207. Fig. 207. The embryo (c) is here seen in profile,

with the double membranous folds, above men-
tioned, rising up just in advance of the head,
and behind the posterior extremity. It must be
understood, of course, that the same thing takes
place on the two sides of the foetus, by the forma-
of FKCU*- tion of lateral folds simultaneously with the
° k±ot- appearance of those in front and behind. As it
a. vueiius. b. External is these folds which are destined to form the

layer of blastodermic . .-, 111^1 n • . • r» i i »

membrane, c. Body of amnion, they are called the " ammotic folds,
embryo, d, d. Amniotic The amniotic folds continue to grow, and ex-

folds. e. Vitelline mem- ,.. . „ 1-11 111

brane. tend themselves, forward, backward, and laterally,

until they approach each other at a point over
the back of the foetus (Fig. 208), which is termed the "amniotic
umbilicus." Their opposite edges afterward actually come in con-
tact with each other at this point, and adhere together, so as to
shut in a space or cavity (Fig. 208, b) between their inner surface
and the body of the foetus. This space, which is filled with a clear
fluid, is called the amniotic cavity. At the same time, the intestinal
canal has begun to be formed, and the umbilical vesicle has been
partially separated from it, by the constriction of the abdominal
walls on the under surface of the body.

There now appears a prolongation or diverticulum (Fig. 208, c)
growing out from the posterior portion of the intestinal canal, and
following the course of the amniotic fold which has preceded it ;
occupying, as it gradually enlarges and protrudes, the space left

AMNION AND ALLANTOIS.

601

Fig. 208.

FECUNDATED EGO,
farther advanced. — a.
Umbilical vesicle, b.
Am niotic cavity, c. Al-
lantois.

Fig. 209.

vacant by the rising up of the amniotic fold. This diverticulum
is the commencement of the allantois. It is an elongated mem-
branous sac, continuous with the posterior portion of the intestine,
and containing bloodvessels derived from those
of the intestinal circulation. The cavity of the
allantois is also continuous with the cavity of
the intestine.

After the amniotic folds have approached and
touched each other, as already described, over
the back of the foetus, at the amniotic umbilicus,
the adjacent surfaces, thus brought in contact,
fuse together, so that the cavities of the two
folds, coming respectively from front and rear,
are separated only by a single membranous par-
tition (Fig. 209, c) running from the inner to the
outer lamina of the amniotic folds. This parti-
tion itself soon after atrophies and disappears ; and the inner and
outer laminae become consequently separated from each other. The
inner lamina (Fig. 209, a) which remains con-
tinuous with the integument of the fcetus, in-
closing the body of the embryo in a distinct
cavity, is called the amnion (Fig. 210, b), and
its cavity is known as the amniotic cavity.
The outer lamina of the amniotic fold, on the
other hand (Fig. 209, b), recedes farther and
farther from the inner, until it comes in con-
tact with the original vitelline membrane, still
covering the exterior of the egg ; and by con-
tinued growth and expansion it at last fuses
with the vitelline membrane and unites with
its substance, so that the two membranes form
but one. This membrane, formed by the fusion
and consolidation of two others, constitutes then
the external investing membrane of the egg.

The allantois, during all this time, is increas-
ing in size and vascularity. Following the course of the amniotic
folds as before, it insinuates itself between them, and of course soon
comes in contact with the external investing membrane just de-
scribed. It then begins to expand laterally in every direction,
enveloping more and more the body of the foetus, and bringing its
vessels into contact with the external membrane of the egg.

FECUNDATED Eoo,
with allantois nearly com^
plete.— a. Inner lamina of
amniotic fold. b. Outer la-
inina of ditto, c. Point
•where the amniotic folds
come in contact. The allan-
tois is seen penet ating be-
tween the inner and outer
laminae of the amuiotie
folds.

602 AMNION AND ALLANTOIS.

By a continuation of the above process, the allantois at last
grows to such an extent as to envelope completely the body of the
embryo, together with the amnion ; its two
Fig. 210. extremities coming in contact with each

other and fusing together over the back of
the foetus, just as the amniotic folds had
previously done. (Fig. 210.) It lines, there-
fore, the whole internal surface of the in-
vesting membrane with a flattened, vascu-
lar sac, the vessels of which come from the
interior of the body of the foetus, and which
with still communicates with the cavity of the

allantois fully formed.— a. Urn- intestinal Canal.

b'.lical vesicle, b. Aranion. c. „ , ,

Aiiantois. It is evident, from the above description,

that there is a close connection between the

formation of the amnion and that of the allantois. For it is only
in this manner that the allantois, which is an extension of the in-
ternal layer of the blastodermic membrane, can come to be situated
outside the foetus and the amnion, and be brought into relation
with external surrounding media. The two laminas of the amni-
otic folds, in fact, by separating from each other as above described,
open a passage for the allantois, and allow it to come in contact
with the external membrane of the egg.

In order to explain more fully the physiological action of the
allantois, we shall now proceed to describe the process of develop-
ment, as it takes place in the egg of the fowl.

In order that the embryo may be properly developed in any
case, it is essential that it be freely supplied with air, warmth,
moisture, and nourishment. The egg of the fowl contains already,
when discharged from the generative passages, a sufficient quantity
of moisture and albuminous material. The necessary warmth is
supplied by the body of the parent during incubation ; while the
atmospheric gases can pass and repass through the porous egg-
shell, and by endosmosis through the fibrous membranes which
line its cavity.

When the egg is first laid, the vitellus, or yolk, is enveloped in
a thick layer of semi-solid albumen. On the commencement of
incubation, a liquefaction takes place in the albumen immediately
above that part of the vitellus which is occupied by the cicatri-
cula ; so that the vitellus rises or floats upward toward the surface,
by virtue of its specific gravity, and the cicatricula comes to be

DEVELOPMENT OF THE CHICK. 603

placed almost immediately underneath the lining membrane of the
egg-shell. As the cicatricula is the spot from which the process of
embryonic development commences, the body of the young fcetus
is by this arrangement placed in the most favorable position for
the reception of warmth and other necessary external influences
through the egg-shell. The liquefied albumen is also absorbed by
the^itelline membrane, and the vitellus thus becomes larger, softer,
and more diffluent than before the commencement of incubation.

As soon as the circulatory apparatus of the embryo has been.
fairly formed, two minute arteries are seen to run out from its
lateral edges and spread into the neighboring parts of the blasto-
dermic membrane, breaking up into inosculating branches, and
covering the adjacent portions of the vitellus with a plexus of
capillary bloodvessels. The space occupied in the blastodermic
membrane, on the surface of the vitellus, by these vessels, is called
the area vasculosa. (Fig. 211.) It is of a nearly circular shape,

Fig. 211.

Eoo OF FOWL during earl7 periods of incubation ; showing the body of the embryo, and the
area vasculosa partially covering the surface of the vitellus.

and is limited, on its outer edge, by a terminal vein or sinus, called
the " sinus terminalis." The blood is returned to the body of the
foetus by two veins which penetrate beneath its edges, one near the
head and one near the tail.

The area vasculosa tends to increase in extent, as the develop-
ment of the fcetus proceeds and its circulation becomes more active.
It soon covers the upper half, or hemisphere, of the vitellus, and
the terminal sinus then runs like an equator round the middle of
the vitelline sphere. As the growth of the vascular plexus con-

604 AMNION AND ALLANTOIS.

tinues, it passes this point, and embraces more and more of the in-
ferior, as well as of the superior hemisphere, the vessels converging
toward its under surface, until at last nearly the whole of the
vitellus is covered with a network of inosculating capillaries.

The function of the vessels of the area vasculosa is to absorb
nourishment from the cavity of the vitelline sac. As the albumen
liquefies during the process of incubation, it passes by endosmosis,
more and more abundantly, into the vitelline cavity ; the whole
vitellus growing constantly larger and more fluid in consistency.
The blood of the foetus, then circulating in the vessels of the area
vasculosa, absorbs freely the oleagino-albuminous matters of the
vitellus, and, carrying them back to the foetus by the returning
veins, supplies the newly-formed tissues and organs with abun-
dance of appropriate nourishment.

During this period the amnion and the allantois have been also
in process of formation. At first the body of the foetus lies upon
its abdomen, as in the cases previously described ; but, as it increases
in size, it alters its position so as to lie more upon its side. The
allantois then, emerging from the posterior portion of the abdominal
cavity, turns directly upward over the body of the foetus, and comes
immediately in contact with the shell membrane. (Fig. 212.) It

Fig. 212.

Eaa OF FOWL at a more advanced period of development. The body of the foetus is enveloped
by the amnion, and has the umbilical vesicle hanging from its under surface; while the vascular
allantois is *een turning upward and spreading out over the internal surface of the shell-membrane.

then spreads out rapidly, extending toward the extremities and
down the sides of the egg, enveloping more and more completely

DEVELOPMENT OF THE CHICK. 605

the foetus and the vitelline sac, and taking the place of the albumen
which has been liquefied and absorbed.

It will also be seen, by reference to the figure, that the umbilical
vesicle is at the same time formed by the separation of part of the
vitellus from the abdomen, of the chick ; and the vessels of the area
vasculosa, which were at first distributed over the vitellus, now
ramify, of course, upon the surface of the umbilical vesicle.

At last the allantois, by its continued growth, envelopes nearly
the whole of the remaining contents of the egg ; so that toward the
later periods of incubation, at whatever point we break open the
egg, we find the internal surface of the shell-membrane lined with
a vascular membranous expansion, supplied by arteries which
emerge from the abdomen of the foetus.

It is easy to see, accordingly, with what readiness the absorption
and exhalation of gases may take place by means of the allantois.
The air penetrates from the exterior through the minute pores of
the calcareous shell, and then acts upon the blood in the vessels of
the allantois very much in the same manner that the air in the minute
bronchial tubes and air- vesicles of the lungs acts upon the blood in
the pulmonary capillaries. Examination of the egg, furthermore,
at various periods of incubation, shows that changes take place in
it which are entirely analogous to those of respiration.

The egg, in the first place, during its development, loses water by
exhalation. This exhalation is not a simple effect of evaporation,
but is the result of the nutritive changes going on in the interior
of the egg ; since it does not take place, except in a comparatively
slight degree, in unimpregnated eggs, or in those which are not
incubated, though they may be freely exposed to the air. The
exhalation of fluid is also essential to the processes of development,
for it has often been found, in hatching eggs by artificial warmth,
that if the air of the chamber in which they are inclosed become
unduly charged with moisture, so as to retard or prevent further
exhalation, the eggs readily become spoiled, and the development
of the embryo is arrested. The loss of weight during natural incu-
bation, principally due to the exhalation of water, has been found
by Baudrimont and St. Ange' to be over 15 per cent, of the entire
weight of the egg.

Secondly, the egg absorbs oxygen and exhales carbonic acid.
The two observers mentioned above, ascertained that during eigh-

1 Du Developpement du Foetus. Paris, 1850, p. 143.

606 AMN10N AND ALLANTOIS.

teen days' incubation, the egg absorbs nearly 2 per cent, of its
weight of oxygen, while the quantity of carbonic acid exhaled from
the sixteenth to the nineteenth day of incubation amounts to no less
than 3 grains in the twenty -four hours.1 It is curious to observe,
also, that in the egg during incubation, as well as in the adult
animal, more oxygen is absorbed than is returned by exhalation'
under the form of carbonic acid.

It is evident, therefore, that a true respiration takes place, by
means of the allantois, through the membranes of the shell.

The allantois, however, is not simply an organ of respiration ; it
takes part also in the absorption of nutritious matter. As the pro-
cess of development advances, the skeleton of the young chick, at
first entirely cartilaginous, begins to ossify. The calcareous mat-
ter, necessary for this ossification, is, in all probability, derived from
the shell. The shell is certainly lighter and more fragile toward
the end of incubation than at first ; and, at the same time, the cal-
careous ingredients of the bones increase in quantity. The lime-
salts, requisite for the process of ossification, are apparently ab-
sorbed from the shell by the vessels of the allantois, and by them
transferred to the skeleton of the growing chick ; so that, in the
same proportion that the former becomes weaker, the latter grows
stronger. This diminution in density of the shell is connected not
only with the development of the skeleton, but also with the final
escape of the chick from the egg. This deliverance is accomplished
mostly by the movements of the chick itself, which become, at a
certain period, sufficiently vigorous to break out an opening in the
attenuated and weakened egg-shell. The first fracture is generally
accomplished by a stroke from the end of the bill ; and it is pre-
cisely at this point that the solidification of the skeleton is most
advanced. The egg-shell itself, therefore, which at first only serves
for the protection of the imperfectly-formed embryo, afterward
furnishes the materials which are used to accomplish its own demo-
lition, and at the same time to effect the escape of the fully deve-
loped foetus.

Toward the latter periods of incubation, the allantois becomes
more and more adherent to the internal surface of the shell- mem-
brane. At last, when the chick, arrived at the full period of de-
velopment, escapes from its confinement, the allantoic vessels are
torn off at the umbilicus ; and the allantois itself, cast off as a use-

1 Op. cit., pp. 138 and 149.

DEVELOPMENT OF THE CHICK. 607

less and effete organ, is left behind in the cavity of the abandoned
egg-shell. The allantois is, therefore, strictly speaking, a foetal
organ. Developed as an accessory structure from a portion of the
intestinal canal, it is exceedingly active and important during the
middle and latter periods of incubation; but when the chick is
completely formed, and has become capable of carrying on an in-
dependent existence, both the amnion and the allantois are detached
and thrown off as obsolete structures, their place being afterward
supplied by other Organs belonging to the adult condition.

608 DEVELOPMENT OF THE EGG IN HUMAN SPECIES.

CHAPTER X.

DEVELOPMENT OF THE EGG IN THE HUMAN
SPECIES.— FORMATION OF THE CHORION.

Fig. 213.

have already described, in a preceding chapter, the manner
in which the outer lamina of the amniotic fold becomes adherent
to the adjacent surface of the vitelline membrane, so as to form
with it but a single layer ; and in which these two membranes, thus
fused and united with each other, form at that time the single ex-
ternal investing membrane of the egg. The allantois, in its turn,
afterward comes in contact with the investing membrane, and lies
immediately beneath it, as a double vascular membranous sac. In
the egg of the human subject the development of the membranes,
though carried on essentially upon the same plan with that which
we have already described, undergoes, in addition, some further
modifications, which we shall now proceed to explain.

The first of these peculiarities is that the allantois, after spread-

ing out upon the inner surface of
the external investing membrane,
adheres to, and fuses with it, just
as the outer lamina of the amni-
otic fold has previously fused
with the vitelline membrane. At
the same time, the two layers be-
longing to the allantois itself also
come in contact and fuse toge-
ther; so that the cavity of the
allantois is obliterated, and instead
of forming a membranous sac con-
taining fluid, this organ is convert-
ed into a simple vascular membrane.
(Fig. 213.) This membrane,

moreover, being, after a time, thoroughly fused and united with the
two which have preceded it, takes the place which was previously

HUMAN Ov0M, about the end of the first
mouth ; showing formation of chorion. — 1.
Umbilical vesicle. 2. Amnion. 3. Chorton.

FORMATION OF THE CHORION. 609

occupied by them. It is then termed the chorion, and thus becomes
the sole external investing membrane of the egg.

We find, therefore, that the chorion, that is, the external coat or
investment of the egg, is formed successively by three distinct
membranes, as follows: first, the original vitelline membrane;
secondly, the outer lamina of the amniotic fold ; and, thirdly, the
allantois ; the last predominating over the two former by the rapidity
of its growth, and absorbing them into its substance, so that they
become finally completely incorporated with its texture.

It is easy to see, also, how, in consequence of the above process,
the body of the foetus, in the human egg, becomes inclosed in two
distinct membranes, viz., the amnion, which is internal and conti-
nuous with the foetal integument, and the chorion, which is external
and supplied with vessels from the cavity of the abdomen. The
umbilical vesicle is, of course, situated between the two ; and the
rest of the space between the chorion and the amnion is occupied
by a semi-fluid gelatinous material, somewhat similar in appearance
to that of the vitreous body of the eye.

The obliteration of the cavity of the allantois takes place very
early in the human subject, and, in fact, keeps pace almost entirely
with the progress of its growth ; so that this organ never presents,
in the human egg, the appearance of a hollow sac, filled with
fluid, but rather that of a flattened vascular membrane, enveloping
the body of the foetus, and forming the external membrane of the
egg. Notwithstanding this difference, however, the chorion of the
human subject, in respect to its mode of formation, is the same
thing with the allantois of the lower animals ; its chief peculiarity
consisting in the fact that its opposite surfaces are adherent to each
other, instead of remaining separate and inclosing a cavity filled
with fluid.

The next peculiarity of the human chorion is, that it becomes
shaggy. Even while the egg is still very small, and has but recently
found its way into the uterine cavity, its exterior is already seen
to be covered with little transparent prominences, like so many
villi (Fig. 213), which increase the extent of its surface, and assist
in the absorption of fluids from without. The villi are at this time
quite simple in form, and altogether homogeneous in structure.

As the egg increases in size, the villi rapidly elongate, and be-
come divided and ramified by the repeated budding and sprouting
of lateral offshoots from every part. After this process of growth
39

610 DEVELOPMENT OF THE EGG IN HUMAN SPECIES.

Fig. 214.

has gone on for some time, the external surface of the chorion pre-
sents a uniformly velvety or shaggy appearance, owing to its being
covered everywhere with these tufted and compound villosities.

The villosities themselves, when examined by the microscope,
have an exceedingly well-marked and characteristic appearance.
(Fig. 214.) They originate from the surface of the chorion by a

somewhat narrow stem, and divide
into a multitude of secondary and
tertiary branches, of varying size
and figure ; some of them slender
and filamentous, others club-shaped,
many of them irregularly swollen at
various points. All of them termi-
nate by rounded extremities, giving
to the whole tuft a certain resem-
blance to some varieties of sea-weed.
The larger trunks and branches of
the villosity are seen to contain nu-
merous minute nuclei, imbedded in
a nearly homogeneous, or finely gra-
nular substratum. The smaller ones
appear, under a low magnifying
power, simply granular in texture.

These villi are altogether peculiar
in appearance, and quite unlike any
other structure which may be met with in the body. Whenever we
find, in the uterus, any portion of a membrane having villosities
like these, we may be sure that pregnancy has existed; for such
villosities can only belong to the chorion, and the chorion itself is
a part of the foetus. It is developed, as we have seen, as an out-
growth from the intestinal canal, and can only exist, accordingly,
as a portion of the fecundated egg. The presence of portions of a
shaggy chorion is therefore as satisfactory proof of the existence
of pregnancy, as if he had found the body of the foetus itself.

While the villosities which we have just described are in pro-
cess of formation, the allantois itself has completed its growth, and
has become converted into a permanent chorion. The bloodvessels
coming from the allantoic arteries accordingly ramify over the
chorion, and supply it with a tolerably abundant vascular network.
The growth of the foetus, moreover, at this time, has reached such
a state of activity, that it requires to be supplied with nourishment

Compound villosity of HUMAN CHO-
RION, ramified extremity. From a three
mouths' foetus. Magnified 30 diameters.

FORMATION OF THE CHORTON.

611

Fig. 215.

Extremity of VILLOSITT op
CHORION, more highlj magni-
fied ; showing the arrangement of
bloodvessels in its interior.

by vascular absorption, instead of the slow process of imbibition,
which has heretofore taken place through the comparatively incom-
plete and structureless villi of the cho-
rion. The capillary vessels, accordingly,
with which the chorion is supplied, begin
to penetrate into the substance of its vil-
losities. They enter the base or stem of
each villosity, and, following every divi-
sion of its compound ramifications, finally
reach its rounded extremities. Here they
turn upon themselves in loops (Fig. 215),
like the vessels in the papilla of the skin,
and retrace their course, to unite finally
with the venous trunks of the chorion.

The villi of the chorion are, therefore,
very analogous in structure to those of
the intestine ; and their power of absorp-
tion, as in other similar instances, corre-
sponds with the abundance of their ramifications, and the extent
of their vascularity.

It must be remembered, also, that these vessels all come from the
abdomen of the foetus ; and that whatever substances are taken up
by them are transported directly to the interior of the embryo, and
used for the nourishment of its tissues. The chorion, therefore, as
soon as its villi and bloodvessels are completely developed, becomes
an exceedingly active organ in the nutrition of the foetus ; and con-
stitutes, in fact, the only means by which new material can be in-
troduced from without.

The existence of this general vascularity of the chorion affords
also, as Coste was the first to point out, a striking indication that
this membrane is in reality identical with the allantois of the
lower animals. If the reader will turn back to the illustrations of
the formation of the amnion and allantois (Chap. IX.), he will see
that the first chorion or investing membrane is formed exclusively
by the vitelline membrane, which is never vascular and cannot be-
come so by itself, since it has no direct connection with the fcetus.
The second chorion is formed by the union of the vitelline mem-
brane with the outer lamina of the amniotic fold. Both lamina
of the amniotic fold are at first vascular, since they are portions of
the external blastodermic layer, and derive their vessels from the
integument of the fcetus. But after the outer lamina has become

612 DEVELOPMENT OF THE EGG IN HUMAN SPECIES.

completely separated from the inner, by the disappearance of the
partition which for a time connected the two with each other (Fig.
209, c), this source of vascular supply is cut off; and the second
chorion cannot, therefore, remain vascular after that period. But
the third or permanent chorion, that is, the allantois, derives its ves-
sels directly from those of the foetus, and retains its connection with
them during the whole period of gestation. A chorion, therefore,
which is universally and permanently vascular, can be no other
than the allantois, converted into an external investing membrane
of the egg.

Thirdly, the chorion, which is at one time, as we have seen, every-
where villous and shaggy, becomes afterward partially bald. This
change begins to take place about the end of the second month.
It commences at a point opposite the situation of the foetus and the
insertion of the foetal vessels. The villosities of this region cease
growing ; and as the entire egg continues to enlarge, the villosities
at the point indicated fail to keep pace with its growth, and with
the progressive expansion of the chorion. They accordingly be-
come at this part thinner and more scattered, leaving the surface
of the chorion comparatively smooth and bald. This baldness in-
creases in extent and becomes more and more complete, spreading

and advancing over the adja-
cent portions of the chorion,
until at least two-thirds of its
surface have become nearly
or quite destitute of villosities.
At the opposite point of the
surface of the egg, however,
that portion, namely, which
corresponds with the insertion
of the foetal vessels, the villosi-
ties, instead of becoming atro-
phied, continue to grow ; and
this portion of the chorion be-
comes even more shaggy and
thickly set than before. The

consequence is that the chorion afterward presents a very different
appearance at different portions of its surface. (Fig. 216.) The
greater part of it is smooth ; but a certain portion, constituting
about one-third of the whole, is covered with a soft and spongy
mass of long, thickly-set, compound villosities. It is this thickened

HTMAN OVUM at end of third month : showing
placental portiou of thn choriou fully fo med.

FORMATION OF THE CIIORION. 613

and shaggy portion, which is afterward concerned in the formation
of the placenta ; while the remaining smooth portion continues to
be known under the name of the chorion. The placental portion
of the chorion becomes distinctly limited and separated from the
remainder by about the end of the third month.

The vascularity of the chorion keeps pace, in its different parts
respectively, with the atrophy and development of its villosities.
As the villosities shrivel and disappear over a part of its extent,
the looped capillary vessels, which they at first contained, disappear
also ; so that the smooth portion of the chorion shows afterward
only a few straggling vessels running over its surface, and does not
contain any abundant capillary plexus. In the thickened portion,
on the other hand, the vessels lengthen and ramify to an extent
corresponding with that of the villosities in which they are situated.
The allantoic arteries, coming from the abdomen of the foetus, enter
the villi, and penetrate through their whole extent ; forming, at the
placental portion of the chorion, a mass of tufted and ramified vas-
cular loops, while over the rest of the membrane they are merely
distributed as a few single and scattered vessels.

The chorion, accordingly, is the external investing membrane of
the egg, produced by the consolidation and transformation of the
allantois. The placenta, furthermore, so far as it has now been
described, is evidently a part of the chorion ; that part, namely,
which is thickened, shaggy, and vascular, while the remainder is
comparatively thin, smooth, and membranous.

614: DEVELOPMENT OF UTERINE MUCOUS MEMBRANE.

CHAPTER XI.

DEVELOPMENT OF UTERINE MUCOUS MEMBRANE.—
FORMATION OF THE DECIDUA.

IN fish, reptiles, and birds, the egg is either provided with a sup-
ply of nutritious material contained within its membranes, or it is
so placed, after its discharge from the body of the parent, that it
can absorb these materials from without. Thus, in the egg of the
bird, the young embryo is supported upon the albuminous matter
deposited around the vitellus ; while in the frog and fish, moisture,
oxygen, saline substances, &c., are freely imbibed from the water
in which the egg is placed.

But in the quadrupeds, as well as in the human species, the egg
is of minute size, and the quantity of nutritious matter which it
contains is sufficient to last only for a very short time. Moreover,
the development of the foetus takes place altogether within the body
of the female, and no supply, therefore, can be obtained directly
from the external media. In these instances, accordingly, the mu-
cous membrane of the uterus, which is found to be unusually
developed and increased in functional activity during the period of
gestation, becomes a source of nutrition for the fecundated egg.
The uterine mucous membrane, thus developed and hypertrophied,
is known by the name of the Decidua.

It has received this name because, as we shall hereafter see, it
becomes exfoliated and thrown off, at the same time that the egg
itself is finally discharged.

The mucous membrane of the body of the uterus, in the unimpreg-
nated condition, is quite thin and delicate, and presents a smooth
and slightly vascular internal surface. There is, moreover, no layer
of submucous cellular tissue between it and the muscular substance
of the uterus; so that the mucous membrane cannot here, as in
most other organs, be easily dissected up and separated from the
subjacent parts. The structure of the mucous membrane itself,
however, is sufficiently well marked and readily distinguishable

FORMATION OF THE DECIDUA.

615

Fig. 2] 7.

UTERINE Mucors MEMBRANE, as
*een in vertical section, —a. Free surface.
b. Attached surface.

Fig. 218.

from that of other parts. It consists, throughout, of minute
tubular follicles, ranged side by side, and running perpendicularly
to the free surface of the mucous membrane. (Fig. 217.) Near
this free surface, they are nearly
straight; but toward the deeper sur-
face of the mucous membrane, where
they terminate in blind extremities,
they become more or less wavy or
spiral in their course. The tubules
are about TJ5 of an inch in diameter,
and are lined throughout with co-
lumnar epithelium. (Fig. 218.) They
occupy the entire thickness of the ute-
rine mucous membrane, their closed
extremities resting upon the subjacent

muscular tissue, while their mouths open into the cavity of the ute-
rus. A few fine bloodvessels penetrate the mucous membrane from
below, and, running upward
between the tubules, encircle
their superficial extremities
with a capillary network.
There is no areolar tissue in
the uterine mucous mem-
brane, but only a small quan-
tity of spindle-shaped fibro-
plastic fibres, scattered be-
tween the tubules.

As the fecundated egg is
about to descend into the
cavity of the uterus, the mu-
cous membrane, above de-
scribed, takes on an increas-
ed activity of growth and
an unusual development. It
becomes tumefied and vascular ; and, as it increases in thickness, it
projects, in rounded eminences or convolutions, into the uterine
cavity. (Fig. 219.) In this process, the tubules of the uterus in-
crease in length, and also become wider ; so that their open mouths
may be readily seen by the naked eye upon the uterine surface, as
numerous minute perforations. The bloodvessels of the mucous
membrane also enlarge and multiply, and inosculate freely with

UTRRIXE Tc BULKS, from mucous membrane of
uuimpregnated human uterus.

616 DEVELOPMENT OF UTERINE MUCOUS MEMBRANE.

each other ; so that the vascular network encircling the tubules be-
comes more extensive and abundant.

The internal surface of the uterus, accordingly, after this process
has been for some time going on, presents a thick, rich, soft, vas-
cular, and velvety lining, quite different from that which is to be
found in the unimpregnated condition. In consequence of this
difference, the lining membrane of the uterus, in the impregnated
condition, was formerly supposed to be an entirely new product,
thrown out by exudation from the uterine surface, and analogous,
in this respect, to the inflammatory exudations of croup and pleu-
risy. It is now known, however, to be no other than the mucous
membrane of the uterus itself, thickened and hypertrophied to an
extraordinary degree, but still retaining all its natural connections
and its original anatomical structure.

The hypertrophied mucous membrane, above described, consti-
tutes the Decidua vera. Its formation is confined altogether to the
body of the uterus, the mucous membrane of the cervix taking no
part in the process, but retaining its original appearance. The
decidua vera, therefore, commences above, at the orifices of the
Fallopian tubes, and ceases below, at the situation of the os inter-
num. The cavity of the cervix, meanwhile, begins to be filled
with an abundant secretion of its peculiarly viscid mucus, which
blocks up, more or less completely, its passage, and protects the
internal cavity. But there is no membranous partition at this time
covering the os internum, and the mucous membranes of the cervix
and of the body of the uterus, though very different in appearance,
are still perfectly continuous with each other. When we cut open
the cavity of the uterus, therefore, in this condition, we find its
internal surface lined with the decidua vera, with the opening of
the os internum below and the orifices of the Fallopian tubes above,
perfectly distinct, and in their natural positions. (Fig. 219.)

As the fecundated egg, in its journey from above downward,
passes the lower orifice of the Fallopian tube, it insinuates itself
between the opposite surfaces of the uterine mucous membrane,
and becomes soon afterward lodged in one of the furrows or de-
pressions between the projecting convolutions of the decidua.
(Fig. 219.) It is at this situation that an adhesion subsequently
takes place between the external membranes of the egg, on the
one hand, and the uterine decidua on the other. Now, at the point
where the egg becomes fixed and entangled, as above stated, a still
more rapid development than before takes place in the uterine

FORMATION OF THE DECIDUA.

617

mucous membrane. Its projecting folds begin to grow up around
the egg in such a manner as to partially inclose it in a kind of
circumvallation of the decidua, and to shut it off, more or less corn-

Fig. 213.

IMPREGNATED UTERCS;
formation of decidua. The decidua is
represented in black ; and the egg is
seen, at the fundus of the uterus, en-
paged between two of its projecting
convolutions.

Fig. 220.

IMPREGNATED UTERUS, with pro-
jecting folds of decidua growing up
around the egg. The narrow opening
where the edges of the folds approach
each other, is seen over the most promi-
neut portion of the egg.

Fiir. 221.

pletely, from the general cavity of the uterus. (Fig. 220.) The egg
is thus soon contained in a special cavity of its own, which still
communicates for a time with the general cavity of the uterus by
a small opening, situated over its most
prominent portion, Avhich is known as the
" decidual umbilicus." As the above pro-
cess of growth goes on, this opening be-
comes narrower and narrower, while the
projecting folds of decidua approach each
other over the surface of the egg. At
last these folds actually touch each other
and unite, forming a kind of cicatrix
which remains for a certain time, to mark
the situation of the original opening.

When the development of the uterus and
its contents has reached this point (Fig.
221), it will be seen that the egg is com-
pletely inclosed in a distinct cavity of its

own ; being everywhere covered with a decidual layer of new for-
mation, which has thus gradually enveloped it, and by which it is
concealed from view when the uterine cavity is laid open. This

UTERTS; —
showing egg completely inclo-ed
by decidua reflexa.

618 DEVELOPMENT OF UTERINE MUCOUS MEMBRANE.

newly -formed layer of decidua, enveloping, as above described, the
projecting portion of the egg, is called the Decidua reflexa ; because
it is reflected over the egg, by a continuous growth from the general
surface of the uterine mucous membrane. The orifices of the uterine
tubules, accordingly, in consequence of the manner in which the
decidua reflexa is formed, will be seen not only on its external sur-
face, or that which looks toward the cavity of the uterus, but also on
its internal surface, or that which looks toward the egg.

The decidua vera, therefore, is the original mucous membrane
lining the surface of the uterus ; while the decidua reflexa is a new
formation, which has grown up round the egg and inclosed it in a
distinct cavity.

If abortion occur at this time, the mucous membrane of the
uterus, that is, the decidua vera, is thrown off, and of course brings
away with it the egg and decidua reflexa. On examining the mass
discharged in such an abortion, the egg will accordingly be found
imbedded in the substance of the decidual membrane. One side
of this membrane, where it has been torn away from its attachment
to the uterine walls, is ragged and shaggy ; the other side, corres-
ponding to the cavity of the uterus, is smooth or gently convoluted,
and presents very distinctly the orifices of the uterine tubules;
while the egg itself can only be extracted by cutting through the
decidual membrane, either from one side or the other, and opening
in this way the special cavity in which it has been inclosed.

During the formation of the decidua reflexa, the entire egg, as
well as the body of the uterus which contains it, has considerably
enlarged. That portion of the uterine mucous membrane situated
immediately underneath the egg, and to which the egg first became
attached, has also continued to increase in thickness and vascularity.
The remainder of the decidua vera, however, ceases to grow as
rapidly as before, and no longer keeps pace with the increasing
size of the egg and of the uterus. It is still very thick and vascu-
lar at the end of the third month ; but after that period it becomes
comparatively thinner and less glandular in appearance, while the
unusual activity of growth and development is concentrated in the
egg, and in that portion of the uterine mucous membrane which is
in immediate contact with it.

Let us now see in what manner the egg becomes attached to the
decidual membrane, so as to derive from it the requisite supply of
nutritious material. It must be recollected that, while the above
changes have been taking place in the walls of the uterus, the

FORMATION OF THE DECIDUA.

619

Fig. 222.

formation of the embryo in the egg, and the development of the
amnion and chorion have been going on simultaneously. Soon
after the entrance of the egg into the uterine cavity, its external
investing membrane becomes covered with projecting filaments, or
viliosities, as previously described. (Chap. X.) These viliosities,
which are at first, as we have seen, solid and non-vascular, insinuate
themselves, as they grow, into the uterine tubules, or between the
folds of the decidual surface with which the egg is in contact, pene-
trating in this way into little cavities or follicles of the uterine
mucous membrane, formed either from the cavities of the tubules
themselves, or by the adjacent surfaces of minute projecting folds.
When the formation of the decidua reflexa is accomplished, the
chorion has already become uniformly
shaggy ; and its viliosities, spreading in all
directions from its external surface, pene-
trate everywhere into the follicles above de-
scribed, both of the decidua vera underneath
it and the contiguous surface of the decidua
reflexa with which it is covered. (Fig. 222.)
In this way the egg becomes entangled
with the decidua, and cannot then be read-
ily separated from it, without rupturing
some of the filaments which have grown
from its surface, and have been received
into the cavity of the follicles. The nu-
tritious fluids, exuded from the soft and
glandular textures of the decidua, are now
readily imbibed by the viliosities of the chorion ; and a more rapid
supply of nourishment is thus provided, corresponding in abun-
dance with the increased and increasing size of the egg.

Very soon, however, a still greater activity of absorption be-
comes necessary ; and, as we have seen in a preceding chapter, the
external membrane of the egg becomes vascular by the formation
of the allantoic bloodvessels, which emerge from the body of the
foetus, to ramify in the chorion, and penetrate everywhere into the
viliosities with which it is covered. Each villosity, then, as it lies
imbedded in its uterine follicle, contains a vascular loop through
which the foetal blood circulates, increasing the rapidity with which
absorption and exhalation take place.

Subsequently, furthermore, these vascular tufts, which are at first
uniformly abundant throughout the whole extent of the chorion,

IMPREGNATED UTERUS:
showing connection between vil-
iosities of chorion and decidual

membranes.

620 DEVELOPMENT OF UTERINE MUCOUS MEMBRANE.

Fig. 223.

disappear over a portion of its surface, while they at the same time
become concentrated and still further developed at a particular
spot, the situation of the future placenta. (Fig. 223.) This is the

spot at which the egg is in contact with
the decidua vera. Here, therefore, both
the decidual membrane and the tufts
of the chorion continue to increase in
thickness and vascularity ; while else-
where, over the prominent portion of
the egg, the chorion not only becomes
bare of villosities, and comparatively
destitute of vessels, but the decidua re-
flexa, which is in contact with it, also
loses its activity of growth, and be-
comes expanded into a thin layer, nearly
destitute of vessels, and without any
remaining trace of tubules or follicles.
The uterine mucous membrane is
therefore developed, during the process
of gestation, in such a way as to provide

for the nourishment of the foetus in the different stages of its growth.
At first, the whole of it is uniformly increased in thickness (decidua
vera). Next, a portion of it grows upward around the egg, and
covers its projecting surface (decidua reflex a). Afterward, both the
decidua reflexa and the greater part of the decidua vera diminish
in the activity of their growth, and lose their importance as a means
of nourishment for the egg ; while that part which is in contact with
the vascular tufts of the chorion continues to grow, becoming ex-
ceedingly developed, and taking an active part in the formation of
the placenta.

In the following chapter, we shall examine more particularly the
structure, and development of the placenta itself, and of those parts
which are immediately connected with it.

PREGNANT UTERUS; showing
formation of placenta, by the united
development of a portion of the de-
cidua and the villosities of the cho-
rion.

THE PLACENTA. 621

CHAPTER XII.

THE PLACENTA.

WE have shown in the preceding chapters that the foetus, during
its development, depends for its supply of nutriment upon the lining
membrane of the maternal uterus ; and that the nutriment, so sup-
plied, is absorbed by the bloodvessels of the chorion, and transported
in this way into the circulation of the foetus. In all instances, ac-
cordingly, in which the development of the foetus takes place within
the body of the parent, it is provided for by the relation thus esta-
blished between two sets of membranes; namely, the maternal
membranes which supply nourishment, and the foetal membranes
which absorb it.

In some species of animals, the connection between the maternal
and foetal membranes is exceedingly simple. In the pig, for ex-
ample, the uterine mucous membrane is everywhere uniformly
vascular ; its only peculiarity consisting in the presence of nume-
rous transverse folds, which project from its surface, analogous to
the valvulae conniventes of the small intestine. The external in-
vesting membrane of the egg, which is the allantois, is also smooth
and uniformly vascular like the other. No special development of
tissue or of vessels occurs at any part of these membranes, and
no direct adhesion takes place between them; but the vascular
allantois or chorion of the foetus is everywhere closely applied to
the vascular mucous membrane of the maternal uterus, each of the
two contiguous surfaces following the undulations presented by the
other. (Fig. 224.) By this arrangement, transudation and absorp-
tion take place from the bloodvessels of the mother to those of the
foetus, in sufficient quantity to provide for the nutrition of the latter.
When parturition takes place, accordingly, in these animals, a very
moderate contraction of the uterus is sufficient to expel its contents.
The egg, displaced from its original position, slides easily forward
over the surface of the uterine mucous membrane, and is at last
discharged without any hemorrhage or laceration of connecting
parts. In other instances, however, the development of the foetus
requires a more elaborate arrangement of the vascular membranes.

622

THE PLACENTA.

In the cow, for example, the external membrane of the egg, beside
being everywhere supplied with branching vessels, presents upon

Fig. 224.

F<ETAL Pro, with its membrane?, contained in cavity of uterus,
c, c. Cavity of uterus, d. Amuiou. e, e. Allautois.

/, a, b, b. Walls of uterus.

various points of its surface no less than from seventy to eighty oval
spots, at each of which the vessels of the chorion are developed into
abundant tufted prominences, hanging from its exterior in thick,
velvety, vascular masses. At each point of the uterine mucous mem-
brane, corresponding with one of these tufted masses, the maternal
bloodvessels are developed in a similar manner, projecting into the
uterine cavity as a flattened rounded mass or cake; which, with that
part of the foetal chorion which is adherent to it, is known by the

Fig. 225.

COTYLEDON OF Cow's UTERI'S, —n, a. Surface of foetal chorion. &, b. Bloodvessels of foetal
chorion. d, d. Bloodvessels of uterine mucous membrane, c, c. Surface of uterine mucous nieui-
braue.

name of the Cotyledon. Each cotyledon forms, therefore, a little
placenta. (Fig. 225.) In its substance the tufted vascular loops
coming from the uterine mucous membrane (d, d) are entangled

THE PLACENTA. 623

with those coming from the membranes of the foetus (b, b). There
is no absolute adhesion between the two sets of vessels, but only
an interlacement of their ramified extremities; and, with a little
care in manipulation, the foetal portion of the cotyledon may be
extricated from the maternal portion, without lacerating either. In
consequence, however, of this intricate interlacement of the vessels,
transudation of fluids will evidently take place with great readiness,
from one system to the other.

The form of placenta, therefore, met with in these animals, is one
in which the bloodvessels of the fcetal chorion are simply entangled
with those of the uterine mucous membrane. In the human sub-
ject, the structure of the placenta is a little more complicated,
though the main principles of its formation are the same as in the
above instances.

From what has been said in the foregoing chapters, it appears
that in the human subject, as well as in the lower animals, the
placenta is formed partly by the vascular tufts of the chorion,
and partly by the thickened mucous membrane of the uterus in
which they are entangled. During the third month, those portions
of the chorion and decidua which are destined to undergo this
transformation become more or less distinctly limited in their form
and dimensions; and a thickened vascular mass, partly maternal
and partly fcetal in its origin, shows itself at the spot where the
placenta is afterward to be developed. This mass is constituted in
the following manner.

It will be recollected that the villi of the chorion, when first
formed, penetrate into follicles situated in the substance of the
uterine mucous membrane ; and that after they have become vas-
cular, they rapidly elongate and are developed into tufted ramifi-
cations of bloodvessels, each one of which turns upon itself in a
loop at the end of the vi41us. At the same time the uterine follicle,
into which the villus has penetrated, enlarges to a similar extent ;
sending out branching diverticula, corresponding with the multi-
plied ramifications of the villus. In fact, the growth of the follicle
and that of the villus go on simultaneously, and keep pace with
each other; the latter constantly advancing as the cavity of the
former enlarges.

But it is not only the uterine follicles which increase in size and
in complication of structure at this period. The capillary blood-
vessels, which lie between them and ramify over their exterior,
also become unusually developed. They enlarge and inosculate
freely with each other; so that every uterine follicle is soon covered

624

THE PLACENTA.

with an abundant network of dilated capillaries, derived from the
bloodvessels of the original decidua. At this time, therefore, each
vascular loop of the foetal chorion is covered, first, with a layer
forming the wall of the villus. This is in contact with the lining
membrane of a uterine follicle, and outside of this again are the
capillary vessels of the uterine mucous membrane ; so that two
distinct membranes intervene between the walls of the fcetal capil-
laries on the one hand and those of the maternal capillaries on the
other, and all transudation must take place through the substance
of these two membranes.

As the formation of the placenta goes on, the anatomical arrange-
ment of the fcetal vessel remains the same. They continue to
form vascular loops, penetrating deeply into the decidual mem-
brane; only they become constantly more elongated, and their
ramifications more abundant and tortuous. The maternal capilla-
ries, however, situated on the outside of the uterine follicles, become
considerably altered in their anatomical relations. They enlarge
excessively ; and, by encroaching constantly upon the little islets
or spaces between them, fuse successively with each other; and,
losing gradually in this way the characters of a capillary network,

become dilated into wide

Fig- 226. sinuses, which communicate

freely with the enlarged vessels
in the muscular walls of the
uterus. As the original capil-
lary plexus occupied the entire
thickness of the hypertrophied
decidua, the vascular sinuses,
into which it is thus converted,
are equally extensive. They
commence at the inferior sur-
face of the placenta, where it is
in contact with the muscular
walls of the uterus, and extend
through its whole thickness,
quite up to the surface of the
foetal chorion.

As the maternal sinuses grow upward, the vascular tufts of the
chorion grow downward, and extend also through the entire thick-
ness of the placenta. At this period, the development of the blood-
vessels, both in the fcetal and maternal portions of the placenta, is
so excessive that all the other tissues, which originally co-existed

Extremity of FCETAL TUFT, from human pla-
centa at term, in its recent condition, a, a. Capil-
lary bloodvessels. Magnified 135 diameters.

THE PLACENTA.

625

Fig. 227.

with them, become retrograde and disappear almost altogether. If
a villus from the foetal portion of the placenta be examined at this
time by transparency, in the fresh condition (Fig. 226) it will be
seen that its bloodvessels are covered only with a layer of homo-
geneous, or finely granular material, -j^Vu °f an incn in thickness,
in which are imbedded small oval-shaped nuclei, similar to those
seen at an earlier period in the villosities of the chorion. The vil-
losities of the chorion are now, therefore, hardly anything more
than ramified and tortuous vascular loops ;
the remaining substance of the villi hav-
ing been atrophied and absorbed in the
excessive growth of the bloodvessels, the
abundance and development of which
can be readily shown by injection from
the umbilical arteries. (Fig. 227.) The
uterine follicles have at the same time
lost all trace of their original structure,
and have become mere vascular sinuses,
into which the tufted fcetal bloodvessels
are received, as the villosities of the cho-
rion were at first received into the uterine
follicles.

Finally, the walls of the fcetal blood-
vessels having come into close contact with the walls of the maternal
sinuses, the two become adherent and fuse together ; so that a time
at last arrives, when we can no longer separate the fcetal vessels, in
the substance of the placenta, from the maternal sinuses, without
lacerating either the one or the other, owing to the secondary
adhesion which has taken place between them.

The placenta, therefore, when perfectly formed, has the structure
which is shown in the accompanying diagram (Fig. 228), repre-
senting a vertical section of the organ through its entire thickness.
At a, a, is seen the chorion, receiving the umbilical vessels from the
body of the foetus through the umbilical cord, and sending out its
compound and ramified vascular tuft& into the substance of the
placenta. At b, b, is the attached surface of the decidua, or uterine
mucous membrane ; and at c, c, c, c, are the orifices of uterine ves-
sels which penetrate it from below. These vessels enter the placenta
in an extremely oblique direction, though they are represented in
the diagram, for the sake of distinctness, as nearly perpendicular.
When they have once penetrated, however, the lower portion of
40

Extremity of FCETAL TUFT of
hnmau placenta; from an injected
spec. men. Magnified 40 diameters.

626 THE PLACENTA.

the decidua, they immediately dilate into the placental sinuses
(represented, in the diagram, in black), which extend through the

Fig. 228.

c

Vertical section of PLACENTA, showing arrangement of maternal and foetal vessels, a, a. Cho-
rion. ft, 6. Decidua. c, c, c, c. Orifices of uterine sinuses.

whole thickness of the organ, closely embracing all the ramifica-
tions of the foetal tufts. It will be seen, therefore, that the placenta,
arrived at this stage of completion, is composed essentially of no-
thing but bloodvessels. No other tissues enter into its structure ;
for all those which it originally contained have disappeared, except-
ing the bloodvessels of the foetus, entangled with and adherent to
the bloodvessels of the mother.

There is, however, no direct communication between the foetal
and maternal vessels. The blood of the foetus is always separated
from the blood of the mother by a membrane which has resulted
from the successive union and fusion of four different membranes,
viz., first, the membrane of the foetal villus ; secondly, that of the
uterine follicle ; thirdly, the wall of the foetal bloodvessel ; and,
fourthly, the wall of the uterine sinus. The single membrane, how-
ever, into which these four finally coalesce, is extremely thin, as
we have seen, and of enormous extent, owing to the extremely
abundant branching and subdivision of the foetal tufts. These tufts,
accordingly, in which the blood of the foetus circulates, are bathed
everywhere, in the placental sinuses, with the blood of the mother ;
and the processes of endosmosis and exosmosis, of exhalation and
absorption, go on between the two with the greatest possible
activity.

THE PLACENTA. 627

It is very easy to demonstrate the arrangement of the foetal
tufts in the human placenta. They can be readily seen by the
naked eye, and rnay be easily traced from their attachment at the
under surface of the chorion to their termination near the uterine
surface of the placenta. The anatomical disposition of the pla-
cental sinuses, however, is much more difficult of examination.
During life, and while the placenta is still attached to the uterus,
they are filled, of course, with the blood of the mother, and occupy
fully one-half the entire mass of the placenta. But when the pla-
centa is detached, the maternal vessels belonging to it are torn off
at their necks (Fig. 228, c, c, c, c), and the sinuses, being then
emptied of blood by the compression to which the placenta is sub-
jected, are apparently obliterated ; and the foetal tufts, falling to-
gether and lying in contact with each other, appear to constitute
the whole of the placental mass. The existence of the placental
sinuses, however, and their true extent, may be satisfactorily de-
monstrated in the following manner.

If we take the uterus of a woman who has died undelivered at
the full term or thereabout, and open it in such a way as to avoid
wounding the placenta, this organ will be seen remaining attached
to the uterine surface, with all its vascular connections complete.
Let the foetus now be removed by dividing the umbilical cord, and
the uterus, with the placenta attached, placed under water, with its
internal surface uppermost. If the end of a blowpipe be now
introduced into one of the divided vessels of the uterine walls, and
air forced in by gentle insufflation, we can easily inflate, first, the
venous sinuses of the uterus itself, and next, the deeper portions
of the placenta ; and lastly, the bubbles of air insinuate themselves
everywhere between the foetal tufts, and appear in the most super-
ficial portions of the placenta, immediately underneath the trans-
parent chorion (a, a, Fig. 228); thus showing that the placental
sinuses, which freely communicate with the uterine vessels, really
occupy the entire thickness of the placenta, and are equally exten-
sive with the tufts of the chorion. We have verified this fact in
the above manner, on four different occasions, and in the presence
of Prof. C. E. Oilman, Prof. Geo. T. Elliot, Dr. Henry B. Sands,
Prof. T. G-. Thomas, Dr. T. C. Finnell, and various other medical
gentlemen of New York.

If the placenta be now detached and examined separately, it will
be found to present upon its uterine surface a number of openings
which are extremely oblique in their position, and which are

628 THE PLACENTA.

accordingly bounded on one side by a very thin, projecting, cres-
centic edge. These are the orifices of the uterine vessels, passing
into the placenta and torn off at their necks, as above described ;
and by carefully following them with the probe and scissors, they
are found to lead at once into extensive empty cavities (the pla-
cental sinuses), situated between the foetal tufts. We have already
shown that these cavities are filled during life with the maternal
blood ; and there is every reason to believe that before delivery,
and while the circulation is going on, the placenta is at least twice
as large as after it has been detached and expelled from the uterus.

The placenta, accordingly, is a double organ, formed partly by
the chorion and partly by the decidua ; and consisting of maternal
and fcetal bloodvessels, inextricably entangled and united with each
other.

The part which this organ takes in the development of the foetus
is an exceedingly important one. From the date of its formation,
at about the beginning of the fourth month, it constitutes the only
channel through which nourishment is conveyed from the mother
to the foetus. The nutritious materials, which circulate in abun-
dance in the blood of the maternal sinuses, pass through the inter
vening membrane by endosmosis, and enter the blood of the fcetus.
The healthy or injurious regimen, to which the mother is subjected,
will accordingly exert an almost immediate influence upon the
child. Even medicinal substances, taken by the mother and ab-
sorbed into her circulation, may readily transude through the pla-
cental vessels ; and they have been known in this way to exert a
specific effect upon the fcetal organization.

The placenta is, furthermore, an organ of exhalation as well as
of absorption. The excrementitious substances, produced in the
circulation of the fcetus, are undoubtedly in great measure disposed
of by transudation through the walls of the placental vessels, to be
afterward discharged by the excretory organs of the mother. The
system of the mother may therefore be affected in this manner by
influences derived from the fcetus. It has been remarked more
than once, in the lower animals, that when the female has two sue
cessive litters of young by different males, the young of the second
litter will sometimes bear marks resembling those of the first male.
In these instances, the peculiar influence which produces the ex
ternal mark must have been transmitted by the first male directly
to the foetus, from the fcetus to the mother, and from the mother to
the foetus of the second litter.

THE PLACENTA. 629

It is also through the placental circulation that those disturbing
effects are produced upon the nutrition of the foetus, which result
from sudden shocks or injuries inflicted upon the mother. There is
now little room for doubt that various deformities and deficiencies of
the foetus, conformably to the popular belief, do really originate, in
certain cases, from nervous impressions, such as disgust, fear or anger,
experienced by the mother. The mode in which these effects may
be produced is readily understood from what has been said above
of the anatomy and functions of the placenta. We know very well
how easily nervous impressions will disturb the circulation in the
brain, the face, the lungs, &c. ; and the uterine circulation is quite
as readily influenced by similar causes, as physicians see every day
in cases of amenorrhoea, menorrhagia, &c. If a nervous shock may
excite premature contraction in the muscular fibres of the pregnant
uterus and produce abortion, as not unfrequently happens, it is cer-
tainly capable of disturbing the course of the circulation through
the same organ. But the foetal circulation is dependent, to a great
extent, on the maternal. Since the two sets of vessels are so closely
entwined in the placenta, and since the foetal blood has here much
the same relation to the maternal, that the blood in the pulmonary
capillaries has to the air in the air- vesicles, it will be liable to de-
rangement from similar causes. If the circulation of air through
the pulmonary tubes be suspended, that of the blood through
the general capillaries is disturbed also. In the same way, what-
ever arrests or disturbs the circulation through the vessels of the
maternal uterus must necessarily be liable to interfere with that
in the foetal capillaries forming part of the placenta. And lastly,
as the nutrition of the foetus is provided for wholly by the placenta,
it will of course suffer immediately from any such disturbance of
the placental circulation. These effects may be manifested either
in the general atrophy and death of the foetus ; or, if the disturbing
cause be slight, in the atrophy or imperfect development of par-
ticular parts ; just as, in the adult, a morbid cause operating through
the entire system, may be first or even exclusively manifested in
some particular organ, which is more sensitive to its influence than
other parts.

The placenta must accordingly be regarded as an organ which
performs, during intra-uterine life, offices similar to those of the
lungs and the intestine after birth. It absorbs nourishment, reno-
vates the blood, and discharges by exhalation various excrementi-
tious matters, which originate in the processes of foetal nutrition.

630

DISCHARGE OF THE OVUM,

CHAPTER XIII.

DISCHARGE OF THE OYUM, AND RETROGRADE
DEVELOPMENT (INVOLUTION) OF THE UTERUS.

DURING the growth of the ovum and the formation of the pla-
cental structures, the muscular substance of the uterus also increases
in thickness, while the whole organ enlarges, in order to accommo-
date the growing foetus and its appendages. The relative positions
of the amnion and chorion, furthermore, undergo a change during
the latter periods of gestation, and the umbilical cord becomes
developed, at the same time, in the following manner.

In the earlier periods of foetal life, the umbilical cord consists
simply of that portion of the allantois lying next the abdomen. It
is then very short, and contains the umbilical vessels running in a
nearly straight course, and parallel with each other, from the abdo-
men of the foetus to the external portions of the chorion. At this
time the amnion closely invests the body of the foetus, so that the

size of its cavity is but little larger
than that of the foetus. (Fig. 229.)
The space between the amnion
and the chorion is then occupied
by an amorphous gelatinous ma-
terial, in which lies imbedded the
umbilical vesicle.

Afterward, however, the am-
nion enlarges faster than the cho-
rion, and encroaches upon the
layer of gelatinous matter situated
between the two (Fig. 230), at
the same time that an albuminous
fluid, the " amniotic fluid," is ex-
uded into its cavity, in constantly

increasing quantity. Subsequently, the gelatinous layer, above de-
scribed, altogether disappears, and the amnion, at about the begin-

Fig. 229.

HUMAN OVTTM about the end of the first
month. -1. Umbilical vesicle. 2. Amnion. 3.
Chorion.

ENLARGEMENT OF THE AMNION.

631

Fig. 230.

HCMAN OVCM at end of third mouth, bhowing
enlargement of amaiou.

ning of the fifth month, comes in contact with the internal surface

of the chorion. Finally, toward the end of gestation, the contact

becomes so close between these

two membranes that they are

partially adherent to each

other, and it requires a little

care to separate them without

laceration.

The quantity of the amniotic
Quid continues to increase dur-
ing the latter period of gesta-
tion in order to accommodate
the movements of the foetus.
These movements begin to be
perceptible about the fifth
month, at which time the
muscular system has already

attained a considerable degree of development, but become after-
ward more frequent and more strongly pronounced. The space
and freedom requisite for these movements are provided for by the
fluid accumulated in the cavity of the amnion.

The umbilical cord elongates, at the same time, in proportion to
the increasing size of the amniotic cavity. During its growth, it
becomes spirally twisted from right to left, the two umbilical arte-
ries winding round the vein in the same direction. The gelatinous
matter, as already described as existing between the amnion and
chorion, while it disappears elsewhere, accumulates in the cord in
considerable quantity, covering the vessels with a thick, elastic en-
velope, which protects them from injury and prevents their being
accidentally compressed or obliterated. The whole is covered by a
portion of the amnion,. which is connected at one extremity with the
integument of the abdomen, and invests the whole of the cord with
a continuous sheath, like the finger of a glove. (Fig. 231.)

The cord also contains, for a certain period, the pedicle or stem
of the umbilical vesicle. The situation of this vesicle, it will be
recollected, is always between the chorion and the amnion. Its
pedicle gradually elongates with the growth of the umbilical cord ;
and the vesicle itself, which generally disappears soon after the
third month, sometimes remains as late as the fifth, sixth, or seventh.
According to Prof. Mayer, of Bonn, it may even be found, by care-
ful search, at the termination of pregnancy. When discovered in

632

DISCHARGE OF THE OVUM.

the middle and latter periods of gestation, it presents itself as a
small, flattened, and shrivelled vesicle, situated underneath the
amnion, at a variable distance from the insertion of the umbilical
cord. A minute bloodvessel is often seen running to it from the
cord, and ramifying upon its surface.

Fig. 231.

GRAVID HUMAN UTERUS AND CONTENTS, showing the relations of the cord, placenta, mem.
branes, &c., about the end of the seventh month.— 1. Decidua vera. 2.. Decidua reflexa. 3. Choriou.
4. Amnion.

The decidua reflexa, during the latter months of pregnancy, is
constantly distended and pushed back by the increasing size of the
egg ; so that it is finally pressed closely against the opposite surface
of the decidua vera, which still lines the greater part of the uterine
cavity. By the end of the seventh month, the opposite surfaces
of the decidua vera and reflexa are in complete contact with each
other, though still distinct and capable of being separated without
difficulty. After that time, they fuse together and become con-
founded with each other ; the two at last forming only a single,
thin, friable, semi-opaque layer, in which no trace of their original
glandular structure can be discovered.

This is the condition of things at the termination of pregnancy.
Then, the time having arrived for parturition to take place, the
hypertrophied muscular walls of the uterus contract forcibly upon
its contents, and the egg is discharged, together with the whole of
the decidual uterine mucous membrane.

SEPARATION OF THE PLACENTA. 633

In the human subject, as well as in most quadrupeds, the mem-
branes of the egg are usually ruptured during the process of par-
turition ; and the foetus escapes first, the placenta and the rest of
the appendages following a few moments afterward. Occasionally,
however, even in the human subject, the egg is discharged entire,
and the foetus liberated afterward by the laceration of the mem-
branes. In each case, however, the mode of separation and expul-
sion is in all particulars the same.

The process of parturition, therefore, consists essentially in a
separation of the decidual membrane, which, on being discharged,
brings away the ovum with it. The greater part of the decidua
vera, having fallen into a state of atrophy during the latter months
of pregnancy, is by this time nearly destitute of vessels, and sepa-
rates, accordingly, without any perceptible hemorrhage. That por-
tion, however, which enters into the formation of the placenta, is,
on the contrary, excessively vascular ; and when the placenta is
separated, and its maternal vessels torn off at their necks, as before
mentioned, a gush of blood takes place, which accompanies or
immediately follows the birth of the foetus. This hemorrhage,
which occurs as a natural phenomenon at the time of parturition,
does not come from the uterine vessels proper. It consists of the
blood which was contained in the placental sinuses, and which is
expelled from them owing to the compression of the placenta by
the walls of the uterus. Since the whole amount of blood thus
lost was previously employed in the placental circulation, and since
the placenta itself is thrown off at the same time, no unpleasant
effect is produced upon the mother by such a hemorrhage, because
the natural proportion of blood in the rest of the maternal system
remains the same. Uterine hemorrhage at the time of parturition,
therefore, becomes injurious only when it continues after complete
separation of the placenta; in which case it is supplied by the
mouths of the uterine vessels themselves, left open by failure of the
uterine, contractions. These vessels are usually instantly closed,
after separation of the placenta, by the contraction of the muscular
fibres of the uterus. They pass, as we have already mentioned, in
an exceedingly oblique direction, from the uterine surface to the
placenta ; and the muscular fibres, which cross them transversely
above and below, necessarily constrict them, and effectually close
their orifices, immediately on being thrown into a state of contraction.

Another very remarkable phenomenon, connected with preg-
nancy and parturition is the appearance in the uterus of a new

634 DISCHARGE OF THE OVUM.

mucous membrane, growing underneath the old, and ready to
take the place of the latter after its discharge.

If the internal surface of the body of the uterus be examined
immediately after parturition, it will be seen that at the spot where
the placenta was attached, every trace of mucous membrane has
disappeared. The muscular fibres of the uterus are here perfectly
exposed and bare ; while the mouths of the ruptured uterine sinuses
are also visible, with their thin, ragged edges hanging into the
cavity of the uterus, and their orifices plugged with more or less
abundant bloody coagula.

Over the rest of the uterine surface, the decidua vera has also
disappeared. Here, however, notwithstanding the loss of the ori-
ginal mucous membrane, the muscular fibres are not perfectly bare,
but are covered with a thin, semi-transparent film, of a whitish color
and soft consistency. This film is an imperfect mucous membrane
of new formation, which begins to be produced, underneath the
old decidua vera, as early as the beginning of the eighth month.
We have seen this new mucous membrane very distinctly in the
uterus of a woman who died undelivered at the above period.
The old mucous membrane, or decidua vera, is at this time some-
what opaque, and of a slightly yellowish color, owing to a partial
fatty degeneration which it undergoes in the latter months of preg-
nancy. It is easily raised and separated from the subjacent parts,
owing to the atrophy of its vascular connections; and the new
mucous membrane, situated beneath it, is readily distinguished by
its fresh color, and healthy, transparent aspect.

The mucous membrane of the cervix uteri, which takes no part
in the formation of the decidua, is not thrown off in parturition,
but remains in its natural position ; and after delivery it may be
seen to terminate at the os internum by an uneven, lacerated edge,
where it was formerly continuous with the decidua vera.

Subsequently, a regeneration of the mucous membrane takes place
over the whole extent of the body of the uterus. The mucous
membrane of new formation, which is already in existence at the
time of delivery, becomes thickened and vascular ; and glandular
tubules are gradually developed in its substance. At the end of
two months after delivery, according to Heschl1 and Longet,2 it has
entirely regained the natural structure of the uterine mucous mem-

1 Zeitschrift der K. K. Gesellschaft der Aerzte, in Wien, 1852.

2 Traite de Physiologie. De la Generation, p. 173.

RETROGRADE DEVELOPMENT OF THE UTERUS. 635

Fig. 232.

MCSCITLAR FIBRES OF U NIMPREG.V ATED
UTERUS; from a woman aged 40, dead of phthisis
pulmonalis.

brane. It unites at the os inter urn, by a linear cicatrix, with the
mucous membrane of the cervix, and the traces of its laceration at
this spot afterward cease to be visible. At the point, however,
where the placenta was at-
tached, the ^regeneration of
the mucous membrane is
less rapid; and a cicatrix-
like spot is often visible at
this situation for several
months after delivery.

The only further change,
which remains to be de-
scribed in this connection,
is the fatty degeneration
and reconstruction of the
muscular substance of the
uterus. This process, which
is sometimes known as the
•'involution" of the uterus,
takes place in the following
manner. The muscular
fibres of the unimpregnated
uterus are pale, flattened,
spindle-shaped bodies (Fig.
232) nearly homogeneous
in structure or very faintly
granular, and measuring
from 5JC to jjfl of an inch
in length, by Tu Jos to ffu'&u
of an inch in width. During
gestation these fibres in-
crease very considerably in
size. Their texture becomes
much more distinctly granu-
lar, and their outlines more
strongly marked. An oval
nucleus also shows itself in

the central part of each fibre. The entire walls of the uterus, at
the time of delivery, are composed of such muscular fibres as
these, arranged in circular, oblique, and longitudinal bundles.

About the end of the first week after delivery, these fibres begin

Fig, 233.

MUSCULAR FIBRES op HUMAW UTERUS, ten
days after parturition ; from a woman dead of puer-
peral fever.

636

DI3CHAKGE OF THE OVUM.

to undergo a fatty degeneration. (Fig. 233.) Their granules be-
come larger and more prominent, and very soon assume the
appearance of molecules of fat, deposited in the substance of the
fibre. The fatty deposit, thus commenced, increases in abundance,
and the molecules continue to enlarge until they become converted
into fully formed oil-globules, which fill the interior of the fibre

more or less completely,
and mask, to a certain ex-
tent, its anatomical cha-
racters. (Fig. 234.) The
universal fatty degenera-
tion, thus induced, gives to
the uterus a softer consist-
ency, and a pale yellowish
color which is characteristic
of it at this period. The
muscular fibres which have
become altered by the fatty
deposit are afterward gra-
dually absorbed and disap-
pear; their place being
subsequently taken by
other fibres of new forma-
tion, which already begin

to make their appearance before the old ones have been completely
destroyed. As this process goes on, it results finally in a complete
renovation of the muscular substance of the uterus. The organ
becomes again reduced in size, compact in tissue, and of a pale
ruddy hue, as in the ordinary unimpregnated condition. This entire
renewal or reconstruction of the uterus is completed, according to
Heschl.1 about the end of the second month after delivery.

MUSCULAR FIBRES OF II UMAX UTERUS, three
weeks after parturition ; from a woman dead of peri-
tonitis.

1 Op. cit.

DEVELOPMENT OF THE EMBRYO.

637

Fig. 235.

CHAPTER XIV.

DEVELOPMENT OF THE EMBRYO— NERVOUS SYSTEM
ORGANS OF SENSE, SKELETON, AND LIMBS.

THE first trace of a spinal cord in the embryo consists of the
double longitudinal fold or ridge of the blastodermic membrane,
which shows itself at an early period, as above described, on each
side the median furrow. The two laminae of which this is com-
posed, on the right and left sides (Fig. 235, a, b), unite with each
other in front, forming a rounded dilatation (c),
the cephalic extremity, and behind at d, forming
a pointed or caudal extremity. Near the pos-
terior extremity, there is a smaller dilatation,
which marks the future situation of the lumbar
enlargement of the spinal cord.

As the laminae above described grow upward
and backward, they unite with each other upon
the median line, so that the whole is converted
into a hollow cylindrical cord, terminating ante-
riorly by a bulbous enlargement, and posteriorly
by a pointed enlargement; the central cavity
which it contains running continuously through
it, from front to rear.

The next change which shows itself is a divi-
sion of the anterior bulbous enlargement into
three secondary compartments or vesicles (Fig.
236), which are partially separated from each other by transverse
constrictions. These vesicles are known as the three cerebral vesi-
cles, from which all the different parts of the encephalon are after-
ward to be developed. The first, or most anterior cerebral vesicle
is destined to form the hemispheres; the second, or middle, the
tubercula quadrigemina ; and the third, or posterior, the medulla
oblongata. All three vesicles are at this time hollow, and their

Formation of CERE-
BRO-SPINAL Axis.—
o, b. Spinal cord. c. Ce-
phalic extremity. d.
Caudal extremity.

638

DEVELOPMENT OF THE EMBRYO.

236.

cavities communicate freely with each other, through the interven-
ing constrictions.

Very soon the anterior and the posterior cerebral vesicles suffer
a further division ; the middle one remain-
ing undivided. The anterior vesicle thus
separates into two portions, of which the
first, or larger, constitutes the hemispheres,
while the second, or smaller, becomes the
optic thalami. The third vesicle also sepa-
rates into two portions, of which the ante*
rior becomes the cerebellum, and the pos-
terior the medulla oblongata.

There are, therefore, at this time five
cerebral vesicles, all of whose cavities com-
municate with each other and with the
central cavity of the spinal cord. The
entire cerebro-spinal axis, at the same time,
becomes very strongly curved in an ante-
rior direction, corresponding with the ante-
rior curvature of the body of the embryo
(Fig. 237); so that the middle vesicle, or
that of the tubercula quadrigemina, occu-
pies a prominent angle at the upper part of

the encephalon, while the hemispheres and the medulla oblongata
are situated below it, anteriorly and posteriorly.

At first, it will be observed, the relative size of the various parts
of the encephalon is very different from that which
they afterward attain in the adult condition. The
hemispheres, for example, are hardly larger than
the tubercula quadrigemina ; and the cerebellum
is very much inferior in size to the medulla oblon-
gata. Soon afterward, the relative position and size
of the parts begin to alter. The hemispheres and
tubercula quadrigemina grow faster than the poste-
rior portions of the encephalon ; and the cerebellum
becomes doubled backward over the medulla oblon-
gata. (Fig. 238.) Subsequently, the hemispheres
rapidly enlarge, growing upward and backward,
so as to cover in and conceal both the optic tha-
lami and the tubercula quadrigemina (Fig. 239); the cerebellum
tending in the same way to grow backward, and projecting farther

Formation of the CEREBRO-
SPINAL Axis. — 1. Vesicle of
the hemispheres. 2. Vesicle of
the tubercala qnadrigemina. 3.
Vesicle of the medulla oblongata.

Fig. 237.

*

FOETAL Pio, five-
eighths of au inch
long, showing brain
and spinal cord. — 1.
Hemispheres. 2. Tu-
bercu'.a quadrigemi-
na. 3. Cerebellum.
4. Medulla oblongata.

NEEVOUS SYSTEM.

639

and farther over the medulla oblongata. The subsequent history
of the development of the encephalon is little more than a con-

Fig. 239.

FOETAL Pia, one and a quarter inch.
long. — 1. Hemispheres. 2. Tubercuia
qnadrigemina. 3. Cerebellum. 4. Me-
dulla oblongaca.

HEAD OF FCETAL PIG, three and a
half inches long.— 1. Hemispheres. 3.
CereOellurn. 4. Medul'a ol-longata.

tinuation of the same process ; the relative dimensions of the parts
constantly changing, so that the hemispheres become, in the adult
condition (Fig. 2-iO), the largest of all the divisions of the ence-

Fig. 240.

BRAI.V OP ADULT PIG.— 1. Hemispheres. 3. Cerebellum. 4. Meduna oblougata.

phalon, while the cerebellum is next in size, and covers entirely
the upper portion of the medulla oblongata. The surfaces, also, of
the hemispheres and cerebellum, which were at first smooth, become
afterward convoluted; increasing, in this way, still farther the
extent of their nervous matter. In the human foetus, these con-
volutions begin to appear about the beginning of the fifth month
(Longet), and grow constantly deeper and more abundant during
the remainder of foetal life.

The lateral portions of the brain growing at the same time more
rapidly than that which is situated on the median line, they soon
project on each side outward and upward • and. by folding over

610 DEVELOPMENT OF THE EMBRYO.

against each other in the median line, form the right and left hemi-
spheres, separated from each other by the longitudinal fissure.
A similar process of growth taking place in the spinal cord results
in the formation of the two lateral columns and the anterior and pos-
terior median fissures of the cord. Elsewhere the median fissure is
less complete, as, for example, between the two lateral halves of the
cerebellum, the two optic thalami and corpora striata, and the two
tubercula quadrigemina ; but it exists everywhere, and marks more
or less distinctly the division between the two sides of the nervous
centres, produced by the excessive growth of their lateral portions.
In this way the whole cerebro-spinal axis is converted into a double
organ, equally developed upon the right and left sides, and partially
divided by a longitudinal median fissure.

Organs of Special Sense. — The eyes are formed by a diverticulum
which grows out on each side from the first cerebral vesicle. This
diverticulum is at first hollow, its cavity communicating with that
of the hemisphere. Afterward, the passage between the two is filled
up with a deposit of nervous matter, and becomes the optic nerve.
The globular portion of the diverticulum, which is converted into
the globe of the eye, has a very thin layer of nervous matter depo-
sited upon its internal surface, which becomes the retina ; the rest
of its cavity being occupied by a gelatinous semi-fluid substance,
the vitreous body. The crystalline lens is formed in a distinct fol-
licle, which is an offshoot of the integument, and becomes partially
imbedded in the anterior portion of the globe of the eye. The
cornea also is originally a part of the integument, and remains
partially opaque until a very late period of development. Its tissue
clears up, however, and becomes perfectly transparent, shortly be-
fore birth.

The iris is a muscular septum which is formed in front of the
crystalline lens, separating the anterior and posterior chambers of
the aqueous humor. Its central opening, which afterward becomes
the pupil, is at first closed by a vascular membrane, the pupillary
membrane, passing directly across the axis of the eye. The vessels
of this membrane, which are derived from those of the iris, subse-
quently become atrophied. They disappear first from its centre,
and afterward recede gradually toward its circumference ; returning
always upon themselves in loops, the convexities of which are directed
toward the centre of the membrane. The pupillary membrane itself
finally becomes atrophied and destroyed, following in this retro-
grade process the direction of its receding bloodvessels, viz., from

SKELETON AXD LIMBS. 641

the centre toward the circumference. It has completely disappeared
by the end of the seventh month. (Cruveilhier.)

The eyelids are formed by folds of the integument, which
gradually project from above and below the situation of the eye-
ball. They grow so rapidly during the second and third months
that their free margins come in contact and adhere together, so that
they cannot be separated at that time without some degree of vio-
lence. They remain adherent from this period until the seventh
month (Guy), when their margins separate and they become per-
fectly free and movable. In the carnivorous animals, however
(dogs and cats), the eyelids do not separate from each other until
eight or ten days after birth.

The internal ear is formed in a somewhat similar manner with
the eyeball, by an offshoot from the third cerebral vesicle; the
passage between them filling up by a deposit of white substance,
which becomes the auditory nerve. The tympanum and auditory
meatus are both offshoots from the external integument.

Skeleton. — At a very early period of development there appears,
as we have already described (Chap. VII.), immediately beneath the
cerebro-spinal axis, a cylindrical cord, of a soft, cartilaginous con-
sistency, termed the chorda dorsalis. It consists of a fibrous sheath
containing a mass of simple cells, closely packed together and
united by adhesive material. This cord is not intended to be a
permanent part of the skeleton, but is merely a temporary organ
destined to disappear as development proceeds.

Immediately around the chorda dorsalis there are deposited soon
afterward a number of cartilaginous plates, which encircle it in a
series of rings, corresponding in number with the bodies of the future
vertebrae. These rings increase in thickness from without inward,
encroaching upon the substance of the chorda dorsalis, and finally
taking its place altogether. The thickened rings, which have been
filled up in this way and solidified by cartilaginous deposit, become
the bodies of the vertebras ; while their transverse and articulating
processes, with the laminae and spinous processes, are formed by
subsequent outgrowths from the bodies in various directions.

When the union of the dorsal plates upon the median line fails
to take place, the spinal canal remains open at that situation, and
presents the malformation known as spina bifida. This malforma-
tion may consist simply in a fissure of the spinal canal, more or less
extensive, in which case it may often be cured, or may even close
spontaneously ; or it may be complicated with an imperfect deve-
41

642 DEVELOPMENT OF THE EMBRYO.

lopment or complete absence of the spinal cord at the same spot,
when it is accompanied of course by paralysis of the lower ex-
tremities, and almost necessarily results in early death.

The entire skeleton is at first cartilaginous. The first points of
ossification show themselves about the beginning of the second
month, almost simultaneously in the clavicle and the upper and
lower jaw. Then come in the following order, the long bones of
the extremities, the bodies and processes of the vertebrae, the bones
of the head, the ribs, pelvis, scapula, metacarpus and metatarsus,
and the phalanges of the fingers and toes. The bones of the carpus,
however, are all cartilaginous at birth, and do not begin to ossify
until a year afterward. The calcaneum and astragalus begin to
ossify, according to Cruveilhier, during the latter periods of foetal
life, but the remainder of the tarsus is cartilaginous at birth. The
lower extremity of the femur begins to ossify, according to the
same author, during the latter half of the ninth month. The pisiform
bone of the carpus is said to commence its ossification later than
any other bone in the skeleton, viz., at from twelve to fifteen years
after birth. Nearly all the bones ossify from several distinct points ;
the ossification spreading as the cartilage itself increases in size,
and the various bony pieces, thus produced, uniting with each other
at a later period, usually some time after birth.

The limbs appear by a kind of budding process, as offshoots of
the external layer of the blastodermic membrane. They are at
first mere rounded elevations, without any separation between the
fingers and toes, or any distinction between the different articula-
tions. Subsequently the free extremity of each limb becomes di-
vided into the phalanges of the fingers or toes ; and afterward the
articulations of the wrist and ankle, knee and elbow, shoulder and
hip, appear successively from below upward.

The posterior extremities, in the human subject, are less rapid in
their development than the anterior. Throughout the term of
foetal life, indeed, the anterior parts of the body are generally more
voluminous than the posterior. The younger the embryo, the larger
are the head and upper extremities in proportion to the rest of the
body. The lower limbs and the pelvis, more particularly, are very
slightly developed in the early periods of growth, as compared with
the spinal column, to which they are attached. The inferior ex-
tremity of the spinal column, formed by the sacrum and coccyx,
projects at this time considerably beyond the pelvis, forming a tail,
like that of the lower animals, which is curled forward toward the

SKELETON AND LIMBS. 643

abdomen, and terminates in a pointed extremity. Subsequently the
pelvis and the muscular parts seated upon it grow so much faster
than the sacrum and coccyx, that the latter become concealed
under the adjoining soft parts, and the rudimentary tail accord-
ingly disappears.

The integument of the embryo is at first thin, vascular, and ex-
ceedingly transparent. It afterward becomes thicker, more opaque,
and whitish in color ; though even at birth it is more vascular than
in the adult condition, and the ruddy color of its abundant capil-
lary vessels is then very strongly marked. The hairs begin to
appear about the middle of intra-uterine life ; showing themselves
first upon the eyebrows, and afterward upon the scalp, trunk and
extremities. The nails are in process of formation from the third
to the fifth month ; and, according to Kolliker, are still covered
with a layer of epidermis until after the latter period. The seba-
ceous matter of the cutaneous glandules accumulates upon the skin
after the sixth month, and forms a whitish, semisolid, oleaginous
layer, termed the vernix caseosa, which is most abundant in the
flexures of the joints, between the folds of the integument, behind
the ears and upon the scalp.

The cells of the epidermis are repeatedly exfoliated after the first
five months of foetal life (Kolliker), and replaced by others of new
formation and of larger size. These exfoliated epidermic cells are
found mingled with the sebaceous matter of the vernix caseosa in
great abundance. This semi-oleaginous layer, with which the in-
tegument is covered, becomes exceedingly useful in the process of
parturition, by lubricating the surface of the body, and allowing it
to pass easily through the generative passages.

64:4 DEVELOPMENT OF THE ALIMENTARY CANAL.

CHAPTER XV.

DEVELOPMENT OF THE ALIMENTARY CANAL
AND ITS APPENDAGES.

WE have already seen; in a preceding chapter, that the intestinal
canal is formed by the internal layer of the blastodermic membrane,
which curves forward on each side, and is thus converted into a
nearly straight cylindrical tube, terminating at each extremity in
a rounded cul-de-sac, and inclosed by the external layer of the
blastodermic membrane. The abdominal walls, however, do not
unite with each other upon the median line until long after the
formation of the intestinal canal ; so that, during a certain period,
the abdomen of the embryo is widely open in front, presenting a
long oval excavation, in which the nearly straight, intestinal tube
is to be seen, running from its anterior to its posterior extremity.

The formation of* the stomach takes place in the following man-
ner : The alimentary canal, originally straight, soon presents two
lateral curvatures at the upper part of the abdomen ; the first to
the left, the second to the right. The first of these curvatures
becomes expanded into a wide sac, projecting laterally from the
median line into the left hypochondrium, forming the great pouch
of the stomach. The second curvature, directed to the right, marks
the boundary between the stomach and the duodenum ; and the
tube at that point becoming constricted and furnished with a circular
layer of muscular fibres, is converted into the pylorus. Immedi-
ately below* the pylorus, the duodenum again turns to the left ; and
these curvatures, increasing in number and complexity, form the
convolutions of the small intestine. The large intestine forms a
spiral curvature ; ascending on the right side, then crossing over
to the left as the transverse colon, and again descending on the left
side, to terminate by the sigmoid flexure in the rectum.

The curvatures of the intestinal canal take place, however, in an
antero-posterior, as well as in a lateral direction, and may be best
studied in a profile view, as in Fig. 241. The abdominal walls are

AND ITS APPENDAGES. 645

here still imperfectly closed, leaving a wide opening at «, b, where
the integument of the foetus becomes continuous with the com-
mencement of the amniotic membrane. The intestine makes at

Fig. 241.

Formation of ALIMENT ART CAXAL. — n, b. Commencement of amnion. c, c. Intestine, d,
Pharynx, e. Urinary bladder. / Allantois. g. Umbilical vesicle, x. Dotted line, showing the
place of formation of the oesophagus.

first a single angular turn forward, and opposite the most promi-
nent portion of this angle is to be seen the obliterated duct, which
forms the stem of the umbilical vesicle, (g.) A short distance below
this point the intestine subsequently enlarges in its calibre, and the
situation of this enlargement marks the commencement of the
colon. The two portions of the intestine, after this period, become
widely different from each other. The upper portion, which is the
small intestine, grows mostly in the direction of its length, and
becomes a very long, narrow, and convoluted tube-: while the lower
portion, which is the large intestine, increases rapidly in diameter,
but elongates less than the former.

At the point of junction of the small and large intestines, a late-
ral bulging or diverticulum of the latter shows itself, and increases
in extent, until the ileum seems at last to be inserted obliquely into
the side of the colon. This diverticulum of the colon is at first
uniformly tapering or conical in shape ; but afterward that portion
which forms its free extremity, becomes narrow and elongated, and
is slightly twisted upon itself in a spiral direction, forming the
appendix vermiformis ; while the remaining portion, which is con-
tinuous with the intestine, becomes exceedingly enlarged, and forms
the caput coli.

The caput coli and the appendix are at first situated near the

646

DEVELOPMENT OF THE ALIMENTARY CANAL

Fig. 242.

umbilicus ; but between the fourth and fifth months (Cruveilhier)
their position is altered, and they then become fixed in the right
iliac region. During the first six months, the internal surface of
the small intestine is smooth. At the seventh month, according to
Cruveilhier, the valvulae conniventes begin to appear, after which
they increase in size till birth. The division of the colon into
sacculi by longitudinal and transverse bands, is also an appearance
which presents itself only during the last half of foetal life. Pre-
vious to that time, the colon is smooth and cylindrical in figure,
like the small intestine.

After the small intestine is once formed, it increases very rapidly
in length. It grows, indeed, at this time, faster than the walls of

the abdomen; so that it can no longer
be contained in the abdominal cavity,
but protrudes, under the form of an in-
testinal loop, or hernia, from the umbili-
cal opening. (Fig. 242.) In the human
embryo, this protrusion of the intestine
can be readily seen during the latter part
of the second month. At a subsequent
period, however, the walls of the abdo-
men grow more rapidly than the intes-
tine. They accordingly gradually en-
velop the hernial protrusion, and at last
inclose it again in the cavity of the ab-
domen.

Owing to an imperfect development
of the abdominal walls, and an imperfect
closure of the umbilicus, this intestinal

protrusion, which is normal during the early stages of foetal life,
sometimes remains at birth, and we then have ^congenital umbilical
hernia. As the parts at that time, however, have a natural tendency
to cicatrize and unite with each other, simple pressure is generally
effectual, in such cases, in retaining the hernia within the abdomen,
and in producing at last a complete cure.

Urinary Bladder, Urethra, &c. — It will be recollected that very
soon after the formation of the intestine, a vascular outgrowth takes
place from its posterior portion, which gradually protrudes from the
open walls of the abdomen in front, until it comes in contact with
the external investing membrane of the egg, and forms, by its con-
tinued growth and expansion, the allantois. (Fig. 241, /.) It is at

FOETAL Pro, showing loop
of intestine, forming umbilical
hernia ; from a specimen iu the
author's possession. From the
convexity of the loop a thin filament
is seen passing to the umbilical
vesicle, which is here flattened into
a leaf-like form.

AND ITS APPENDAGES. 647

first, as we have shown above, a hollow sac ; but, as it spreads out
over the surface of the investing membrane of the egg, its two
opposite walls adhere to each other, so that its cavity is obliterated
at this situation, and it is thus converted into a single vascular
membrane, the chorion. This obliteration of the cavity of the
allantois commences at its external portion, and gradually extends
inward toward the point of its emergence from the abdomen. The
hollow tube, or duct, which connects the cavity of the allantois with
the posterior part of the intestine, is accordingly converted, as the
process of obliteration proceeds, into a solid, rounded cord. This
cord is termed the urachus.

After the walls of the abdomen have come in contact, and united
with each other at the umbilicus, that portion of the above duct
which is left outside the abdominal cavity, forms a part of the um-
bilical cord, and remains connected with the umbilical arteries and
vein. That portion, on the contrary, which is included in the ab-
domen, does not close completely, but remains as a pointed fusiform
sac, terminating near the umbilicus in the solid cord of the urachus,
and still communicating at its base with the lower extremity of the
intestinal canal. This fusiform sac (Fig. 241, e), becomes the uri-
nary bladder ; and in the foetus at term, the bladder is still conical
in form, its pointed extremity being attached, by means of the ura-
chus, to the internal surface of the abdominal walls at the situation
of the umbilicus. Afterward, the bladder loses this conical form,
and its fundus in the adult becomes rounded and bulging.

The urinary bladder, as it appears from the above description, at
first communicates freely with the intestinal cavity. The intestine,
in fact, terminates, at this time, in a wide passage, or cloaca, at its
lower extremity, which serves as a common outlet for the urinary
and intestinal passages. Subsequently, however, a horizontal par-
tition makes its appearance just above the point of junction between
the bladder and rectum, and grows downward and forward in such
a manner as to divide the above-mentioned cloaca into two parallel
and unequal passages. The anterior or smaller of these passages
becomes the urethra, the posterior or larger becomes the rectum ;
and the lower edge of the septum between them becomes finally
united with the skin, forming, at its most superficial part, a tole
rably wide band of integument, the perineum, which intervenes
between the anus and the external portion of the urethra.

The contents of the intestine, which accumulate during foetal life,
vary in different parts of the alimentary canal. In the small intes-

648 DEVELOPMENT OF THE ALIMENTARY CANAL

tine they are semifluid or gelatinous in consistency, of a light
yellowish or grayish-white color in the duodenum, becoming yellow,
reddish-brown and greenish-brown below. In the large intestine
they are of a dark greenish hue, and pasty in consistency ; and the
contents of this portion of the alimentary canal have received the
name of meconium, from their resemblance to inspissated poppy-
juice. The meconium contains a large quantity of fat, as well as
various insoluble substances, probably the residue of epithelial and
mucous accumulations. It does not contain, however, any trace of
the biliary substances (tauro-cholates and glyko-cholates) when care-
fully examined by Pettenkofer's test ; and cannot therefore properly
be regarded, as is sometimes incorrectly asserted, as resulting from
the accumulation of bile. In the contents of the small intestine, on
the contrary, traces of bile may be found, according to Lehmann,1
so early as between the fifth and sixth months. We have also
found distinct traces of bile in the small intestine at birth, but it is
even then in extremely small quantity, and is sometimes altogether
absent.

The meconium, therefore, and the intestinal contents generally,
are not composed principally, or even to any appreciable extent, of
the secretions of the liver. They appear rather to be produced by
the mucous membrane of the intestine itself. Even their yellowish
and greenish color does not depend on the presence of bile, since
the yellow color first shows itself, in very young foetuses, about
the middle of the small intestine, and not at its upper extremity.
The material which accumulates afterward appears to extend from
this point upward and downward, gradually filling the intestine,
and becoming, in the ileum and large intestine, darker and more
pasty as gestation advances.

It is a singular fact, perhaps of some importance in this connec-
tion, that the amniotic fluid, during the latter half of fcetal life,
finds its way, in greater or less abundance, into the stomach, and
through that into the intestinal canal. Small cheesy-looking masses
may sometimes be found at birth in the fluid contained in the
stomach, which are seen on microscopic examination to be no other
than portions of the vernix caseosa exfoliated from the skin into
the amniotic cavity, and afterward swallowed. According to Kol-
liker,2 the soft downy hairs of the foetus, exfoliated from the skin,

' Physiological Chemistry, Philadelphia edition, vol. i. p. 532.
2 Gewebelehre. Leipzig, 1?52, p. 139.

AND ITS APPENDAGES. 649

are often swallowed in the same way, and may be found in the
meconium.

The gastric juice is not secreted before birth ; the contents of the
stomach being generally in small quantity, clear, nearly colorless,
and neutral or alkaline in reaction.

The liver is developed at a very early period. Its size in pro-
portion to that of the entire body is, in fact, very much greater in
the early months than at birth or in the adult condition. In the
foetal pig we have found the relative size of the liver greatest
within the first month, when it amounts to very nearly 12 per cent.
of the entire weight of the body. Afterward, as it grows less rapidly
than other parts, its relative weight diminishes successively to 10
per cent, and 6 per cent. ; and is reduced before birth to 3 or 4 per
cent. In the human subject, also, the weight of the liver at birth
is between 3 and 4 per cent, of that of the entire body.

The secretion of bile takes place, as we have intimated above,
during foetal life, in a very scanty manner. We have found it, in
minute quantity, in the gall-bladder, as well as in the small intes-
tine at birth ; but it does not probably take any active part in the
nutritive or other functions of the foetus before that period.

The glycogenic function of the liver commences during foetal life,
and at birth the tissue of the organ is abundantly saccharine. It is
remarkable, however, that in the early periods of gestation sugar is
produced in the foetus from other sources than the liver. In very
young foetuses of the pig, for example, both the allantoic and
amniotic fluids are saccharine, a considerable time before any sugar
makes its appearance in the tissue of the liver. Even the urine, in
half-grown foetal pigs, contains an appreciable quantity of sugar,
and the young animal is therefore, at this period, in a diabetic con-
dition. This sugar, however, disappears from the urine before birth
and also from the amniotic fluid, as has been ascertained by M. Ber-
nard j1 while the liver begins to produce a saccharine substance, and
to exercise the glycogenic function, which it continues after birth.

Development of the Pharynx, (Esophagus, &c. — We have already
seen that the intestinal canal consists at first of a cylindrical tube
terminated at each extremity of the abdominal cavity by a rounded
cul-de-sac (Fig. 241, c, c) ; and that the openings of the mouth and
anus are subsequently formed by perforations which take place
through the integument and the intervening tissues, and so estab-

: Levonsde Physiologic Experira^ntale, Paris, 1855, p. 398.

650 DEVELOPMENT OF THE ALIMENTARY CANAL

lish a communication with the intestinal tube. The formation of
the anterior perforation, and its appendages, takes place in the fol-
lowing manner : —

After the early development of the intestinal tube in the mode
above described, the head increases in size out of all proportion to
the remainder of the foetus, projecting as a large rounded mass from
the anterior extremity of the body, and containing the brain and the
organs of special sense. This portion soon bends over toward the
abdomen, in consequence of the increasing curvature of the whole
body which takes place at this time. In the interior of this
cephalic mass there is now formed a large cavity (Fig. 241, d), by
the melting down and liquefaction of a portion of its substance.
This cavity is the pharynx. It corresponds by its anterior extre-
mity to the future situation of the mouth ; and by its posterior
portion to the upper end of the intestinal canal, the future situation
of the stomach. It is still, however, closed on all sides, and does
not as yet communicate either with the exterior or with the cavity
of the stomach. There is, accordingly, at this time, no thorax
whatever ; but the stomach lies at the upper extremity of the abdo-
men, immediately beneath the lower extremity of the pharynx, from
which it is separated by a wall of intervening tissue.

Subsequently, a perforation takes place between the adjacent
extremities of the pharynx and stomach, by a short narrow tube,
the situation of which is marked by the dotted lines x, in Fig. 241.
This tube afterward lengthens by the rapid growth of that portion
of the body in which it is contained, and becomes the cesophagm.
Neither the pharynx nor oesophagus, therefore, are, properly speak-
ing, parts of the intestinal canal, formed from the internal layer of
the blastodermic membrane ; but are, on the contrary, formations
of the external layer, from which the entire cephalic mass is pro-
duced. The lining membrane of the pharynx and oesophagus is to
be regarded, also, for the same reason, as rather a continuation of
the integument than of the intestinal mucous membrane ; and even
in the adult, the thick, whitish, and opaque pavement epithelium
of the oesophagus may be seen to terminate abruptly, by a well-
defined line of demarkation, at the cardiac orifice of the stomach ;
beyond which, throughout the remainder of the alimentary canal,
the epithelium is of the columnar variety, and easily distinguish-
able by its soft, ruddy, and transparent appearance.

As the oesophagus lengthens, the lungs are developed on each
side of it by a protrusion from the pharynx which extends and

AND ITS APPENDAGES. 651

becomes repeatedly subdivided, forming the bronchial tubes and
their ramifications. At first, the lungs project into the upper
part of the abdominal cavity ; for there is still no distinction be-
tween the chest and abdomen. Afterward, a horizontal partition
begins to form on each side, at the level of the base of the lungs,
which gradually closes together at a central point, so as to form
the diaphragm, and finally shuts off altogether the cavity of
the chest from that of the abdomen. Before the closure of the
diaphragm, thus formed, is complete, a circular opening exists on
each side the median line, by which the peritoneal and pleural
cavities communicate with each other. In some instances the de-
velopment of the diaphragm is arrested at this point, either on one
side or the other, and the opening accordingly remains permanent.
The abdominal organs then partially protrude into the cavity of
the chest on that side, forming congenital diaphragmatic hernia.
The lung on the affected side also usually remains in a state of
imperfect development. Diaphragmatic hernia of this character is
more frequently found upon the left side than upon the right. It
may sometimes continue until adult life without causing any seri-
ous inconvenience.

The heart is formed, at a very early period, directly in front of
the situation of the oesophagus. Its size soon becomes very large
in proportion to the rest of the body ; so that it protrudes beyond
the level of the thoracic parietes, covered only by the pericardium.
Subsequently, the walls of the thorax, becoming more rapidly
developed, grow over it and inclose it. In certain instances, how-
ever, they fail to do so, and the heart then remains partially or
completely uncovered, in front of the chest, presenting the condition
known as ectopia cordis. This malformation is necessarily latal.

Development of the Face. — While the lower extremity of the
pharynx communicates with the cavity of the stomach, as above
described, its upper extremity also becomes perforated in a similar
manner, and establishes a communication with the exterior. This
perforation is at first wide and gaping. It afterward becomes
divided into the mouth and nasal passages ; and the different parts
of the face are formed round it in the following manner : —

From the sides of the cephalic mass five buds or processes shoot
out, and grow toward each other, so as to approach the centre of
the oral orifice above mentioned. (Fig. 243.) One of them grows
directly downward from the frontal region (i), and is called the
frontal or intermaxillary process, because it afterward contains in

652

DEVELOPMENT OF THE ALIMENTARY CANAL

Fig. 243.

HEAD OF HUMAN EMBKYO,
at about the twentieth day. After
Longet ; from a specimen in the
collection of M. Coste.— 1. Frontal
or intermaxillary process. 2. Pro-
cess of superior maxilla. 3. Pro-
cess of inferior maxilla.

its lower extremity the intermaxillary bones, in which the incisor
teeth of the upper jaw are inserted. The next process (2) origin-
ates from the side of the opening, and, advancing toward the median

line, forms, with its fellow of the opposite
side, the superior maxilla. The processes
of the remaining pair (3) also grow from
the side, and form, by their subsequent
union upon the median line, the inferior
maxilla. The inferior maxillary bone is
finally consolidated, in man, into a single
piece, but remains permanently divided,
in the lower animals, by a suture upon the
median line.

As the frontal process grows from above
downward, it becomes double at its lower
extremity, and at the same time two off-
shoots show themselves upon its sides,
which curl round and inclose two circular
orifices, the opening of the anterior nares ; the offshoots themselves
becoming the alse nasi. (Fig. 244.) The mouth at this period is
very widely open, owing to the imperfect development of the upper

and lower jaw, and the incomplete
formation of the lips and cheeks.

The processes of the superior max-
illa continue their growth, but less
rapidly than those of the inferior ; so
that the two sides of the lower jaw
are already consolidated with each
other, while those of the upper jaw
are still separate.

As the processes of the superior
maxilla continue to enlarge, they also
tend to unite with each other on the
median line, but are prevented from
doing so by the intermaxillary pro-
cesses which grow down between them. They then unite with the
intermaxillary processes, which have at the same time united with
each other, and the upper jaw and lip are thus completed. (Fig.
245.) The external edge of the ala nasi also adheres to the superior
maxillary process and unites with it, leaving only a curved crease

Fig. 244.

H E A D O F H LT M A X E M B R Y O at about

the sixth week. From a specimen iu the
author's possession.

AXD ITS APPENDAGES. 653

or furrow, as a sort of cicatrix, to mark the line of union between
them.

Sometimes the superior maxillary and the intermaxillary pro-
cesses fail to unite with each other; and we then have the mal-
formation known as hare-lip. The
fissure of hare-lip, consequently, as a
general rule, is not situated exactly in
the median line, but a little to one side
of it, on the external edge of the inter-
maxillary process. Occasionally, the
same deficiency exists on both sides,
producing "double hare-lip ;" in whicli
case, if the fissures extend through
the bony structures, the central piece
of the superior maxilla, which is de-
tached from the remainder, contains HEAD OF HCMA* EMBRYO, about

i r, . m ' m thp eud of the second month. — From a

the four upper incisor teeth, and cor- specimen ln the anthor,s P098e8siou.
responds with the intermaxillary bone

of the lower animals. In some rare instances the fissure of hare-
lip is situated in the median line, the two intermaxillary bones
never having united with each other. A case of this kind has
been observed by Prof. Jeffries Wyman.1

The eyes at an early period are situated upon the sides of the
head, so that they cannot be seen in an anterior view. (Fig. 243.)
As development proceeds, they come to be situated farther forward
(Fig. 244), their axes being divergent and directed obliquely for-
ward and outward. At a later period still they are placed on the
anterior plane of the face (Fig. 245), and have their axes nearly
parallel and looking directly forward. This change in the situa-
tion of the eyes is effected by the more rapid growth of the pos-
terior and lateral parts of the head, which enlarge in such a manner
as to alter the relative position of the parts seated in front of them.

The palate is formed by a septum between the mouth and nares,
which arises on each side as a horizontal plate or offshoot from the
superior maxilla. These two plates afterward unite with each
other upon the median line, forming a complete partition between
the oral and nasal cavities. The right and left nasal passages are
also separated from each other by a vertical plate (vomer), which
grows from above downward and fuses with the palatal plates be-

1 Transactions Boston Soc.ety for Medical Improvement, March 9th, 1863.

654 DEVELOPMENT OF THE ALIMENTARY CANAL, ETC.

low. Fissure of the palate is caused by a deficiency, more or less
complete, of one of the horizontal maxillary plates. It is accord-
ingly situated a little on one side of the median line, and is fre-
quently associated with hare-lip and fissure of the upper jaw. The
fissures of the palate and of the lip are very often continuous with
each other.

The anterior and posterior pillars of the fauces are incomplete
vertical partitions, which grow from the sides of the oral cavity,
and tend to separate, by a slight constriction, the cavity of the
mouth from that of the pharynx.

When all the above changes are accomplished, the pharynx,
oesophagus, mouth, nares, and fauces, with their various projections
and divisions, have been successively formed ; and the development
of the upper part of the alimentary canal is then complete.

DEVELOPMENT OF THE KIDXEYS.

655

CHAPTER XVI.

Fig. 246.

DEVELOPMENT OF THE KIDNEYS, WOLFFIAN
BODIES, AND INTERNAL ORGANS OF GENE-
RATION.

THE first trace of a urinary apparatus in the embryo, consists of
two long, fusiform bodies, which make their appearance in the ab-
domen at a very early period, situated on each side the spinal
column. These are known by the name of the Wolffian bodies.
They are fully formed in the human subject, toward the end of the
first month (Coste), at which time they are the largest organs in the
cavity of the abdomen, extending from just below the heart, nearlv
to the posterior extremity of the body. In the foetal pig, when a
little over half an inch in length (Fig. 246), the Wolffian bodies are
rounded and kidney-shaped, and occupy a
very large part of the abdominal cavity.
Their importance may be estimated from the
fact that their weight at this time is equal to
a little over ^ of that of the entire body — a
proportion which is seven or eight times as
large as that of the kidneys in the adult
condition. There are, indeed, at this period
only three organs perceptible in the abdo-
men, viz., the liver, which has begun to be
formed at the upper part of the abdominal
cavity ; the intestine, which is already some-
what convoluted, and occupies its central
portion ; and the Wolffian bodies, which pro-
ject on each side the spinal column.

The Wolffian bodies, in their intimate

structure, closely resemble the adult kidney. They consist of
secreting tubules, lined with epithelium, which run from the outer
toward the inner edge of the organ, terminating at their free ex-

FCETAL Pro, % of an inch
long; from a specimen in the
author's possession. 1. Heart.
2. Anterior extremity. 3. Pos-
terior extremity. 4. Wolffian
boily. The abdominal walls
have been cut away, in on'.er
to show the position of the
Wolffian bodies

656 DEVELOPMENT OF THE KIDNEYS.

tremities in small rounded dilatations. Into each of these dilated
extremities is received a globular coil of capillary bloodvessels, or
glomerulus, similar to that of the adult kidney. The tubules of the
Wolffian body all empty into a common excretory duct, which leaves
the organ at its lower extremity, and communicates afterward with
the lower part of the intestinal canal, just at the point where the
diverticulum of the allantois is given off, and where the urinary
bladder is afterward to be situated. The principal, if not the
only distinction, between the minute structure of the Wolffian
bodies and that of the true kidneys, consists in the size of the
tubules and of their glomeruli, these elements being considerably
larger in the Wolffian body than in the kidney. In the foetal
pig, for example, when about an inch and a half in length, the
diameter of the tubules of the Wolffian body is 2 /, 0 of an inch,
while in the kidney of the same foetus, the diameter of the tubules
is only ^\^ of an inch. The glomeruli in the Wolffian bodies
measure ^ of an inch in diameter, while those of the kidney mea-
sure only y^ of an inch. The Wolffian bodies are therefore urinary
organs, so far as regards their anatomical structure, and are some-
times known, accordingly, by the name of the "false kidneys."
There is little doubt that they perform, at this early period, a func-
tion analogous to that of the kidneys, and separate from the blood
of the embryo an excrementitious fluid which is discharged by the
ducts of the organ into the cavity of the allantois.

'Subsequently, the Wolffian bodies increase for a time in size,
though- not so rapidly as the rest of the body ; and consequently
their relative magnitude diminishes. Still later, they begin to
suffer an absolute diminution or atrophy, and become gradually
less and less perceptible. In the human subject, they are hardly
to be detected after the end of the second month (Longet), and in
the quadrupeds also they completely disappear long before birth.
They are consequently foetal organs, destined to play an important
part during a certain stage of development, but to become after-
ward atrophied and absorbed, as the physiological condition of the
foetus alters. During the period, however, of their retrogression
and atrophy, other organs appear in their neighborhood, which
become afterward permanently developed. These are, first, the
kidneys, and secondly, the internal organs of generation.

The kidneys are formed just behind the Wolffian bodies, and are
at first entirely concealed by them in a front view, the kidneys
being at this time not more than a fourth or a fifth part the size of

WOLFFIAN BODIES.

657

Fig. 2 7.

the Wolffian bodies. (Fig. 247.) As the kidneys, however, subse-
quently enlarge, while the Wolffian bodies diminish, the propor-
tions existing between the two organs are
reversed ; and the Wolffian bodies at last
come to be mere small rounded or ovoid
masses, situated on the anterior surface
of the kidneys. (Figs. 248 and 249.) The
kidneys, during this period, grow more
rapidly in an upward than in a downward
direction, so that the Wolffian bodies
come to be situated near their inferior
extremity, and seem to have performed
a sliding movement from above down-
ward, over their anterior surface. This F(KTAL Pl0t one and B balf
apparent sliding movement, or descent inrhPH lon*- From a "P^imea in

P , _Tr . „ , ,. . . . . the author's possession.— 1. Wolffi.. a

of the \\ olffian bodies, is owing entirely body. 2 Kidney,
to the rapid growth of the kidneys in an
upward direction, as we have already explained.

The kidneys, during the succeeding periods of foetal life, become
in their turn very largely developed in proportion to the rest of the
organs ; attaining a size, in the foetal pig, equal to 7'? (in weight)
of the entire body. This proportion, however, diminishes again
very considerably before birth, owing
to the increased development of other
parts. In the human foetus at birth,
the weight of the two kidneys taken
together is T£g that of the entire
body.

Internal Organs of Generation. —
About the same time that the kidneys
are formed behind the Wolffian bodies,
two oval-shaped organs make their
appearance in front, on the inner side of
the Wolffian bodies and between them
and the spinal column. These bodies are
the internal organs of generation ; viz.,
the testicles in the male, and the ovaries
in the female. At first they occupy

precisely the same situation and present precisely the same appear-
ance, whether the foetus is afterward to belong to the male or the
female sex. (Fig. 243.)
42

Fig. 248.

INTERNAL GROANS OF GENE-
RATION, &c ; in a foetal pig three
inches long. From a specimen in the
author's possession. — 1, 1 Kidneys.
2,2. Wolffian bodies. 3,3. Internal
organ* of generation ; te^ticl^s or
ovaries. 4. Urinary bladder turned
over in front. 5. Intestine.

653 DEVELOPMENT OF THE KIDNEYS.

A short distance above the internal organs of generation there
commences, on each side, a narrow tube or duct, which runs from
above downward along the anterior border of the Wolfnan body,
immediately in front of and parallel with the excretory duct of this
organ. The two tubes, right and left, then approach each other
below ; and, joining upon the median line, empty, together with
the ducts of the Wolffian bodies, into the base of the allantois, or
what will afterward be the base of the urinary bladder. These tubes
serve as the excretory ducts of the internal organs of generation ;
and will afterward become the vasa deferentia in the male, and the
Fallopian tubes in the female. According to Coste, the vasa defe-
rentia at an early period are disconnected with the testicles ; and
originate, like the Fallopian tubes, by free extremities, presenting
each an open orifice. It is only afterward, according to the same
author, that the vasa deferentia become adherent to the testicles, and
a communication is established between them and the tubuli semi-
niferi. In the female, the Fallopian tubes remain permanently
disconnected with the ovaries, except by the edge of the fimbriated
extremity ; which in many of the lower animals becomes closely
adherent to the ovary, and envelopes it more or less completely.

Male Organs of Generation ; Descent of the Testicles. — In the male
foetus there now commences a movement of translation, or change
of place, in the internal organs of generation, which is known as
the "descent of the testicles." In consequence of this movement,
the above organs, which are at first placed near the middle of the
abdomen, and directly in front of the kidneys, come at last to be
situated in the scrotum, altogether outside and below the abdominal
cavity. They also become inclosed in a distinct serous sac of their
own, the tunica vaginalis testis. This apparent movement of the
testicles is accomplished in the same manner as that of the Wolf-
fian bodies, above mentioned, viz., by a disproportionate growth of
the middle and upper portions of the abdomen and of the organs
situated above the testicles, so that the relative position of these
organs becomes altered. The descent of the testicles is accompanied
by certain other alterations in the organs themselves and their
appendages, which take place in the following manner.

By the upward enlargement of the kidneys, both the Wolfnan
bodies and the testicles are soon found to be situated near the
lower extremity of these organs. (Fig. 249.) At the same time, a
slender rounded cord (not represented in the figure) passes from
the lower extremity of each testicle in an outward and downward

MALE ORGANS OF GENERATION.

659

Fig. 249.

INTERNAL ORGANS OF GENERATION,
&c., in a foetal pig nearly four inches long.
From a specimen in the author's possession. —
1, 1. Kidneys. 2, 2. Wolffian bodies. 3, 3.
Testicles. 4. Urinary bladder. 5. Intestine.

direction, crossing the corresponding vas deferens a short distance
above its union with its fellow of the opposite side. Below this
point, the cord spoken of continues to run obliquely outward and
downward; and, passing through
the abdominal walls at the situa-
tion of the inguinal canal, is in-
serted into the subcutaneous tis-
sues near thesymphysis pubis.
The lower part of this cord be-
comes the gubernaculum testis ; and
muscular fibres are soon developed
in its substance which may be
easily detected, even in the human
foetus, during the latter half of
gestation. At the period of birth,
however, or soon afterward, these
muscular fibres disappear and can
no longer be recognized.

All that portion of the excre-
tory tube of the testicle which is situated outside the crossing of the
gubernaculum, is destined to become afterward convoluted, and
converted into the epididymis. That portion which is situated in-
side the same point remains comparatively straight, but becomes
considerably elongated, and is finally known as the vas deferens.

As the testicles descend still farther in the abdomen, they con-
tinue to grow, while the Wolffian bodies, on the contrary, diminish
rapidly in size, until the latter become much smaller than the tes-
ticles ; and at last, when the testicles have arrived at the internal
inguinal ring, the Wolffian bodies have altogether disappeared, or
at least have become so much altered that their characters are no
longer recognizable. In the human foetus, the testicles arrive at
the internal inguinal ring, about the termination of the sixth month
(Wilson).

During the succeeding month, a protrusion of the peritoneum
takes place through the inguinal canal, in advance of the testicle ;
while the last named organ still continues its descent. As it then
passes downward into the scrotum, certain muscular fibres are given
off from the lower border of the internal oblique muscle of the
abdomen, growing downward with the testicle, in such a manner as
to form a series of loops upon it, and upon the elongating spermatic
cord. These loops constitute afterward the cremaster muscle.

660 DEVELOPMENT OF THE KIDNEYS,

At last, the testicles descend fairly to the bottom of the scrotum,
the gubernaculum constantly shortening, and the vas deferens
elongating as it proceeds. The convoluted portion of the efferent
duct, viz., the epididymis, then remains closely attached to the body
of the testicle; while the vas deferens passes upward, in a reverse
direction, enters the abdomen through the inguinal canal, again
bends downward, and joins its fellow of the opposite side ; after
which they both open into the prostatic portion of the urethra by
distinct orifices, situated on each side the median line. At the
same time, two diverticula arise from the median portion of the
vasa deferentia, and, elongating in a backward direction, underneath
the base of the bladder, become developed into two compound
sacculated reservoirs — the vesiculss seminales.

The left testicle is a little later in its descent than the right, but
it afterward passes farther into the scrotum, and, in the adult condi-
tion, usually hangs a little lower than its fellow of the opposite side.
After the testicle has fairly passed into the scrotum, the serous
pouch, which preceded its descent, remains for a time in communi-
cation with the peritoneal cavity. In many of the lower animals,
as, for example, the rabbit, this condition is permanent ; and the
testicle, even in the adult animal, may be alternately drawn down-

ward into the scrotum, or retracted into
Fig. 250. the abdomen, by the action of the guber-

naculum and the cremaster muscle. But
in the human foetus, the two opposite
surfaces of the peritoneal pouch, covering
the testicle, approach each other at the
inguinal canal, forming at that point a
constriction or neck, which partly shuts
off the testicle from the cavity of the
abdomen. By a continuation of this pro-
cess, the serous surfaces come actually
Formation of TCNICA VA- in contact with each other, and, adhering

OINALIS TKSTIS.— 1. Testicle , , . ,,-,. ~^n

nearly at the bottom of the Hero- together at thlS Situation (Fig. 2oO, 4),

turn. 2 Cavity of tnnica va^nnlis. form a k^ Qf CicatriX, Or UmbilicUS, bv

:* Cavity of peritoneum. 4. Obliter- i i

peritoneal «ac. the complete closure and consolidation of

which the cavity of the tunica vaginalis
(vj) is finally shut off altogether from the general cavity of the
peritoneum (3). The tunica vaginalis testis is, therefore, originally
a part of the peritoneum, from which it is subsequently separated
by the process just described.

FEMALE GROANS OF GENERATION. 661

The separation of the tunica vaginalis from the peritoneum is
usually completed in the human subject before birth. But some-
times it fails to take place at the proper time, and the intestine is
then apt to protrude into the scrotum, in front of the spermatic
cord, giving rise, in this way, to a congenital inguinal hernia. (Fig.
251.) The parts implicated, however, in this malformation, have
still, as in the case of congenital umbili-
cal hernia, a tendency to unite with each Fig. 251.
other and obliterate the unnatural open-
ing; and if the intestine be retained by
pressure in the cavity of the abdomen,
cicatrization usually takes place at the
inguinal canal, and a cure is effected.

The descent of the testicle, above de-
scribed, is not accomplished by the forci-
ble traction of the muscular fibres of the
gubernaculum, as has been described by

Certain Writers, but by a Simple prOCeSS C ox G KMT Ail* GTTT. VAT, HKR-
f> .1^1- i • T /v» KIA. — 1. Testicle. 2,2,2. lutes-

of growth taking place in different parts, tiue.
in different directions, at successive

periods of foetal life. The gubernaculum, accordingly, has no
proper function as a muscular organ, in the human subject, but is
merely the anatomical vestige, or analogue, of a corresponding
muscle in certain of the lower animals, where it has really an
important function to perform. For in them, as we have already
mentioned, both the gubernaculum and the cremaster remain fully
developed in the adult condition, and are then employed to elevate
and depress the testicle, by the alternate contraction of their mus-
cular fibres.

Female Organs of Generation. — At an early period, as we have
mentioned above, the ovaries have the same external appearance,
and occupy the same position in the abdomen, as the testicles in the
opposite sex. The descent of the ovaries also takes place, to a great
extent, in the same manner with the descent of the testicles. When.
in the early part of this descent, they have reached the level of the
lower edge of the kidneys, a cord, analogous to the gubernaculum,
may be seen proceeding from their lower extremity, crossing the
efferent duct on each side, and passing downward, to be attached
to the subcutaneous tissues at the situation of the inguinal ring.
That part of the duct situated outside the crossing of this cord,
becomes afterward convoluted, and is converted into the Fallopian

662 DEVELOPMENT OF THE KIDNEYS, ETC.

tube; while that point which is inside the same point, becomes con-
verted into the uterus. The upper portion of the cord itself becomes
the liyament of the ovary ; its lower portion, the round ligament of
the uterus.

As the ovaries continue their descent, they pass below and be-
hind the Fallopian tubes, which necessarily perform at the same
time a movement of rotation, from before backward and from
above downward ; the whole, together with the ligaments of the
ovaries and the round ligaments, being enveloped in double folds
of peritoneum, which enlarge with the growth of the parts them-
selves, and constitute finally the broad ligaments of the uterus.

It will be seen from what has been said above, that the situation
occupied by the Wolffian bodies in the female is always the space
between the ovaries and the Fallopian tubes; for the Wolffian
bodies accompany the ovaries in their descent, just as, in the male,
they accompany the testicles. As these bodies now become grad-
ually atrophied, their glandular structure disappears altogether;
but their bloodvessels, in many instances, remain as a convoluted
vascular plexus, occupying the situation above mentioned. The
Wolman bodies may therefore be said, in these instances, to un-
dergo a kind of vascular degeneration. This peculiar degeneration
is quite evident in the Wolffian bodies of the foetal pig, some time
before the organs have entirely lost their original form. In the
cow, a collection of convoluted bloodvessels may be seen, even in
the adult condition, near the edge of the ovary, and between the
two folds of peritoneum forming the broad ligament. These are
undoubtedly vestiges of the Wolffian bodies, which have undergone
the vascular degeneration above described.

While the above changes are taking place in the adjacent organs,
the two lateral halves of the uterus fuse with each other more and
more upon the median line, and become covered with an exces-
sively developed layer of muscular fibres. In the lower animals,
the uterus remains divided at its upper portion, running out into
two long conical tubes or cornua (Fig. 182), presenting the form
known as the uterus bicornis. In the human subject, however, the
fusion of the two lateral halves of the organ is nearly complete ;
so that the uterus presents externally a rounded, but somewhat
flattened and triangular figure (Fig. 183), with the ligaments of the
ovary and the round ligaments passing off from its superior angles.
But, internally, the cavity of the organ still presents a strongly
marked triangular form, the vestige of its original division.

FEMALE ORGANS OF GENERATION. 663

Occasionally the human uterus, even in the adult condition re-
mains divided into two lateral portions by a vertical septum, which
runs from the middle of its fundus downward toward the os in-
ternum. This septum may even be accompanied by a partial
external division of the organ, corresponding with it in direction
and producing the malformation known as "uterus bicornis." or
" double uterus."

The os internum and os externum are produced by partial con-
strictions of the original generative passage ; and the anatomical
distinctions between the body of the uterus, the cervix and the
vagina, are produced by the different development of the mucous
membrane and muscular tunic in its corresponding portions.
During foetal life, however, the neck of the uterus grows much
faster than its body; so that, at the period of birth, the entire
organ is very far from presenting the form which it exhibits in the
adult condition. In the human fcetus at term, the cervix uteri
constitutes nearly two-thirds of the entire length of the organ;
while the body forms but little over one-third. The cervix, at
this time, is also much larger in diameter than the body; so that
the whole organ presents a tapering form from below upward.
The arbor vitaa uterina of the cervix is at birth very fully de-
veloped, and the mucous membrane of the body is also thrown
into three or four folds which radiate upward from the os internum.
The cavity of the cervix is filled with a transparent semi-solid
mucus.

The position of the uterus at birth is also different from that
which it assumes in adult life ; nearly the entire length of the organ
being above the level of the symphysis pubis, and its inferior
extremity passing below that point only by about a quarter of an
inch. It is also slightly anteflexed at the junction of the body and
cervix. After birth, the uterus, together with its appendages, con-
tinues to descend ; until, at the period of puberty, its fundus is
situated just below the level of the symphysis pubis.

The ovaries at birth are narrow and elongated in form. They
contain at this time an abundance of eggs; each inclosed in a
Graafian follicle, and averaging 5.J? of an inch in diameter. The
vitellus, however, is imperfectly formed in most of them, and in
some is hardly to be distinguished. The Graafian follicle at this
period envelopes each egg closely, there being nothing between its
internal surface and the exterior of the egg, excepting the thin
layer of cells forming the "membrana granulosa." Inside this

664 DEVELOPMENT OF THE KIDNEYS, ETC.

layer is to be seen the germinative vesicle, with the germinative
spot, surrounded by a faintly granular vitellus, more or less
abundant in different parts. Some of the Graafian follicles con-
taining eggs are as large as 4^ of an inch; others as small as 7^55.
In the very smallest, the cells of the membrana granulosa appear
to fill entirely the cavity of the follicle, and no vitellus or germina-
tive vesicle is to be seen.

DEVELOPMENT OF THE CIRCULATORY APPARATUS. 665

CHAPTER XVII.

DEVELOPMENT OF THE CIRCULATORY
APPARATUS.

THERE are three distinct forms or phases of development assumed
by the circulatory system during different periods of life. These
different forms of the circulation are intimately connected with the
manner in which nutrition and respiration, or the renovation of the
blood, are accomplished at different epochs ; and they follow each
other in the progress of development, as different organs are em-
ployed in turn to accomplish the above functions. The first form
is that of the vitelline circulation, which exists at a period when the
vitellus, or the umbilical vesicle, is the sole source of nutrition for
the foetus. The second is the placental circulation, which lasts
through the greater part of foetal life, and is characterized by the
existence of the placenta; and the third is the complete or adult
circulation, in which the renovation and nutrition of the blood are
provided for by the lungs and the intestinal canal.

First, or Vitelline Circulation. — It has already been shown, in a
previous chapter, that when the body of the embryo has begun to
be formed in the centre of the blastodermic membrane, a number
of bloodvessels shoot out from its sides, and ramify over the
remainder of the vitelline sac, forming, by their inosculation, an
abundant vascular plexus. The area occupied by this plexus in the
blastodermic membrane around the foetus is, as we have seen, the
" area vasculosa." In the egg of the fowl (Fig. 252), the plexus is
limited, on its external border, by a terminal vein or sinus — the
" sinus terminalis ;" and the blood of the embryo, after circulating
through the capillaries of the plexus, returns by several venous
branches, the two largest of which enter the body near its anterior
and posterior extremities. The area vasculosa is, accordingly, a
vascular appendage to the circulatory apparatus of the embryo,
spread out over the surface of the vitellus for the purpose of absorb-
ing from it the nutritious material requisite for the growth of the

666 DEVELOPMENT OF THE CIRCULATORY APPARATUS.

newly-formed tissues. In the egg of the fish (Fig. 253), the princi-
pal vein is seen passing up in front underneath the head ; while the
arteries emerge all along the lateral edges of the body. The entire

Fig. 252.

Fig. 253.

EGO OF FOWL in process of development, showing area vasculosa, with vitelline circulation,
terminal sinus, &c.

vitellus, in this way, becomes covered with an abundant vascular
network, connected with the internal circulation of the foetus by
arteries and veins.

Very soon, as the embryo and the entire egg increase in size,
there are two arteries and two veins which become
larger than the others, and which subsequently
do the whole work of conveying the blood of
the foetus to and from the area vasculosa. These
two arteries emerge from the lateral edges of
the foetus, on the right and left sides ; while the
two veins re-enter at about the same point, and
nearly parallel with them. These four vessels are
then termed the omphalo-mesenteric arteries and
veins.

The arrangement of the circulatory apparatus
in the interior of the body of the foetus, at this time, is as follows :
The heart is situated at the median line, just beneath the head and
in front of the oesophagus. It receives at its lower extremity the
trunks of the two omphalo-mesenteric veins, and at its upper
extremity divides into two vessels, which, arching over backward,
attain the anterior surface of the vertebral column, and then run
from above downward along the spine, quite to the posterior

EGG OF FISH (Jar
rabacca), showing vitel
line circulation.

PLACEXTAL CIRCULATION.

667

extremity of the foetus. These arteries are called the vertebral
arteries, on account of their course and situation, running parallel
with the vertebral column. They give of£ throughout their course,
many small lateral branches, which supply the body of the foetus,
and also two larger branches — the omphalo-mesenteric arteries —
which pass out, as above described, into the area vasculosa. The
two vertebral arteries remain separate in the upper part of the body,
but soon fuse with each other a little below the level of the heart ;
so that, below this point, there remains afterward but one large
artery, the abdominal aorta, running from above downward along
the median line, giving off the omphalo-mesenteric arteries to the
area vasculosa, and supplying smaller branches to the body, the
walls of the intestine, and the other organs of the foetus.

The above description shows the origin and formation of the first
or vitelline circulation. A change, however, now begins to take
place, by which the vitellus is superseded, as an organ of nutrition,
by the placenta, which takes its place; and the second or placental
circulation becomes established in the following manner : —

Second Circulation. — After the umbilical vesicle has been formed
by the process already described, a part of the vitellus remains in-
cluded in it, while the rest is retained in the abdomen and inclosed
in the intestinal canal. As these

two organs (umbilical vesicle and Fls- 254<

intestine) are originally parts of
the same vitelline sac, they remain
supplied by the same vascular
system, viz : the omphalo-mesen-
teric vessels. Those which remain
within the abdomen of the foetus
supply the mesentery and intes-
tine ; but the larger trunks pass
outward, and ramify upon the
walls of the umbilical vesicle.
(Fig. 254.) At first, there are,
as we have mentioned above,
two omphalo-mesenteric arteries
emerging from the body, and two
omphalo-mesenteric veins return-
ing to it ; but soon afterward, the two arteries are replaced by a
common trunk, while a similar change takes place in the two veins.
Subsequently, therefore, there remains but a single artery and a

Diagram of YOCNG EMBRYO AJTD ITS
VESSELS, showing circulation of umbilical
vesicle, and also that of allantois, beginning to
be formed.

668 DEVELOPMENT OF THE CIRCULATORY APPARATUS.

single vein, connecting the internal and external portions of the
vitelline circulation.

The vessels belonging to this system are therefore called the
omphalo-mesenteric vessels, because a part of them (omphalic ves-
sels) pass outward, by the umbilicus, or " omphalos," to the umbili-
cal vesicle, while the remainder (mesenteric vessels) ramify upon
the mesentery and the intestine.

At first, the circulation of the umbilical vesicle is more import-
ant than that of the intestine ; and the omphalic artery and vein
appear accordingly as large trunks, of which the mesenteric ves-
sels are simply small branches. (Fig. 25-i.) Afterward, however,
the intestine rapidly enlarges, while the umbilical vesicle dimi-
nishes, and the proportions existing between the two sets of vessels
are therefore reversed. (Fig. 255.) The mesenteric vessels then

Fig. 255.

Diagram of EMBRYO AND ITS VESSELS; showing the second circulation. The pharynx,
oesophagus, and intestinal canal, have become further developed, and the mesenteric arteries have
enlarged, while the umbilical vesicle and its vascular branches are very much reduced in size. The
large umbilical arteries are seeu passing out to the placenta.

come to be the principal trunks, while the omphalic vessels are
simply minute branches, running out along the slender cord of the
umbilical vesicle, and ramifying in a few scanty twigs upon its
surface.

DEVELOPMENT OF THE ARTERIAL SYSTEM. 669

In the mean time, the allantois is formed by a protrusion from
the lower extremity of the intestine, which, carrying with it two
arteries and two veins, passes out by the anterior opening of the
body, and comes in contact with the external membrane of the
egg. The arteries of the allantois, which are termed the umbilical
arteries, are supplied by branches of the abdominal aorta ; the um-
bilical veins, on the other hand, join the mesenteric veins, and
empty with them into the venous extremity of the heart. As the
umbilical vesicle diminishes, the allantois enlarges ; and the latter
soon becomes converted, in the human subject, into a vascular
chorion, a part of which is devoted to the formation of the placenta.
(Fig. 255.) As the placenta soon becomes the only source of nutri-
tion for the foetus, its vessels are at the same time very much
increased in size, and preponderate over all the other parts of the
circulatory system. During the early periods of the formation of
the placenta, there are, as we have stated above, two umbilical
arteries and two umbilical veins. But subsequently one of the
veins disappears, and the whole of the blood is returned to the body
of the fcetus by the other, which becomes enlarged in proportion.
For a long time previous to birth, therefore, there are in the umbili-
cal cord two umbilical arteries, and but a single umbilical vein.

Such is the second, or placental circulation. It is exchanged, at
the period of birth, for the third or adult circulation, in which the
blood which had previously circulated through the placenta, is
diverted to the lungs and the intestine. These are the organs
upon which the whole system afterward depends for the nourish-
ment and renovation of the blood.

During the occurrence of the above changes, certain other altera-
tions take place in the arterial and venous systems, which will now
require to be described by themselves.

Development of the Arterial System. — At an early period of deve-
lopment, as we have shown above, the principal arteries pass off
from the anterior extremity of the heart in two arches, which curve
backward on each side, from the front of the body toward the
vertebral column, after which they again become longitudinal in
direction, and receive the name of "vertebral arteries." Very soon
these arches divide successively into two, three, four, and five
secondary arches, placed one above the other, along the sides of
the neck. (Fig. 256.) These are termed the cervical arches. In the
fish, these cervical arches remain permanent, and give off from their
convex borders the branchial arteries, in the form of vascular tufts,

670 DEVELOPMENT OF THE CIRC-ULATORY APPARATUS.

to the gills on each side of the neck ; but in the human subject and
the quadrupeds, the branchial tufts are never developed, and the
cervical arches, as well as the trunks with which they are con-
nected, become modified by the progress of development in the

following manner: —

Fig. 256.

Fig. 257.

Early condition of ARTERIAL SYSTEM:
showing the heart (1), with its two ascend-
ing arterial trunks, giving off on each side
five cervical arches, which terminate in the
vertebral arteries (2, 2). The vertebral arte-
ries unite below the heart to form the
aorta (3).

Adult condition of ARTERIAL SYS-
TEM.—1,1. Carotids. 2, 2. Vertebrals.
3, 3. Right and left subclavians. 4, 4.
Right and left superior intercostals. 5.
Left aortic arch, which remains perma-
nent. 6. Right aortic arch, which dis-
appears.

The two ascending arterial trunks on the anterior part of the
neck, from which the cervical arches are given off] become con-
verted into the carotids. (Fig. 257, 1,1.) The fifth, or uppermost
cervical arch, remains at the base of the brain as the inosculation,
through the circle of Willis, between the internal carotids and the
basilar artery, which is produced by the union of the two verte-
brals. The next, or fourth cervical arch, may be recognized in an
inosculation which is said to be very constant between the superior
thyroid arteries, branches of the carotids, and the inferior thyroids,
which come from the subclavians at nearly the same point from
which the vertebrals are given off. The next, or third cervical arch,
remains on each side, as the subclavian artery (3, 3). This vessel,

DEVELOPMENT OF THE ARTERIAL SYSTEM. 671

though at first a mere branch of communication between the caro-
tid and the vertebral, has now increased in size to such an extent
that it has become the principal trunk, from which the vertebral
itself is given off as a small branch. Immediately below this point'
of intersection, also, the vertebral artery diminishes very much in
relative size, loses its connection with the abdominal aorta, and
supplies only the first two intercostal spaces, under the name of the
superior intercostal artery (4, 4). The second cervical arch becomes
altered in a very different manner on the two opposite sides. On
the left side, it becomes enormously enlarged, so as to give off, as
secondary branches, all the other arterial trunks which have been
described, and is converted in this manner into the arch of the
aorta (o). On the right side, however, the corresponding arch (e)
becomes smaller and smaller, and at last altogether disappears ; so
that, finally, we have only a single aortic arch, projecting to the
left of the median line, and continuous with the thoracic and abdo-
minal aorta.

The first cervical arch remains during foetal life upon the left
side, as the " ductus arteriosus," presently to be described. In the
adult condition, however, it has disappeared equally upon the right
and left sides. In this way the permanent condition of the arterial
circulation is gradually established in the upper part of the body.

Corresponding changes take place, however, during the same
time, in the lower part of the body. Here the abdominal aorta
runs undivided, upon the median line, quite to the end of the
spinal column; giving off" on each side successive lateral branches,
which supply the intestine and the parietes of the body. When
the allantois begins to be developed, two of these lateral branches
accompany it, and become, consequently, the umbilical arteries.
These two vessels increase so rapidly in size, that they soon appear
as divisions of the aortic trunk ; while the original continuation of
this trunk, running to the end of the spinal column, appears only
as a small branch given off at the point of bifurcation. When the
lower limbs begin to be developed, they are supplied by two small
branches, given off from the umbilical arteries near their origin.

Up to this time the pelvis and posterior extremities are but
slightly developed. Subsequently, however, they grow more
rapidly, in proportion to the rest of the body, and the arteries
which supply them increase in a corresponding manner. That
portion of the umbilical arteries, lying between the bifurcation of
the aorta and the origin of the branches going to the lower ex-

672 DEVELOPMENT OF THE CIRCULATORY APPARATUS.

tremities, becomes the common iliacs, which in their turn afterward
divide into the umbilical arteries proper, and the femorals. Sub-
sequently, by the continued growth of the pelvis and lower
extremities, the relative size of their vessels is still further in-
creased ; and at last the arterial system in this part of the body
assumes the arrangement which belongs to the latter periods of
gestation. The aorta divides, as before, into the two common iliacs.
These also divide into the external iliacs, supplying the lower ex-
tremities, and the internal iliacs, supplying the pelvis; and this
division is so placed that the umbilical or hypogastric arteries arise
from the internal iliacs, of which they now appear to be secondary
branches.

After the birth of the foetus, and the separation of the placenta,
the hypogastric arteries become partially atrophied, and are con-
verted, in the adult condition, into solid, rounded cords, running
upward toward the umbilicus. Their lower portion, however,
remains pervious, and gives off arteries supplying the urinary
bladder. The obliterated hypogastric arteries, therefore, the rem-
nants of the original umbilical or allantoic arteries, run upward
from the internal iliacs along the sides of the
Fig. 258. urinary bladder, which is the remnant of the ori-

ginal allantois itself. The terminal continuation
of the original abdominal aorta, is the arteria
sacra media, which, in the adult, runs downward
on the anterior surface of the sacrum, supplying
branches to the rectum and the anterior sacral

nerves.

Development of the. Venous System. — According
to the observations of M. Coste, the venous system
at first presents the same simplicity and symmetry
with the arterial. The principal veins of the
body consist of two long venous trunks, the ver-
tebral veins (Fig. 258), which run along the sides
of the spinal column, parallel with the vertebral
arteries. They receive in succession all the inter-
Eariy condition of VK- costal veins, and empty into the heart by two

>ous SYSTEM; show- 1,1 t n -t ,1 t /• XT •

ing the vertebral veins lateral trunks of equal size, the canals of Cuvier.
emptying into the heart When the inferior extremities become developed,

hy two lateral trunks, . . . . . .

the "canals of cuvier." their two veins, returning from below, join the

vertebral veins near the posterior portion of the

body ; and, crossing them, afterward unite with each other, thus

DEVELOPMENT OF THE VEXOUS SYSTEM.

673

constituting another vein of new formation
(Fig. 259, a), which runs upward a little to the
right of the median line, and empties by itself
into the lower extremity of the heart. The
two branches, by means of which the veins of
the lower extremities thus unite, become after-
ward, by enlargement, the common iliac veins ;
while the single trunk (a) resulting from their
union becomes the vena cava inferior. Subse-
quently, the vena cava inferior becomes very
much larger than the vertebral veins ; and its
two branches of bifurcation are afterward re-
presented by the two iliacs.

Above the level of the heart, the vertebral
and intercostal veins retain their relative size
until the development of the superior extremi-
ties has commenced. Then two of the inter-
costal veins increase in diameter (Fig. 259), and
become converted into the right and left sub-
clavians; while those portions of the vertebral
veins situated above the subclavians become the
right and left jugulars. Just below the junction
of the jugulars with the subclavians, a small
branch of communication now appears between
the two vertebrals(Fig. 259, b), passing over from
left to right, and emptying into the right verte-
bral vein a little above the level of the heart ; so
that a part of the blood coming from the left side
of the head, and the left upper extremity, still
passes down the left vertebral vein to the heart
upon its own side, while a part crosses over by
the communicating branch (I), and is finally
conveyed to the heart by the right descending
vertebral. Soon afterward, this branch of com-
munication enlarges so rapidly that it prepon-
derates altogether over the left superior verte-
bral vein, from which it originated (Fig. 260),
and, serving then to convey all the blood coming
from the left side of the head and left upper
extremity over to the right side above the heart,
it becomes the left vena innominate.
43

Fig. 259.

VENOCS STSTEM far-
ther advanced, showing
f 'i-riKition of iliac and sub-
clavian veins. — n. Vein of
new formation, which be-
comes the inferior vena
cava. b. Transverse branch
of new formation, which
afterward become* the lefc
vena innominata.

Fig. 260.

Furthe • development of
the V E .\ o c s SYSTEM.—
The vertebral veins are
much diminished in size,
and the canal of Cuvier, on
the left side, is gradual y
disappearing, c. Trans-
verse branch of new forma-
tion, which is to become
the vena azygos minor.

674 DEVELOPMENT OF THE CIRCULATORY APPARATUS.

Fig. 261.

On the left side, that portion of the superior vertebral vein, which
is below the subclavian, remains as a small branch of the vena in-
nominata, receiving the six or seven upper intercostal veins ; while
on the right side it becomes excessively enlarged, receiving the
blood of both jugulars and both subclavians, and is converted into
the vena cava superior.

The left canal of Cuvier, by which the left vertebral vein at first
communicates with the heart, subsequently becomes atrophied and
disappears; while on the right side it becomes excessively enlarged,
and forms the lower extremity of the vena cava superior.

The superior and inferior venae cavae, accordingly, do not cor-
respond with each other so far as regards their
mode of origin, and are not to be regarded as
analogous veins. For the superior vena cava
is one of the original vertebral veins; while
the inferior vena cava is a totally distinct vein,
of new formation, resulting from the union of
the two lateral trunks coming from the infe-
rior extremities.

The remainder of the vertebral veins finally
assume the condition shown in Fig. 261, which
is the complete or adult form of the venous
circulation. At the lower part of the abdomen,
the vertebral veins send inward small trans-
verse branches, which communicate with the
vena cava inferior, between the points at which
they receive the intercostal veins. These
branches of communication, by increasing in
size, become the lumbar veins (7), which, in the
adult condition, communicate with each other
by arched branches, a short distance to the side
of the vena cava. Above the level of the
lumbar arches, the vertebral veins retain their
original direction. That upon the right side
still receives all the right intercostal veins, and
becomes the vena azygos major (s). It also
receives a small branch of communication from
its fellow of the left side (Fig. 260, c), and this branch soon enlarges
to such an extent as to bring over to the vena azygos major all the
blood of the five or six lower intercostal veins of the left side,
becoming, in this way, the vena azygos minor (a). The six or seven

Adult condition of Vi>
NOUS SYSTEM. — 1. Right
auricle of heart. 2. Vena
cava superior. 3, 3. Jugular
veins. 4,4. Subclavian veins
:>. Vena cava inferior. 6, 6
Iliac veins. 7. Lumbar veins
S. Vena azygos major. 9
Vena azygos minor. 10. Sa
perior intercostal vein.

DEVELOPMENT OF THE HEPATIC CIKCULATION. 675

upper intercostal veins on fhe left side still empty, as before, into
their own vertebral vein (10), which, joining the left vena innomi-
nata above, is known as the superior intercostal vein. The left canal
of Cuvier has by this time entirely disappeared ; so that all the
venous blood now enters the heart by the superior or the inferior
vena cava. But the original vertebral veins are still continuous
throughout, though very much diminished in size at certain points ;
since both the greater and lesser azygous veins inosculate below
with the superior lumbar veins, and the superior intercostal vein
also inosculates below with the lesser azygous, just before it passes
over to the right side.

There are still two parts of the circulatory apparatus, the deve-
lopment of which presents peculiarities sufficiently important to
be described separately. These are, first, the liver and the ductus
venosus, and secondly, the heart, with the ductus arteriosus.

Development of the Hepatic Circulation and the Ductus Venosus. —
The liver appears at a very early period in the upper part of the
abdomen, as a mass of glandular and vascular tissue, which is deve-
loped around the upper portion of the
omphalo-mesenteric vein, just below its FiS-

termination in the heart. (Fig. 262.) As
soon as the organ has attained a con-
siderable size, the omphalo-mesenteric
vein (i) breaks up in its interior into a
capillary plexus, the vessels of which
unite again into venous trunks, and so
convey the blood finally to the heart.
The omphalo-mesenteric vein below the Early form of HEPATIC
liver then becomes the portal vein ; while ™™

above the liver, and between that organ Heart. The dotted line shows the

ill ' i n situation of the future umbilical

and the heart, it receives the name of vein.

the hepatic vein (2). The liver, accord-

ingly, is at this time supplied with blood entirely by the portal vein,

coming from the umbilical vesicle and the intestine ; and all the

blood derived from this source must pass through the hepatic cir-

culation befo're reaching the venous extremity of the heart.

But soon afterward the allantois makes its appearance, and be-
comes rapidly developed into the placenta ; and the umbilical vein
coming from it joins the omphalo-mesenteric vein in the substance
of the liver, and takes part in the formation of the hepatic capillary
plexus. As the umbilical vesicle, however, becomes atrophied, and

676 DEVELOPMENT OF THE CIRCULATORY APPARATUS.

Fig. 263.

HEPATIC CIRCULATION
farther advanced. — 1. Portal vein.
2. Umbilical vein,
vein.

the intestine also remains inactive, while the placenta increases in
size and in functional importance, a time soon arrives when the

liver receives more blood by the umbilical
vein than by the portal vein. (Fig. 263.)
The umbilical vein then passes into the
liver at the longitudinal fissure, and sup-
plies the left lobe entirely with its own
branches. To the right it sends off a large
branch of communication, which opens in-
to the portal vein, and partially supplies
the right lobe with umbilical blood. The
liver is thus supplied with blood from two
different sources, the most abundant of
3. Hepatic which is the umbilical vein ; and all the
blood entering the liver circulates, as be-
fore, through its capillary vessels.

But we have already seen that the liver is much larger, in pro-
portion to the entire body, at an early period of foetal life than in
the later months. In the foetal pig, when very young, it amounts

to nearly twelve per cent, of the
weight of the whole body ; but be-
fore birth it diminishes to seven, six,
and even three or four per cent. For
some time, therefore, previous to
birth, there is much more blood re-
turned from the placenta than is re-
quired for the capillary circulation
of the liver. Accordingly, a vascular
duct or canal is formed in its interior,
by which a portion of the placental
blood is carried directly through the
organ, and conveyed to the heart
without having passed through the
This duct is

Fig. 264.

HEPATIC CIRCULATION during lat-
ter part of foetal life.— 1. Portal vein. 2.

Umbilical vein. 3. Left branch of umbili- Jl6PatK Capillaries,
cal vein. 4. Right branch of umbilical Called the DuctllS VeUOSUS.
vein. 5. Ductus venosus. 6. Hepatic
vein.

The ductus venosus is formed by a
gradual dilatation of one of the he-
patic capillaries at (5) (Fig. 264), which, enlarging excessively, be-
comes at last converted into a wide canal, or branch of communi-
cation, passing directly from the umbilical vein below to the hepatic
vein above. The circulation through the liver, thus established, is

DEVELOPMENT OF THE HEPATIC CIRCULATION. 677

Fig. 265.

as follows : A certain quantity of venous blood still enters through
the portal vein ( i ), and circulates in a part of the capillary system
of the right lobe. The umbilical vein (a), bringing a much larger
quantity of blood, enters the liver also, a little to the left, and the
blood which it contains divides into three principal streams. One
of them passes through the left branch (3) into the capillaries of the
left lobe ; another turns off through the right branch (4), and, join-
ing the blood of the portal vein, circulates through the capillaries
of the right lobe ; while the third passes directly onward through
the venous duct (5), and reaches the hepatic vein without having
passed through any part of the capillary plexus.

This condition of the hepatic circulation continues until birth.
At that time, two important changes take place. First, the pla-
cental circulation is altogether cut off; and secondly, a much larger
quantity of blood than before begins
to circulate through the lungs and
the intestine. The superabundance
of blood, previously coming from the
placenta, is now diverted into the
lungs ; while the intestinal canal, en-
tering upon the active performance of
its functions, becomes the sole source
of supply for the hepatic venous
blood. The following changes, there-
fore, take place at birth in the ves-
sels of the liver. (Fig. 265.) First,
the umbilical vein shrivels and be-
comes converted into a solid rounded
cord (i). This cord may be seen, in
the adult condition, running from the
internal surface of the abdominal
walls, at the umbilicus, to the longi-
tudinal fissure of the liver. It is then
known under the name of the round

ligament. Secondly, the ductus venosus also becomes obliterated,
and converted into a fibrous cord. Thirdly, the blood entering the
liver by the portal vein (i), passes off by its right branch, as before,
to the right lobe. But in the branch (4), the course of the blood is
reversed. This was formerly the right branch of the umbilical
vein, its blood passing in a direction from left to right. It now
becomes the left branch of the portal vein ; and its blood passes

Adult form of HEPATIC CmcrLA-
TIOS.— 1. Portal vein. 2. Obliterated
umbilical vein, forming the round liga-
ment; the continuation of the dotted
lines through the liver shows the situa-
tion of the obliterated ductus venosus.
3. Hepatic vein. 4. Left branch of portal
vein.

678 DEVELOPMENT OF THE CIRCULATORY APPARATUS.

from right to left, to be distributed to the capillaries of the left

lobe.

According to Dr. Guy, the umbilical vein is completely closed at
the end of the fifth day after birth.

Development of the Heart, and the Ductus Arteriosus. — When the
embryonic circulation is first established, the heart is a simple tubu-
lar sac (Fig. 266), receiving the veins at its lower extremity, and
giving off the arterial trunks at its upper extremity. By the pro-
gress of its growth, it soon becomes twisted upon itself; so that the
entrance of the veins, and the exit of the arteries, come to be placed
more nearly upon the same horizontal level (Fig. 267); but the
entrance of the veins (i) is behind and a little below, while the exit
of the arteries (2) is in front and a little above. The heart is, at
this time, a simple twisted tube ; and the blood passes through it
in a single continuous stream, turning upon itself at the point of
curvature, and passing directly out by the arterial orifice.

Fig. 266.

Fig. 267.

Fig. 268.

\

Earliest form of F<ETAL
HEART. — 1. Venous ex-
tremity. 2. Arterial ex-
tremity.

FCETAL HF.ART, twisted
upou itself. — 1. Venous ex-
tremity. 2. Arterial extre-
mity.

FCETAL HEART, divided
into right and left cavities. —
1. Venous extremity. 2.
Arterial extremity. 3, 3.
Pulmonary branches.

Soon afterward, this single cardiac tube is divided into two paral-
lel tubes, right and left, by a longitudinal partition, which grows
from the inner surface of its walls and follows the twisted course
of the organ itself. (Fig. 268.) This partition, which is indicated
in the figure by a dotted line, extends a short distance into the
commencement of the primitive arterial trunk, dividing it into two
lateral halves, one of which is in communication with the right side
of the heart, the other with the left.

About the same time, the pulmonary branches (3, 3) are given
off from each side of the arterial trunk near its origin ; and the
longitudinal partition, above spoken of, is so placed that both these
branches fall upon one side of it, and are both, consequently, given
off from that division of the artery which is connected with the right
side of the heart.

DEVELOPMENT OF THE HEART.

679

Fig. 269.

F<KTAL HK ART still farther
developed. — 1 Aorta. 2. Pul-
monary artery. 3, 3. Pul-
monary branches 4. Ductus
arteriosus.

Very soon a superficial line of demarcation, or furrow, shows
itself upon the external surface of the heart, corresponding in situa-
tion with the internal septum; while at the root of the arterial
trunk this furrow becomes much deeper, and finally the two lateral
portions of the vessel are separated from each other altogether, in
tEe immediate neighborhood of the heart,
joining again, however, a short distance be-
yond the origin of the pulmonary branches.
(Fig. 269.) It then becomes evident that
the left lateral division of the arterial trunk
is the commencement of the aorta ( i ); while
its right lateral division is the trunk of the
pulmonary artery (2), giving off the right
and left pulmonary branches (3,3), at a short
distance from its origin. That portion of
the pulmonary trunk (4) which is beyond
the origin of the pulmonary branches, and
which communicates freely with the aorta, is the .Ductus arteriosus.

The ductus arteriosus is at first as large as the pulmonary trunk
itself; and nearly the whole of the blood, coming from the right
ventricle, passes directly onward through the arterial duct, and
enters the aorta without going to the lungs. But as the lungs
gradually become developed, they require a larger quantity of
blood for their nutrition, and the pulmonary branches increase in
proportion to the pulmonary trunk and the ductus arteriosus. At
the termination of foetal life, in the
human subject, the ductus arteriosus
is about as large as either one of the
pulmonary branches ; and a very con-
siderable portion of the blood, there-
fore, coming from the right ventricle
still passes onward to the aorta with-
out being distributed to the lungs.

But at the period of birth, the lungs
enter upon the active performance of
the function of respiration, and imme-
diately require a much larger supply
of blood. The right and left pul-
monary branches then enlarge, so as
to become the two principal divisions
of the pulmonary trunk. (Fig. 270.) The ductus arteriosus at the

Fig. 270.

HEART OF IXFAXT, showing dis-
appearance of arterial duct after birth.
— 1. Aorta. 2. Pulmonary artery. 3,
3. Pulmonary branches. 4. Ductus
arteriosus becoming obliterated.

6SO DEVELOPMENT OF THE CIRCULATORY APPARATUS.

same time becomes contracted and shrivelled to such an extent
that its cavity is obliterated ; and it is finally converted into an im-
pervious, rounded cord, which remains until adult life, running
from the point of bifurcation of the pulmonary artery to the under
side of the arch of the aorta. The obliteration of the arterial duct
is complete, at latest, by the tenth week after birth. (Guy.)

The two auricles are separated from the two ventricles by hori-
zontal septa which grow from the internal surface of the cardiac
walls ; but these septa remaining incomplete, the auriculo-ventricu-
lar orifices continue pervious, and allow the free passage of the
blood from the auricles to the ventricles.

The interventricular septum, or that which separates the two
ventricles from each other, is completed at a very early date ; but
the interauricular septum, or that which is situated between the
two auricles, remains incomplete for a long time, being perforated
by an oval-shaped opening, the foramen ovale, allowing, at this
situation, a free passage from the right to the left side of the heart.
The existence of the foramen ovale arid of the ductus arteriosus
gives rise to a peculiar crossing of the streams of blood in passing
through the heart, which is characteristic of foetal life, and which
may be described as follows : —

It will be found upon examination that the two venae cava?,
superior and inferior, do not open into the auricular sac on the
same plane or in the same direction; for while the superior vena
cava is situated anteriorly, and is directed downward and forward,
the inferior is situated quite posteriorly, and passes into the auricle
in a direction from right to left, and transversely to the axis of
the heart. A nearly vertical curtain or valve at the same time
hangs downward behind the orifice of the superior vena cava and
in front of the orifice of the inferior. This curtain is formed by
the lower edge of the septum of the auricles, which, as we have
before stated, is incomplete at this age, and which terminates
inferiorly and toward the right in a crescentic border, leaving at
that part an oval opening, the foramen ovale. The stream of blood,
coming from the superior vena cava, falls accordingly in front of
this curtain, and passes directly downward, through the auriculo-
ventricular orifice, into the right ventricle. But the inferior vena
cava, being situated farther back and directed transversely, opens,
properly speaking, not into the right auricle, but into the left; for
its stream of blood, falling behind the curtain above mentioned,
passes across, through the foramen ovale, directly into the cavity of

DEVELOPMENT OF THE HEART.

681

Fig. 271.

the left auricle. This direction of the current of blood, coming
from the inferior vena cava, is further secured by a peculiar mem-
branous valve, which exists at this period, termed the Eustachian
valve. This valve, which is very thin and transparent (Fig. 271, /),
is attached to the anterior border of the orifice of the inferior vena
cava, and terminates by a crescentic edge, directed toward the left ;
the valve, in this way, standing
as an incomplete membranous
partition between the cavity of
the inferior vena cava and that
of the right auricle. A bougie,
accordingly, placed in the in-
ferior vena cava, as shown in
Fig. 271, lies naturally quite
behind the Eustachian valve,
and passes directly through
the foramen ovale, into the left
auricle.

The two streams of blood,
therefore, coming from the su-
perior and inferior vena3 cavoa,
cross each other upon entering
the heart. This crossing of the
streams does not take place,
however, as it is sometimes
described, in the cavity of the
right auricle ; but, owing to the
peculiar position and direction
of the two veins at this period,
with regard to the septum of

the auricles, the stream coming from the superior vena cava enters
the right auricle exclusively, while that from the inferior passes
almost directly into the left auricle.

It will also be seen, by examining the positions of the aorta, pul-
monary artery, and ductus arteriosus, at this time, that the arteria
innominata, together with the left carotid and left subclavian, are
given off from the arch of the aorta, before its junction with the
ductus arteriosus, and this arrangement causes the blood of the two
venae cavse, not only to enter the heart in different directions, but
also to be distributed, after leaving the ventricles, to different parts
of the body. (Fig. 272.) For the blood of the superior vena cava

HKARTOF HUMAN fee. rrs, at the end of the
sixth month ; from a specimen in the author's pos-
session.— a. Inferior vena cava. b. Superior vena
cava c. Cavity of riirlit auricle, laid open from
the front, d. Appendix auricularis. e. Cavity of
rik'ht ventricle, also laid open. /. Eustachian valve.
The bougie, which is placed in the inferior vena
cava, can be seen passing behind the Eustachian
valve, just below the point indicated by /, then
crossing behind the cavity of the right au icle, and
passing through the foramen ovale, to the left side
of the heart.

682 DEVELOPMENT OF THE CIRCULATORY APPARATUS.

Fig 272.

passes through the right auricle downward into the right ventricle,
thence through the pulmonary artery and ductus arteriosus, into
the thoracic aorta, while the blood of the inferior vena cava, enter-
ing the left auricle, passes into the left ventricle, thence into the arch
of the aorta, and is distributed to the head and upper extremities,
before reaching the situation of the arterial duct. The two streams,
therefore, in passing through the heart, cross each other both behind
and in front. The venous blood, returning from the head and

upper extremities by the superior
vena cava, passes through the abdo-
minal aorta and the umbilical arte-
ries, to the lower part of the body,
and to the placenta ; while that re-
turning from the placenta, by the
inferior vena cava, is distributed to
the head and upper extremities,
through the vessels given off from
the arch of the aorta.

This division of the streams of
blood, during a certain period of
foetal life, is so complete that Dr.
John Eeid,1 on injecting the infe-
rior vena cava with red, and the
superior with yellow, in a seven
months' human foetus, found that

the red had passed through the foramen ovale into the left auricle
and ventricle and arch of the aorta, and had filled the vessels of
the head and upper extremities; while the yellow had passed into
the right ventricle, pulmonary artery, ductus arteriosus, and tho-
racic aorta, with only a slight admixture of red at the posterior
part of the right auricle. All the branches of the thoracic and
abdominal aorta were filled with yellow, while the whole of the red
had passed to the upper part of the body.

We have repeated the above experiment several times on the
foetal pig, when about one-half and three-quarters grown, first taking
the precaution to wash out the heart and large vessels with a wa-
tery injection, immediately after the removal of the foetus from the
body of the parent, and before the blood had been allowed to coagu-
late. The injections used were blue for the superior vena cava,

Diagram of CIRCULATION THROUGH
THE F<ETAL HKART. — a. Superior vena
cava. b. Inferior vena cava. c, c, n, c. Arch
of aorta aud its branches, d. Pulmonary
artery.

Edinburgh Medical and Surgical Journal, vol. xliii. 1835.

DEVELOPMENT OF THE HEART. 633

and yellow for the inferior. The two syringes were managed, at
the same time, by the right and left hands : their nozzles being
firmly held in place by the fingers of an assistant. \Yhen the
points of the syringes were introduced into the veins, at equal dis-
tances from the heart, and the two injections made with equal force
and rapidity, it was found that the admixture of the colors which
took place was so slight, that at least nineteen-twentieths of the
yellow injection had passed into the left auricle, and nineteen-twen-
tieths of the blue into the right. The pulmonary artery and ductus
arteriosus contained a similar proportion of blue, and the arch of
the aorta of yellow. In the thoracic and abdominal aorta, however
contrary to what was found by Dr. Keid, there was always an ad-
mixture of the two colors, generally in about equal proportions.
This discrepancy may be owing to the smaller size of the head and
upper extremities, in the pig, as compared with those of the human
subject, which would prevent their receiving all the blood coming
from the left ventricle ; or to some differences in the manipulation
of these experiments, in which it is not always easy to imitate ex-
actly the force and rapidity of the different currents of blood in
the living foetus. The above results, however, are such as to leave
no doubt of the principal fact, viz., that up to an advanced stage of
foetal life, by far the greater portion of the blood coming from the
inferior vena cava passes through the foramen ovale, into the left
side of the heart ; while by far the greater portion of that coming
from the head and upper extremities passes into the right side of
the heart, and thence outward by the pulmonary trunk and ductus
arteriosus. Toward the latter periods of gestation, this division
of the venous currents becomes less complete, owing to the three
following causes : —

First, the lungs increasing in size, the two pulmonary arteries, as
well as the pulmonary veins, enlarge in proportion ; and a greater
quantity of the blood, therefore, coming from the right ventricle,
instead of going onward through the ductus arteriosus, passes to
the lungs, and returning thence by the pulmonary veins to the left
auricle and ventricle, joins the stream passing out by the arch of
the aorta.

Secondly, the Eustachian valve diminishes in size. This valve,
which is very large and distinct at the end of the sixth month
(Fig. 271), subsequently becomes atrophied to such an extent that,
at the end of gestation, it has altogether disappeared, or is at least
reduced to the condition of a very narrow, almost imperceptible

684 DEVELOPMENT OF THE CIRCULATORY APPARATUS.

membranous ridge, which can exert no influence on the direction
of the current of blood passing by it. Thus, the cavity of the infe-
rior vena cava, at its upper extremity, ceases to be separated from
that of the right auricle ; and a passage of blood from one to the
other may, therefore, more readily take place.

Thirdly, the foramen ovale becomes partially closed by a valve
which passes across its orifice from behind forward. This valve,
which begins to be formed at a very early period, is called the
valve of the foramen ovale. It consists of a thin, fibrous sheet, which
grows from the posterior surface of the auricular cavity, just to the
left of the foramen ovale, and projects into the left auricle, its free
edge presenting a thin crescentic border, and being attached, by its
two extremities, to the auricular septum upon the left side. This
valve does not at first interfere at all with the flow of blood from
right to left, since its edge hangs freely and loosely into the cavity
of the left auricle. It only opposes, therefore, during the early
periods, any accidental regurgitation from left to right.

But as gestation advances, while the walls of the heart con-
tinue to enlarge, and its cavities to expand in every direction, the
fibrous bundles, forming the valve, do not elongate in proportion-
The valve, accordingly, becomes drawn downward more and more
toward the foramen ovale. It thus comes in contact with the edges
of the interauricular septum, and unites with its substance; the
adhesion taking place first at the lower and posterior portion, and
proceeding gradually upward and forward, so as to make the pas-
sage, from the right auricle to the left, more and more oblique in
direction.

At the same time, an alteration takes place in the position of the
inferior vena cava. This vessel, which at first looked transversely
toward the foramen ovale, becomes directed more obliquely for-
ward ; so that, the Eustachian valve having mostly disappeared, a
part of the blood of the inferior vena cava enters the right auricle,
while the remainder still passes through the equally oblique open-
ing of the foramen ovale.

At the period of birth a change takes place, by which the
foramen ovale is completely occluded, and all the blood coming
through the inferior vena cava is turned into the right auricle.

This change depends upon the commencement of respiration.
A much larger quantity of blood than before is then sent to the
lungs, and of course returns from them to the left auricle. The
left auricle, being then completely filled with the pulmonary blood,

DEVELOPMENT OF THE HEART. 685

no longer admits a free access from the right auricle through the
foramen ovale ; and the valve of the foramen, pressed backward
more closely against the edges of the septum, becomes after a time
adherent throughout, and obliterates the opening altogether. The
cutting off of the placental circulation diminishes at the same time
the quantity of blood arriving at the heart by the inferior vena
cava. It is evident, indeed, that the same quantity of blood which
previously returned from the placenta by the inferior cava, on the
right side of the auricular septum, now returns from the lungs, by
the pulmonary veins upon the left side of the same septum ; and it
is owing to all these circumstances combined, that while before birth
a portion of the blood always passed from the right auricle to the
left through the foramen ovale, no such passage takes place after
birth, since the pressure is then equal on both sides of the auricular
septum.

The fcetal circulation, represented in Fig. 272, is then replaced
by the adult circulation, represented in Fig. 273.

Fig. 273.

Diagram of ADULT CiscrLATroxTHRotraHTHK HEART.— ", n. Superior and inferior vena;
cavse. >>. Rijrht ventricle, c. Pulmonary artery, dividing into right and left branches, d. Pulmo-
nary vein. e. Left ventricle. /. Aorta.

That portion of the septum of the auricles, originally occupied
by the foramen ovale, is accordingly constituted, in the adult con-
dition, by the valve of the foramen ovale, which has become adhe-

686 DEVELOPMENT OF THE CIRCULATORY APPARATUS.

rent to the edges of the septum. The auricular septum in the adult
heart is, therefore, thinner at this spot than elsewhere ; and presents,
on the side of the right auricle, an oval depression, termed the fossa
ovalis, which indicates the site of the original foramen ovale. The
fossa ovalis is surrounded by a slightly raised ring, the annulus
ovalis, representing the curvilinear edge of the original auricular
septum.

The foramen ovale is sometimes completely obliterated within a
few days after birth. It often, however, remains partially pervious
for several weeks or months. We have a specimen, taken from a
child of one year and nine months, in which the opening is still
very distinct; and it is not unfrequent to find a small aperture
existing even in adult life. In these instances, however, although
the adhesion and solidification of the auricular septum may not be
complete, yet no disturbance of the circulation results, and no ad-
mixture of blood takes place between the right and left sides of the
heart ; since the passage through the auricular septum is always
very oblique in its direction, and its valvular arrangement prevents
any regurgitation from left to right, while the complete filling of
the left auricle with pulmonary blood, as above mentioned, equally
opposes any passage from right to left.

DEVELOPMENT OF THE BODY AFTER BIRTH. 687

CHAPTER XVIII.

DEVELOPMENT OF THE BODY AFTER BIRTH.

THE newly-born infant is still very far from having arrived at a
state of complete development. The changes through which it has
passed during intra-uterine life are not more marked than those
which are to follow during the periods of infancy, childhood, and
adolescence. The anatomy of the organs, both internal and ex-
ternal, their physiological functions, and even the morbid derange-
ments to which they are subject, continue to undergo gradual and
progressive alterations, throughout the entire course of subsequent
life. The history of development extends, properly speaking, from
the earliest organization of the embryonic tissues to the complete
formation of the adult body. The period of birth, accordingly,
marks only a single epoch in a constant series of changes, some of
which have preceded, while many others are to follow.

The weight of the newly -born infant is a little over six pounds.
The middle point of the body is nearly at the umbilicus, the head
and upper extremities being still very large, in proportion to the
lower extremities and pelvis. The abdomen is larger and the
chest smaller, in proportion, than in the adult. The lower extremi-
ties are curved inward, as in the foetal condition, so that the soles of
the feet look obliquely toward each other, instead of being directed
horizontally downward, as at a subsequent period. Both upper
and lower extremities are habitually curled upward and forward
over the chest and abdomen, and all the joints are constantly in a
semi-flexed position.

The process of respiration is very imperfectly performed for
some time after birth. The expansion of the pulmonary vesicles,
and the changes in the circulatory apparatus described in the pre-
ceding chapter, far from being sudden and instantaneous, are
always more or less gradual in their character, and require an
interval of several days for their completion. Respiration, indeed

688 DEVELOPMENT OF THE BODY AFTER BIRTH.

seems to be accomplished, during this period, to a considerable
extent through the skin, which is remarkably soft, vascular, and
ruddy in color. The animal heat is also less actively generated
than in the adult, and requires to be sustained by careful protec-
tion, and by contact with the body of the mother. The young
infant sleeps during the greater part of the time ; and even when
awake there are but few manifestations of intelligence or percep-
tion. The special senses of sight and hearing are dull and inex-
citable, though their organs are perfectly formed ; and even
consciousness seems present only to a very limited extent. Volun-
tary motion and sensation are nearly absent ; and the almost con-
stant irregular movements of the limbs, observable at this time,
are evidently of a reflex or automatic character. Nearly all the
nervous phenomena, indeed, presented by the newly-born infant,
are of a similar nature. The motions of its hands and feet, the act
of suckling, and even its cries and the contortions of its face, are
reflex in their origin, and do not indicate the existence of any
active volition, or any distinct perception of external objects.
There is at first but little nervous connection established with the
external world, and the system is as yet almost exclusively occu-
pied with the functions of nutrition and respiration.

This preponderance of the simple reflex actions in the nervous
system of the infant, is observable even in the diseases to which it
is peculiarly subject for some years after birth. It is at this age
that convulsions from indigestion are of most frequent occurrence,
and even temporary strabismus and paralysis, resulting from the
same cause. It is well known to physicians, moreover, that the
effect of various drugs upon the infant is very different from that
which they exert upon the adult. Opium, for example, is very
much more active, in proportion to the dose, in the infant than in
the adult. Mercury, on the other hand, produces salivation with
greater difficulty in the former than in the latter. Blisters excite
more constitutional irritation in the young than in the old subject ;
and antimony, when given to children, is proverbially uncertain
and dangerous in its operation.

The difference in the anatomy of the newly-born infant, and that
of the adult, may be represented, to a certain extent, by the fol-
lowing list, which gives the relative weight of the most important
internal organs at the period of birth and that of adult age ; the
weight of the entire body being reckoned, in each case, as 1000.
The relative weight of the adult organs has been calculated from

F(ETCS AT TERM.

Weight of the entire body

. 1000.00

" " encephalon

148.00

" " liver .

37.00

heart

7.77

kidneys .

6.00

" " renal capsules c

1.63

" " thyroid gland .

0.60

" " thymus gland «.

3.00

DEVELOPMENT OF THE BODY AFTER BIRTH. 689

the estimates of Cruveilheir, Solly, "Wilson, &c. ; that of the organs
in the foetus at term from our own observations.

ADULT.
1000.00
23.00
29.00
4.17
4.00
0.13
0.51
0.00

It will be observed that most of the internal organs diminish in
relative size after birth, owing principally to the increased develop-
ment of the osseous and muscular systems, both of which are in a
very imperfect condition throughout intra-uterine life, but which
come into activity during childhood and youth.

Within the first day after birth the remains of the umbilical
cord begin to wither, and become completely desiccated by about
the third day. A superficial ulceration then takes place about the
point of its attachment, and it is separated and thrown off within
the first week. After the separation of the cord, the umbilicus
becomes completely cicatrized by the tenth or twelfth day after
birth. (Guy.)

An exfoliation and renovation of the cuticle also take place
over the whole body soon after birth. According to Kolliker, the
eyelashes, and probably all the hairs of the body and head are
thrown off and replaced by new ones within the first year.

The teeth in the newly-born infant are but partially developed,
and are still inclosed in their follicles, and concealed beneath the
gums. They are twenty in number, viz., two incisors, one canine,
and two molars, on each side of each jaw. At birth there is a thin
layer of dentine and enamel covering their upper surfaces, but
the body of the tooth and its fangs are formed subsequently by
progressive elongation and ossification of the tooth-pulp. The
fully-formed teeth emerge from the gums in the following order.
The central incisors in the seventh month after birth; the lateral
incisors in the eighth month ; the anterior molars at the end of the
first year ; the canines at a year and a half; and the second molars
at two years (Kolliker). The eruption of the teeth in the lower
jaw generally precedes by a short time that of the corresponding
teeth in the upper.

During the seventh year a change .begins to take place by which
44

690 DEVELOPMENT OF THE BODY AFTER BIRTH.

the first set of teeth are thrown off and replaced by a second or
permanent set, differing in number, size, and shape from those
which preceded. The anterior permanent molar first shows itself
just behind the posterior temporary molar, on each side. This
happens at about six and a half years after birth. At the end of
the seventh year the middle incisors are thrown off and replaced
by corresponding permanent teeth, of larger size. At the eighth
year a similar exchange takes place in the lateral incisors. In the
ninth and tenth years, the anterior and second molars are replaced
by the anterior and second permanent bicuspids. In the twelfth
year, the canine teeth are changed. In the thirteenth year, the
second permanent molars show themselves ; and from the seven-
teenth to the twenty-first year, the third molars, or " wisdom teeth,"
emerge from the gums, at the posterior extremities of the dental
arch. (Wilson.) The jaw, therefore, in the adult condition, contains
three teeth on each side more than in childhood, making in all
thirty-two permanent teeth ; viz., on each side, above and below,
two incisors, one canine, two bicuspids, and three permanent
molars.

The entire generative apparatus, which is still altogether inactive
at birth, begins to enter upon a condition of functional activity
from the fifteenth to the twentieth year. The entire configuration
of the body alters in a striking manner at this period, and the dis-
tinction between the sexes becomes more complete and well
marked. The beard is developed in the male ; and in the female
the breasts assume the size and form characteristic of the condition
of puberty. The voice, which is shrill and sharp in infancy and
childhood, becomes deeper in tone, and the countenance assumes a
more sedate and serious expression. After this period, the mus-
cular system increases still further in size and strength, and the
consolidation of the skeleton also continues ; the bony union of its
various parts not being entirely accomplished until the twenty-fifth
or thirtieth year. Finally, all the different organs of the body
arrive at the adult condition, and the entire process of development
is then complete.

INDEX.

ABSORBENT glands, 168, 317

vessels, 167, 317
Absorption, 162

by bloodvessels, 165

by lacteals, 168

of fat, 171

of different liquids by animal sub-
stances, 312

of oxygen in respiration, 243

by egg during incubation, 606

of calcareous matter by allantois,

606
Acid, carbonic, 242, 246

lactic, in gastric juice, 139

in souring milk, 99, 336

glyko-cholic, 180

tauro-cholic, 181

pneumic, 247

uric, 347, 354

oxalic in urine, 360
Acid fermentation of urine, 360
Acidity of gastric juice, cause of, 139

of urine, 353
Acini, of liver, 338
Adipose vesicles, 90

digestion of, 158, 159
Adult circulation, 670

establishment of, 685
Aerial respiration, 233
Age, influence of, on exhalation of car-
bonic acid, 250

on comparative weight of organs,

689
Air, quantity of, used in respiration, 238

alterations of, in respiration, 241

circulation of, in lungs, 239
Air-cells of lungs, 235
Air-chamber, in fowl's egg, 552
Albumen, 100

of the blood, 224

in milk, 335

of the egg, how produced, 550

its liquefaction and absorption dur-
ing development of foetus, 602-
604
Albuminoid substances, 95

digestion of, 141
Albuminose, 142

interference with Trommer's test.
143

with action of iodine and starch,
144

Alimentary canal in different animals,
116, 119

development of, 644
Alkalies, effect of, on urine, 354
Alkaline chlorides, 71-74

phosphates, 77

carbonates, 76, 77

Alkaline fermentation of urine, 360
Alkalescence of blood, due to carbonates,

76
Allantois, 599

formation of, 601

in fowl's egg, 604

function of, 605

in fostal pig, 622
Alligator, brain of, 382
Amnion, 509

formation of, 600

enlargement of, during latter part of
pregnancy, 630

contact with chorion, 631
Amniotic folds, 600
Amniotic fluid, 630

its use, 631

contains sugar at a certain period,

648

Amniotic umbilicus, 600
Analysis, of animal fluids, 64, 65

of milk, 112, 334

of wheat flour, 112

of oatmeal, 112

of eggs, 113

of meat, 113

of saliva, 124, 126

of gastric juice, 139

of pancreatic juice, 155

of bile, 176

of blood-globules, 218

of blood-plasma, 223

of mucus, 328

of sebaceous matter, 329

of perspiration, 331

of butter, 336

of urine, 352

of fluid of thoracic duct, 318

of chyle and lymph, 320
ANDRAL AND GAVARRET, production of

carbonic acid in respiration, 250
Animal functions, 59
Animal heat, 253-263

in different species, 255

mode of generation, 257

(691 )

692

INDEX.

Animal heat influenced by local causes,
261

in different organs, 262

increase of, after section of sympa-
thetic nerve, 521

Animal and vegetable parasites, 532
Animalcules, infusorial, 529

mode of production, 530
Annulus ovalis, 686
Anterior columns of spinal cord, 380

their excitability, 402
Aorta, development of, 670
Aplysia, nervous system of, 375
Appetite, disturbed by anxiety, &c., 149

necessary to digestion of food, 149
Aquatic respiration, 233
Arch of aorta, formation of, 671
Arches, cervical, 670

transformation of, 671
Area pellucida, 590

vasculosa, 603, 666
Arteries, 281

motion of blood in, 282

pulsation of, 283-285

elasticity of, 281, 286

rapidity of circulation in, 289

omphalo-mesenteric, 666

vertebral, 669

umbilical, 669
Arterial pressure, 287
Arterial system, development of, 669-672
Articulata, nervous system of, 376

reflex action in, 377
Articulation of tapeworm, 541
Arytenoid cartilages, 240

movements of, 241
Assimilation, 324

destructive, 341
Auditory apparatus, 505

nerves, 447, 507
Auricle, single, of fish, 265

double, of reptiles, birds, and mam-
malians, 266, 267

contraction of, 279
Auriculo-ventricular valves, action of,

269

Axis-cylinder, of nervous filaments, 370
Aztec children, 426
Azygous veins, formation of, 673

BEAUMONT, Dr., experiments on Alexis St.

Martin, 135-146
BERNARD, on the different kinds of saliva,

125
on effect of dividing Steno's duct,

131

on digestion of fat in intestine, 155
on formation of liver-sugar, 200, 202,

203
on decomposition of bicarbonates in

lung, 247

on temperature of blood in different
organs, 262

BIDDER AND SCHMIDT, on daily quantity
of bile, 188

on effect of excluding bile from in-
testine, 195

on reabsorption of bile, 196
Bile, 175

composition of, 176

tests for, 184

daily quantity of, 188

functions of, 193

reaction with gastric juice, 193

reabsorption, 196

mode of secretion, 337
Biliary salts, 177

of human bile, 183
Biliverdine, 103, 176

tests for, 184

passage into the urine, 357
Blastodermic membrane, 6b8
Blood, 213

red globules of, 214

white globules, 220

plasma, 223

coagulation of, 225

buffy coat, 230

entire quantity of, 231

alterations of, in respiration, 243

temperature of, 254

in different organs, 262

circulation of, 264

through the heart, 270
through the arteries, 282
through the veins, 290
through the capillaries, 296
BOUSSINGAULT, on chloride of sodium in
food, 73

on internal production of fat, 93
Brain, 381, 417

of alligator, 382

of rabbit, 383

human, 386, 417

remarkable cases of injury to, 419,
420

size of, in different races, 423, 424
in idiots, 425

development of, 638, 639
Branchiae, 232

of meno-branchus, 233
Broad ligaments, formation of, 662
Bronchi, division of, 234, 235

ciliary, motion in, 239
Brunner's glands, 152
Buffy coat of the blood, 230
Butter, 335

composition of, 336

condition in milk, 91, 335
Butyrine, 336

Canals of Cuvier, 672
Capillaries, 295

their inosculation, 296

motion of blood in, 297
Capillary circulation, 296

INDEX.

693

Capillary circulation, causes of, 298
rapidity of, 301, 302
peculiarities of, in different parts,

303

Cnput coli, formation of, 645
Carbonic acid, in the breath, 242

proportion of, to oxygen absorbed,

242, 243

in the blood, 243
origin of, in lungs, 247
in the blood, 248
in the tissues, 248
mode of production, 248
daily quantity of, 250
variations of, 250

exhaled by skin, 252 r

by egg, during incubation, 606
absorbed by vegetables, 260
Carbonate of lime, 76
of soda, 76
of potassa, 77
of ammonia, in putrefying urine,

360
Cardiac circulation, in foetus, 682

in adult, 685
Carnivorous animals, respiration of, 50,

243

urine of, 345
Cartilagine, 102
Caseine, 100
Cat, secretion of bile in, 188

closure of eyelids, after division of

sympathetic, 522
Catalytic action, 98
of pepsin, 142

Centipede, nervous system of, 376
Centre, nervous definition of, 373
Cerebrum, 419. See Hemispheres.
Cerebral ganglia, 382. See Hemi-
spheres.
Cerebellum, 429

effects of injury to, 431
removal of, 431-434
function of, 430
development of, 638, 639
Cerebro-spinal system, 378, 379

development of, 037
Cervix uteri, 554
in foetus, 663
Cervical arches, 670

transformation of, 671
Changes, in egg, while passing through

oviduct, 548, 551

in hepatic circulation at birth, 677
in comparative size of organs, after

birth, 6S9
CIIEVREUIL, experiments on imbibition,

312

Chick, development of, 602-607
Children, Aztec, 426
Chloride of sodium, 71

its proportion in the animal tissues
and fluids, 72

Chloride of sodium, importance of, in the
food, 73

mode of discharge from the body, 74

partial decomposition of, in the body*

74

Chloride of potassium, 74
Cholesterin, 176
Chorda dorsalis, 591
Chorda tympani, 488
Chordae vocales, movement of, in respi-
ration, 240«

action of, in the production of vocal
sounds, 464

obstruction of glottis by, after divi-
sion of pneuinogastric, 466, 4 ,7
Chorion, formation of, 608

villosities of, 610

source of vascularity of, 611

union with decidua, 619
Chyle, 153, 169, 320

in lacteals, 170

absorption of, 171

by intestinal epithelium, 172

in blood, 173
Ciliary motion, in bronchi, 221

in Fallopian tubes, 573
Ciliary nerves, 514
Circulation, 264

in the heart, 270

in the arteries, 282

in the veins, 290

in the capillaries, 297

rapidity of, 302

peculiarities of, in different parts,
304

in liver, 339

in placenta, 621-629
Circulatory apparatus, development of,

665-686
j Civilization, aptitude for, of different

races, 424

Classification of cranial nerves, 448
Clot, formation of, 225

separation from serum, 226

buffed and cupped, 230
Coagulation, 98

of fibrin, 223

of blood, 225

of white substance of Schwann, in

nerve-fibres, 3tJ9

COLIN, on unilateral mastication, 127
Cold, resistance to, by animals, 253

effect of, when long continued, 254
Colostrum, 333
Coloring matters, 102

of blood, 102, 218

of the skin, 103

of bile, 103

of uriue, 103
Commissure, of spinal cord, cray, 3S1

white, 381

transverse, of cerebrum, 3S7

of cerebellum, 387

694

INDEX.

Commissures, nervous, 373

olfactory, 382, 418
Congestion, of ear, &c., after division of

sympathetic, 521

Convolvulus, sexual apparatus of, 540
Consentaneous action of muscles, 430
Contact, of chorion and aninion, 631

of decidua vera and reflexa, 632
Contraction, of stomach during diges-
tion, 145

of spleen, 208

of blood-clot, 226

of diaphragm and intercostal mus-
cles, 236

of posterior crico-arytenoid muscles,
241

of ventricles, 275

of muscles after death, 389

of sphincter ani, 414

of rectum, 414

of urinary bladder, 415

of pupil, under influence of light,
, 367, 435, 501
after division of sympathetic,

522

Cooking, effect of, on food, 114
Cord, spinal, 379, 398

umbilical, 631

withering and separation of, 689
Corpus callosum, 387
Corpus luteum, 576

of menstruation, 576-580

of pregnancy, 580-585

three weeks after menstruation, 578

four weeks after menstruation, 579

nine weeks after menstruation, 579

at end of second month of preg-
nancy, 582

at end of fourth month, 582

at term, 583

disappearance of, after delivery, 584
Corpora Malpighiana, of spleen, 191
Corpora striata, 383, 419
Corpora olivaria, 384
Corpora Wolffiana, 655
COSTE, on rupture of Graafian follicle in

menstruation, 572, 573
Cranial nerves, 446

classification of, 448

motor, 449

sensitive, 449, 450
Creatine, 346
Creatinine, 346
Cremaster muscle, formation of, 659

function of, in lower animals, 660
Crystals, of stearine, 87

and margarine, 88

of cholesterin, 177

of glyko-cholate of soda, 178

of biliary matters of dog's bile, 182

of urea, 343

of creatine, 346

of creatinine, 346

Crystals, of urate of soda, 347
of uric acid, 354
of oxalate of lime, 360
of triple phosphate, 362
Crystallizable sustances of organic ori-
gin, 79
Crossing of fibres in medulla oblongata,

385, 404
of sensitive fibres in spinal cord,

405

of fibres of optic nerves, 436, 437
of streams of blood in foetal heart,

681, 682
CRDIKSHANK, rupture of Graafian follicle

in menstruation, 572
Cumulus proligerus, 567
Cutaneous respiration, 252

perspiration, 330
Cuticle, exfoliation of, during foetal life,

643

after birth, 689
Cysticercus, 537

transformation of into tsenia, 538
production of, from eggs of tsenia,
539

Death, a necessary consequence of life,

526

Decidua, 614
vera, 616
reflexa, 618

union with chorion, 619
its discharge in cases of abortion,

618

at the time of delivery, 633
Decussation of anterior columns of spinal

cord, 385, 404
of optic nerves, 436, 437
Degeneration, fatty, of muscular fibres

of uterus, after delivery, 635
Deglutition, 133

retarded by division of Steno's duct,

131
by division of pneumogastric,

463
Dentition, first, 689

second, 690
Descent of the testicles, 658

of the ovaries, 661
Destructive assimilation, 341
Development of the impregnated egg, 586
of allantois, 601
of chorion, 608

of villosities of chorion, 610, 611
of decidua, 615, 616
of placenta, 621-620
of nervous system, 637
of eye, 640
of ear, 641
of skeleton, 641
of limbs, 642
of integument, 643
of alimentary canal, 464, C46

INDEX.

695

Development of urinary passages, 646

of liver, 649, 675

of pharynx and oesophagus, 650

of face, 651

of Wolffian bodies, 655

of kidneys, 656

of internal generative organs, 657

of circulatory apparatus, 665

of arterial system, 669

of venous system, 672

of hepatic circulation, 675

of heart, 678

of the body after birth, 687
Diabetes, 357

in foatus, 649
Diaphragm, action of in breathing, 237

formation of, 651
Diaphragmatic hernia, 651
Diet, influence of on nutrition, 108

on products of respiration, 243

on formation of urea, 345
of urate of soda, 348
Diffusion of gases in lungs, 239
Digestion, 115

of starch, 150

of fats, 153

of sugar, 150

of organic substances, 141

time required for, 146
Digestive apparatus of fowl, 117

of ox, 118

of man, 119
Discharge of eggs from ovary, 549

independent of sexual intercourse,
565

mechanism of, 568

during menstruation, 572
Discus proligerus, 567
Distance and solidity, application of, by

the eye, 501, 502
Distinction between corpora lutea of

menstruation and pregnancy, 585
Diurnal variations, in exhalation of car-
bonic acid, 252

in production of urea, 345

in density and acidity of urine, 351
Division of nerves, 371

of heart, into right and left cavities,

678

DOBSOX, on variation in size of spleen, 208
DRAPEE, John C.. on production of urea,

345
Drugs, effect of, on newly born infant,

688
Ductus arteriosus, 679, 682

closure of, 679, 680

venosus, 676

obliteration of, 677
Duodenal glands, 152

fistula, 190
DUTROCHET, on temperature of plants, 25 G

on endosmosis of water with differ-
ent liquids, 309

Ear, 505

muscular apparatus of, 506

development of, 641
Earthy phosphates, 74, 77

iu urine, 353

precipitated by addition of an alkali,

O'}-i

Ectopia cordis, 651
%g, 544

its contents, 545

where formed, 546

of frog, 547, 548

of fowl, 549

changes in, while passing through

the oviduct, 549-552
pre-existence of, in ovary, 563
development of, at period of puberty,

564
periodical ripening and discharge,

565
discharge of, from Graafian follicle,

568
impregnation of, how accomplished,

561
development of, after impregnation,

586

of fowl, showing area vasculosa, 603
ditto, showing formation of allantois,

604
of fish, showing vitelline circulation,

666
attachment of, to uterine mucous

membrane, 617
discharge of from uterus, at the time

of delivery, 633

condition of in newly born infant, 663
Elasticity, of spleen, 208

of red globules of blood, 216
of lungs, 235, 237
of costal cartilages, 237
of vocal cords, 241
of arteries, 281
Electrical current, effect of on muscles,

389

on nerve, 391
different effects of direct and inverse,

394

Electrical fishes, phenomena of, 396
j Electricity, no manifestations of in irri-
tated nerve, 397
Elevation of temperature, after division

of sympathetic, 261, 521
Elongation of heart in pulsation, 275

anatomical causes of, 276
Embryo, formation of, 586
Embryonic spot, 590
Eucephalon, 381, 417

ganglia of, 386
Endosmosis, 307

of fatty substances, 171
in capillary circulation, 314
conditions of, 308
cause of, 311

: x: z z

of iodide of potassim, 3W

ofanopine,313
of nax Tomiea, 314

o ?
of aankn, during jng-

ZV_:r. .-; . :;1

Entomb enejsted, 534

nKide of production, 536
IfrithdiM, in saliva, 134

of gastric fcffieles, 134

of intestine, doing digestion, 172

of fa fp*«l KCff gJL-t

173

<fti OwllM*, :>:.

in different kinds of

•Mi, H

i- if. —

of, 93

in the body, 94
as ingredients of the

food, i«:«

7;.:-- r_i-.-r; :: •/_- ' '. -•-.: -.4
Fatt> da&eueiiliuii of daeidua, 634

of muscular fibres of oieros, after

:- .-.V. '
¥eees,160

reorcans,546

:: -:c. :,:
•I :;-:. Ml
of sow, 553

«' '* " ~* - ••• '. — i— «^.- " ^; r * .1.

"V:.f 1

acid, of vine, 359
alkaline, of ditto, 360
Fibrin, K«0

of the blood, 223

. :i*-; i: - ::' ii.:

raiding qoantitj of, in blood of dif.

T-:L-. __4

i--- 4-; I

of, panljns senribilitj of

-':: ;" '

ling«db«»A 0^456

= -l;i r-:: ::. -.' .
Fbh, cirembtiom of, 247

Rah, electrical,

::-:-:
•Tbnimai

of.Stt

:: ri'.i-.-. :r~
Kstula, jwrtne, Dr.

ofev.459

:,-i^:, - -

::'. --I

n

l^:;:z ::'. 1".

Prof. Austin, Jr., stereonne, in
contents of latpt intestine, 160
«holesten,m blood of jngolar rein,

in

: .;,:r i--.-'..,. 1-

of,665
::. -T

134
of Liebexkuhn,m

INDEX.

697

Follicles, of Brunner's glands, 152

(jrniatian, 54»J, 567

of uterus, 554, (J15
Food, 105

composition of, 112

daily quantity required, 113

effect of cooking on, 114
Foramen ovale, 680

valve of, 664

closure of, 684

Force, nervous, nature of, 395
Formation of sugar in liver, 200

in fetus, 64^
Fossa ovalis, 680
Functions, animal, 59

vegetative, 58

of teeth, 121

of saliva, 129

of gastric juice, 141

of pancreatic juice, 155

of intestinal juices, 153

of bile, 193

of spleen, 210

of mucus, 328

of sebaceous matter, 329

of perspiration, 331

of the tears, 332

Galvanism, action of, on muscles, 389

on nerves, 391
Ganglion, of spinal cord, 380

of tuber annuiare, 438

of medulla oblongata, 439

Casseriau, 451

of Andersch, 460

pueumogastric, 461

ophthalmic, 514

spheno-palatiue, 489, 514

submaxillary, 514

otic, 515

seniiluuar, 516

impar, 516

Ganglionic system of nerves, 379, 514
Ganglia, nervous, 372

of radiata, 373

of mollusca, 375

of articulata, 376

of posterior roots of spinal nerves,
3bO

of alligator's brain, 382

of rabbit's brain, 383

of medulla oblongata, 384

of human brain, 386

of great sympathetic, 514

olfactory, 382, 418

optic, 3b2, 434
Gases, diffusion of, in lungs, 239

absorption and exhalation of, by

lungs, 244
by the tissues, 248
Gastric follicles, 134
Gastric juice, mode of obtaining, 137

composition of, 139

j Gastric juice, action on food, 141

interference with Trommer's test, 143
interference with action of starch

and iodine, 144
daily quantity of, 147
solvent action of, on stomach, after

death, 149
Gelatine, how produced, 64

effect of feeding animals on, 109
Generation, 527

spontaneous, 527
of infusoria, 530
of parasites, 533
of encysted entozoa, 535
of taenia, 538
sexual, by germs, 540
Germ, nature of, 540
Germination, heat produced in, 238
Germinative vesicle, 545

disappearance of, in mature egg, 586
Germinative spot, 545
Gills, of fish, 232

of menobranchus, 233
Glands, of Brunner, 152
mesenteric, 168
vascular, 210
Meibomian, 329
perspiratory, 330
action of, in secretion, 324
Glandulae solitariae and agminatse, 162
Globules, of blood, 213
red, 214

different appearances of, under

microscope, 214, 215
mutual adhesion of, 215
color, consistency, and structure

of, 216

action of water on, 217
composition of, 218
size, &c., in different animals,

219
white, 220

action of acetic acid on, 221
red and white, movement of, in

circulation, 297
Globuline, 101, 218
Glomeruli, of Wolffian bodies, 656
Glosso-pharyngeal nerve, 459

action of, in swallowing, 460
Glottis, movements of, in respiration, 240
in formation of voice, 464
closure of, after section of pneunio-

gastrics, 467
Glycine, 181
Glyco-cholic acid, 180
Glyco-cholate of soda, 180

its crystallization, 178, 179
Glycogenic function of liver, 200

in foetus, 649
Glycogenic matter, 204

its conversion into sugar, 204
GOSSELIN, experiments on imbibition by
cornea, 313

698

INDEX.

Graafian follicles, 516, 567

structure of, 567

rupture of, and discharge of egg, 568

ruptured during menstruation, 672

condition of foetus at terra, 663
Gray substance, of nervous system, 372

of spinal cord, 380

of brain, 386

its want of irritability, 417
Great sympathetic, 514

anatomy of, 515

sensibility and excitability of, 517

connection of, with special senses,
518

division of, influence on animal heat,
521

on pupil and eyelids, 522

reflex actions of, 524
Gubernaculum testis, 659

function of, in lower animals, 661
Gustatory nerve, 452, 483

HAMMOND, Prof. Win. A., on effects of
non -nitrogenous diet, 108

on production of urea, 344
Haematine, 102, 218
Hairs, formation of, in embryo, 643
Hare-lip, 653

HARVEY, on motions of heart, 273
Hearing, sense of, 505

apparatus of, 506

analogy of with touch, 510, 511
Heart, 265

of fish, 265

of reptiles, 266

of mammalians, 267

of man, 268

circulation of blood through, 270

sounds of, 270

movements of, 273

impulse, 279

development of, 651, 678
Heat, vital, of animals, 253

of plants, 256

how produced, 257

increased by division of sympathetic

nerve, 261, 521
Hemispheres, cerebral, 419

remarkable cases of injury to, 419,
420

effect of removal, on pigeons, 421

efl'ect of disease, in man, 422

comparative size of, in different races,
423

functions of, 425

development of, 638

Hemorrhage, from placenta, in parturi-
tion, 633
Hepatic circulation, 339

development of, 675

Herbivorous animals, respiration of, 50,
243

urine of, 346, 348

Hernia, congenital, diaphragmatic, 651
umbilical, 646
inguinal, 661
Hippurate of soda, 348
Hunger and thirst, continue after divi-
sion of pneumogastric, 473
Hydrogen, displacement of gases in blood

by, 245
exhalation of carbonic acid in an

atmosphere of, 249

Hygroscopic property of organic sub-
stances, 97
Hypoglossal nerve, 477

Imbibition, 307

of liquids, by different tissues, 312

by cornea, experiments on, 313
Impulse, of heart, 279
Infant, newly-born, characteristics of, 687
Inflammation of eyeball, after division

of 5th pair, 455
Infusoria, 529

different kinds of, 530

conditions of their production, 531

Schultze's experiment on generation

of, 532

Ingiiinal hernia, congenital, 661
Injection of placental sinuses from ves-
sels of uterus, 627

Inorganic substances, as proxhnate prin-
ciples, 69

their source and destination, 78
Inosculation, of veins, 291

of capillaries, 296

of nerves, 372
Insalivation, 123

importance of, 131

function of, 132
Inspiration, how accomplished, 236

movements of glottis in, 240
Instinct, nature of, 444
Integument, respiration by, 252

development of, 643
Intellectual powers, 422

in animals, 444
Intestine, of fowl, 117

of man, 119

juices of, 150

digestion in, 150-159

epithelium of, 172

disappearance of bile in, 196

development of, 593, 644
Intestinal digestion, 150
Intestinal juices, 151

action of, on starch, 153
Involution of uterus after delivery, 635
Iris, movements of, 367, 435, 501, 518

after division of sympathetic, 522
Irritability, of gastric mucous membrane,
137

of the heart, 276

of muscles, 389

of nerves, 391

INDEX.

JACKSON, Prof. Samuel, on digestion of fat

in intestine, 154
Jaundice, 185

yellow color of urine in, 357

Kidneys, peculiarity of circulation in,

305
elimination of medicinal substances

by, 357

formation of, 656

KCCIIENMEISTER, experiments on produc- i
tiouoftseniafromcysticercuri, 1
538 '

of cysticercus from eggs of
taeiiia, 539

Lachrymal secretion, 332

its function, 333
Lactation, 333

variations in composition of milk

during, 337
Lacteals, 168, 170, 319

and lymphatics, 167, 172
Larynx, action of, in respiration, 222

in formation of voice, 464
nerves of, 462, 464
protective action of, 466
movements in respiration, 466
LASSAIGNE, experiments on saliva, 132

analysis of lymph, 318
Layers, external and internal, of blasto-

derniic membrane, 688
Lead, salts of, action in distinguishing

the biliary matters, 183
LEHMAXN, on formation of carbonates in

blood, 76

on total quantity of blood, 231
on effects of non-nitrogenous diet,

108

Lens, crystalline, action of, 495
LEUCKART, on production of cysticercus,

539
LIEBIG, on absorption of different liquids

under pressure, 310

Ligament of the ovary, formation of, 662
Limbs, formation of, in frog, 594
in human embryo, 642
Liver, vascularity of, 338
lobules of, 338, 339
secreting cells, 339, 340
formation of sugar in, 200
congestion of, after feeding, 207
development of, 649, 675
Liver cells, 92, 340

their action in secretion, 340
Liver-sugar, formation of, 200
after death, 203
in foetus, 649
Lobules, of lung, 235
of liver, 338, 339
Local production of carbonic acid, 248

of animal heat, 261
Local variations of circulation, 305

LOXGET, on interference of albuminose

with Trommer's test, 143
on sensibility of glosso-pharyngeal

nerve, 459
on irritability of anterior spinal

roots, 401

LOXGET AND MATTEUCCI, experiment on
signs of electricity in an irritated
nerve, 397

Long and short-sightedness, 496
Lungs, structure of, in reptiles, 234

in man, 235
alteration of, after division of pneu-

mogastrics, 469
Lymph, 169, 318

quantity of, 320
Lymphatic system, 168, 317

MAGNUS, on proportions of oxygen and

carbonic acid in blood, 245
Male organs of generation, 556

development of, 658
Malpighian bodies of spleen, 209
Mammalians, circulation in, 267
Mammary gland, structure of, 333

secretion of, 334
MARCET, on excretiue, 160
MAREY, M., experiments on arterial pul-
sation, 285
Mastication, 121

unilateral, in ruminating animals,
127

retarded by suppressing saliva, 131
Mecouium, 648
Medulla oblongata, 384, 439

ganglia of, 385, 386

reflex action of, 440

effect of destroying, 442

development of, 6bb
Meibomian glands, 329
Melanine, 103

Membrane, blastodermic, 688
Membrana granulosa, 567
Membrana tympani, action of, 508
Memory, connection of, with cerebral

hemispheres, 425

Menobranchus, size of blood-globules in,
220

gills of, 233

spermatozoa of, 557
Menstruation, 570

commencement and duration of, 571

phenomena of, 571

rupture of Graafian follicles in, 572

suspended during pregnancy, 571,

581

Mesenteric glands, 168, 317
MICHEL, Dr. Myddleton, rupture of Graaf-

ian follicle in menstruation, 572
Milk, 333

composition and properties of, 333,
334

microscopic characters, 335

700

INDEX.

Milk, souring and coagulation of, 336

variations in, during lactation, 337
Milk-sugar, 83

converted into lactic acid, 336
Mollusca, nervous system of, 375
MOORE AND PENNOCK, experiments on

movements of heart, 275
Motion, 400

Motor cranial nerves, 449
Motor nervous fibres, 403
Motor oculi cornrnunis, 450

externus, 451
Movements, of stomach, 145

of intestine, 164

of heart, 273

of chest, in respiration, 237

of glottis, 240

associated, 408

of foetus, 631
Mucosine, 101
Mucous follicles, 327
Mucous membrane, of stomach, 133

of intestine, 151

of tongue, 483

of uterus, 554, 615
Mucus, 327

composition and properties of, 328

of mouth, 125

of cervix uteri, 554
Muscles, irritability of, 388

directly paralyzed by sulpho-cyanide
of potassium, 390

consentaneous action of, 430

of respiration, 236
Muscular fibres, of spleen, 208, 209

of heart, spiral and circular, 277
Muscular irritability, 388

duration after death, 388

exhausted by repeated irritation,

390
Musculine, 102

Nails, formation of, in embryo, 643
NEGRIER, on rupture of Grraafian follicle,

in menstruation, 572
Nerve-cells, 372
Nerves, division of, 372

inosculation of, 373

irritability of, 390

spinal, 39 S

cranial, 446

olfactory, 446

optic, 447

auditory, 447

oculo-motorius, 450

patheticus, 451

motor externus, 451

masticator, 452

facial, 456

hypoglossal, 477

spinal accessory, 474

trifacial (5th pair), 451

glosso-pharyngeal, 459

Nerves, pneumogastric, 461

superior and inferior laryngeal, 4G2

great sympathetic, 514
Nervous filaments, 368

of brain, 309

of sciatic nerve, 370

motor and sensitive, 375
Nervous force, how excited, 391

nature of, 395

Nervous tissue, two kinds of, 368
Nervous irritability, 390

how shown, 391

duration of, after de'ath, 391

exhausted by excitement, 392

destroyed by woorara, 393

distinct from muscular, 395

nature of, 395
Nervous system, 365

general structure and functions of,
365-387

of radiata, 373

of mollusca, 375

of articulata, 376

of vertebrata, 379

reflex action of, 374

Network, ..capillary, in Peyer's glands,
162

in web of frog's foot, 296

in lobule of liver, 339
Newly-born infant, weight of, 687

respiration in, 687

nervous phenomena of, 688

comparative size of organs in, 689
NEWPORT, on temperature of insects, 256
Nitric acid, action of, on bile-pigment,
184

precipitation of uric acid by, 354
Nitrogen, exhalation of, in respiration,

242
Nutrition, 61-364

Obliteration, of ductus venosus, 677

of ductus arteriosus, 680
Oculo-motorius nerve, 450
(Esophagus, paralysis of, after division
of pneumogastric, 463

development of, 645, 650
OEstruation, phenomena of, 569
Oleaginous substances, 86

in different kinds of food, 88

condition of, in the tissues and
fluids,' 88-93

partly produced in the body, 93

decomposed in the body, 94
in the blood, 170

indispensable as ingredients of the
food, 107

insufficient for nutrition, 108
Olfactory apparatus, 489

protected by two sets of muscles, 520

commissures, 382, 418
Olfactory ganglia, 382, 418

their function, 418

INDEX.

701

Olfactory nerves, 489
Olivary bodies, 384
Omphalo-mesenteric vessels, 666
Ophthalmic ganglion, 514
Optic ganglia, 382, 434
Optic nerves, 447

decussation of, 436,437
Optic thalami, 418

development of, 638
Organs of special sense, 483, 489, 493,
507

development of, 640
Organic substances, 95

indefinite chemical composition of,
95

hygroscopic properties, 97

coagulation of, 98

catalytic action, 98

putrefaction, 99

source and destination, 104

digestion of, 141
Origin, of plants and animals, 527

of infusoria, 529

of animal and vegetable parasites,
532

of encysted entozoa, 534
Ossification of skeleton, 642
Osteiue, 102
Otic ganglion, 515
Ovary, 541

of taenia, 541

of frog, 547

of fowl, 551

of human female, 553
Ovaries, descent of, in foetus, 661

condition at birth, 663
Oviparous and viviparous animals, dis-
tinction between, 563
Oxalic acid, produced in urine, 360
Oxygen, absorbed in respiration, 242

daily quantity consumed, 242

state of solution in blood, 245

dissolved by blood-globules, 245

absorbed by the tissues, 248

exhaled by plants, 260

Palate, formation of, 653
Pancreatic juice, 153

mode of obtaining, 154

composition of, 155

action on fat, 155

daily quantity of, 155
Pancreatine, 101

in pancreatic juice, 155
PANIZZA, experiment on absorption by

bloodvessels, 165

Paralysis, after division of anterior root
of spinal nerve, 402

direct, after lateral injury of spinal
cord, 405

crossed, after lateral injury of brain,
405

facial, 458

Paralysis of muscles, by sulpho-cyanide

of potassium, 390
of motor nerves, by woorara, 393,

413
of sensitive nerves, by strychnine,

413

of voluntary motion and sensation,
after destroying tuber annulare,
438
of pharynx and oesophagus, after

section of pneumogastrics, 463
of larynx, 465, 467
of muscular coat of stomach, 473
Paraplegia, reflex action of spinal cord

in 411
Parasites, 532

conditions of development of, 533
mode of introduction into body, 534
sexless, reproduction of, 535
Parotid saliva, 126
Parturition, 633

Par vagum, 461. See Pneumogastric
Patheticus nerve, 451
PELOUZE, composition of glycogenic mat-
ter, 204

Pelvis, development of, 642
PEXXOCK AND MOORE, experiments on

movements of heart, 275
Pepsine, 101

in gastric juice, 139
Perception of sensations, after removal

of hemispheres, 422
destroyed, after removal of tuber

annulare, 438
Periodical ovulation, 563
Peristaltic motion, of stomach, 145
of intestine, 164
of oviduct, 548, 550
PERKINS, Maurice, composition of parotid

saliva, 126
Perspiration, 330

daily quantity of, 331
composition and properties of, 331
function, in regulating temperature,

331

Pettenkofer's test for bile, 185
Peyer's glands, 162
Pharynx, action of, in swallowing, 460,

461

formation of, 650
Phosphate of lime, its proportion in the

animal tissues and fluids, 74
in the urine, 353
precipitated by alkalies, 354
Phosphate, triple, in putrefying urine,

362
Phosphates, alkaline, 77

in urine, 353
earthy, 74, 77

in urine, 353

of magnesia, soda, and potassa, 77
Phosphorus, not a proximate principle, 63
Physiology, definition of, 49

'02

IXDEX.

Phrenology, 427

objections to, 428

practical difficulties of, 428, 429
Pigeon, after removal of cerebrum, 421

of cerebellum, 431
Placenta, 621

comparative anatomy of, 622

formation of, in human species, 623

foetal tufts of, 625

maternal sinuses of, 626

injection of, from uterine vessels,
627

function of, 628

separation of, in delivery, 633
Placental circulation, 624, 628
Plants, vital heat of, 256

generative apparatus of, 540
Plasma of the blood, 223
Pneumic acid, 247
Pneumogastric nerve, 461

its distribution, 462

action of, on pharynx and resopha-

gus, 463
on larynx, 464
in formation of voice, 464
in respiration, 466

effect of its division on respiratory
movements, 466, 467

cause of death after division of, 470

influence of, on oesophagus and sto-
mach, 473

Pneumogastric ganglion, 461
POGGIALE, on glycogenic matter in but-
cher's meat, 205
Pons Varolii, 387
Portal blood, quantity of fibrin in, 224

temperature of, 262
Portal vein, in liver, 338

development of, 675
Posterior columns of spinal cord, 381
Primitive trace, 590
Production, of sugar in liver, 200

of carbonic acid, 246

of animal heat, 253

of urea in blood, 343

of infusorial animalcules, 529

of animal and vegetable parasites,

532
Proximate principles, 61

definition of, 63

mode of extraction, 64

manner of their association, 65

varying proportions of, 60

three distinct classes of, 67
Proximate principles of the first class
(inorganic), 69

of the second class (crystallizable
substances of organic origin), 79

of the third class (organic sub-
stances), 95
Ptyaline, 124
Puberty, period of, 565

signs of, in female, 570

Pulsation, of heart, 270 .

in living animal, 274

of arteries, 282
Pupil, action of, 367, 435

contraction of, after division of sym-
pathetic, 522
Pupillary membrane, 640
Putrefaction, 99

of the urine, 358

Pyramids, anterior, of medulla oblon-
gata, 384

Quantity, daily, of water exhaled, 71

of food, 113

of salivaj 128

of gastric juice, 147

of pancreatic juice, 155

of bile, 188

of air used in respiration, 238

of oxygen used in respiration, 242

of carbonic acid exhaled, 250

of lymph and chyle, 320

of fluids secreted and reabsorbed, 323

of material absorbed aiid discharged,
363

of perspiration, 331

of urine, 349

of urea, 344

of urate of soda, 348
Quantity, entire, of blood in body, 231

Rabbit, brain of, 383

Races of men, different capacity of, for

civilization, 424

Radiata, nervous system of, 373
Rapidity of circulation, 302
Reactions, of starch, 82

of sugar, 84

of fat, 86

of saliva, 124, 125

of gastric juice, 139

of intestinal juice, 153

of pancreatic juice, 155

of bile, 175

of mucus, 328

of milk, 334

of urine, 353
Reasoning powers, 425

in animals, 444
Red globules of blood, 213
Reflex action, 374

in centipede, 377

of spinal cord, 408

of medulla oblongata, 440

of tuber annulare, 443

of brain, 444

of optic tubercles, 435

in newly born infant, 688
Regeneration, of uterine mucous mem-
brane after pregnancy, 633, 634

of walls of uterus, 635
REGNAULT AND REISET, on absorption of
oxygen, 243

INDEX.

703

REID, Dr. John, experiment on crossing

of streams in foetal heart, 682
Reproduction, 525

nature and object of, 525, 527

of parasites, 533

of taenia, 538

by germs, 540
Reptiles, circulation of, 266
Respiration, 232

by gills, 233

by lungs, 234

by skin, 252

changes in air during, 241

changes in blood, 243

of newly born infant, 687
Respiratory movements of chest, 236

of glottis, 240

after section of pneumogastrics, 466

after injury of spinal cord, 441
Restiform bodies, 385
Rhythm of heart's movements, 279
Rotation of heart during contraction, 278
Round ligament of the uterus, formation
of, 6(J2

of liver, 677

Rumination, movements of, 118, 127
Rupture of Graafian follicle, 568

in menstruation, 572
Rutting condition, in lower animals, 569

Saccharine substances, 83

in stomach and intestine, 150

in liver, 200

in blood, 207

in urine, 357
Saliva, 123

different kinds of, 125

daily quantity of, 127

action on boiled starch, 129

variable, 130

does not take place in stomach, 130

physical function of saliva, 131

quantity absorbed by different kinds

of food, 132
Salivary glands, 125
Salts, biliary, 177

of the blood, 225

of urine, 353
Saponification, of fats, 87
SCHARLIXG, on diurnal variations in exha-
lation of carbonic acid, 252
SCHULTZE, experiment on generation of

infusoria, 531

Scolopendra, nervous system of, 376
Sebaceous matter, 328

composition and properties of, 329

function of, 329

in fetus, 643
Secretion, 324

varying activity of, 326

of saliva, 125

of gastric juice, 137

of intestinal juice, 152

Secretion of pancreatic juice, 154

of bile, 188, 337

of sugar in liver, 200

of mucus, 327

of sebaceous matter, 328

of perspiration, 330

of the tears, 332

of bile in fcetua, 649
Segmentation of the vitellus, 587
Seminal fluid, 556

mixed constitution of, 560
Sensation, 398

remains after destruction of hemi-
spheres, 422

lost after removal of tuber annulare,
438

special conveyed by pneurnogastric

nerve, 440, 466, 468

Sensation and motion, distinct seat of, in
nervous system, 400

in spinal cord, 403

Sensibility, of nerves to electric current,
391

and excitability, definition, of, 400

seat of, in spinal cord, 403

in brain, 417

of facial nerve, 459

of hypoglossal nerve, 477

of spinal accessory, 475

of great sympathetic, 517
Sensibility, general and special, 478

special, of olfactory nerves, 446, 489

of optic nerves, 447

of auditory nerves, 447

of lingual branch of 5th pair, 484

of glosso-pharyngeal, 460
, of pueumogastric, 468
Sensitive nervous filaments, 375
Sensitive fibres, crossing of, in spinal cord,
405

of facial nerve, source of, 459
Sensitive cranial nerves, 449
Septa, inter-auricular and inter-ventri-
cular, formation of, 678, 680
S£QUARD, on crossing of sensitive fibres

in spinal cord, 4U5
Serum, of the blood, 227
Sexes, distinctive characters of, 540
Sexless entozoa, 534
Sexual generation, 540
Shock, effect of, in destroying nervous

irritability, 393
SIEBOLD, on production of taenia from

cysticercus, 538
Sight, 492

apparatus of, 493. See Vision.
Sinus terminalis, of area vasculosa, 665
Sinuses, placental, 624, 626
Skeleton, development of, 641
Skin, respiration by, 252

sebaceous glands of, 328

perspiratory glands of, 330

development of, 643

704:

INDEX.

Smell, 488

ganglia of, 382, 489

nerves of, 446, 489

injured by division of 5th pair, 454
SMITH, Dr. Southwood, on cutaneous and

pulmonary exhalation, 331
Solar plexus of sympathetic nerve, 516
Solid bodies, vision of with two eyes, 502
Sounds, of heart, 270

how produced, 271

vocal, how produced, 464

destroyed by section of inferior la-

ryngeal nerves, 465

of spinal accessory, 475

Sounds, acute and grave, transmitted by

membrana tympani, 508
Special senses, 478
Species, mode of continuation, 527
Spermatic fluid, 556

mixed constitution of, 560
Spermatozoa, 556

movements of, 558

formation of, 559
Spina bifida, 641
Spinal accessory, 474

sensibility of, 475

communication of, with pneumogas-
tric, 475

influence of, on larynx, 475
Spinal column, formation of, 591, 641
Spinal cord, 379, 398

commissures of, 381

anterior and posterior columns, 381

origin of nerves from, 380

sensibility and excitability of, 403

crossed action of, 404

reflex action of, 408 ,

protective action of, 413, 414

influence on sphincters, 414

effect of injury to, 414

on respiration, 441

formation of, in embryo, 591, 645
Spinal nerves, origin of, 380
Spleen, 208

Malpighian bodies of, 209

extirpation of, 211
Spontaneous generation, 527
Starch, 79

proportion of, in different kinds of
food, 80

varieties of, 80-82

reactions of, 82

action of saliva on, 129

digestion of, 150
Starfish, nervous system of, 373
Stercorine, 160
Stereoscope, 503

St. Martin, case of gastric fistula in, 135
Strabismus, after division of motor oculi
communis, 451

of motor externus, 451
Striated bodies, 419
Sublingual gland, secretion of, 125

Submaxillary ganglion, 514
gland, secretion of, 125
Sudoriparous glands, 330
Sugar, 83

varieties of, 83

composition of, 84

tests for, 84

fermentation of, 85

proportion in different kinds of fofcd,

86

source and destination, 86
produced in liver, 200
discharged by urine in disease, 357
Sugar in liver, formation of, 200
percentage of, 202
produced in hepatic tissue, 203
from glycogenic matter, 204
absorbed by hepatic blood, 206
decomposed in circulation, 206
Sulphates, alkaline, in urine, 353
Sulphur of the bile, 181

not discharged with the feces, 197
Swallowing, 131

retarded by suppression of saliva,

133

by division of pneumogastric, 463
Sympathetic nerve, 514
its distribution, 515
sensibility and excitability of, 517
influence of, on special senses, 518
on pupil, 518

on nutrition of eyeball, 455
on nasal passages, 520
on ear, 520, 521
on temperature of particular

parts; 521
reflex actions of, 524

Tadpole, development of, 592

transformation into frog, 594
Tsenia, 536

produced by metamorphosis of cys-
ticercus, 538

single articulation of, 541
Tapeworm, 536

mode of generation, 537
Taste, 481

nerves of, 483

conditions of, 485

injury of, by paralysis of facial nerve,

487

Taurine, 181
Tauro-cholate of soda, 181

microscopic characters of, 179
Tauro-cholic acid, 181
Tears, 332

their function, 332
Teeth, of serpent, ] 21

of polar bear, 122

of horse, 122

of man, 123

first and second sets of, 689
Temperature of the blood, 254

INDEX.

Temperature of different species of ani-
mals, 255

of the blood in different organs, 262

elevation of, after section of sympa-
thetic nerve, 261, 521
Tensor tympani, action of, 506, 508
Tests, for starch, 82

for sugar, 84

for bile, 184

Pettenkofer's, 185
Testicles, 559

periodical activity of, in fish, 5G1

development of, 658

descent of, 658, 659
Tetanus, pathology of, 410
Thalami, optic, in rabbit, 383

in man, 418

function of, 419
Thoracic duct, 168, 170
Thoracic respiration, 441
Tongue, motor nerve of, 477

sensitive, 452, 456, 483
Trichina spiralis, 535
Tricuspid valve, 268. See Auriculo-ven-

tricular

Triple phosphate, in putrefying urine, 362
Trommer's test for sugar, ,V4

interfered with by gastric juice, 143
Tuber annulare, 386, 438

effect of destroying, 438

action of, 439
Tubercula quadrigemina, 382, 431

reflex action of, 435

crossed action of, 436

development of, 637, 638
Tubules of uterine mucous membrane,

615

Tufts, placental, 625

Tunica vaginalis testis, formation of, 660
Tympanum, function of, in hearing, 508

Umbilical cord, formation of, 631

withering and separation of, 689
Umbilical hernia, 646
Umbilical vesicle, 596

in human embryo, 597

in chick, 604

disappearance of, 631
Umbilical vein, formation of, 669

obliteration of, 677
Umbilicus, abdominal, 592

amniotic, 600

decidual, 617
Unilateral mastication, in ruminating

animals, 127
Urate of soda, 347

its properties, source, daily quantity,

&c., 348

Urates of potassa and ammonia, 348
Urachus, 647
Urea, 343

source of, 343

mode of obtaining, 344

45

Urea, conversion into carbonate of am-
monia, 344
daily quantity of, 344
diurnal variations in, 345
decomposed in putrefaction of urine,
360

Uric acid, 347, 354

Urine, 349

general character and properties of,

349

quantity and specific gravity, 350
diurnal variations of, 351
composition of, 352
reactions, 353

interference with Trommer's test, 355
accidental ingredients of, 35 r>
acid fermentation of, 359
alkaline fermentation of, 360
final decomposition of, 363

Urinary bladder, paralysis and inflam-
mation of, after injury to spinal
cord, 415
formation of, in embryo, 647

Urosacine, 103

Uterus, of lower animals, 553
of human female, 554
mucous membrane of, 614
changes in, after impregnation, 615
involution of, after delivery, 634
development of, in foetus, 661
position of, at birth, 663

Uterine mucous membrane, 614
tubules of, 615
conversion into decidua, 615
exfoliation of, at the time of delivery,

633
its renovation, 634

Valve, Eustachian, 681

of foramen ovale, 684
Valves, cardiac, action of, 268

cause of heart:s sounds, 271
Vasa deferentia, formation of, 658
Vapor, watery, exhalation of, 71

from lungs, 242

from the skin, 252

Variation, in quantity of bile in different
animals, 188

in production of live^-sugar, 202

in size of spleen, 208

in rapidity of coagulation of blood,
227

in size of glottis in respiration, 240

in exhalation of carbonic acid, 250

in temperature of blood in different
parts, 262

in composition of milk during lac-
tation, 337

in quantity of urea, 345

in density and acidity of urine, 350
Varieties of starch, 80

of suear, 83

of fat, 86

706

IXDEX.

Varieties of biliary salts in different ani-
mals, 182

Vegetable food, necessary to man, 106
Vegetable parasites, 532
Vegetables, production of heat in, 256

absorption of carbonic acid and ex-
halation of oxygen by, 49, 260
Vegetative functions, 58
Veins, 290

their resistance to pressure, 290

absorption by, 165

action of valves in, 293

motion of blood through, 291

rapidity of circulation in, 294

omphalo-meseuteric, 666

umbilical, 669

vertebral, 672
Vense cavse, formation of, 673

position of, in foetus, 681
Vena azygos, superior and inferior, for-
mation of, 673

Venous system, development of, 672
Ventricles of heart, single in fish and
reptiles, 265, 266

double in birds and mammalians,
267

situation of, 268

contraction and relaxation of, 269

elongation during contraction, 275

muscular fibres of, 277
Vernix caseosa, 643
Vertebrata, nervous system of, 378
Vertebrae, formation of, 591, 641
Vesicles, adipose, 90

pulmonary, 235

seminal, 560
Vesiculse seminales, 560

formation of, 660

Vicarious secretion, non-existence of, 325
Vicarious menstruation, nature of, 325
Villi, of intestine, 163

absorption by, 164

of chorion, 609-611
Vision, 492

ganglia of, 382, 434

nerves of. 447, 493

apparatus of, 493

distinct, at different distances, 496

circle of, 499

Vision, of solid bodies with both eyes, 502
Vital phenomena, their nature and pecu-
liarities, 54
Vitellus, 541

segmentation of, 587

formation of, in ovary of fostus, 663
Vitelline circulation, 665

membrane, 544

spheres, 587

Vocal sounds, how produced, 464
Voice, formation of, in larynx, 464

lost, after division of spinal acces-
sory nerve, 475

Volition, seat of, in tuber annulare, 438
Vomiting, peculiar, after division of
pneurnogastrics, 473

Water, as a proximate principle, 69

its proportion in the animal tissues

and fluids, 70
its source, 70

mode of discharge from the body, 71
Weight of organs, in comparative, newly

born infant and adult, 689
White globules of the blood, 220
action of acetic acid on, 221
sluggish movement of, in circula-
tion, 297

White substance, of nervous system, 368
of Schwanu, 368
of spinal cord, 380
of brain, insensible and inexcitable,

417
Withering and separation of umbilical

cord, after birth, 689
Wolffian bodies, 655
structure of, 656
atrophy and disappearance of, 656,

657

vestiges of, in adult female, 662
WYMAN, Prof. Jeffries, on cranial nerves

of Rana pipiens, 449
fissure of hare-lip on median line,
637

Yellow color, of nrine in jaundice, 357
of corpus luteum, 579

Zona pellucida, 544

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ANATOMICAL ATLAS.

By Professors H. H. SMITH and W. E. HORNER, of the University of Pennsyl-
vania. 1 vol. 8vo., extra cloth, with nearly 650 illustrations. 13T See SMITH, p. 26.

ABEL (F. A.), F. C. S. AND C. L. BLOXAM.

HANDBOOK OF CHEMISTRY, Theoretical, Practical, and Technical; with a
Recommendatory Preface by Dr. HOFMANN. In one large octavo volume, extra cloth, of 662
pages, with illustrations. $3 25.

ASHVVELL (SAMUEL), M. D.,

Obstetric Physician and Lecturer to Guy's Hospital, London.

A PRACTICAL TREATISE ON THE DISEASES PECULIAR TO WOMEN.

Illustrated by Cases derived from Hospital and Private Practice. Third American, from the Third
and revised London edition. In one octavo volume, extra cloth, of 528 pages. $3 00.

The most useful practical work on the subject in
the English language. — Boston Med. and Surg.
Journal.

The most able, and certainly the most standard
and practical, work on female diseases that we hav«
yet seen. — Medico-Ckirurgical Review.

ARNOTT (NEILL), M. D.
ELEMENTS OF PHYSICS j or Natural Philosophy, General and Medical.

Written for universal u*e, in plain or non-technical language. A new edition, by ISAAC HAYS,
M. D. Complete in one octavo volume, leather, of 484 pages, with about two hundred iilustra
tions. $2 00.

BIRD (GOLD1NG), A. M., M . D., Ac.
URINARY DEPOSITS : THEIR DIAGNOSIS, PATHOLOGY, AND

THERAPEUTICAL INDICATIONS. Edited by EDMUND LLOYD BIRKETT, M. D. A new
American, from the last and enlarged London edition. Witheighty il lustrations on wood. In one
handsome octavo volume, of a^out 400 pages, extra cloth. $2 75. (Just Ready.)

Itcan scarcely be necessary for us to say anything . to the extension and satisfactory employment of our
of the merits of this well-known Treatise, which so therapeutic resources. In the preparation of this
admirably brings into practical application the re- ! newt dition of his work, it isobvious that Dr. Gold-
suits of those microscopical and chemical re- ! ing Bird has spared no pains to render it a faunful
searches regarding the physiology and pathology representation of the present state of scientific
of the urinary secretion, which have contributed so , knowledge on the subject it embraces.— Srir/iAan**
much to tae increase of our diagnostic powers, and Foreign Med.-Cair. Rsi-itic.

BENNETT (J. HUGHES), M.D., F. R. S. E.,

Professor of Clinical Medicine in the University of Edinburgh, &c.

THE PATHOLOGY AND TREATMENT OF PULMONARY TUBERCU-
LOSIS, and on the Local Medication of Pharyngeal and Laryngeal Diseases frequently mistaken
for or associated withj Phthisis. One vol. Svo.,extra cloth, with wood-cuts, pp.130. $125.

BARLOW (GEORGE H.), M . D.

Physician to Guy's Hospital, London, &c.

A MANUAL OF THE PRACTICE OF MEDICINE. With Additions by D.

F. CONDIE, M. D., author of" A Practical Treatise on Diseases of Children," 62x5. In one hand-
some octavo volume, extra cloth, of over 600 pages. $2 75. .

We recommend Dr. Barlow's Manual in the warm-
est manner as a most valuable vade-mecum. \Ve
bave had frequent occasion to consult it, and have

found it clear, concise, practical, and aoand. Bot-

ton Med. and Surg. Journal.

BLANCHARD & LEA'S MEDICAJU

BUDD (GEORGE), M. D., F. R. S.,

Professor of Medicine in King's College, London.

ON DISEASES OF THE LIVER. Third American, from the third and
enlarged London edition. In one very handsome octavo volume, extra cloth, with four beauti-
fully colored plates, and numerous wood-cuts, pp. 500. $3 00.
Has fairly established for itself a place among the I the text the most striking novelties which have cha-

elassical medical literature of England.— British \ racterized the recent progress of hepatic physiology

and Foreign Medico-Chir. Review. \ and pathology : so that although the size of the book

I is not perceptibly changed, the history of liver dis-
Dr. Budd's Treatise on Diseases of the Liver is j eases is made more complete, and is kept upon a level

now a standard work in Medical literature, and dur- with the pr0gress of modern science. *

ing the intervals which have elapsed between the
successive editions, the author has incorporated into

It is the best

work on Diseases of the Liver in any language. —
London Med. Times and Gazette.

BUCKNILL (J. C.), M. D., AND DANIEL H. TUKE, M. D.,

Medical Superintendent of the Devon Lunatic Asylum. Visiting Medical Officer to the York Retreat.

A MANUAL OF PSYCHOLOGICAL MEDICINE; containing the History,

Nosology, Description, Statistics, Diagnosis, Pathology, and Treatment of INSANITY. With
a Plate. In one handsome octavo volume, of 536 pages, extra cloth. $3 00.
The increase of mental disease in its various forms, and the difficult questions to which it is
constantly giving rise, render the subject one of daily enhanced interest, requiring on the part of
the physician a constantly greater familiarity with this, the most perplexing branch of his profes-
sion. At the same time there has been for some years no work accessible in this country, present-
jng the results of recent investigations in the Diagnosis and Prognosis of Insanity, and the greatly
improved methods of treatment which have done so much in alleviating the condition or restoring
the health of the insane. To fill this vacancy the publishers present this volume, assured that
the distinguished reputation and experience of the authors will entitle it at once to the confidence
of both student and practitioner. Its scope may be gathered from the declaration of the authors
that "their aim has been to supply a text book which may serve as a guide in the acquisition of
such knowledge, sufficiently elementary to be adapted to the wants of the student, and sufficiently
modern in its views and explicit in its teaching to suffice for the demands of the practitioner."

BENNETT (HENRY), M. D.
A PRACTICAL TREATISE ON INFLAMMATION OF THE UTERUS,

ITS CERVIX AND APPENDAGES, and on its connection with Uterine Disease. To which
is added, a Review of the present state of Uterine Pathology. Fifth American, from the third
English edition. In one octavo volume, of ab'out 500 pages, extra cloth. $2 00.

BROWN (ISAAC BAKER),

Surgeon- Accoucheur to St. Mary's Hospital, &c.

ON SOME DISEASES OF WOMEN ADMITTING OF SURGICAL TREAT-

MENT. With handsome illustrations. One vol. 8vo., extra cloth, pp. 276. $160.

Mr. Brown has earned for himself a high reputa- and merit the careful attention of every surgeon-
tion in the operative treatment of sundry diseases accoucheur. — Association Journal.
and injuries to which females are peculiarly subject. „, , ...

We can truly say of his work that it is animportant | .We haveno hesitation in recommending thi. book
addition to obstetrical literature. The operative
suggestions and contrivances which Mr. Brown de-
scribes, exhibit mach practical sagacity and skill,

female complaints a part of their study and practice.
— Dublin (quarterly Journal.

PRACTICAL

AVith a laudable desire to keep the book tip to the
scientific mark of the present age, every improve-
ment in analytical method has been introduced. In
conclusion, we would only say that, familiar from
long acquaintance with each page of the former
issues of this little book, we gladly place beside
them another presenting so many acceptable im-
provements and additions. — Dublin Medical Press,
Jan. 7, 1863.

BOWMAN (JOHN E.), M.D.
HANDBOOK OF MEDICAL CHEMISTRY. Edited by C.

L. BLOXAM. Third American, from the fourth and revised English Edition. In one neat volume,
royal l'/imo., extra cloth with numerous illustrations, pp.351. $175. (Now Ready, May, 1863.)
Of this well-known handbook we may say that this new edition is not merely a reprint of the last.
it retains all its old simplicity and clearness of ar-
rangement and description, whilst it has received
from the able editor those finishing touches which
the progress of chemistry has rendt red necessary. —
London Med. Times and Gazette, Nov. 29, 1862.

Nor is anything hurried over, anything shirked;
open the book where you will, you find the same
careful treatment of the subject manifested, ana the
best process for the attainment of the particular ob-
ject in view lucidly detailed and explained. And

BY THE SAME AUTHOR.

INTRODUCTION TO PRACTICAL CHEMISTRY, INCLUDING ANA-
LYSIS. Third American, from the third and revised London edition. With numerous illus-
trations. In one neat vol., royal i£ino., extra cloth. $175. (Just Ready.)

BEALE ON THE LAWS OF HEALTH IN RE-
LATION TO MIND AND BODY. A Series of
Letters from an old Practitioner to a Patient. In
one volume, royal 12mo., extra cloth, pp. 296.
80 cents.

,/SUSHNAN'S PHYSIOLOGY OF ANIMAL AND
VEGETABLE LIFE; a Popular Treatise, on the
Functions and Phenomena of Organic Life. In
•one handsome royal 12mo. volume, extra eioth,
wi th over 100 illustrations . pp . 234 , 80 centfl .

BUCKLER ON THE ETIOLOGY, PATHOLOGY.
AND TREATMENT OF FIBRO-BRONCHI-
TIS AND RHEUMATIC PNEUMONIA. ID
one 8vo. volume, extra cloth, pp.150. SI 25.

BLOOD AND URINE (MANUALS ON). BY
JOHN WILLIAM GRIFFITH, G. OWEN
REESE, AND ALFRED MARKWICK. One
thick volume, royal 12mo., extra cloth, with
plates, pp.460. $1 25.

BRODIE'S CLINICAL LECTURES ON SUR-
GERY. 1 vol. 8 vo. cloth. 350pp. 8125.

AND SCIENTIFIC PUBLICATIONS.

BUMSTEAD (FREEMAN J.) M. D.,
Lecturer on Venereal Diseases at the College of Pnysiciana and Surgeons, New York, &e.

THE PATHOLOGY AND TREATMENT OF VENEREAL DISEASES,

including the results of recent investigations upon the subject. With illustrations on wood, la
one very handsome octavo volume, of nearly 700 pages, extra cloth; $4 00.

By far the most valuable contribution to this par-
ticular branch of practice that has seen the light
within the iasc score of years. His clear and accu-
rate descriptions of the various forms of venereal
disease, and especially the methods of treatment he
proposes, are worthy of the highest encomium. In
these respects it is better adapted for the assistance
of the every-day practitioner than any other with
which we are acquainted. In variety of methods
proposed, in minuteness of direction, guided by care-
ful discrimination of varying forms affd complica-
tions, we write down the book as unsurpassed. It
is a work which should be in the possession of every
practitioner. — Chicago Med. Journal. Nov. 1S61.

The foregoing admirable volume comes to us, em-
bracing the whole subject of syphilology, resolving
many a doubt, correcting and confirming many an
entertained opinion, and in our estimation the best,
completes!, fullest monograph on this subject in our
language. As far as the author's labors themselves
are concerned, we feel it a duty to say that he has
not only exhausted his subject, but he has presented
to us, without the slightest hyperbole, the best di-
gested treatise on these diseases in our language.
He has carried its literature down to the present
moment, and has achieved his task in a manner
which cannot but redound to his credit. — British,
American Journal, Oct. 1S61.

We believe this treatise will come to be regarded
as high authority in this branch of medical practice,
and we cordially commend it to the favorable notice
of our brethren in the profession. For our own part,
we candidly confess that we have received n-any
new ideas from its perusal, as well as modified many
views which we have long, and, as we now think,
erroneously entertained, on the subject of syphilis.

To sum up all in a few words, this book is one which
no practising physician or medical student can very
\vell afford to do without. — American Med. Times,
Nov. 2, 1861.

The whole work presents a complete history of
venereal diseases, comprising mu?h interesting and
valuable material that has been spread through med-
ical journals within the last twenty years— the pe-
riod of many experiment* and investigations on the
subject — the whole carefully digested by the aid of
the author's extensive personal experience, and

1 offered to the profession in an admirable form. Its
completeness is secured by good plates, which are
especially full in the anatomy of the genital organs.
We have examined it with great satisfaction, and
congratulate the medical profession in America on
the nationality of a work that may fairly be called
original.— Berkshire Med. Journal, Dec. 1861.

One thing, however, we are impelled to say, that
we have met with no other book on syphilis, in the
English language, which gave so full, clear, and
impartial views of the important subjects or,
it treats. We cannot, however, refrain from ex-
pressing our satisfaction with the full and perspicu-
ous manner in which the subject has been presented,
and the careful attention to minute details, so use-
ful— not to say indispensable — in a practical ireatiae.
In conclusion, if we may be pardoned the use of a
phrase now become stereotyped, but which we here
employ in all seriousness and sincerity, we do not
hesitate to express the opinion that Dr. Bums lead's
Treatise on Venereal Diseases is a " work without

j which no medical library will hereafter be consi-

I dered complete." — Boston Med. and Surg. Journal.

| Sept. 5,1861.

BARCLAY (A. W.), M. D.,

Assistant Physician to St. George's Hospital, kc.

A MANUAL OF MEDICAL DIAGNOSIS ; being an Analysis of the Signs

and Symptoms of Disease. Second American from the second and revised London edition. In
one neat octavo volume, extra cloth, of 451 pages. $2 50.

The demand for a second edition of this work shows that the vacancy which it attempts to sup-
ply has been recognized by the profession, and that the efforts of the author to meet the want have
been successful. The revision which it has enjoyed will render it better adapted than before to
afford assistance to the learner in the prosecution of his studies, and to the practitioner who requires
a convenient and accessible manual for speedy reference in the exigencies of his daily duties. For
this latter purpose its complete and extensive Index renders it especially valuable, offering facilities
for immediately turning to any class of symptoms, or any variety of disease.

The task of composing jmch^ a work is neither an j We hope the volume will have an extensive cir-
culation, not among students of medicine only, but
practitioners also. They will never regret a faith-
ful study of its pages.— Cincinnati Lancet.

An important acquisition to medical literature.
It is a work of high merit, both from the vast im-
portance of the subject upon which it treats, aod
also from the real ability displayed in ;*s elabora-
tion. In conclusion, let us bespeak for this volume
that attention of every student of our art which it

easy nor a light one ; but Dr. Barclay has performed
it in a manner which meets our most unqualified
approbation. He is no mere theorist; he knows his
work thoroughly, and in attempting to perform it,
has not exceeded his powers. — British Med. Journal .

We venture to predict that the work will be de-
servedly popular, and soon become, like Watson's
Practice, an indispensable necessity to the practi-
tioner.— N. A. Med. Journal.

An inestimable work of reference for the young
practitioner and student.— Nashville Med. Journal .

so richly deserves— that place in every medical
library which it can so well adora.-- Peninsular
Medical Journal.

BARTLETT (ELISHA), M. D.
THE HISTORY, DIAGNOSIS, AND TREATMENT OF THE FEVERS

OF THE UNITED STATES. Anew and revised edition. By ALONZO CLARK, M. D., Prof.

of Pathology and Practical Medicine in the N. Y. College of Physicians and Surg sons, <fcc. la

one octavo volume, of six hundred pages, extra cloth. Price $3 00.

It is a work of great practical value and interest, [ stood deservedly high since its first publication. It
containing much that is new relative to the several will be seen that it has now reached its fourth edi-
diseases of which it treats, and, with the additions tion under the supervision of Prof. A. Clark, a gen-

of the editor, is fully up to the times. The distinct'
ive features of the different forms of fever are plainly
and forcibly portrayed, and the lines of demarcation
carefully and accurately drawn, and to the Ameri-
can practitioner is a more valuable and safe guide
than any work on fever extant. — Ohio Med. and
Surg. Journal.
This excellent monograph on febrile disease, has

tleinan who, from the nature of his studies and pur-
suits, is well calculated to appreciate and discuss
the many intricate and difficult questions in patho-
logy. His annotations add much to the interest of
the work, and have brought it well up to the condi-
tion of the science as it exists at the present day
in regard to this class of diseases.— Southern Med.
and Surg, Journal

BLANCHARD & LEA'S MEDICAL

BRANDE (WM. T.) D. C. L., AND ALFRED S. TAYLOR, M. D., F. R. S.

Of her Majesty's Mint, &c. Professor of Chemistry and Medical Jurisprudence in

Guy's Hospital.

CHEMISTRY. ID one handsome 8vo. volume of 696 pages, extra cloth. $3 50.

(Now Ready, May, 1863 )

« Having been engaged in teaching Chemistry in this Metropolis, the one for a period of forty,
and the other for a period of thirty years, it has appeared to us that, m spite of the number of books
already existing, there was room for an additional volume, which should be especially adapted for
the u<e of students. In preparing such a volume for the press, we have endeavored to bear in
mind, that the student in the present day has much to learn, and but a short time at his disposal for
the acquisition of this learning."— AUTHORS' PREFACE.

In reprinting this volume, its passage through the press has been superintended by a competent
chemist, who has sedulously endeavored to secure the accuracy so necessary in a work of this
nature. No notes or additions have been introduced, but the publishers have been favored by the
authors with some corrections and revisions of the first twenty-one chapters, which have been duly
inserted.

In so progressive a science as Chemistry, the latest work always has the advantage of presenting
the subject as modified by the results of the latest investigations and discoveries. That this advan-
tage has been made the most of, and that the work possesses superior attractions arising from its
clearness, simplicity of style, and lucid arrangement, are manifested by the unanimous testimony
of the English medical press.

It needs no great sagacity to foretell that this book
will be, literally, the Handbook in Chemistry of the
student and practitioner. For clearness of language,
accuracy of description, extent of information, and
freedom from pedantry and mysticism of modern
chemistry, no other text-book comes into competition
with it. The result is a work which for fulness of
matter, for lucidity of arrangement, for clearness of
style, is as yet without a rival. And long will it be
without a rival. For, although with the necessary
advance of chemical knowledge addenda will be re-
quired, there will be little to take away. The funda-
mental excellences of the book will remain, preserv-
ing it for years to come, what it now is, the best guide
to the study of Chemistry yet given to the world.—
London Lancet, Dec. 20, 1862.

Most assuredly, time has not abated one whit of the
fluency, the vigor, and the clearness with which they
not only have composed the work before us, but have,
so to say, cleared the ground for it, by hitting right

and left at the affectation, mysticism, and obscurity
which pervade some late chemical treatises. Thus
conceived, and worked out in the most sturdy, com-
mon sense method, this book gives, in the clearest aud
most summary method possible, all the facts and doc-
trines of chemistry, with more especial reference to
the wants of the medical student. — London Medical
Times and Gazette, Nov. 29, 1862.

If we are not very much mistaken, this book will
occupy a place which none has hitherto held among
chemists; for, by avoiding the errors of previous au-
thors, we have a work which, for its size, is certainly
the most perfect of any in the English language.
There are several points to be noted in this volume
which separate it widely from any of its compeers —
its wide application, not to the medical student only,
nor to the student in chemistry merely, but to every
branch of science, art, or commerce which is in any
way connected with the domain of chemistry. — LOT*'
. Review, Feb. 1863.

BARWELL (RICHARD,) F. R, C. S.,

Assistant Surgeon Charing Cross Hospital, Sec.

A TREATISE ON DISEASES OF THE JOINTS. Illustrated with engrav-
ings on wood. In one very handsome octavo volume, of about 500 pages, extra cloth; $3 00.

ing and faithful delineations of disease. — London
Med. Times and Gazette, Feb. 9, 1861.

This volume will be welcomed, as the record of
much honest research and careful investigation into

At the outset we may state that the work is
worthy of much praise, and bears evidence of much
thoughtful and careful inquiry, and here and there
"of no slight originality. We have already carritd
thi* notice further than we intended to do, but not
to the extent the work deserves. We can only add,
that the perusal of it has afforded us great pleasure.
The author has evidently worked very hard at his
subject, and his investigations into the Physiology
and Pathology of Joints have been carried on in a
manner which entitles him to be listened to with

attention and respect. We must not omit to men- I OD t'iie successful completion of his arduous task.—
tion the very admirable plates with which the vo- London Lancet, March 9, 1861.
lame is enriched. We seldom meet with such strik- I

the nature and treatment of a most important class
of disorders. We cannot conclude this notice of a
valuable and useful book without calling attention
to the amount of bonafide work it contains. It is no
slight matter for a volume to show laborious inves-
tigation, and at the same time original thought, on
the part of its author, whom v e may congratulate

CARPENTER (WILLIAM B.), M. D., F. R. S., fcc.,

Examiner in Physiology and Comparative Anatomy in the University of London.

f HE MICROSCOPE AND ITS REVELATIONS. With an Appendix con-

taining the Applications of the Microscope to Clinical Medicine, &c. By F. G. SMITH, M. D.

Illustrated by four hundred and thirty-four beautiful engravings on wood. In one large and very

handsome octavo volume, of 724 pages, extra cloth, $4 50.

The great importance of the microscope as a means of diagnosis, and the number of microsco-
pists who are also physicians, have induced the American publishers, with the author's approval, to
add an Appendix, carefully prepared by Professor Smith, on the applications of the instrument to
clinical medicine, together with an account of American Microscopes, their modifications and
accessories. This portion of the work is illustrated with nearly one hundred wood-cuts, and, it is
hoped, will adapt the volume more particularly to the use of the American student.

Those who are acquainted with Dr. Carpenter's
previous writings on Animal and Vegetable Physio-
logy, will fully understand how vast a store of know-
ledge he is able to bring to bear upon so comprehen-
sive a subject as the revelations of the microscope ;
and even those who have no previous acquaintance
with the construction or uses of this instrument,
will find abundance of information conveyed in clear

The additions by Prof. Smith give it a positive
claim upon the profession, for which we doubt not
he will receive their sincere thanks. Indeed, we
know not where the student of medicine will find
such a complete and satisfactory collection of micro-
scopic facts bearing upon physiology and practical
medicine as is contained in Prof. Smith 'e appendix;
and this of itself, it seems to us, is fully worth the

aad simple language.— Med, Times and Gazette. \ cost of the volume.— LovisvilU Medical Review.

AND SCIENTIFIC PUBLICATIONS.

CARPENTER (WILLIAM B.), M. D., F. R. S.,

Examiner in Physiology and Comparative Anatomy in the University of London.

PRINCIPLES OF HUMAN PHYSIOLOGY; with their chief applications to

Psychology, Pathology, Therapeutics, Hygiene, and Forensic Medicine. A new American, from
the last and revised London edition. With nearly three hundred illustrations. Edited, with addi-
tions, by FRANCIS GURNEY SMITH, M. D., Professor of the Institutes of Medicine in the Pennsyl-
vania Medical College, &c. In one very large and beautiful octavo volume, of about nine hundred
large pages, handsomely printed, extra cloth, $4 50 ; strongly bound in leather, with raised bands,

For upwards of thirteen years Dr. Carpenter's! To eulogize this great work would be superfluous,
work has been considered by the profession gene- I We should observe, however, that in this edition
rally, both in this countryand England, as the most ' the author has remodelled a large portion of the
valuable compendium on the subject of physiology former, and the editor has added much matter of in-
m our language. This distinctionit owes to the high terest, especially in the form of illustrations. Wo
attainments and unwearied industry of its accom- may confidently recommend it as the most complete
piished author. The present edition (which, like the work on Human Physiology in our language —
last American one, was prepared by the author him- Southern Med. and Surg. Journal.
•elf), is the result of such extensive revision, that it : The most complete work on the aci j

may almost be considered a new work. We need i.,^,, Am £,,/ r/>«r«/,z

hardly say, in concluding this brief notice, that while * Q*ua«e— Am- Med- Journal.
the work is indispensable to every student of medi- The most complete work now extant in our Ian-
cine in this country, it will amply repay the practi- guage.— JV. O. Med. Register.

tioner for its perusal by the interest and value of its i The best text-book in the language on this ex-
eontents.— Boston Med. and Surg. Journal. tensive subject.— L ondon Med. Times.

This is a standard work— the text-book used by all
medical students who read the English language.
It has passed through several editions in order to

A complete cyclopaedia of this branch of science.
— N. Y. Med. Times.
The profession of this country, and

keep pace with the rapidly growing science of Phy- ' of Europe, have anxiously and fo'r 'some time awaited
siology. Nothing need be said in its praise, for its the announcement of this new edition of Carpenter'*
merits are universally known ; we have nothing to ! Human Physiology. His former editions have for
say of its defects, for they only appear where the | many years been almost the only text-book on Phy-
ecienee of which it treats is incomplete. — Western , siology in all our medical schools, and its circnla-
Lancet. tion among the profession has been unsurpassed by

The most complete exposition of physiology which ! an>" work in any department of medical science .
any language can at present give.— Brit, and For. [t ls Quite unnecessary for us to speak of thi»
Med -Chirurg Review work as its merits would justify. The mere an-

nouncement of its appearance will afford the highest

The greatest, the most reliable, and the best book ' pleasure to every student of Physiology, while iti
on the subject which we know of in the English perusal will be of infinite service in advancing
[*aguage.— Stetkoscopt. , physiological science.— Ohio Med.andSicrg. Jottrn

BY THE SAME AUTHOR.

ELEMENTS (OR MANUAL) OF PHYSIOLOGY, INCLUDING PHYSIO-
LOGICAL ANATOMY. Second American, from a new and revised London edition. With
one hundred and ninety illustrations. In one very handsome octavo volume, leather, pp. 566.
$3 00.

In publishing the first edition of this work, its title was altered from that of the London volume >
by the substitution of the word "Elements" for that of " Manual," and with the author's sanction
the title of "Elements" is still retained as being more expressive of the scope of the treatise.

BY THE SAME AUTHOR.

PRINCIPLES OF COMPARATIVE PHYSIOLOGY. New American, from

the Fourth and Revised London edition. In one large and handsome octavo volume, with over
three hundred beautiful illustrations, pp. 752. Extra cloth, $5 25.

This book should not only be read but thoroughly i no man, we believe, could have brought to so suc-
•tudied by every member of the profession. None | cessful an issue as Dr. Carpenter. It required for
are too wise or old, to be benefited thereby. But i its production a physiologist at once deeply read ia
especially to the younger class would we cordially ; the labors of others, capable of taking a general,
commend it as best fitted of any work in the English critical, and unprejudiced view of those labors, ana
language to qualify them for the reception and com- : of combining the varied, heterogeneous materials at
prehension of those truths which are daily being de- his disposal, so as to form an harmonious whole.
veloped in phy siology .—Medical Counsellor. We feel that this abstract can give the reader a very

Without pretending to it, it is an encyclopedia of ! imperfect idea of the fulness of this work, and no
the subject, accurate and complete in all respects— ; ldea °f its unity, of the admirable macner in which
a truthful reflection of the advanced state at which ' material has been brought, from the most various
the science has now arrived.— Dublin Quarterly sources, to conduce to its completeness, of the lucid-
Journal of Medical Science ltv of tne reasoning it contains, or of the clearness

! of language in which the whole is clothed. Not the

A truly magnificent work-in itself a perfect phy- 1 profession only, but the scientific world at large,
Biological study.— Ranktng't Abstract. ' must feel deepl£ indebted to Dr. Carpenter for thii

This work stands without its fellow. It is one great work. It must, indeed, add largely even to
few men in Europe could have undertaken ; it is one j his high reputation.— Medical Timtt.

BY THE SAME AUTHOR, (preparing.)

PRINCIPLES OF GENERAL PHYSIOLOGY, INCLUDING ORGANIC

CHEMISTRY AND HISTOLOGY. With a General Sketch of the Vegetable and Animal
Kingdom. In one large and very handsome octavo volume, with several hundred illustrations.

BY THE SAME AUTHOR.

A PRIZE ESSAY ON THE USE OF ALCOHOLIC LIQUORS IN HEALTH

AND DISEASE. New edition, with a Preface by D. F. CONDIE, M. D., and explanations of
•cientific words. In one neat 12mo. volume, extra cloth, pp. 178. 50 cents.

BLANCHARD & LEA'S MEDICAL

CONDIE (D. F.), M. D., &c.
A PRACTICAL TREATISE ON THE DISEASES OP CHILDREN. Fifth

edition, revised and augmented. In one large volume, 8vo., extra cloth, of over 750 pages. $3 25.

In presenting a new and revised edition ot this favorite work, the publishers have only to state
that the author has endeavored to render it in every respect "a complete and faithful exposition of
the pathology and therapeutics of the maladies incident to the earlier stages of existence — a full
and exact account of the diseases of infancy and childhood." To accomplish this he has subjected
the whole work to a careful and thorough revision, rewriting a considerable portion, and adding
several new chapters. In this manner it is hoped that any deficiencies which may have previously
existed have been supplied, that the recent labors of practitioners and observers have been tho-
roughly incorporated, and that in every point the work will be found to maintain the high reputation
it has enjoyed as a complete and thoroughly practical book of reference in infantile affections.

A few notices of previous editions are subjoined.

Dr. Condie's scholarship, acumen, industry, and
practical sense are manifested in this, as in all his
numerous contributions to science. — Dr. Holmes's
Report to the American Medical Association.

Taken as a whole, in our judgment, Dr. Condie's
Treatise is the one from the perusal of which the
practitioner in this country will rise with the great-
est satisfaction. — Western Journal of Medicine and
Surgery.

One of the best works upon the Diseases of Chil-
dren in the English language.— We stern Lance t.

We feel assured from actual experience that no
physician's library can be complete without a copy
of this work.— N. Y. Journal of Medicine.

A veritable paediatric encyclopaedia, and an honor
to American medical literature. — Ohio Medical and
Surgical Journal.

We feel
fession wi

hut as the VERY BEST u Practical Treatise on the
Diseases of Children." — American Medical Journal.

In the department of infantile therapeutics, the
work of Dr. Condie is considered one of the best
which bus been published in the English language.
— The Stethoscope.

persuaded that the American medical pro-
ill soon regard it not only as a very good,
e VERY BEST "Practical Treatise on the

We pronounced the first edition to be the best
work on the diseases of children in the English
language, and, notwithstanding all that has been
published, we still regard it in that light. — Medical
Examiner.

The value of works by native authors on the dis-
eases which the physician is called upon to combat,
will be appreciated by all ; and the work of Dr. Con-
die has gained for itself the character of a safe guide
for students, and a useful work for consultation by
those engaged in practice.— N. Y. Med. Times.

This is the fourth edition of this deservedly popu-
lar treatise. During the interval since the last edi-
tion, it has been subjected to a thorough revision
by the author; and all new observations in the
pathology and therapeutics of children have been
included in the present volume. As we said btfore,
we do not know of a better book on diseases of chil-
dren, and to a large part of its recommendations we
yield an unhesitating concurrence. — Buffalo Med.
Journal.

Perhaps the most full and complete work now be-
'ore the profession of the United States; indeed, w«
may say in the English language. It is vastly supe-
rior to most of its predecessors.— Transylvania M«d.
fournal

CHFUSTISON (ROBERT), M. D., V. P. R. 5. E., Ac.
A DISPENSATORY; or. Commentary on the Pharmacopoeias of Great Britain

and the United States ; comprising the Natural History, Description, Chemistry, Pharmacy, Ac-
tions, Uses, and Doses of the Articles of the Materia Medica. Second edition, revised and im-
proved, with a Supplement containing the most important New Remedies. With copious Addi-
tions, and two hundred and thirteen large wood-engravings. By R. EGLESFELD GRIFFITH, M. D.
In one very large and handsome octavo volume, extra cloth, of over 1000 pages. $3 50.

COOPER (BRANSBY B.), F. R. S.
LECTURES ON THE PRINCIPLES AND PRACTICE OF SURGERY.

In one very large octavo volume, extra cloth, of 750 pages. $3 00.

COOPER ON DISLOCATIONS AND FRAC-
TURES OF THE JOINTS.— Edited by BRANSBY
B. COOPER, F.R.S., &c. With additional Ob-
servations by Prof. J. C. WARREN. A new Ame-
rican edition. In one handsome octavo volume,
extra cloth, of about 500 pages, with numerous
illustrations on wood. $3 25.

COOPER ON THE ANATOMY AND DISEASES
OF THE BREAST, with twenty-five Miscellane-
ous and Surgical Papers. One large volume, im-
perial 8vo., extra cloth, with 252 figures, on 36
plates. $2 50.

COOPER ON THE STRUCTURE AND DIS-
EASES OF THE TEST1S, AND ON THE
THYMUS GLAND. One vol. imperial 8vo., ex-
tra cloth, with 177 figures on 29 plates. $2 00.

COPLAND ON THE CAUSES, NATURE, AND
TREATMENT OF PALSY AND APOPLEXY.

In one volume, royal 12mo., extra cloth, pp. 326.
80 cents.

CLYMER ON FEVERS; THEIR DIAGNOSIS,
PATHOLOGY, AND TREATMENT. In ona

octavo volume, leather, of 600 pages. $1 50.

COLOMBAT DE L'ISERE ON THE DISEASES
OF FEMALES, and on the special Hygiene of
their Sex. Translated, with many Notes and Ad-
ditions, by C. D. MEIGS, M. D. Second edition,
revised and improved. In one large volume, oc-
tavo, leather, with numerous woou-cuts. pp. 720 .

CARSON (JOSEPH), M. D.,

Professor of Materia Medica and Pharmacy in the University of Pennsylvania.

SYNOPSIS OF THE COURSE OF LECTURES ON MATERIA MEDICA

AND PHARMACY, delivered in the University of Pennsylvania. With three Lectures on
the Modus Operandi of Medicines. Third edition, revised. In one handsome octavo volume.
(Now Ready.) $2 25.

CURLING (T. B.), F. R.S.,

Surgeon to the London Hospital, President of the Hunterian Society, &c.

A PRACTICAL TREATISE ON DISEASES OF THE TESTIS, SPERMA-
TIC CORD, AND SCROTUM. Second American, from the second and enlarged Engiibb. edi-
tion. In one handsome octavo volume, extra cloth, with numerous illustrations, pp. 420. 52 00

AND SCIENTIFIC PUBLICATIONS.

CHURCHILL (FLEETWOOD), M. D., M. H. I. A.
ON THE THEORY AND PRACTICE OF MIDWIFERY. A new American

from the fourth revised and enlarged London edition. With Notes and Additions, by D. FRANCIS

CONDIE, M. D., author of a "Practical Treatise on the Diseases of Children," &c. With 194
-rations. Inone very handsome octavo volume, of nearly 700 large pages, extra cloth, S3 50:

leather, $4 00.

This work has been so long an established favorite, both as a text-book for the learner and as a
reliable aid in consultation for the practitioner, that in presenting a new edition it is only necessary
to call attention to the very extended improvements which it has received. Having had the benefit
of two revisions by the author since the last American reprint, it has been materially enlarged, and
Dr. Churchill's well-known conscientious industry is a guarantee that every portion has been tho-
roughly brought up with the latest results of European investigation in all departments of the sci-
ence and art of obstetrics. The recent date of the last Dublin edition has not left much of novelty
for the American editor to introduce, but he has endeavored to insert whatever has since appeared,
together with such matters as his experience has shown him would be desirable for the American
student, including a large number of illustrations. With the sanction of the author he has added
in the form of an appendix, some chapters from a little "Manual for Mid wives and Nurses," re-
cently issued by Dr. Churchill, believing that the details there presented can hardly fail to prove of
advantage to the junior practitioner. Tne result of all -these additions is that the work now con-
tains fully one-half more matter than the last American edition, with nearly one-half more illus-
trations, so that notwithstanding the use of a smaller type, the volume contains almost two hundred
pages more than before.

No effort has been spared to secure an improvement in the mechanical execution of the work
equal to that which the text has received, and the volume is confidently presented as one of the
handsomest that has thus far been laid before the American profession; while the very low price
at which it is offered should secure for it a place in every lecture-room and on every office table.

A better book in which to learn these important
points we have not met than Dr. Churchill's. Every
page of it is full of instruction; the opinion of all
writers of authority is given on questions of diffi-
culty, as well as the directions and advice of the
learned author himself, to which he adds the result
of statistical inquiry, putting statistics in their pro
per place and giving them their due weight, and no
more. We have never read a book more free from
professional jealousy than Dr. Churchill's. It ap-
pears to be written with the true design of a book on

Were we reduced to the necessity of having but
»ne work on midwifery, and permitted to choose,
we would unhesitatingly take Churchill.— Western
Med. and Surg. Journal.

It is impossible to conceive a more useful and
elegant manual than Dr. Churchill's Practice of
Midwifery. — Provincial Medical Journal.

Certainly, in our opinion, the very best work on
he subject which exists.— N. Y. Annalist.

No work holds a higher position, or is more de-

medicine, viz : to give all that is known on the sub- j serving of being placed in the hands of the tyro

iect of which he treats, both theoretically and prac-
tically, and to advance such opinions of his own as
he believes will benefit medica.1 science, and insure
the safety of the patient. We have said enough to
convey to the profession that this book of Dr. Chur-
chill's is admirably suited for a book of reference
for the practitioner, as well as a text-book for the
etudent, and we hope it may be extensively pur-
chased amongst our readers. To them we most
strongly recommend it. — Dublin Medical Press.

To bestow praise on a book that has received such
marked approbation would be superfluous. We need
only say, therefore, that if the first edition was
thought worthy of a favorable reception by the
medical public, we can confidently affirm that this
will be found much more so. The lecturer, the
practitioner, and the student, may all have recourse
to its pages, and derive from their perusal much in-
terest and instruction in everything relating to theo-
retical and practical midwifery.— Dublin Quarterly
Journal of Medical Science.

A work of very great merit, and such as we can
confidently recommend to the study of every obste-
tric practitioner.— London Medical Gazetts.

Few treatises will be found better adapted as 8
text-book for the student, or as a manual for tht
frequent consultation of the young practitioner .--
American Medical Journal.

the advanced student, or the practitioner. — Medical
Examiner.

Previous editions have been received with mark-
ed favor, and they deserved it; but this, reprinted
from aver> late Dublin edition, carefully revised
and brought up by the author to the present time,
does present an unusually accurate and able expo-
sition of every important particular embraced in
the department of midwifery. * * The clearness,
directness, and precision of its teachings, together
with the great amount of statistical research which
its text exhibits, have served to place it already in
the foremost rank of works in this department of re-
medial science.— N. O. Med. and Surg. Journal.

In our opinion, it forms one of the best if not the
very best text-book and epitome of obstetric scienco
which we at present possess in the English lan-
guage.— Monthly Journal of Medical Science.

The clearness and precision of style in which it in
written, and the great amount of statistical research
which it contains, have served to place it in the first
rank of works in this departmentof medical science.
— N. Y. Journal of Medicine.

This is certainly the moot perfect system extant,
[t is the best adapted for the purposes of a text-
book, and that which he whose necessities confine
bum to one book, should select in preference to all
) tiiers. — Southern Medical and Surgical Journal.

BY THE SAME ATTTHOR. (Lately Published.)

ON THE DISEASES OF INFANTS AND CHILDREN. Second American

Edition, revised and enlarged by the author. Edited, with Notes, by W. V. KEATING, M. D. In

one large and handsome volume, extra cloth, of over 700 pages. $3 25.

In preparing this work a second time for the American profession, the author has spared no
labor in giving it a very thorough revision, introducing several new chapters, and rewriting others,
while every portion of the volume has been subjected to a severe scrutiny. The efforts of the
American editor have been directed to supplying such information relative to matters peculiar
to this country as might have escaped the attention of the author, and the whole may, there-
fore, be safely pronounced one of the most complete works on the subject accessible to the Ame-
rican Profession. By an alteration in the size of the page, these very extensive additions have
been accommodated without unduly increasing the size of the work.

BY THE SAME AUTHOR.

ESSAYS ON THE PUERPERAL FEVER, AND OTHER DISEASES PE-
CULIAR TO WOMEN. Selected from the writings of British Authors previous to the close of
the Eighteenth Century. In one neat octavo volume, extra cloth, of about 450 pages. $2 50.

10 BLANCHARD & LEA'S MEDICAL

CHURCHILL (FLEETWOOD), M. D.f M. R. I. A., Ac.

ON THE DISEASES OF WOMEN; including those of Pregnancy and Child-
bed. A new American edition, revised by the Author. With Notes and Additions, by D. FRAN-
CIS CONDIE, M. D., author of "A Practical Treatise on the Diseases of Children." With nume-
rous illustrations. In one large and handsome octavo volume, extra cloth, of 768 pages. $3 00.
This edition of Dr. Churchill's very popular treatise may almost be termed a new work, so
thoroughly has he revised it in every portion. It will be found greatly enlarged, and completely
brought up to the most recent condition of the subject, while the very handsome series of illustra-
tions introduced, representing such pathological conditions as can be accurately portrayed, present
a novel feature, and afford valuable assistance to the young practitioner. Such additions as ap-
peared desirable for the American student have been made by the editor, Dr. Condie, while a
marked improvement in the mechanical execution keeps pace with the advance in all other respects
which the volume has undergone, while the price has been kept at the former very moderate rate ,

It comprises, unquestionably, one of the most ex-
act and comprehensive expositions of the present
state of medical knowledge in respect to the diseases
of women that has yet been published.— Am. Journ.
Med. Sciences.

This work is the most reliable which we possess
on this subject; and is deservedly popular with the
profession. — Charleston Med. Journal, July, 1857.

We know of no author who deserves that appro-
bation, on "the diseases of females," to the same

extent that Dr. Churchill does. His, indeed, is the
only thorough treatise we know of on the subject ;
and it may be commended to practitioners and stu-
dents as a masterpiece in its particular department.
— Tht Western Journal of Medicine and Surgery.

As a comprehensive manual for students, or a
work of reference for practitioners, it surpasses any
other that has ever issued on the same subject from
the British press. — Dublin Quart. Journal.

DICKSON (S. H.), M. D.,

Professor of Practice of Medicine in the Jefferson Medical College, Philadelphia.

ELEMENTS OF MEDICINE; a Compendious View of Pathology and Thera-
peutics, or the History and Treatment of Diseases. Second edition, revised. In one large and
handsome octavo volume, ol 750 pages, extra cloth. $3 75.

The steady demand which has so soon exhausted the first edition of this work, sufficiently shows
that the author was not mistaken in supposing that a volume of this character was needed — an
elementary manual of practice, which should present the leading principle* of medicine with the
practical results, in a condensed and perspicuous manner. Disencumbered of unnecessary detail
and fruitless speculations, it embodies what is most requisite for the student to learn, and at the
same time what the active practitioner wants when obliged, in the daily calls of his profession, to
refresh his memory on special points. The clear and attractive style of the author renders the
whole easy of comprehension, while his long experience gives to his teachings an authority every-
where acknowledged. Few physicians, indeed, have had wider opportunities for observation and
experience, and few, perhaps, have used them to better purpose. As the result of a long life de-
voted to study and practice, the present edition, revised and brought up to the date of publication,
will doubtless maintain the reputation already acquired as a condensed and convenient American
text-book on the Practice of Medicine.

DRUITT (ROBERT), M.R. C.S., &c.
THE PRINCIPLES AND PRACTICE OF MODERN SURGERY. A new

and revised American from the eighth enlarged and improved London edition. Illustrated with

four hundred and thirty-two wood-engravings. In one very handsomely printed octavo volume

of nearly 700 large pages, extra cloth,. $3 50 ; leather, $4 00.

A work which like DRUITT'S SURGERY has for so many years maintained the position of a lead-
ing favorite with all classes of the profession, needs no special recommendation to attract attention
to a revised edition. It is only necessary to state that the author has spared no pains to keep the
work up to its well earned .reputation of presenting in a small and convenient compass the latest
condition of every department of surgery, considered both as a science and as an art; and that the
services of a competent American editor have been employed to introduce whatever novelties may
have escaped the author's attention, or may prove of service to the American practitioner. As
several editions have appeared in London since the issue of the last American reprint, the volume
has had the benefit of repeated revisions by the author, resulting in a very thorough alteration and
improvement. The extent of these additions may be estimated from the fact that it now contains
about one-third more matter than the previous American edition, and that notwithstanding the
adoption of a smaller type, the pages have been increased by about one hundred, while nearly two
hundred and fifty wood-cuts have been added to the former list of illustrations.

A marked improvement will also be perceived in the mechanical and artistical execution of the
work, which, printed in the best style, on new type, and fine paper, leaves little to be desired as
regards external finish ; while at the very low price affixed it will be found one of the cheapest
volumes accessible to the profession.

This popular volume, now a most comprehensive
work on surgery, has undergone many corrections,
improvements, and additions, and the principles and
the practice of the art have been brought down to
the latest record and observation. Of the operations
in surgery it is impossible to speak too highly. The
descriptions are so clear and concise, and the illus-
trations so accurate and numerous, that the student
can have no difficulty, with instrument in hand, and
book by his side, over the dead body, in obtaining
a proper knowledge and sufficient tact in this much
neglected department of medical education. — British
and Foreign Medico-Chirurg. Review, Jan. 1360.

In the present edition the author has entirely re-

nothing of real practical importance has been omit-
ted ; it presents a faithful epitome of everything re-
lating t > surgery up to the present hour. It is de-
servedly a popular manual, both with the student
and practitioner.— London Lancet, Nov. 19, 1859.

In closing this brief notice, we recommend as cor-
dially as ever this most useful and comprehensive
hand-book. It must prove a vast assistance, not
only to the student of surgery, but also to the busy
practitioner who may not have the leisure to devote
himself to the study of more lengthy volumes —
London Med. Times and Gazette, Oct. 22, 1859.

In a word, this eighth edition of Dr. Druitt'a

written many of the chapters, and has incorporated Manual of Surgery is all that the surgical student
the various improvements and additions in modern j or practitioner could desire. — Dublin Quaritrijr
•urgery. On carefully going over it, we find tiiat , Journal of Med. Sciences, Nov. 1S59.

AND SCIENTIFIC P UBLIC ATI ONS.

II

DALTON, JR. (J. C.), M. D.

Professor of Physiology in the College of Physicians, New York.

A TREATISE ON HUMAN PHYSIOLOGY, designed for the use of Students

and Practitioners of Medicine. Third edition, revised, with nearly three hundred illustrations

on wood. In one very beautiful octavo volume, of 700 pages, extra cloth, $4 50. (Just Ready ,

!Sb4.)

The rapid demand for another edition of this work sufficiently shows that the author has suc-
ceeded in his efforts to produce a text-book of standard and permanent value, embodying- within
a moderate compass all that is definitely and positively known within the domain of Human
Physiology. His high reputation as an original observer and investigator, is a guarantee that in
again revising it he has introduced whatever is necessary to render it thoroughly on a level with
the advanced science of the day, and this has been accomplished without unduly increasing the
size of the volume.

No exertion has been spared to maintain the high standard of typographical execution which has
rendered this work admittedly one of the handsomest volumes as" yet produced in this country.

It will be seen, therefore, that Dr. Dalton's best own original views and experiments, together with
efforts have been directed towards perfecting his a desire to supply what he considered some deficien-
work. The additions are marked by the same fea- cies in the first edition, have already made the pre-
tures which characterize the remainder of the vol- sent one a necessity, and it will no doubt be even
Hine, and render it by far the most desirable text- more eagerly sought for than the first. That it in
book on physiology to place in the hands of the not merely a reprint, will be seen from the author's
student which, so far as we are aware, exists in statement of the following principal additions and
the English language, or perhaps in any other. We alterations which he has made. The present, like
therefore have no hesitation in recommending Dr. the first edition, is printed in the highest style of the
Dalton's book for the classes for which it is intend- printer's art, and the illustrations are truly admira-
ed, satisfied as we are that it is better adapted to ble tor their clearness in expressing exactly what
their use than any other work of the kind to which their author intended. — Boston Medical and Surgi-

they have access. — American Journal of the Med.
Sciences, April, 1861.

It is, therefore, no. disparagement to the many

cal Journal, March 28, 1661.

It is unnecessary to give a detail of the additions ;
suffice it to say, that they are numerous and import-
ant, and such as will render the work still more

books upon physiology, most excellent in their day,

to say that Dalton's is the only one that gives us the valuable and acceptable to the profession as a learn-

seience as it was known to the best philosophers ed and original treatise on this all-important branch

throughout the world, at the beginning of the cur- of medicine. All that was said in commendation

rent year. It states in comprehensive but concise of the getting up of the first edition, and the superior

diction, the facts established by experiment, or style of the illustrations, apply with equal force to

other method of demonstration, and details, in an this. No better work on physiology can be placed

understandable manner, how it is done, but abstains in the hand of the student.— St. Louis Medical and

from the discussion of unsettled or theoretical points. Surgical Journal, May, 1S61.

Herein it is unique ; and these characteristics ren- Thege additions, while tes ifying to the learning

dent a text- book without a rival, for those who and industry of the author, render the book exceed-

desire to study physiological science as it is known ingly ugeful, as the most complete expose of a sci-

to its most successful cultivators. And it isphysi- ensce of which Dr. Dalton is doubtless the ablest

oiogy thus presented that lies at the foundation of representative on this side of the Atlantic.— New

correct pathological knowledge ; and this in turn is Orleans Med. Times, May, 1861.
the basis of rational therapeutics ; so that patholo- '

py, in fact, becomes of prime importance in the , A.second edition of this deservedly popular work*

proper discharge of our everv-day practical duties, having been called for m the short space of two

-Cincinnati Lancet, May, 1861. years, the author has supplied deficiencies, whicn

existed in the former volume, and has thus more

Dr. Dalton needs no word of praise from us. He completely fulfilled his design of presenting to the

is universally recognized as among the first, if not profession a reliable and precise text- book, and one

the very first, of American physiologists now living, which we consider the best outline on the subject

The first edition of his admirable work appeared but of which it treats, in any language.— N. American

two years since, and the advance of science, his Medico-Chirurg. Review, May, 1861.

DUNGLISON, FORBES, TWEEDIE, AND CONOLLY.
THE CYCLOPAEDIA OF PRACTICAL MEDICINE: comprising Treatises on

the Nature and Treatment of Diseases, Materia Medica, and Therapeutics, Diseases of Women

and Children, Medical Jurisprudence, fee. &c. In four large super-royal octavo volumes, of

3254 double-columned pages, strongly and handsomely bound, with raised bands. $12 00.

*#* This work contains no less than four hundred and eighteen distinct treatises, contributed by
•ixty-eight distinguished physicians, rendering it a complete library of re feience for the country
practitioner.

The most complete work on Practical Medicine > The editors are practitioners of established repu-
•xtant: or, at least, in our language.— Buffalo tation, and the list of contributors embraces many
Medical and Surgical Journal. of the most eminent professors and teachers of Lon-

don, Edinburgh, Dublin, and Glasgow. It is, in-

For reference, it is above all price to every prac- > deed, the great merit of this work that theprincipal
titioner. — Western Lancet. articles have been furnished by practitioners who

One of the most valuable medical publications of have no<; onl>- devoted especial attention to the dis
the day— as a work of reference it is invaluable.— ***** abou* which th.ey have written, but have
Western Journal oj Medicine and Surgery. al«° enjoyed opportunity for an extensive practi-

cal acquaintance with them and whose reputation

It has been to us, both as learner and teacher, a carries the assurance of their competency justly to
work for ready and frequent reference, one in which appreciate the opinions of others, while it stampi
modern English medicine is exhibited in the most the

advantageous light. — Medical Examiner.

irown doctrines with high and just authority. —
American Medical Journal.

DEWEES'S COMPREHENSIVE SYSTEM OF
MIDWIFERY. Illustrated by occasional cases
and many engravings. Twelfth edition, with the
author's last improvements and corrections. In
one octavo volume, extra cloth . of 600 pages . S3 20.

DEWEES'S TREATISE ON THE PHYSICAL

AND MEDICAL TREATMENT OF CHILD
REN. The last edition. In one volume, octavo,
extra cloth, 548 pages. $2 80

DEWEES'S TREATISE ON THE DISEASES
OF FEMALES. Tenth edition. In one volume,
octavo extra cloth, 532 pages, with plates. 83 00.

BLANCHARD & LEA'S MEDICAL

DUNGLISON (ROBLEY), M. D.,

Professor of Institutes of Medicine in the Jefferson Medical College, Philadelphia.

NEW AND ENLARGED EDITION.
MEDICAL LEXICON; a Dictionary of Medical Science, containing a concise

Explanation of the various Subjects and Terms of Anatomy, Physiology, Pathology, Hygiene.
Therapeutics. Pharmacology, Pharmacy, Surgery, Obstetrics, Medical Jurisprudence", Dentistry,
dec. Notices of Climate and of Mineral Waters; Formulae for Officinal, Empirical, and Dietetic
Preparations, &c. With French and other Synonymes. Revised and very greatly enlarged.
In one very large and handsome octavo volume, of 992 double-columned pages, in small type ;
strongly bound in leather. Price $4 00.

Especial care has been devoted in the preparation of this edition to render it in every respect
worthy a continuance of the very remarkable favor which it has hitherto enjoyed. The rapid
sale of FIFTEEN large editions, and the constantly increasing demand, show that it is regarded by
the profession as the standard authority. Stimulated by this fact, the author has endeavored in the
present revision to introduce whatever might be necessary " to make it a satisfactory and desira-
ble— if not indispensable — lexicon, in which the student may search without disappointment for
every term that has been legitimated in the nomenclature of the science." To accomplish this,
large additions have been found requisite, and the extent of the author's labors may be estimated
from the fact that about Six THOUSAND subjects and terms have been introduced throughout, ren-
dering the whole number of definitions about SIXTY THOUSAND, to accommodate which, the num-
ber of pages has been increased by nearly a hundred, notwithstanding an enlargement in the size
of the pag-e. The medical press, both in this country and in England, has pronounced the work in-
dispensable to all medical students and practitioners, and the present improved edition will not lose
that enviable reputation.

The publishers have endeavored to render the mechanical execution worthy of a volume of such
universal use in daily reference. The greatest care has been exercised to obtain the typographical
accuracy so necessary in a work of the kind. By the small but exceedingly clear type employed,
an immense amount of matter is condensed in its thousand ample pages, while the binding will be
found strong and durable. With all these improvements and enlargements, the price has been kept
at the former very moderate rate, placing it within the reach of all.

This work, the appearance of the fifteenth edition
of which, it has become our duty and pleasure to
announce, is perhaps the most stupendous monument
of labor and erudition in medical literature. One
would hardly suppose after constant use of the pre-
ceding editions, where we have never failed to find
a sufficiently full explanation of ever} medical term,
that in this edition "about six thousand subjects
and terms have been added," with a careful revision
and correction of the entire work. It is only neces-
sary to announce the advent of this edition to make
it occupy the place of the preceding one on the table
of every medical man, as it is without doubt the best
and most comprehensive work of the kind which has
ever appeared.— Buffalo Med. Journ., Jan. 1858.

The work is a monument of patient research,
skilful judgment, and vast physical labor, that will
perpetuate the name of the author more effectually
than any possible device of stone or metal. Dr.
Dunglison deserves the thanks not only of the Ame-
rican profession, but of the whole medical world. —
North Am. Medico-Chir. Review, Jan. 1858.

A Medical Dictionary better adapted for the wants
of the profession than any other with which we are
acquainted, and of a character which places it far
above comparison and competition.— Am. Journ.
Med. Sciences, Jan. 1858.

We need only say, that the addition of 6,000 new
terms, with their accompanying definitions, may be
said to constitute a new work, by itself. We have
examined the Dictionary attentively, and are most
happy to pronounce it unrivalled of its kind. The
erudition displayed, and the extraordinary industry
which must have been demanded, in its preparation
and perfection, redound to the lasting credit of its
author, and have furnished us with a volume indis-
pensable at the present day, to all who would find
themselves au niveau with the highest standards of
medical information.— Boston Medical and Surgical
Journal, Dee. 31, 1857.

Good lexicons and encyclopedic works generally
are the most labor-saving contrivances which lite-
rary men enjoy; and the labor which is required to
produce them in the perfect manner of this example
is something appalling to contemplate. The author

tells us in his preface that he has added about six
thousand terms and subjects to this edition, which,
before, was considered universally as the best work
of the kind in any language.— Silliman's Journal.
March, 1858.

He has razed his gigantic structure to the founda-
tions, and remodelled^ and reconstructed the entire
pile. No less than six thousand additional subjects
and terms are illustrated and analyzed in this new
edition, swelling the grand aggregate to beyond
sixty thousand ! Thus is placed before the profes-
sion a complete and thorough exponent of medical
terminology, without rival or possibility of rivalry.
— Nashville Journ. of Med. and Surg., Jan. 1858.

It is universally acknowledged, we believe, that
this work is incomparably the best and most com-
plete Medical Lexicon in the English language.
The amount of labor which the distinguished author
has bestowed upon it is truly wonderful, and the
learning and research displayed in its preparation
are equally remarkable. Comment and commenda-
tion are unnecessary, as no one at the present day
thinks of purchasing any other Medical Dictionary
than this. — St. Louis Med. and Surg. Journ., Jan.
1858. ,

It is the foundation stone of a good medical libra-
ry, and should always be included in the first list of
books purchased by the medical student. — Am. Med.
Monthly, Jan. 1858.

A very perfect work of the kind, undoubtedly the
most perfect in the English language. — Med. and
Surg. Reporter, Jan. 1858.

It is now emphatically the Medical Dictionary of
the English language, and for it there is no substi-
tute.— N. H. Med. Journ., Jan. 1858.

It is scarcely necessary to remark that any medi-
cal library wanting a copy of Dunglisou's Lexicon
must be imperfect. — Cin. Lancet, Jan. 1858.

We have ever considered it the best authority pub-
lished, and the present edition we may safely say hai
no equal in the world. — Peninsular Med. Journal*
Jan. 1858.

The most complete authority on the subject to b«
foundin any language. — Va. Med. Journal, Feb. '58.

BY THE SAME AUTHOR.

THE PRACTICE OF MEDICINE. A Treatise on Special Pathology and The-
rapeutics. Third Edition. In two large octavo volumes, leather, of 1,500 pages. $6 25.

AND SCIENTIFIC PUBLICATIONS.

DUNGLISON (ROBLEY), M.D.,

Professor of Institutes of Medicine in the Jefferson Medical College, Philadelphia.

HUMAN PHYSIOLOGY. Eighth edition. Thoroughly revised and exten-
sively modified and enlarged, with five hundred and thirty-two illustrations. In two large an<l
handsomely printed octavo volumes, extra cloth, of about 1500 pages. $7 00.

In revising this work for its eighth appearance, the author has spared no labor to render it worthy
a continuance of the very great favor which has been extended to it by the profession. The whole
contents have been rearranged, and to a great extent remodelled ; the investigations which of late
years have been so numerous and so important, have been carefully examined and .incorporated,
and the work in every respect has been brought up to a level with the present state of the subject!
The object of the author has been to render it a concise but comprehensive treatise, containing the
whole body of physiological science, to which the student and man of science can at all times refer
with the certainty of finding whatever they are in search of, fully presented in all its aspects ; and
on no former edition has the author bestowed more labor to secure this result.

We believe that it can truly be said.no more com- j The best work of the kind in the English lan-
plete repertory of facts upon the subject treated, j gaage. — Silliman's Journal.

can anywhere be found The author has, moreover, | The pregent edition the anthor has made a fec,
that enviable tact at description and that facility ; mirror of the 8cience as it is at the present hour,
and ease of expression which render him peculiarly Ag a work on phy8iology proper, the science of
acceptable to the casual, or the studious reader, j the functions performed by the body, the student wil!
This faculty, so requisite m setting forth many find it all h£ wisher-Nashville Journ. of Med
graver and less attractive subjects, lends additional , .

charms to one always fascinating.— Boston Med. . That he has succeeded, most admirably succeeded
*nd Sure. Journal. m hls P«rP°se, is apparent from the appearance of

: an eighth edition. It is now the great encyclopaedia

The most complete and satisfactory system of | on the subject, and worthy of a place in every phy-
Physiology in the English language. — Arner . Med . \ siciaLn"1 e library. — Western Lancet.
Journal.

BY THE SAME AUTHOR. (A new edition.}

GENERAL THERAPEUTICS AND MATERIA MEDICA; adapted for a

Medical Text-book. With Indexes of Remedies and of Diseases and their Remedies. SIXTH
EDITION, revised and improved. With one hundred and ninety-three illustrations. lu two large
and handsomely printed octavo vols., extra cloth, of about 1100 pages. $6 00.

In announcing a new edition of Dr. Dunglison's ' The work will, we have little doubt, be bought
General Therapeutics and Materia Medica, we have ; and read by the majority of medical students; its
no words of commendation to bestow upon a work size, arrangement, and reliability recommend it to
whose merits have been heretofore so often and so ; all; no one, we venture to predict, will study it
justly extolled. It must not be supposed, however, , without profit, and there are few to whom it will
that the present is a mere reprint of the previous not be in some measure useful as a work of refer -
edition; the character of the author for laborious \ ence. The young practitioner, more especially, will
research, judicious analysis, and clearness of ex- : find the copious indexes appended to this edijion of
pression, is fully sustained by the numerous addi- great assistance in the selection and preparation of
tions he has made to the work, and the careful re- suitable formulae. — Charleston Med. Journ. and Re-
vision to which he has subjected the whole. — N. A. , view, Jan. 1858.
M«dico-Ckir. Review, Jan. 1858.

BY THE SAME AUTHOR. (A new Edition.]

NEW REMEDIES, WITH FORMULAE FOR THEIR PREPARATION AND

ADMINISTRATION. Seventh edition, with extensive Additions. In one very large octavo
volume, extra cloth, of 770 pages. $3 75.

One of the most useful of the author's works. —
Southern Medical and Surgical Journal.

This elaborate and useful volume should be
found in every medical library, for as a book of re-
ference, for physicians, it is unsurpassed by any

The great learning of the author, and his remark-
able industry in pushing his researches into every
source whence information is derivable, have enabled
him to throw together an extensive mass of facte
and statements, accompanied by full reference to

other work in existence, and the double index for authorities; which last feature renders the work
diseases and for remedies, will be found greatly to f practically valuable to investigators who desire to
anhanceits value.— New York Med. Gazette. examine the original papers. -The American Journal

| of Pharmacy.

ELLIS (BENJAMIN), M.D.
THE MEDICAL FORMULARY : being a Collection of Prescriptions, derived

from the writings and practice of many of the most eminent physicians of America and Europe.
Together with the usual Dietetic Preparations and Antidotes for Poisons. To which is added
an Appendix, on the Endermic use of Medicines, and on the use of Ether and Chloroform. The
whole accompanied with a few brief Pharmaceutic and Medical Observations. Jl/leventh edition .
carefully revised and much extended by ROBERT P. THOMAS, M. D., Professor of Materia Me-
dica in the Philadelphia College of Pharmacy. In one volume, 8vo., of about 350 pages. $2 25.
(Just Ready.)

On no previous edition of this work has there been so complete and thorough a revision The
extensive changes in the new United States Pharmacopoeia have necessitated corresponding- alter-
ations in the Formulary, to conform to that national standard, while the progress made i:i the:
materia medica and the arts of prescribing and dispensing during the la>t ten years have been care-
fully noted and incorporated throughout. It is therefore presented as not only worthy a continuance
of the favor so long enjoyed, but as more valuable than ever to the practitioner and pharmaceutist.
Those who possess previous editions will find the additional matter of sufficient importance to
warrant their adding the present to their libraries.

14

BLANCHARD & LEA'S MEDICAL

ERICHSEN (JOHN),

Professor of Surgery in University College, London, Ac.

THE SCIENCE AND ART OF SURGERY; BEING A TREATISE ON SURGICAL

INJURIES, DISEASES, AND OPERATIONS. New and improved American, from the second enlarged

and carefully revised London edition. Illustrated with over four hundred engravings on wood.

In one large and handsome octavo volume, of one thousand closely printed pages, extra cloth,

$4 50; leather, raised bands. $5 25.

The very distinguished favor with which this work has been received on both sides of the Atlan-
tic has stimulated the author to render it even more worthy of the position which it has so rapidly
attained as a standard authority. Every portion has been carefully revised, numerous additions
have been made, and the most watchful care has been exercised to render it a complete exponent
of the most advanced condition of surgical science. In this manner the work has been enlarged by
about a hundred pages, while the series of engravings has been increased by more than a hundred,
rendering it one of the most thoroughly illustrated volumes before the profession. The additions of
the author having rendered unnecessary most of the notes of the former American editor, but little
has been added in this country; some few notes and occasional illustrations have, however, been
introduced to elucidate American modes of practice.

It is, in our humble judgment, decidedly the best ; step of the operation, and not deserting him until th«

book of the kind in the English language. Stran
that just such books are notoftener produced by p
lic teachers of surgery in this country and Great

nge
ub-

Britain Indeed, it is a matter of great astonishment.

but no less true than astonishing, that of the many j subject fai'thfully'exhibited

works on surgery republished in this country within estimate of it in the *ggr

the last fifteen or twenty years as text-books for

medical students, this is the only one that even ap

final issue of the case is decided. — Sethoscope.

Embracing, as will be perceived, the whole surgi-
cal domain, and each division of itself almost com

proximates to the fulfilment of the peculiar wants of
youngmen justentermguponthe study ofthisbranch
of the profession. — Western Jour, of Med. and Surgery.

Its value is greatly enhanced by a very copious
well-arranged index. We regard this as one of the
most valuable contributions to modern surgery. To
one entering his novitiate of practice, we regard it
the most serviceable guide which he can consult. He
will find a fulness of detailleadinghim through every

plete and perfect, each chapter full and explicit, each
", we can only express out

estimate of it in the aggregate. We consider it an
excellent contribution to surgery, as probably the

best single volume now extant on the subject, and
with great pleasure we add it to our text-books. —
Nashville Journal of Medicine and Surgery.

Prof. Erichsen's work, for its size, has not been
surpassed; his nine hundred and eight pages, pro-
fusely illustrated, are rich in physiological, patholo-
gical, and operative suggestions, doctrines, details,
and processes ; and will prove a reliable resource
for information, both to physician and surgeon, in th«
hour of peril. — N. 0. Med. and Surg. Journal.

FLINT (AUSTIN), M. D.,

Professor of the Theory and Practice of Medicine in the University of Louisville, *c.

PHYSICAL EXPLORATION AND DIAGNOSIS OF DISEASES AFFECT-
ING THE RESPIRATORY ORGANS. In one large and handsome octavo volume, extra
cloth, 636 pages. $3 00.

We regard it, in point both of arrangement and of
the marked ability of its treatment of the subjects,
as destined to take the first rank in works of this
class. So far as our information extends, it has at
present no equal. To the practitioner, as well as
the student, it will be invaluable in clearing up the
diagnosis of doubtful cases, and in shedding light
npon difficult phenomena. — Buffalo Med. Journal.

A work of original observation of thehighest merit
We recommend the treatise to every one who wishe*
to become a correct auscultator. Based to a very

large extent upon cases numerically examined, it l lse>ne !"Jleie,

carries theevidYnr.e of careful ntndv and disnrimina- amplified the more important points. In this re

a work based upon original observation, and pos-
sessing no ordinary merit. — N. Y. Journal of Med.
This is an admirable book, and because of its ex-
traordinary clearness and entire mastery of < he sub-
jects discussed, has mads itself indispensable to
those who are ambitious of a thorough knowledge
of physical exploration. — Nashville Journ of Med.

The arrangement of the subjects discussed is easy,
natural, such as to present the facts in the most
forcible light. Where the author has avoided being
tediously minute or diffuse, he has nevertheless fully

carries the evidence of careful study and discrimina-
tion upon every page. It does credit to the author,
and, through him, to the profession in this country
It is, what we cannot call every book upon auscul-
tation, a readable book. — Am. Jour. Med. Sciences
This volume belongs to a class of works which
confer honor upon their authors and enrich the do-
main of practical medicine. A cursory examination

spect, indeed, his labors will take precedence, and
be the means of inviting to this useful department a
more general attention. — O. Med. and Surg. Journ.

We hope these few extracts taken from Dr. Flint's
work may convey some idea of its character and
importance. We would, however, advise every phy-
sician to at once place it in his library, feeling as-

Flint in

will satisfy the scientific physician that Dr. j sured that it maybe consulted with great benefit
in this treatise has added to medical literature I both b oun and old.— Louisville Review.

BY THE SAME AUTHOR. (Now Ready.)

A PRACTICAL TREATISE ON THE DIAGNOSIS, PATHOLOGY, AND

TREATMENT OF DISEASES OF THE HEART. In one neat octavo volume, of about
500 pages, extra cloth. $2 75.

We do nof know that Dr. Flint has written any- > fencing to employ the very words of thedistinguished
thing which is not first rate ; but this, his latest con- I author, wherever it was possible, we have essayed
tribution to medfcal literature, in our opinion, sur- to condense into the briefest spacea general view of

11 *u- ~*u — nnu» , 1, : <, ,. hjg observations and suggestions, and to direct the

attention of our brethren to the abounding stores of
valuable matter herecollected and arranged for their
use and instruction. No medical library will here-
after be considered complete without this volume ;
and we trust it will promptly find its way into the
hands of every A mei ican student and physician. —
N. Am. Med. Chir. Review.

With more than pleasure do we hail the advent of
this work, for it fills a wide gap on the list of text-
books for our schools, and is, for the practitioner,
the luost valuable practical work of its kind. — JV. O.
Med. News.

passes all the others. The work is most comprehen-
sive in its scope, and most sound in the views it enun-
ciates. The descriptions are clear and methodical;
the statements are substantiated by facts, and are
made with such simplicity and sincerity, that with-
out them they would carry conviction. The style
is admirably clear, direct, and free from dryness
W ith Dr. Walshe's excellent, treatise before us, we
have no hesitation in saying that Dr. Flint's book is
the best work on the heart in the English language.
— Boston Med. and Surg. Journal.

We have thus endeavored to present our readers
with a fair analysis of this remarkable work. Pre-

AMD SCIENTIFIC PUBLICATIONS. 15

FOWNES (GEORGE), PH. D., «tc.
A MANUAL OF ELEMENTARY CHEMISTRY; Theoretical and Practical.

With one hundred and ninety-seven illustrations. Edited by ROBERT BRIDGES, M. D. In one

large royal 12mo volume, of 600 pages, extra cloth, $1 75.

The death of the author having placed the editorial care of this work in the practised hands of
Drs. Bence Jones and A. W. Hoffman, everything has been done in its revision which experience
could suggest to keep it on a level with the rapid advance of chemical science. The additions
requisite to this purpose have Recess-hated an enlargement of the page, notwithstanding which the
work has been increased by about fifty pages. At the same time every care has been used to
maintain its distinctive character as a condensed manual for the student, divested of all unnecessary
detail or mere theoretical speculation. The additions have, of course, been mainly in the depart-
ment of Organic Chemistry, which has made such rapid progress within the last few years, but
yet equal attention has been bestowed on the other branches of the subject — Chemical Physics and
Inorganic Chemistry — to present all investigations and discoveries of importance, and to' keep up
the reputation of the volume as a complete manual of the whole science, admirably adapted for the
learner. By the use of a small but exceedingly clear type the matter of a large octavo is compressed
within the convenient and portable limits of a moderate sized duodecimo, and at the very low price
affixed, it is offered as one of the cheapest volumes before the profession.

Dr. Fownes' excellent work has been universally
recognized everywhere in his own and this country,
as the best elementary treatise on chemistry in the
English tongue, and is very generally adopted, we
believe, as the standard text- book in all cur colleges,
both literary and scientific.— Charleston Med.Journ.
and Review.

A standard manual, which has long enjoyed the
reputation of embodying much knowledge in a small j A work well adapted to the wants of the student,
•pace. The author has achieved the difficult task of i It is an excellent exposition of the chief doctrine*
condensation with masterly tact. His book is con- and facts of modern chemistry. The size of the work,
else without being dry, and brief without being too ! and still more the condensed yet perspicuous style
dogmatical or general.— Virginia Med. and Surgical in which it is written, absolve it from the charges
Journal. very properly urged against most manuals termed

popular.— Edinburgh Journal of Medical Science.

The work of Dr. Fownes has long been before
the public, and its merits have been fully appreci-
ated as the best text-book on chemistry now in
existence. We do not, of course, place it in a rank
superior to the works of Brande, Graham, Turner,
Gregory, or Gmelin, but we say that, aa a work
for students, it is preferable to any of them.— Lon-
don Journal of Medicine.

FISKE FUND PRIZE ESSAYS. — THE EF- I EDWARD WARREN. M.D., of Edenton.N. C. To-
FECTS OF CLIMATE ON TUBERCULOUS gether in one neat 8vo. volume, extra cloth. «1 00.
DISEASE. ByEnwTN LM.M.R.C.S , London, | FRICK ON RENAL AFFECTIONS; their Diag,
and THE INFLUENCE OF PREGNANCY ON nosis and Pathology. With illustrations. One
THE DEVELOPMENT OF TUBERCLES By | volume, royal 12mo., extra cloth. 75 cents.

FERGUSSON (WILLIAM), F. R. S.,

Professor of Surgery in King's College, London, &c.

A SYSTEM OF PRACTICAL SURGERY. Fourth American, from the third

and enlarged London edition. In one large and beautifully printed octavo volume, of about 700
pages, with 393 handsome illustrations, leather. $3 00.

GRAHAM (THOMAS), F. R. S.
THE ELEMENTS OF INORGANIC CHEMISTRY, including the Applica-

lions of the Science in the Arts. New and much enlarged edition, by HENRY WATTS and ROBERT
BRIDGES, M. D. Complete in one large and handsome octavo volume, of over 800 very large
pages, with two hundred and thirty-two wood-cuts, extra cloth. $4 50.
^fc*^ Part II., completing the work from p. 431 to end, with Index, Title Matter, &c., may be

had separate, cloth backs and paper sides. Price $2 50.

From Prof. E. N. Horsford, Harvard College. afford to be without this edition of Prof. Graham's
It has, in its earlier and less perfect editions, been Elements.— Silliman's Journal, March, 1858.

familiar to me, and the excellence of its plan and From Prof. Wolcott Gibbs, N. Y. Free Academy.

the clearness and completeness of its discussions, The work is an admirable one in all respects, and

have long been my admiration. its republication here cannot fail to exert a positive

No reader of English works on this science can influence upon the progress of science in this country.

GRIFFITH (ROBERT E.), M. D., &.C.
A UNIVERSAL FORMULARY, containing the methods of Preparing and Ad-

ministering Officinal and other Medicines. The whole adapted to Physicians and Pharmaceu-
tists. SECOND EDITION, thoroughly revised, with numerous additions, by ROBERT P. THOMAS,
M. D., Professor of Materia Medica in the Philadelphia College of Pharmacy. In one large and
handsome octavo volume, extra cloth, of 650 pages, double columns. $3 25.

It was a work requiring much perseverance, and | This is a work of six hundred and fifty one page?,
when published was looked upon as by far the best! embracing all on the subject of preparing; and admi-
work of its kind that had issued from the American ,iistering medicines that can be desired by the physi
press. Prof Thomas has certainly "-improved," as j cian and pharmaceutist. — Western Lancet
well as added to this Formulary, and has rendered it The amountof useful, every-day matter. for a prac-
additionally deserving of the confidence of pharma- licing physician, is really immense.- Boston Med
eentists and physicians.— Jim. Journal of Pharmacy. and Surg. Journal.

We are happy to announce a new and improved This edit.on has been greatly improved bv the re
edmon of this, one of the most valuable and useful vision and ample additions of Dr Thomas, and is
works that have emanated from an American pen now, we be|ieve OHe of the mos; complete work?
It would do credit to any country, and will be found of its kind iu a . iailgua^. The additions amount
of daily usefulness to practitioners of medicine ; it is lo about seventy pages, and nc effort has been spared
better adapted to their purposes than the dispensato , lo illc;ude in them all the recent improvements A
nes.— Southern Med. and Surg. Journal. work of thb kiud »ppears lo us indispensable to the

Itisoneofthe most useful books a country practi- physician, and there is none we can more cordially
tiouer can possibly have. — Medical Chronicle, recommend. — N. If. Journal of Medieint.

BLANCHARD & LEA'S MEDICAL

GROSS (SAMUEL D.), M. D.,

Professor of Surgery in the Jefferson Medical College of Philadelphia, Ac.

Enlarged Edition.

A SYSTEM OF SURGERY : Pathological, Diagnostic, Therapeutic, and Opera-
tive. Illustrated by TWELVE HUNDRED AND TWENTY-SEVEN ENGRAVINGS. Second edition,
much enlarged and carefully revised. In two large and beautifully printed octavo volumes, of
about twenty-two hundred pages ; strongly bound in leather. Price $13.

The exhaustion in little more than two years of a large edition of so elaborate and comprehen-
sive a work as this is the best evidence that the author was not mistaken in his estimate of the
want which existed of a complete American System of Surgery, presenting the science in all its
necessary details and in all its branches. That he has succeeded in the attempt to supply this want
is shown not only by the rapid sale of the work, but also by the very favorable manner in which it
has been received by the organs of the profession in this country and in Europe, and by the fact that
a translation is now preparing in Holland — a mark of appreciation not often bestowed on any scien-
tific work so extended in size.

The author has not been insensible to the kindness thus bestowed upon his labors, and in revising
the work for a new edition he has spared no pains to render it worthy of the favor with which it
has been received. Every portion has been subjected to close examination and revision ; any defi-
ciencies apparent have been supplied, and the results of recent progress in the science and art oi
surgery have been everywhere introduced ; while the series of illustrations has been enlarged by
the addition of nearly three hundred wood-cuts, rendering it one of the most thoroughly illustrated
works ever laid before the profession. To accommodate these very extensive additions, the work
has been printed upon a smaller type, so that notwithstanding the very large increase in the matter
and value of the book, its size is more convenient and less cumbrous than before. Every care has
been taken in the printing to render the typographical execution unexceptionable, and it is confi-
dently presented as a work in every way worthy of a place in even the most limited library of the
practitioner or student.

Has Dr. Gross satisfactorily fulfilled this object?
A careful perusal of his volumes enables us to give
an answer in the affirmative. Not only has he given
to the reader an elaborate and well-written account
of his osyn vast experience, but he has not failed to
embody in his pages the opinions and practice of
surgeons in this and other countries of Europe. The
result has been a work of such completeness, that it
has no superior in the systematic treatises on sur-
gery which have emanated from English or Conti-
nental authors. It has been justly objected that
these have been far from complete in many essential
particulars, many of them having been deficient in
some of the most important points which should
characterize such works. Some of them have been
elaborate — top elaborate— with respect to certain
diseases, while they have merely glanced at, or
given an unsatisfactory account of, others equally
important to the surgeon. Dr. Gross has avoided
this error, and has produced the most complete work
that has yet issued from the press on the science and
practice of surgery. It is not, strictly speaking, a
Dictionary of Surgery, but it gives to the reader all
the information that he may require for his treatment
of surgical diseases. Having said so much, it might
appear superfluous to add another word; but it is
only due to Dr. Gross to state that he has embraced
the opportunity of transferring to his pages a vast

Of Dr. Gross's treatise on Surgery we can say
no more than that it is the most elaborate and com-
plete work on this branch of the healing art which
has ever been published in any country. A sys-
tematic work, it admits of no analytical review;
but, did our space permit, we should gladly give
some extracts from it, to enable our readers to judge
of the classical style of the author, and the exhaust-
ing way in which each subject is treated. — Dublin
Quarterly Journal of Med. Science.

The work is so superior to its predecessors in
matter and extent, as well as in illustrations and
style of publication, that we can honestly recom-
mend it as the best work of the kind to be taken
home by the young practitioner — Am. Med. Journ.

With pleasure we record the completion of this
long-anticipated work. The reputation which the
author has for many years sustained, both as a sur-
geon and as a writer, had prepared us to expect a
treatise of great excellence and originality: but we
confess we were by no means prepared for the work
which is before us — the most complete treatise upon
surgery ever published, either in this or any other
country, and we might, perhaps, safely say, the
most original. There is no subject belonging pro-
perly to surgery which has uot received from the
author a due share of attention. Dr. Gross has sup-

plied a want in surgical literature which has long
been felt by practitioners; he has furnished us with
a complete practical treatise upon surgery in all its
departments. As Americans, we are proud of the
achievement ; as surgeons, we are most sincerely
thankful to him for his extraord nary labors in our
behalf.— N. Y. Review and Buffalo Med. Journal.

number of engravings from English and other au-
thors, illustrative of the pathology and treatment of
surgical diseases. To these are added several hun-
dred original wood-cuts. The work altogether com-
mends itself to the attention of British surgeons,
from whom it cannot fail to meet with extensive
patronage. — London Lancet, Sept. 1, 1860.

BY THE SAME AUTHOR.

ELEMENTS OF PATHOLOGICAL ANATOMY. Third edition, thoroughly

revised and greatly improved. In one large and very handsome octavo volume, with about three

hundred and fifty beautiful illustrations, of which a large number are from original drawings,

extra cloth. $4 75.

The very rapid advances in the Science of Pathological Anatomy during the last few years have
rendered essential a thorough modification of this work, with a view of making it a correct expo-
nent of the present state of the subject. The very careful manner in which this task has been
executed, and the amount of alteration which it has undergone, have enabled the author to say that
" with the many changes and improvements now introduced, the work may be regarded almost as
a new treatise," while the efforts of the author have been seconded as regards the mechanical
execution of the volume, rendering it one of the handsomest productions of the American press.

We most sincerely congratulate the author on the We have been favorably impressed with the gene-

successful manner in which he has accomplished his
proposed object. His book is most admirably cal-
culated to fill up a blank which has long been felt to
exist in this department of medical literature, and
as such must become very widely circulated amongst
all classes of the profession. — Dublin Quarterly
Journ. of Med. Science, Nov. 1857.

ral manner in which Dr. Gross has executed his task
of affording a comprehensive digest of the present
state of the literature of Pathological Anatomy , and
have much pleasure in recommending his work to
our readers, as we believe one well deserving of
diligent perusal and careful study.— Montreal Med,

Chron., Sept. 1857.
BY THE SAME AUTHOR.

A PRACTICAL TREATISE ON FOREIGN BODIES IN THE AIR-PAS-

SAGES. Jn one handsome octavo volume, extra cloth, with illustrations, pp. 468. $2 75.

AND SCIENTIFIC PUBLICATIONS* :7

GROSS (SAMUEL D.), M. D.,

Professor of Surgery in the Jefferson Medical College of Philadelphia, <tc.

A PRACTICAL TREATISE ON THE DISEASES, INJURIES, AND

MALFORMATIONS OF THE URINARY BLADDER, THE PROSTATE GLAND, AND
THE URETHRA. Second Edition, revised and much enlarged, with one hundred and eighty-
four illustrations. In one large and very handsome octavo volume, of over nine hundred pages.,
extra cloth, $4 75.
Philosophical in its design, methodical in its ar- ' agree with us, that there is no work in the English

rangement, ample and sound in its practical details, ; language which can make any just pretensions to

it may in truth be said to leave scarcely anything to ' be its equal. — N. Y. Journal of Medicine.

be desired on so important a subject.— Boston Med.

*nd Surg. Journal.
Whoever will peruse the vast amount of valuable

practical information it contains, will, we think.

A voiume replete with truths and principles of th«
most value in the investigation of these diseases. —

utmost val

American Medical Journal.

GRAY (HENRY), F. R. S.,

Lecturer on Anatomy at St. George's Hospital, London, &c.

ANATOMY, DESCRIPTIVE AND SURGICAL. The Drawings by H. V.

CARTER, M. D., late Demonstrator on Anatomy at St. George's Hospital ; the Dissections jointly
by the AUTHOR and Dr. CARTER. Second American, from the second revised and improved
London edition. In one magnificent imperial octavo volume, of over 800 pages, with 388 large
and elaborate engravings on wood. Price in extra cloth, $6 25.

The speedy exhaustion of a large edition of this work is sufficient evidence that its plan and exe-
cution have been found to present superior practical advantages in facilitating the study of Analo-
.my. In presenting it to the profession a second time, the author has availed himself of the oppor-
tunity to supply any deficiencies which experience in its use had shown to exist, and to correct
any errors of detail, to which the first edition of a scientific work on so extensive and complicated
a science is liable. These improvements have resulted in some increase in the size of the volume,
while twenty-six new wood-cuts have been added to the beautiful series of illustrations which
form so distinctive a feature of the work. The American edition has been passed through the press
under the supervision of a competent professional man, who has taken every care to render it in
all respects accurate, and it is now presented, without any increase of price, as fitted to maintain
and extend the popularity which it has everywhere acquired.

With little trouble, the busy practitioner whose i work of Mr. Gray to the attention of the medical
knowledge of anatomy may have become obscured by profession, feeling certain that it should be regarded

as one of the most valuable contributions ever made

want of practice, may now resuscitate his former
anatomical lore, and. be ready for any emergency,
ft is to this class of individuals, and not to the stu-
dent alone, that this work will ultimately tend to
be of most incalculable advantage, and we feel sat-
isfied that the library of the medical man will soon
be considered incomplete in which a copy of this
work does not exist.— Madras Quarterly Journal
of Med. Science, July, 1861.

to educational literature.— JV. Y. Monthly Review.
Dec. 1859.

In this view, we regard the work of Mr. Gray as
far better adapted to the wants of the profession,
and especially of the student, than any treatise on
anatomy yet published in this country . It is destined,
we believe, to supersede all others, both as a manual
of dissections, and a standard of reference to the

This edition is much improved and enlarged, and gtudent of general or relative anatomy. — JV. Y.
contains several new illustrations by Dr. Westma- | Journai Of Medicine, Nov. 1859.
cott. The volume is a complete companion to the ;

dissecting-room, and saves the necessity of the stu- In our judgment, the mode of illustration adopted
dent possessing a variety of "Manuals."-rAeLo»- iQ the present volume cannot but present manyad-
on Lancet, i-eo. y, ibbl. j vantages to the student of anatomy. To the zealous

The work before us is one entitled to the highest i disciple of Vesalius, earnestly desirous of real im-
praise, and we accordingly welcome it as a valu- i provement, the book will certainly be of immense
able addition to medical literature. Intermediate ' value; but, at the same time, we must also confess
in fulness of detail between the treatises of S.iar- ! that to those simply desirous of "cramming" it
pey and of Wilson, its characteristic merit lies in '.. will be an undoubted godsend. The peculiar value
the number and excellence of the engravings it . of Mr. Gray's mode, of illustration is nowhere more
contains. Most of these are original, of much markedly evident than in the chapter on osteology,
larger than ordinary size, and admirably executed. \ and especially in those portions which treat of the
The various parts are also lettered after the plan ; bones of the head and of their development. The
adopted in Holden^s Osteology. It would be diffi- i study of these parts is thus made one of comparative
cult to over-estimate the advantages offered by this i ease, if not of positive pleasure : and those bugbears
mode of pictorial illustration. Bones, ligaments, of the student, the temporal and sphenoid bones, are
muscles, bloodvessels, and nerves are each in turn shorn of half their terrors. It is, in our estimation,
figured, and marked with their appropriate names; an admirable and complete text-book for the student,
thus enabling the student to comprehend, at a glance, i and a useful work of reference for the practitioner;
what would otherwise often be ignored, or at any its pictorial character forming a novel element, to
rate, acquired only by prolonged and irksome ap- ; which we have already sufficiently alluded.— Am.
plication. In conclusion, we heartily commend the ! Journ. Med. Sci.} July, 1859.

GIBSON'S INSTITUTES AND PRACTICE OF f TICE OF AUSCULTATION AND OTHER

SURGERY. Eighth edition, improved and al- i MODES OF PHYSICAL DIAGNOSIS, IN DIS-

tered. With thirty-four plates. In two handsome I EASES OF THE LUNGS AND HEART. Se-

octavo volumes, containing about 1,000 pages, i cond edition. 1 vol. royal 12mo., ex. cloth, pp.

leather, raised band^. $650. \ 304. SI 00.

GARDNER'S MEDICAL CHEMISTRY, for the '\ HOLLAND'S MEDICAL NOTES AND RE-

use of Students and the Profession. In one royal ; FLECTIONS. From the third London edition,

lamo. vol., cloth, pp. 396, with wood-cuts. 81. J in one handsome octavo volume, extra cloth. S3.

6feS?£™AT^AS °F JATl!0£OGICAL Hlp.-lHORNKR'S SPECIAL ANATOMY AND HIS-
TOLOGY Translated, with Notes and Addi- I TOLOGY. Eighth edition. Extensively revised
tions. by JOSEPH LEIDY, M. D. In one volume., j and modiued. In two large octavo volumes, ex-
very large imperial quarto, extra cloth, with 320 tra cloth of more than 1000 pagea with over 3W
copper- plate fagures, plain and eolored, $500. ! illustrations. 8600.

HUGHES' INTRODUCTION TO THE P^RAC- i

IS

BLANCHARD & LEA'S MEDICAL

HAMILTON (FRANK H.), M. D.,

Professor of Surgery in the Long Island College Hospital.

A PRACTICAL TREATISE ON FRACTURES AND DISLOCATIONS.

Second edition, revised and improved. In one large and handsome octavo volume, of over 750
pages, with nearly 300 illustrations, extra cloth, $4 15. (Just Ready, May, 1863.)

The early demand for a new edition of this work shows that it has been successful in securing
the confidence of the profession as a standard authority for consultation and reference on it* import-
ant and difficult subject. In again passing it through the press, the author has taken the opportu-
nity to revise it carefully, and introduce whatever improvements have been suggested by further
experience and observation. An additional chapter on Gun-shot Fractures will be found to adapt
it still more fully to the exigencies of the time.

Among the many good workers at surgery of whom
America may now boast n ot the leapt is F rank Hast-
ings Hamilton; and the volume before us is (we say

it with a pang of wounded patriotism) the best and
handiest book on the subject in the English lan-
guage. It is in vain to attempt a review of it;
nearly as vain to seek for any sins, either of com-
mission or omission. We have seen no work on
practical surgery which we would sooner recom-
mend to our brother surgeons, especially those of
" the services," or those whose practice lies in di

When we say, however, that we believe it will at
once take its place as the best book for consultation
by the practitioner ; and that it will form the most
complete, available, and reliable guide in emergen-
cies of every nature connected with its subjects ; and
also that the student of surgery may make it his text-
book with entire confidence, and with pleasure also,
from its agreeable and easy style — we think our own
opinion may be gathered as to its value. — Boston
Medical and Surgical Journal, March 1, 1860.
The work is concise, judicious, and accurate, and

tricts where a man has necessarily to rely on his adapted to the wants of the student, practitioner,
own unaided resources. The practitioner will had and mvestigator, honorable to the author and to the
in it directions for nearly every possible aceiaent, | profession.— Chicago Med. Journal. March. 1860.
easily found and comprehended ; and much pleasant '
reading for him to muse over in the after considera-

tion of his cases.— Edinburg h Med. Journ. Feb . 1661.

This is a valuable contribution to the surgery of
most important affections, and is the more welcome,
inasmuch as at the present time we do not possess
a single complete treatise on Fractures and Dislo-
cations in the English language. It has remained for
our American brother to produce a complete treatise
upon the subject, and bring together in a convenient

We regard this work as an honor not only to its
author, but to the profession of our country. Were
we to review it thoroughly, we could not convey to
the mind of the reader more forcibly our honest
opinion expressed in the few words — we think it the
best book of its kind extant. Every man interested
in surgery will soon have this work on his desk.
He who does not, will be the loser. — New Orleans
Medical News, March, 1860.

Dr. Hamilton is fortunate in having succeeded in

form those alterations and improvements that have j filling. the void go ionff feit wjth wnat cannot fail
been made from time to time in the treatment of these to be at once accepted as a model monograph in some
affections. One great and valuable feature in the I respects, and a work of classical authority. \Ve
work before us is the fact that it comprises all the , sin£ereiy congratulate the profession of the United
improvements introduced into the practice of both States on the appearance of such a publication from
English and American surgery, and though far from j one of their nu^ber. We have rea8on to be proud
omitting mention of our continental neighbors, the j of it as an original work, both in a literary and s,:i-
author by no means encourages the notion— but too j entific point 06f view an^ to esteera it as a valuable
prevalent in some quarters- that nothing is good ide in a moBt difficuit and important branch of
unless imported from France or Germany. The gtudy and practice. On every account, therefore,
latter half of the work is devoted to the considera- we h'o e that it may soon be widely known abroad
tion of the various dislocations and their appropri- as an evidence of genuine progress on this side of

ate treatment, and its merit is fully equal to that of
the preceding portion.— The London Lancet. May 5,
1860.

It is emphatically the book upon the subjects of
which it treats, and we cannot doubt that it will
continue so to be for an indefinite period of time.

the Atlantic, and further, that it may be still more
widely known at home as an authoritative teacher
from which every one may profitably learn, and as
affording an example of honest, well-directed, and
untiring industry in authorship whjch every surgeon
may emulate.- Am. Med. Journal, April, 1860.

HODGE (HUGH L.), M. D.,

Professor of Midwifery and the Diseases of Women and Children in the University of Pennsylvania, &c.

ON DISEASES PECULIAR TO WOMEN, including Displacements of the

Uterus. "With original illustrations. In one beautifully printed octavo volume, of nearly 500

pages, extra cloth. $3 25.

recur — these, taken in connection with the entire
competency of the author to render a correct ac-
count of their nature, their causes, and their appro-
priate management — his ample experience, his ma-
tured judgment, and his perfect conscientiousness —
invest this publication with an interest and value to
which few of the medical treatises of a recent date
can lay a stronger, if, perchance, an equal claim. —

'VVe will say at once that the work fulfils its object
capitally well: and we will moreover venture the
assertion that it will inaugurate an imnroved prac-
tice throughout this whole country. The secrets of
the author's success are so clearly revealed that the
attentive student cannot fail to insure a goodly por-
tion of similar success in his own practice. It is a
credit to all medical literature; and we add, that
the physician who does not place it in his library,
and who does not faithfully con its pages, will lose
a vast deal of knowledge that would be most useful
to himself and beneficial to his patients. It is a
practical work of the highest order of merit; and it
will take rank as such immediately.— Maryland and
Virginia Medical Journal, Feb. 1861.

This contribution towards the elucidation of the
pathology and treatment of some of the diseases
peculiar to women, cannot fail to meet with a favor-
able reception from the medical profession. The
character of the particular maladies of which the
work before us treats; their frequency, variety, and
obscurity ; the amount of malaise and even of actual
Buffering by which they are invariably attended;
their obstinacy, the difficulty with which they are
overcome, and tlieir disposition again and again to

can lay a stronger, if, perchance, an c
Am. Journ. Med. Sciences, Jan. 1861.

Indeed, although no part of the volume is not emi-
nently deserving of perusal and study, we think that
the nine chapters devoted to this subject, are espe-
cially so, and we know of no more valuable mono-
graph upon the symptoms, prognosis, and manage-
ment of these annoying maladies than is constituted
by this part of the work. We cannot but regard it
as one of the most original and m >st practical worts
of the day ; one which every accoucheur and physi-
cian should most carefully read; for we are per-
suaded that he will arise from its perusal with new
ideas, which will induct him int.o a more rational
practice in regard to many a suffering female, who
may have placed her health in his hands. — British
American Journal, Feb. 1861.

The illustrations, which are all original, are drawn to a uniform scale of one-half the natural size.

AND SCIENTIFIC PUBLICATIONS 19

HODGE (HUGH L.), M. D.,
Late Professor of Midwifery, &c.. in the University of Pennsylvania.

PRINCIPLES AND PRACTICE OF OBSTETRICS. In one large quarto

volume, with one hundred and fifty-eight figures on thirty-two beautifully executed lithographic

plates, and numerous wood-cuts in the text. (In Press.)

This? work, embodying the results of an extensive practice for more than forty years, cannot fail
to prove of the utmost value to all who are engaged in this department of medicine. The author's
position as one of the highest authorities on the subject in this country is well known, and the fruit
of his ripe experience and long observation, carefully matured and elaborated, must serve as an
invaluable text-book for the student and an unfailing counsel for the practitioner in the emergencies
which so frequently arise in obstetric practice.

The illustrations will form a novel feature in the work. The lithographic plates are all original,
and to insure their absolute accuracy they have all been copied from photographs taken expressly
for the purpose. In ordinary obstetrical plates, the positions of the fcetus are represented by dia-
grams or sections of the patient, which are of course purely imaginary, and their correctness is
scarcely more than a matter of chance with the artist. Their beauty as pictures is thereby increased
without corresponding utility to the student, as in practice he must" for the most part depend for his
diagnosis upon the relative positions of the foetal skull and the pelvic bones of the mother. It is,
therefore, desirable that the points upon which he is in future to rely, should form the basis of his
instruction, and consequently in the preparation of these illustrations the skeleton has alone been
used, and the aid of photography invoked, by which a series of representations has been secured of
the strictest and most rigid accuracy. It is easy to recognize the value thus added to the very full
details on the subject of the MECHANISM OF LABOUR with which the work abounds

It may be added that no pains or expense will be spared to render the mechanical execution of the
volume worthy in every respect of the character and value of the teachings it contains.

HABERSHON (S. O.), M. D.,

Assistant Physician to and Lecturer on Materia Medica and Therapeutics at Guy's Hospital, &c.

PATHOLOGICAL AND PRACTICAL OBSERVATIONS ON DISEASES

OF THE ALIMENTARY CANAL, CESOPHAGUS, STOMACH, C^CUM, AND INTES-
TINES. With illustrations on wood. In one handsome octavo volume of 312 page*, extra
cloth $1 75.

HOBLYN (RICHARD D.), M. D.

A DICTIONARY OF THE TERMS USED IN MEDICINE AND THE

COLLATERAL SCIENCES. A new American edition. Revised, with numerous Additions,
by ISAAC HAYS, M. D., editor of the" American Journal of the Medical Sciences."' In one large
royal 12mo. volume, leather, of over 500 double columned pages. $1 50.
To both practitioner and student, we recommend i use ; embracing every department of medical science

this dictionary as being
in definition, and suffic

convenient in size, accurate
x;ientiy full and complete for
ordinary consultation.— Charleston Med. Jour*.

down to the very latest date. — Western Lancet.

been a favorite with
It'is the best book of definitions we have, and

Hoblyn's Dictionary has long
us. It is the best book of deni

US. 1 L IB tllC UCfcl LJUVB. Ul UOJlUHaUUO WO AMBTV4 dim

We know of no dictionary better arranged and ought always to be upon the student's table.—
lapted. Itisnotencumbered with the obsoleteterms ' "
of a bygone age, but it contains all that are now in

JONES (T. WHARTON), F. R. S.,

Professor of Ophthalmic Medicine and Surgery in University College, London, 4c.

THE PRINCIPLES AND PRACTICE OF OPHTHALMIC MEDICINE

AND SURGERY. With one hundred and seventeen illustrations. Third and revised Ameri-
can, with additions from the secono London edition. In one handsome octavo volume, extra
cloth, of 455 pages. $3 00.

Seven, years having elapsed since the appearance of the last edition of this standard work, very
considerable additions have been found necessary to adapt it thoroughly to the advance of ophthal-
mic science. The introduction of the ophthalmoscope has resulted in adding greatly to our know-
ledge of the pathology of the diseases of the eye, particularly of its more deeply seated tissues, and
corresponding improvements in medical treatment and operative procedures have been introduced.
All these matters the editor has endeavoured to add, bearing in mind the character of the volume as a
condensed and practical manual. To accommodate this unavoidable increase in the size of the work,
its form Mas been changed from a duodecimo to an octavo, and it is presented as worthy a continu-
ance of the favour which has been bestowed on former editions.

A complete series of "test-types" for examining the accommodating power of the eye, will be
found an important and useful addition.

JONES (C. HANDFIELD), F.R.S., & EDWARD H. SIEVEKINQ, M.D.,

Assistant Physicians and Lecturers in St. Mary's Hospital, London.

A MANUAL OF PATHOLOGICAL ANATOMY. First American Edition,

Revised. With three hundred and ninety-seven handsome wood engravings. In one large and

beautiful octavo volume of nearly 750 pages, extra cloth. $3 75.

As a concise text-book, containing, in acondensed obliged toglean from a great number of monographs,
form, a complete outline of what is known in the and the field was so extensive that but few cultivated
domain of Pathological Anatomy, it is perhaps the it with any degree of success. As a simple work
best work in the English language. Its great merit of reference, therefore, it is of great value to the
consists in its completeness and brevity, and in this ; student of pathological anatomy, and should be in
respect it supplies a great desideratum in our lite- every physician's library. — Western Lancet.
ratare. Heretofore the student of pathology was

20

BLANCHARD & LEA'S MEDICAL

KIRKES (WILLIAM SENHOUSE), M.D.,

Demonstrator of Morbid Anatomy at St. Bartholomew's Hospital, &c.

A MANUAL OF PHYSIOLOGY. A new American, from the third and

improved London edition. With two hundred illustrations. In one large and handsome royal
12mo. volume, extra cloth, pp. 586. $2 00.

This is a new and very much improved edition of
Dr. Kirkes' well-known Handbook of Physiology.
It combines conciseness with completeness, and is,
therefore, admirably adapted for consultation by the
bnsy practitioner. — Dublin Quarterly Journal.

One of the very best handbooks of Physiology we
possess — presenting just such an outline of the sci-
ence as the student requires during his attendance
upon a course of lectures, or for reference whilst
preparing for examination. — Am. Medical Journal.

Its excellence is in its compactness, its clearness,

and its carefully cited authorities. It is the most
convenient of text-books. These gentlemen, Messrs.
Kirkes and Paget, have the gift of telling us what
we want to know, without thinking it necessary
to tell us all they know. — Boston Med. and Surg.
Journal,

For the student beginning this study, and the
practitioner who has but leisure to refresh big
memory, this book is invaluable, as it contains all
that it is important to know. — Charleston Mid.
Journal.

KNAPP'S TECHNOLOGY ; or, Chemistry applied
to the Arts and to Manufactures. Edited by Dr.
RONALDS, Dr. RICHARDSON, and Prof. W. R.
JOHNSON. In two handsome 8vo. vols. , extra cloth,
with about 500 wood- engravings. $6 00-.

LAYCOCK'S LECTURES ON THE PRINCf-
PLES AND METHODS OF MEDICAL OB-
SERVATION AND RESEARCH. For the Use

of Advanced Students and Junior Practitioners.
In one royal ISmo. volume, extra cloth. Price $1.

LALLEMAND AND WILSON.
A PRACTICAL TREATISE ON THE CAUSES, SYMPTOMS, AND

TREATMENT OF SPERMATORRHOEA. By M. LALLEMAND. Translated and edited by

HENRY J McDouGALL. Third American edition. To which is added ON DISEASES

OF THE VESICUL^E SEMINALES; AND THEIR ASSOCIATED ORGANS. With special refer-
ence to the Morbid Secretions of the Prostatic and (Jrethral Mucous Membrane. By MARR.IS
WILSON, M. D. In one neat octavo volume, of about 400 pp., extra cloth. $2 00.

LA ROCHE (R.), M. D., &c.
YELLOW FEYER, considered in its Historical, Pathological, Etiological, and

Therapeutical Relations. Including a Sketch of the Disease as it has occurred in Philadelphia
from 1699 to 1854, with an examination of the connections between it and the fevers known under
the same name in other parts of temperate as well as in tropical regions. In two large and
handsome octavo volumes of nearly 1500 pages, extra cloth. $7 00.

From Professor S. U. Dicleson, Charleston, S. C.,
September 18, 1855.

A monument of intelligent and well applied re-
Bearch, almost without example. It is, indeed, in
itself, a large library, and is destined to constitute
the special resort as a book of reference, in the
subject of which it treats, to all future time.

We have not time at present, engaged as we are,
by day and by night, in the work of combating this
very disease, now prevailing in oui- city, to do more
than give this cursory notice of what we consider
as undoubtedly the most able and erudite medical
publication our country has yet produced. But in
view of the startling fact, that this, the most malig-

nant and unmanageable disease of modern times,
has for several years been prevailing in our country
to a greater extent than ever before; that it is no
longer confined to either large or small cities, but
penetrates country villages, plantations, and farm-
houses ; that it is treated with scarcely better suc-
cess now than thirty or forty years ago ; that there
is vast mischief done by ignorant pretenders to know-
ledge in regard to the disease, and in view of the pro-
bability that a majority of southern physicians will
be called upon to treat the disease, we trust that this
able and comprehensive treatise will be very gene-
rally read in the south.— Memphis Med. Recorder.

BY THE SAME AUTHOR.

PNEUMONIA ; its Supposed Connection, Pathological and Etiological, with Au-
tumnal Fevers, including an Inquiry into the Existence and Morbid Agency of Malaria. In one
handsome octavo volume, extra cloth, of 500 pages. $3 00.

LAWRENCE (W.), F. R. S., &c. %

A TREATISE ON DISEASES OF THE EYE. A new edition, edited,

with numerous additions, and 243 illustrations, by ISAAC HAYS, M. D., Surgeon to Will's Hospi-
tal, &c. In one very large and handsome octavo volume, of 950 pages, strongly bound in leather
with raised bands. $600.

LUDLOW (J. L.), M. D.
A MANUAL OF EXAMINATIONS upon Anatomy, Physiology, Surgery,

Practice of Medicine, Obstetrics, Materia Medica, Chemistry, Pharmacy, and Therapeutics. To
which is added a Medical Formulary. Third edition, thoroughly revised and greatly extended
and enlarged. With 370 illustrations. In one handsome royal 12mo. volume, ol 816 large
pages, extra cloth, $2 50; leather, $3 00.

We know of no better companion for the student
during the hours spent in the lecture room, or to re-
fresh, at a glance, his memory of the various topics

crammed into his head by the various professors to
whom he is compelled to listen.— Western Lancet.
May, 1857.

AND SCIENTIFIC PUBLICATIONS. 21

LEHMANN (C. G.)
PHYSIOLOGICAL CHEMISTRY. Translated from the second edition by

GEORGE E. DAY, M. D., F. R. S., &c., edited by R. E. ROGERS, M. D., Professor of Chemistry
in the Medical Department of the University of Pennsylvania, with illustrations selected from
Funke's Atlas of Physiological Chemistry, and an Appendix of plates. Complete in two large
and handsome octavo volumes, extra cloth, containing 1200 pages, with nearly two hundred illus-
trations. $6 00.
The work of Lehraann stands unrivalled as the I The most important contribution as yet made to

most comprehensive book of reference and informa- | Physiological Chemistry.— Am. Journal Med. Sci-

tion extant on every branch of the subject on which | tnces, Jan. 1556.

it treats. — Edinburgh Journal of Medical Science. \

BY THE SAME AUTHOR.

MANUAL OF CHEMICAL PHYSIOLOGY. Translated from the German,

with Notes and Additions, by J. CHESTON MORRIS, M. D., with an Introductory Essay on Vital
Force, by Professor SAMUEL JACKSON, M. D., of the University of Pennsylvania. With illus-
trations on wood. In one very handsome octavo volume, extra cloth, of 336 pages. $2 25.

LYONS (ROBERT D.), K. C. C.,

Late Pathologist in-chief to the British Army in the Crimea, &c.

A TREATISE ON FEVER; or, selections from a course of Lectures on Fever.
Being part of a course of Theory and Practice of Medicine. In one neat octavo volume, of 362
pages, extra cloth; $200. (Just Issued.)

This is an admirable work upon the most remark- ) Lyons' work on Fever to the attention of the pro-
able and most important class of diseases to which i fession. It is a work which cannot fail to enhance
mankind are liable.— Med. Journ. of N. Carolina, the author's previous well-earned reputation, as a

May, 1861.
We have great pleasure in recommending Dr.

diligent, careful, and accurate observer.— British,

Med. Journal, March 2, 1861.

MEIGS (CHARLES D.), M. D.,

Lately Professor of Obstetrics, &c. in the Jefferson Medical College, Philadelphia.

OBSTETRICS : THE SCIENCE AND THE ART. Fourth edition, revised

and improved. With one hundred and twenty-nine illustrations. In one beautifully printed octav«
volume, of seven hundred and thirty large pages, extra cloth, $3 50 ; leather, $4 00. (Now
Ready, Feb. 1863.)

FROM THE AUTHOR'S PREFACE.

" [n this edition I have endeavored to amend the work by changes in its form ; by careful cor-
rections of many expressions, and by a few omissions and some additions as to the text.

"The Student will find that I have recast the article on Placenta Praevia, which I was led to do
out of my desire to notice certain new modes of treatment which I regarded as not only ill founded
as to the philosophy of our department, but dangerous to the people.

" In changing the form of my work by dividing it into paragraphs or sections, numbered from 1
to 959, 1 thought to present to the reader a common-plnce book of the whole volume. Such a table
of contents ought to prove both convenient and useful to a Student while attending public lectures."

A work which has enjoyed so extensive a reputation and has been received with such general
favor, requires only the assurance that the author has labored assiduously to embody in his new
edition whatever has been found necessary to render it fully on a level with the most advanced
state of the subject. Both as a text-book for the student and as a reliable work of reference for
the practitioner, it is therefore to be hoped that the volume will be found worthy a continuance of
the confidence reposed in previous editions.

BY THE SAME AUTHOR. (JllSt Issued.)

WOMAN: HER DISEASES AND THEIR REMEDIES. A Series of Lec-
tures to his Class. Fourth and Improved edition. In one large and beautifully printed octav*
volume, extra cloth, of over 700 pages. $3 60.
In other respects, in our estimation, too much can- ; which cannot fail to recommend the volume to the

not be said in praise of this work. It abounds with attention of the reader. — Ranking' s Abstract.

SEJJSfiOT Itcontainsavastamountofpracticalknowledge

the diseases of females, it is not excelled, and pro- *>7 one w^° has accurately observed and retained
bably not equalled in the English language'. On the ; ">« experience of many years.- JD«Z>.'tn Quarterly
whole, we know of no wort on the diseases of wo- Jov

men which we can so cordially commend to the Full of important matter, conveyed in a ready and
•indent and practitioner as the one before us.— Ohio j agreeable manner.— St. Louis Med. and Surg. Jour.
Med. and Surg. Journal.

mi. u j r • i_ i_ There is an off-hand fervor, a glow, and a warm-

The body of the book is worthy of attentive con- . aeartedness infecting the eff jrt of Dr. Meigs, which
•{deration, and is evidently the production of a ia entirely captivating, and which absolutely hur-
clever, thoughtful, and sagacious physician. Dr. I ries the reader through from beginning to end. Be-
Meigs's letters on the diseases of the external or- , aide8) the book teems with solid instruction, and
gans, contain many interesting and rare cases, and • it shows the very highest evidence of ability, viz.,
"yS7 1?Tstructlv? observations. We take our leave the clearness with which the information is pre-
of Dr. Meigs, with a high opinion of his talents and 8ented. We know of no better test of one's under-
ongmality.— The British and Foreign Mcdico-C'hi- j standing a subject than the evidence of the power
rurgical Review. of iucidly explaining it. The most elementary, as

Every chapter is replete with practical instruc- I well as the obscurest subjects, under the pencil of
tion, and bears the impress of being the composition Prof. Meigs, are isolated and made to stand out in
of an acute and experienced mind. There is a terse- I such bold relief, as to produce distinct impressions
ness, and at the same time an accuracy in his de- upon the mind and memory of the reader. — Tiu
•Grip tion of symptoms, and in the rules for diagnosis, j Charleston Med. Journal.

22

BLANCHARD ft LEA'S MEDICAL

MEIGS (CHARLES DJ..M. D.,

Lately Professor of Obstetrics, &c.,"in Jefferson Medical College, Philadelphia.

ON THE NATURE, SIGNS, AND TREATMENT OF CHILDBED

FEVER. In a Series of Letters addressed to the Students of his Class. In one handsome
octavo volume, extra cloth, of 365 pages. $2 50.

The instructive and interesting author of this
work, whose previous labors have placed his coun-
trymen under deep and abiding obligations, again

lectable book. * * * This treatise upon child-
bed fevers will have an extensive sale, being des-
tined, as it deserves, to find a place in the library

of every practitioner who scorns tolag in the rear.
Nashville Journal of Medicine and Surgery.

challenges their admiration in the fresh and vigor-
ous, attractive and racy pages before us. It is a de-

BY THE SAME AUTHOR J WITH COLORED PLATES.

A TREATISE ON ACUTE AND CHRONIC DISEASES OF THE NECK

OF THE UTERUS. With numerous plates, drawn and colored from nature in the highest
style of art. In one handsome octavo volume, extra cloth. $4 50.

MACLISE (JOSEPH), SURGEON.
SURGICAL ANATOMY. Forming one volume, very large imperial quarto,

With sixty-eight large and splendid Plates, drawn in the best style and beautifully colored. Con-
taining one hundred and ninety Figures, many of them the size of life. Together with copious
and explanatory letter-press. Strongly and handsomely bound in extra cloth, being one of the
cheapest and best executed Surgical works as yet issued in this country. $11 00.

Gentlemen preparing for service in the field or hospital will find these plates
of the highest practical value, either for consultation in emergencies or to refresh
their recollection of the dissecting room.

%* The size of this work prevents its transmission through the post-office as a whole, but those
who desire to have copies forwarded by mail, can receive them in five parts, done up in stout
wrappers. Price $9 00.

One of the greatest artistic triumphs of the age
in Surgical Anatomy.— Britis h American Medical
Journal.

No practitioner whose means will admit should
fail to possess it.— Ranking' & Abstract.

arallel in point of accu-
Inglish language.— N. Y.

we have not language to do it justice. — Ohio Medi-
cal and Surgical Journal.

The most accurately engraved and beautifully
colored plates we have ever seen in an American
book — one of the best and cheapest surgical works
ever published. — Buffalo Medical Journal.

It is very rare that so elegantly printed, so well
illustrated, and BO useful a work, is offered at so
moderate a price.— Charleston Medical Journal.

Its plates can boast a superiority which places
them almost beyond the reach of competition .—Medi-
cal Examiner.

Country practitioners will find these plates of im-
mense value.— N. Y. Medical Gazette.

A work which has no j
racy and cheapness in the
Journal of Medicine.

We are extremely gratified to announce to th«
profession the completion of this truly magnificent
work, which, as a whole, certainly stands unri-

Too much cannot be said in its praise; indeed, W"J*> "'"Y"' faa tt *""""*> ^* •••«*"; »-«"««> •""*-

vailed, both for accur-acy of drawing, beauty of

coloring, and all the requisite explanations of tha
subject in hand. — Tht Neu Orleans Medical and
Surgical Journal.

This is by far the ablest work on Surgical Ana-
tomy that has come under our observation. W«
know of no other work that would justify a stu-
dent, in any degree, for neglect of actual dissec-
tion. In those sudden emergencies that BO often
arise, and which require the instantaneous command
of minute anatomical knowledge, a work of this kind
keeps the details of the dissecting-room perpetually
fresh in the memory .—Tht Western Journal of Mt&*~
cine and Surgery.

MILLER (HENRY), M. D.,

Professor of Obstetrics and Diseases of Women and Children in the University of Louisville.

PRINCIPLES AND PRACTICE OP OBSTETRICS, &c. ; including the Treat-

ment of Chronic Inflammation of the Cervix and Body of the Uterus considered as a frequent
cause of Abortion. With about one hundred illustrations on wood. In one very handsome oc-
tavo volume, of over 600 pages, extra cloth. $3 75.

We congratulate the author that the task is done.
We congratulate him that he has given to the medi-
cal public a work which will secure for him a high
and permanent position among the standard autho-
rities on the principles and practice of obstetrics.
Congratulations are not less due to the medical pro-
fession of this country, on the acquisition of a trea-
tise embodying the results of the studies, reflections,
and experience of Prof. Miller.— Buffalo Medical
Journal.

In fact, this volume must take its place among the
•tandard systematic treatises on obstetrics ; a posi-

tion to which its merits justly entitle it. — The Cin-
cinnati Lancet and Observer.

A most respectable and valuable addition to our
home medical literature, and" one reflecting credit
alike on the author and the institution to which he
is attached. The student will find in this work a
most useful guide to his studies; the country prac-
titioner, rusty in his reading, can obtain from its
pages a fair resume of the modern literature of the
science; and we hope to see this American produc-
tion generally consulted by the profession.— V*.
Med. Journal.

MACKENZIE (W.), M.D.,

Surgeon Oculist in Scotland in ordinary to Her Majesty, &c. &c.

A PRACTICAL TREATISE ON DISEASES AND INJURIES OF THE

EYE. To which is prefixed an Anatomical Introduction explanatory of a Horizontal Section of
the Human Eyeball, by THOMAS WHARTON JONES, F. R. S. From the Fourth Revised and En-
larged London Edition. With Notes and Additions by ADDINELL HEWSON, M. D., Surgeon to
Wills Hospital, &c. &c. In one very large and handsome octavo volume, extra cloth, with plates
and numerous wood-cuts. $5 25.

The treatise of Dr. Mackenzie indisputably holds I We consider it the duty of every one who has the
the firstplace, and forms, in respect of learning and love of his profession and the welfare of his patient
research, an Encyclopaedia unequalled in extent by | at heart, to make himself familiar with this the most

any ot
— Dix

other work of the kind,eitherEnglish or foreign, complete work in the English language upon thedis-
ixon on Diseases of the Ey«. \ eases of the eye.— Med. Times and Gazettt.

AND SCIENTIFIC PUBLICATIONS.

23

MILLER (JAMES), F. R. S. E.,

Professor of Surgery in the University of Edinburgh, &c.

PRINCIPLES OF SURGERY. Fourth American, from the third and revised
Edinburgh edition. In one large and very beautiful volume, extra cloth, of 700 pages, with
two hundred and forty illustrations on wood. $3 75.

BY THE SAME AUTHOR.

THE PRACTICE OF SURGERY. Fourth American from the last Edin-

burgh edition. Revised by the American editor. Illustrated by three hundred and sixty-four
engravings on wood. In one large octavo volume, extra cloth, of nearly 700 pages. $3 75.
No encomium of ours could add to the popularity i his works, both on the principles and practice ot
of Miller's Surgery. Its reputation in this country ; surgery have been assigned the highest rank. If we
is unsurpassed by that of any other work, and, when were limited to but one work on surgery, that one
taken in connection with the author's Principles of should be Miller's, as we regard it as superior to all
Surgery, constitutes a whole, without reference to i others.— St. Louis Med. and Surg. Journal.
which no conscientious surgeon would be willing to
n Med.

and Surg. Journal. \ The author has in this and his" Principles," pre-
^

profound an impression in so short a time as the writing is ordinal, impassive, and engaging, ener-

ifrJ!!r-?nple" ^ •'!? **??*?£ °f Sur?er\ by i getic, concise, and lucid. Few have the°faculty of

-or so richly merited the reputation they ! Condensing so much in small space, and at the same

have acquired. The author is an eminently sensi- j time 8O persistently holding theattention. Whether

We, practical, and well-informed man, who knows ; as a text.book for student! or a book of reference

.xactly what he is talking about and exactly how to for practitioners, it cannot be too strongly recom-

talk it.-Kentucky Medical Recorder. mended .-5<m<Aer» Journal of Med. and Physical

By the almost unanimous voice of the profession, Scienets.

MORLAND (W. W.), M. D.,

Fellow of the Massachusetts Medical Society, <kc.

DISEASES OF THE URINARY ORGANS; a Compendium of their Diagnosis,

Pathology, and Treatment. With illustrations. In one large and handsome octavo volume, of

about 600 pages, extra cloth. $3 50.

Taken as a whole, we can recommend Dr. Mor- ! refer. This desideratum has been supplied by Dr.
land's compendium as a very desirable addition to j Morland, and it has been ably done. He has placed
the library of every medical or surgical practi- i before us a full, judicious, and reliable digest.
tioner. — B rit. and For.Med.-Ckir. Rev., April, 1859. j Bach subject is treated with sufficient minuteness.

Every medical practitioner whose attention has I yet in a succinct, narrational style, such as to recder
been to any extent attracted towards the class of j the wort one of great interest, and one which wi I
diseases to which this treatise relates, must have prove m the highest_ degree useful to the genera!
often and sorely experienced the want of some full,
yet concise recent compendium to which he could

practitioner. — N. Y. Journ. of Medicine,

BY THE SAME AUTHOR.

THE MORBID EFFECTS OF THE RETENTION IN THE BLOOD OF

THE ELEMENTS OF THE URINARY SECRETION. Being the Dissertation to which the
Fiske Fund Prize was awarded, July 11, 1861. In one small octavo volume, 83 pages, extra
cloth. 75 cents.

MONTGOMERY (W. F.), M. D., M. R. I. A., &c.,

Professor of Midwifery in the King and Queen's College of Physicians in Ireland, &c.

AN EXPOSITION OF THE SIGNS AND SYMPTOMS OF PREGNANCY.

With some other Papers on Subjects connected with Midwifery. From the second and enlarged

English edition. With two exquisite colored plates, and numerous wood-cuts. In one very

handsome octavo volume, extra cloth, of nearly 600 pages. $3 75.

A book unusually rich in practical suggestions. — fresh, and vigorous, and classical is our author's
Am. Journal Med. Sciences, Jan. 1857. style; and one forgets, in th« renewed charm of

These several subjects so interesting in them- ' 2veiT page, that it, and every line, and every word
•elves, and so important, every one of them, to the has been weighed and reweighed through years of
most delicate and precious of social relations, con- preparation ; that this is of all others the book of
trolling often the honor and domestic peace of a Obstetric Law, on each of its several topics ; on all
family, the legitimacy of offspring, or the life of its P0111*8 connected with pregnancy, to be everywhere
parent are all treated with an elegance of diction, received as a manual of special jurisprudence, at
fulness of illustrations, acuteness and justice of rea- once announcing fact, affording argument, estabhsh-
Boning, unparalleled in obstetrics, and unsurpassed in in? precedent, and governing alike the juryman, ad-
medicine. The reader's interest can never flag, so vocate, and judge. -N. A. Med.-Chir. Review.

MOHR (FRANCIS), PH. D., AND REDWOOD (THEOPHI LUS).
PRACTICAL PHARMACY. Comprising the Arrangements, Apparatus, and

Manipulations of the Pharmaceutical Shop and Laboratory. Edited, with extensive Additions,
by Prof. WILLIAM PROCTER, of the Philadelphia College of Pharmacy. In one handsomely
printed octavo volume, extra cloth, of 570 pages, with over 500 engravings on wood. $2 75

MAYNE'S DISPENSATORY AND THERA-
PEUTICAL REMEMBRANCER. With every
Practical Formula contained in the three British
Pharmacopoeias. Edited, with the addition of the
Formulae of the U. S. Pharmacopoeia, by R. E.
.D 1 12mo. vol. ex. cl., 300 pp. 75 c.

MALGAIGNE'S OPERATIVE SURGERY, based
on Normal and Pathological Anatomy. Trans-
lated from the French by FREDERICK BRITTAN,
A . B . , M . D . Wi th numerous il lustrations on wood .
In one handsome octavo volume, extra cloth, oi
nearly six hundred pages. S3 25.

24 BLANCHARD & LEA'S MEDICAL

NErLL (JOHN), M. D.,

Surgeon to the Pennsylvania Hospital, See.', and

FRANCIS GURNEY SMITH, M.D.,

Professor of Institutes of Medicine in the Pennsylvania Medical College.

AN ANALYTICAL COMPENDIUM OF THE VARIOUS BRANCHES

OF MEDICAL SCIENCE ; for the Use and Examination of Students. A new edition, revised
and improved. In one very large and handsomely printed royal 12mo. volume, of about one
thousand pajres, with 374 wood-cuts, extra cloth, $3 25. Strongly bound in leather, with raised
bands. $3 50.

This work is again presented as eminently worthy of the favor with which it has hitherto
been received. As a book for daily reference by the student requiring a guide to his more elaborate
text-books, as a manual for preceptors desiring to stimulate their students by frequent and accurate
examination , or as a source from which the practitioners of older date may easily and cheaply acquire
a knowledge of the changes and improvement in professional science, its reputation is permanently
established.
The best work of the kind with which we are I the students is heavy, and review necessary for an

acquainted. — Med. Examiner.

Having made free use of this volume in our ex-
aminations of pupils, we can speak from experi-
ence in recommending it as an admirable compend
for students, and as especially useful to preceptors
who examine their pupils. It will save the teacher
much labor by enabling him readily to recall all of
the points upon which his pupils should be ex-
amined. A work of this sort should be in the hands
of every one who takes pupils into his office with a
view of examining them; and this is unquestionably
the best of its class. — Transylvania Med. Journal,

In the rapid course of lectures, where work for

examination, a compend is not only valuable, but
it is almost a sine qua won. The one before us is,
in most of the divisions, the most unexceptionable
of all books of the kind that we know of. The
newest and soundest doctrines and the latest im-
provements and discoveries are explicitly, though
concisely, laid before the student. There is a clasa
to whom we very sincerely commend this cheap book
as worth its weight in silver — that class is the gradu-
ates in medicine of more than ten years' standing,
who have not studied medicine since. They will
perhaps find out from it that the science is not exactly
now what it was when they left it off. — The Stetho-
scope.

NELIGAN (J. MOORE), M. D., M. R. I. A., &c.
ATLAS OF CUTANEOUS DISEASES. In one beautiful quarto volume, extra

cloth, with splendid colored plates, presenting nearly one hundred elaborate representations of

disease. $4 75.

This beautiful volume is intended as a complete and accurate representation of all the varieties
of Diseases of the Skin. While it can be consulted in conjunction with any work on Practice, it has
especial reference to the author's " Treatise on Diseases of the Skin," so favorably received by the
profession some years since. The publishers feel justified in saying that few more beautifully exe-
cuted plates have ever been presented to the profession of this country.

Neligan's Atlas of Cutaneous Diseases supplies a I give, at a coup d'ail, the remarkable peculiarities
long existent desideratum much felt by the largest of each individual variety. And while thus the dis-
class of our profession. It presents, in quarto size, ease is rendered more definable, there is yet no loss
16 plates, each containing from 3 to 6 figures, and of proportion incurred by the necessary concentra-
forming in all a total of 90 distinct representations tion. Each figure is highly colored, and so truthful
of the different species of skin affections, grouped "
together in genera or families. The illustrations
have been taken from nature, and have been copied

has the artist been that the most fastidious observer
could not justly take exception to the correctness of
the execution of the pictures under his scrutiny—

with such fidelity that they present a striking picture Montreal Med. Chronicle.
of life; in which the reduced scale aptly serves to

BY THE SAME AUTHOR.

A PRACTICAL TREATISE ON DISEASES OF THE SKIN. Fourth

American edition. In one neat royal 12mo. volume, extra cloth, of 334 pages. $1 25.

°SS? *££, THE DIFFERENT FORMS OF I One vol. royal 12mo., extra cloth with numerous
THE SKELETON, AND OF THE TEETH. | illustrations. 81 25.

PIRRIE (WILLIAM), F. R. S. E.,

Professor of Surgery in th,e University of Aberdeen.

THE PRINCIPLES AND PRACTICE OF SURGERY. Edited by JOHN

NEILL, M. D., Professor of Surgery in the Penna. Medical College, Surgeon tothe Pennsylvania
Hospital, &c. In one very handsome 8vo. volume, extra cloth, of 780 pages, with 316 illustrations.
So 7o.

We know of no other surgical work of a reason- i rately discussed the principles of surgery, and a
able size, wherein there is so much theory and prac- safe and effectual practice predicated upon them,
tice, or where subjects are more soundly or clearly I Perhaps no work upon this subject heretofore issued
taught— The Stethoscope. I is so fun upon the science of the art of surgery.—

Prof. Pirrie, in the work before us, has elabo- 1 Nashville Journal of Medicine and Surgery.

PARKER (LANGSTON),

Surgeon to the Queen's Hospital, Birmingham.

THE MODERN TREATMENT OF SYPHILITIC DISEASES, BOTH PRI-
MARY AND SECONDARY; comprising the Treatment of Constitutional and Confirmed Syphi-
lis, by a safe and successful method. With numerous Cases, Formula, and Clinical Observa-
tions. From the Third and entirely rewritten London edition.- In one neat octavo volume,
extra cloth, of 316 pages. $1 75.

AND SCIENTIFIC PUBLICATIONS.

PARRISH (EDWARD),
Lecturer on Practical Pharmacy and MateritMedica in the Pennsylvania Academy of Medicine, &c.

AN INTRODUCTION TO PRACTICAL PHARMACY. Designed as a Text-

Book lor the Student, and as a Guide for the Physician and Pharmaceutist. With many For-
mulae and Prescriptions. Third edition, greatly improved. In one handsome octavo volume,
of nearly 850 pages, with several hundred Illustrations, extra cloth. SD 00. (Just Ready.)
Though for some time out of print, the appearance of a new edition of this work has b-r-en de-
layed for the purpose of embodying in it the results of the new U. S. Pharmacopoeia. The pub-
lication of this latter has enabled the author to complete his revision in the most thorough manner.
Those who have been waiting for the work may therefore rely on obtaining a volume completely
on a level with the most advanced condition of pharmaceutical science.

The favor with which the work has thus far been received shows that the author was not mis-
taken in his estimate of the want of a treatise which should serve as a practical text-book for all
engaged in preparing- and dispensing medicines. Such a guide was indispensable not only to the
educated pharmaceutist, but also to that large class of practitioners throughout the country who
are obliged to compound their own prescriptions, and who during their collegiate course have no
opportunity of obtaining a practical familiarity with the necessary processes and manipulations.
The rapid 'exhaustion of two large editions is evidence t£at the author has succeeded in thoroughly
carrying out his object. Since the appearance of the la*t edition, much has been done to perfect
the science ; the new Pharmacopoeia has introduced many changes to which the profession must
conform ; and the author has labored assiduou>ly to embody in his work all that physicians and
pharmaceutists can ask for in such a volume. The new matter alone will thus be found wo.lu
more than the very moderate cost of the work to those who have been using the previous editions.

edition, containing the added results of his recent
and rich experience as an observer, teacher, and
practic tl operator in the pharmaceutical laboratory.
The excellent plan of the first is more thoroughly,
—Peninsular Med. Journal, Jan. 15tiO.
Of course, all apothecaries who have not already

All that we can say of it is that to the practising
physician, and especially the country physician,
who is generally his own apothecary, there is hard-
ly any book that might not better be dispensed with
It is at the same time a dispensatory and a pharma-
cy.— Louisville Review.

A careful examination of this work enables us to
speak of it in the highest terms, as being the best
treatise on practical pharmacy with winch we are
acquainted, and an invaluable vide-mecum, not only
to the apothecary and to those practitioners who
are accustomed to prepare tleir own medkines, but
to every medical man and medical student. — Boston
Med. and Surg. Journal.

This is altogether one of the most useful books
we have seen. It is just what we have long felt to
be needed by apothecaries, students, and practition-
ers of med icine, most of whom in this country have
to put up their own prescriptions. It bears, upon
every page, the impress of practical knowledge,
conveyed in a plain common sense manner, und
adapted to the comprehension of all who may read
it. — Southern Med. and Surg. Journal.

That Edward Parrish, in writing a book upon
practical Pharmacy some few years ago — one emi-
nently original and unique — did the medical and
pharmaceutical professions a great and valuable ser-
vice, no one, we think, who has had access to its or quite all the most useful infor nation on the sub-'
pages will deny; doubly welcome, then, is this new ( ject. — Charleston Med. Jour. and Review, Jan. 1860.

PEASLEE (E. R.), M. D.,

Professor of Physiology and General Pathology in the New York Medical College.

HUMAN HISTOLOGY, in its relations to Anatomy, Physiology, and Pathology;
for the use of Medical Students. With four hundred and thirty-four illustrations. lu one hand-
some octavo volume, extra cloth, of over 600 pages. $3 75.

a copy of the first edition will procure one of this ;
it is, therefore, to physicians residing in the country
and in small towns, who cannot avail themselves of
the skill of an educated pharmaceutist, that we
would especially commend this work. In it they
will find all that they desire to know, and should
know, but very little of which they do really snow
in reference to this important collateral branch of
their profession; for it is a well established fact,
that, in the education of physicians, while the sci-
ence of medicine is geneially well taught, very
little attention is paid to the art of preparing them
for use, and we know not how this defect can be so
well remedied as by procuring and consulting Dr.
Parrish's excellent work.— Si. Louis Med. Journal.
Jan. I860.

We know of no work on the subject which would
be more indispensable to the physician or student
desiring information on the subjectof which it treats.
With Griffith's i; Medical Formulary" and this, the
practising physician would be supplied with nearly

'

it embraces a library upon the topics discussed
within itself, and is just what the teacherand learner
need. We have not only the whole subject of His-
tology, interesting in itself, ably and fully discussed,

We would recommend it as containing a summary
of all that is known of the important subjects which
it treats ; of all that is in the great works of Simon
and Lehmann, and the organic chemists in general.

but what is ot infinitely greater interest to the stu- Master this one volume, and you know all that la
dent, because of greater practical value, are its re- j known of the great fundamental principles of medi-

lations to Anatomy, Physiology, and Pathology,
which are here fully and satisfactorily set forth.—
Nashville Journ. of Med. and Surgery.

cine, and we have no hesitation in saying that it
is an honor to the American medical profession. —
St. Louis Mtd. and Surg. Journal.

ROKITANSKY (CARL), M.D.,
Curator of the Imperial Pathological Museum, and Professor at the University of Vienna, &c.

A MANUAL OF PATHOLOGICAL ANATOMY. Four volumes, octavo,

bound in two, extra cloth, of about 1200 pages. Translated by W. E. SWAINE, EDWARD SIEVK-
KING, C. H. MOOSE, and G. E. DAY. $5 50.

The profession is too well acquainted with the re-
futation of Rokitansky's work to need our assur-
ance that this is one of the most profound, thorough,
and valuable books ever issued from the medical
press. It is sui generis, and has no standard of com-
parison. It is only necessary to announce that it is
issued in a form as cheap as is compatible with its
size and preservation, and its sale follows as a
matter of course. No library can be called com-
plete without it.— Buffalo Med. Journal.

An attempt to give our readers any adequate idea
of the vast amount of instruction accumulated in

these volumes, would be feeble and hopeles*. The
effort of the distinguished author to concentrate
in a small space his great fund of knowledge, has
go charged his text wan vaiuaoJe trutns, tnat any
attempt of a reviewer to epitomize is at once para-
lyzed, and must end in a failure.— Western Lancet.
As this is the highest source of knowledge upon
the important subject of wliich it treats, no real
student can afford to be without it. The American
publisners have entitled themselves to the thanks of
the profession of their country, for this timeous and
beautiful edition.— Nashville Journal of Medicine.

BLANGHARD & LEA'S MEDICAL

RIGBY (EDWARD), M. D.,

Senior Physician to the General Lying-in Hospital, &c.

A SYSTEM OF MIDWIFERY. With Notes and Additional Illustrations.

Second American Edition. One volume octavo, extra cloth, 422 pages. $2 50.

BY THE SAME AUTHOR.

ON THE CONSTITUTIONAL. TREATMENT OF FEMALE DISEASES.

In one neat royal 12mo. volume, extra cloth, of about 250 pages. $1 00.

RAMSBOTHAM (FRANCIS H.), M.D.
THE PRINCIPLES AND PRACTICE OF OBSTETRIC MEDICINE AND

SURGERY, in reference to the Process of Parturition. A new and enlarged edition, thoroughly
revised by the Author. With Additions by W. V. KEATING, M. D., Professor of Obstetrics, &c., in
the Jefferson Medical College, Philadelphia. In one large and handsome imperial octavo volume,
of 650 pages, strongly bound in leather, with raised bands; with sixty- four beautiful Plates, and
numerous Wood-cuts in the text, containing in all nearly 200 large and beautiful figures. $6 00.

From Prof. Hodge, of the University of Pa.

To the American public, it is most valuable, from its intrinsic undoubted excellence, and as being
the best authorized exponent of British Midwifery. Its circulation will, I trust, beextensive throughout
our country.

It is unnecessary to say anything in regard to the
utility of this work. It is already appreciated in our
country for the value of the matter, the clearness of
its style, and the fulness of its illustrations. To the
physician's library it is indispensable, while to the
student as a text-book, from which to extract the
material for laying the foundation of an education on
obstetrical science, it has no superior. — Ohio Med.
and Surg. Journal.

The publishers have secured its success by the

truly elegant style in which they have brought it
out, excelling themselves in its production, espe-
cially in its plates. It is dedicated to Prof. Meigs,
and has the emphatic endorsement of Prof. Hodge,
as the best exponent of British Midwifery. We
know of no text-book which deserves in all respects
to be more highly recommended to students, and we
could wish to see it in the hands of every practitioner,
for they will find it invaluable for reference.— Med.
Gazette.

RICORD (P.), M. D.

A TREATISE ON THE VENEREAL DISEASE. By JOHN HUNTER, F. R. 8.

. With copious Additions, by PH. RICORD, M.D. Translated and Edited, with Notes, by FREEMAN
J. BUMSTEAD, M.D., Lecturer on Venereal at the College of Physicians and Surgeons, New York.
Second edition, revised, containing a resume of RICORD'S RECENT LECTURES ON CHANCRE. In
one handsome octavo volume, extra cloth, of 550 pages, with eight plates. $3 25.

lie. In conclusion we can say that this is incon'

Every one will recognize the attractiveness and
ralue which this work derives from thus presenting
the opinions of these two masters side by side. But,
it must be admitted, what has made the fortune of
the book, is the fact that it contains the "most com-
plete embodiment of the veritable doctrines of the
Hopital du Midi," which has ever been made pub-

testablythe best treatise on syphilis with which we
are acquainted, and, as we do not often employ the
phrase, we may be excused for expressing the hope
that it may find a place in the library of every phy-
sician.— Virginia Med. and Surg. Journal.

BY THE SAME AUTHOR.

RICORD'S LETTERS ON SYPHILIS. Translated by W. P. LATTIMORE, M. D-

In one neat octavo volume, of 270 pages, extra cloth. $2 00.

ROYLE'S MATERIA MEDICA AND THERAPEUTICS 5 including the

Preparations of the Pharmacopoeias of London, Edinburgh, Dublin, and of the United States.
With many new medicines. Edited by JOSEPH CARSON, M. D. With ninety-eight illustration*.
In one large octavo volume, extra cloth, of about 700 pages. $3 00.

SMITH (HENRY H.), M. D., AND HORN ER (W I LLI AM E.), M. D.
AN ANATOMICAL ATLAS, illustrative of the Structure of the Human Body.

In one volume, large imperial octavo, extra cloth, with about six hundred and fifty beautiful

figures. $3 50.

The plan of this Atlas, which renders it so pe- I of the kind that has yet appeared ; and wemust add.
culiarly convenient for the student, and its superb the very beautiful manner in which it is "got up"
artistical execution, have been already pointed out. I is so creditable to the country as to be flattering
We must congratulate the student upon the comple- to our national pride.— American Medical Journal.
tion of this Atlas, as it is the most convenient work

SHARPEY (WILLIAM), M. D., JONES QUAIN, M. D., AND

RICHARD QUAIN, F. R. S., &c.
HUMAN ANATOMY. Revised, with Notes and Additions, by JOSEPH LEIDY,

M. D., Professor of Anatomy in the University of Pennsvlvania. Complete in two large octavo
volumes, extra cloth, of about thirteen hundred pages. With over 500 illustrations. $6 00.

SOLLY ON THE HUMAN BRAIN; itsStructure,
Physiology, and Diseases. From the Second and
much enlarged London edition. In one octavo
volume, extra cloth, of 500 pages, with 120 wood-
cuts. $2 00.

SKEY'S OPERATIVE SURGERY. In one very

handsome octavo volume, extra cloth, of over 650
pages, with about one hundred wood-cuts. $3 25.
SIMON'S GENERAL PATHOLOGY, as conduc-
ive to the Establishment of Rational Principles
for the prevention and Cure of Disease. In one
octavo volume, extra cloth, of 212 pages. $1 25.

AND SCIENTIFIC PUBLICATIONS.

STILLE (ALFRED), M. D.
THERAPEUTICS AND MATERIA MEDIC A; a Systematic Treatise on the

Action and Uses of Medicinal Agents, including their Description and History. In two large

and handsome octavo volumes, of 1789 pages, leather. $9 00.

This work is designed especially for the student and practitioner of medicine, and treats the various
articles of the Materia Medica from the point of view of the bedside, and not ot the shop or of the
lecture-room. While thus endeavoring to give all practical information likely to be useful with
respect to the employment of special remedies in special affections, and the results to be anticipated
from their administration, a copious Index of Diseases and their Remedies renders the work emi-
nently fitted for reference by showing at a glance ihe different means which have been employed,
and enabling the practitioner to extend his resources in difficult cases with all that the experience
of the profession has suggested.

Rarely, indeed, have we had submitted to us a ; The most recent authority is the one last men-
work on medicine so ponderous in its dimensions ; tioned, Stille. His great work on " Materia Medi-
as that now before us, and yet so fascinating in its j ca and Therapeutics," published last year, in two

octavo volumes, of some sixteen hundred pages,
while it embodies the results of the Isbor of others

contents. It is, therefore, with a peculiar gratin-
cation that we recognize in Dr. Stille the posses-
sion of many of those more distinguished qualifica-
tions which entitle him to approbation, and which

up to tne time of publication, is enriched with a
great amount of original observation and research.

justify him in coming before his medical brethren i We would draw attention, by the way, to the very
as an instructor. A comprehensive knowledge, , convenient mode in which the Index is arranged in
tested by a sound and penetrating judgment, joined j this work. There is first an " Index of Remedies;'
to a love of progress— which a discriminating spirit ' next an " Index of Diseases and their Remedies."
of inquiry has tempered so as to accept nothing new Such an arrangement of the Indices, in our opinion,
because it is new, and abandon nothing old because-; greatly enhances the practical value of books of this
it is old, but which estimates either accorting to its kind. In tedious, obstinate cases of disease, where
relations to a just logic and experience — manifests j we have to try one remedy after another until our
itself everywhere, and gives to the guidance of the j stock is pretty nearly exhausted, and we are almost
author all the assurance of safety which the diffi- ! driven to our wit's end, such an index as the second
culties of his subject can allow. In conclusion, we j of the two just mentioned, is precisely what we
earnestly advise our readers to ascertain for thtrn- want. — London Med. Times and Gazette, April, 1861
selves, by a study of Dr. Stille's volumes, the great We think thia work will do much to obviate tlie
value and interest of -the stores of knowledge , they reluctance to a tho rough investigation of thi s branch
present. We have pleasure in referring rather to of &cientl&c 8tudy fof in the wfde ra e Of medical
the ample treasury of undoubted truths, the real and ; ,lterature treasured in the English tonlue, we shal
assured conquest of medicine, accumulated by Dr. j toardl find a work written in | style msore'clear 23
Stille in his pages ; and commend the sum of his la- ; 8im()ie cunveymg forcibly the facts taught, and yet
bors to the attention of our readers, as alike honor- ,free from turgidny and redundancy. TlTere fsa fas-
and creditable to the zeal, the cination in ftg y that will Jsure to u aaw**e
[gmentof him wno has garnered ; popaiarity and attentive perusal, and a degree of
the whole so carefully .-Edinburgh Med. Journal. [is£fulness not often attained through the influence
We knew that the task would be conscientiously of a single work. The author has much enhanced
performed, and that few, if any, among the distm- the practical utility of his book by passing briefly
guished medical teachers in this country are better over the physical, botanical, and commercial history
qualified than he to prepare a systematic treatise of medicines, and directitg attention chiefly to their
on therapeutics in accordance with the present re- physiological action, and their application for the
quirements of medical science. Our preliminary amelioration or cure of disease. He ignores hypothe-
satisfied us that we si? and theory which are soalluring to many medical

examination of the work has

were not mistaken in our anticipations. —

leans Medical News, March, 1360.

writers, and so liable to lead them astray, and con-
fines hinruelf to such facts as have been tried in the
crucible of experience.— Chicago Medical Journal .

SIMPSON (J. YJ, M. D.,

Professor of Midwifery, &c., in the University of Edinburgh, &e.

CLINICAL LECTURES ON THE DISEASES OP WOMEN. With nu-
merous illustrations. In one handsome octavo volume, of over 500 pages, extra cloth, $3 00.
(Now Ready, 1863.)

This valuable work having passed through the columns of " THE MEDICAL NEWS AND LIBRARY"
for I860, ISbl, and 1862, is now completed, and may be had separate in one handsome volume.

The principal topics embraced in tne Lectures are Vet-ico- Vaginal Fistula, Cancer of the Uterus,
Treatment of Carcinoma by Caustics, Dysmeuorrhoea, Amenorrhoea, Closures, Contractions, &c.,
of the Vagina, Vulvitis, Causes of Death after Surgical Operations, Surgical Fever, Phlegmasia
Dolens, Coccyodinia, Pelvic Cellulitis, Pelvic Haematoma, Spurious Pregnancy, Ovarian Dropsy,
Ovariotomy, Cranioclasm, Diseases of the Fallopian Tubes, Puerperal Mania, Sub-Involution and
Super-Involution of the Uterus, &c. &c.

As a series of monographs on these important topics — many of which receive little attention
in the ordinary text-books — elucidated with the extensive experience and readiness of resource for
which Professor Simpson is so distinguished, there are few practitioners who will not find in it»
pages matter of the utmost importance in the treatment of obscure and difficult cases.

SALTER (H. tH.), M. D.
ASTHMA; its Pathology, Causes, Consequences, and Treatment.

8vo., extra cloth. (Just Ready.) $175.
The portion of Dr. Sailer's work whish is devoted
to treatment, is ot great practical interesc and value

Iii one Tol.

convey a just notion of the practical value of this
part of hi* work. This our space forbius, and this

He treats successively of the influence of the differ- we shall little regret, if, by our silence, we should

ent drugs which have been found useful in relieving
the asthmatic paroxysm, so far as he has had an op-
portunity of testing their merits, and it would be
necessary to follow him step by step in his remarks,
not only on the medicinal, but also on the dietetic
and hygienic treatment of the disease, in order to

ind uce our readers to possess themselves of the book
itself; a book which, without doubt, deserves to be
ranked among the most valuable of recent contribu-
tions to the medical literature of this country. —
Ranking 's Abstract, Jan , 1961.

28 BLANCHARD & LEA'S MEDICAL

SARGENT (F. W.), M. D.
ON BANDAGING AND OTHER OPERATIONS OF MINOR SURGERY.

New edition, with an additional chapter on Military Surgery. One handsome royal 12mo. vol.,
of nearly 400 pages, with 184 wood cuts. Extra cloth, $1 50. (Now Ready.)
The value of this work as a handy and convenient manual for surgeons engaged in active duty, has
induced the publishers to render it more complete for those purposes by the addition of a chapter
on gun-shot wounds and other matters peculiar to military surgery. In its present form, there-
fore, with no increase in price, it will be found a very cheap and convenient vade-mecum for con-
sultation and reference in the daily exigencies of ^military as well as civil practice.

We consider that no better book could be placed
in the hands of an hospital dresser, or the young sur-
geon, whose education in this respect has not been
perfected. We most cordially commend this volume
as one which the medical student should most close-
ly study, to perfect himself in these minor surgical
operations in which neatness and dexterity are so
much required, and on which a great portion of his
reputation as a future surgeon must evidently rest.
And to the surgeon in practice it must prove itself
a valuable volume, as instructive on many points
which he may have forgotten. — British American
Journal, May, 1862.

The instruction given upon the subject of Ban-
daging, is alone of great value, and while the author
modestly proposes to instruct the students of medi-
cine, and the younger physicians, we will say that
experienced physicians will obtain many exceed-
ingly valuable suggestions by its perusal. It will
be found one of the most satisfactory manuals for re-
ference in the field, or hospital yet published; thor-
oughly adapted to the wants of Military surgeons,
and at the same time equally useful for ready and
convenient reference by surgeons everywhere.—
Buffalo Med. and Surg. Journal, June, 1862.

SMITH (W. TYLER), M. D.,

Physician Accoucheur to St. Mary's Hospital, &c.

ON PARTURITION, AND THE PRINCIPLES AND PRACTICE OF

OBSTETRICS. In one royal 12mo. volume, extra cloth, of 400 pages. $1 25.

BY THE SAME AUTHOR.

A PRACTICAL TREATISE ON THE PATHOLOGY AND TREATMENT

OF LEUCORRHCEA. With numerous illustrations. In one very handsome octavo volume,
extra cloth, of about 250 pages. $1 50.

TANNER (T. H.), M. D.,

Physician to the Hospital for Women, &c.

A MANUAL OF CLINICAL MEDICINE AND PHYSICAL DIAGNOSIS.

To which is added The Code of Ethics of the American Medical Association. Second
American Edition. In one neat volume, small 12mo., extra cloth, 87j cents.

TAYLOR (ALFRED S.), M. D., F. R. S.f

Lecturer on Medical Jurisprudence and Chemistry in Guy's Hospital.

MEDICAL JURISPRUDENCE. Fifth American, from the seventh improved

and enlarged London edition. With Notes and References to American Decisions, by EDWARD
HARTSHORNE,M.D. In one large Svo. volume, extra clolh, of over 700 pages. $3 25.
This standard work having had the advantage of two revisions at the hands of the author since
the appearance of the last American edition, will be found thoroughly revised and brought up com-
pletely to the present state of the science. As a work of authority, it must therefore maintain iis
position, both as a text-book for the student, and a compendious treatise to which the practitioner
can at all times refer in cases of doubt or difficulty.

No work upon the subject can be put into the
hands of students either of law or medicine which
will engage them more closely or profitably ; and
none could be offered to the busy practitioner of
either calling, for the purpose of casual or hasty
reference, that would be more likely to afford the aid
desired. We therefore recommend it as the best and
safest manual for daily use.— American Journal ojf
Medical Sciences.

It is not excess of praise to say that the volume

American and British legal medicine. It should be
in the possession of every physician, as the subject
is ore of great and increasing importance to the
public as well as to the profession.— St. Louis Med
and Surg. Journal.

This work of Dr. Taylor's is generally acknow-
ledged to be one of the ablest extant on the subject
of medical jurisprudence. It is certainly one of the
most attractive books that we have met with ; sup-

Alt 10 IlVt ^.Ai^tco wi iJiaiot. bv »«*J fcU-CL* W1C VUlUJIiC — ,1 i_ i_ i , .

before us is the very best treatise extant on Medical ! pl>1?g 80f much ,b("h to~ 1Dterest and instruct, that

Jurisprudence. In saying this, we do not wish to
be understood as detracting from the merits of the

we do not hesitate to affirm that after having once
commenced its perusal, few could be prevailed upon
to desist before completing it. In the last London

pleting it.

edition, all the newly observed and accurately re-
corded facts have been inserted, including mucto

s rent of cemica1' Micr°6cop*cai> ***

ng fro

excellent works of Beck, Ryan, Trail!, Guy, and
others; but in interest and value we think it must
be conceded that Taylor is superior to anything that

has preceded it. — JV. W. Medical and Surg. Journal t . .- «•- '

. . ' l inoiogicai research, besides papers on numerous

It IB at once comprehensive and eminently prac- subjects never before pubiished.—GViar/esfon, Med.
tical, and by universal consent ttanus at the head of I Journal and Review.

BY THE SAME AUTHOR.

ON POISONS, IN RELATION TO MEDICAL JURISPRUDENCE AND

MEDICINE. Second American, from a'second and revised London edition. In one large
octavo volume, of 755 pages, extra cloth. $3 50.

Mr. Taylor's position as the leading medical jurist of England, has conferred on him extraordi-
nary advantages in acquiring experience on these subjects, nearly all cases of moment beimr
referred to him for examination, as an expert whose testimony is generally accepted as final
The results of his labors, therefore, as gathered together in this volume, carefully weighed and
silted, and presented in the clear and intelligible style for which he is noted, may be received
as an acknowledged authority, and as a guide to be followed with implicit confidence.

BY THE SAME AUTHOR AND WM. BRANDE.

CHEMISTRY. In one volume 8vo, See "BRANDE," p, 6.

AND SCIENTIFIC PUBLICATIONS.

TODD (ROBERT BENTLEY), M. D., F. R. S.,

Professor of Physiology in King's College, London; and
WILLIAM BOWMAN, F. R. S.,

Demonstrator of Anatomy in King's College, London.

THE PHYSIOLOGICAL ANATOMY AND PHYSIOLOGY OF MAN. With

about three hundred large and beautiful illustrations on wood. Complete in one large octavo
volume, of 950 pages, extra cloth. Price $4 50.

Itis more concise than Carpenter's Principles, and
more modern than tne accessible edition of Muller's
Elements; its details are b*ef, but sufficier.it; its
descriptions vivid ; its illustrations exact and copi-
ous ; and its language terse and perspicuous. —

A magnificent contribution to British medicine,
and the American physician who shall fail to peruse
it, wih have failed to read one of the most instruc-
tive books of the nineteenth centur^.— N. O. Med.
and Surg. Journal.

Charleston Med. Journal.

TODD (R. B.) M. D., F. R. S., &c.
CLINICAL LECTURES ON CERTAIN DISEASES OF THE URINARY

ORGANS AND ON DROPSIES. In one octavo volume, 284 pages, extra cloth. $1 50.

BY THE SAME AUTHOR.

CLINICAL LECTURES ON CERTAIN ACUTE DISEASES. In one neat

octavo volume,, of 320 pages, extra cloth. $1 75.

TOYNBEE (JOSEPH), F. R. S.,

'Aural Surgeon to, and Lecturer on Surgery at, St. Mary's Hospital.

A PRACTICAL TREATISE ON DISEASES OF THE EAR; their Diag-

nosis, Pathology, and Treatment. Illustrated with one hundred engravings on wood. In one

very handsome octavo volume, extra cloth, $3 00.

The work is a rnodel of its kind, and every page Surgery, it is without a rival in onr language or any
and paragraph oi it are worthy of the most thorough : other. — Charleston Med. Journ. and Rev., Sept. 1860
study. Considered all in ail-as an original work, j The work of Mr> Toynbee is undoubtedly, upon
well written, philosophically elaborated, and happi- th whol th most valljabie produciion of £e k^nd
Iv-illustrated with cases and drawings-it is by far ; in ^ laagaage. The author has long Deen known
the ablest monograph that has ever appeared on the ;by hfs nuVroua monographs uponlubjects con-
anatomy and diseases of the ear, and one of the most | nected Wlth disease8 of the ear, and ia now regarded
valuable contributions to the art and science of sur- as the hl hest authoritv on most points in his de-
gery in the nineteenth century.— N. Amer. Medico- partment of science. Mr. Toyabee's work, as we
Chtrurg. Review, Sept. 1860. „ already said, is undoubtedly the moat reliable

We are speaking within the limits of modest ac- ; guide for the study of the diseases of the ear in any
knowledgment, and with a sincere and unbiassed ! language, and should be in the library of every phy-
judgment, when we affirm that as a treatise on Aural sician. — Chicago Med. Journal, July, 1860.

WILLIAMS (C. J. B.), M.D., F. R. S.,

Professor of Clinical Medicine in University College, London, &c.

PRINCIPLES OF MEDICINE. An Eleraentaiy View of the Causes, Nature,

Treatment, Diagnosis, and Prognosis of Disease; with brief remarks on Hygienics, or the pre-
servation of health. A new American, from the third and revised London edition. In one octavo '
volume, extra cloth, oi about 500 pages. $2 50.

WHAT TO OBSERVE
AT THE BEDSIDE AND AFTER DEATH, IN MEDICAL CASES.

Published under the authority of the London Society for Medical Observation. A new American,

from the second and revised Londou edition. In one very handsome volume, royal 12mo., extra

cloth. $1 00.

To the observer who prefers accuracy to blunders I One of the finest aids to a young practitioner we
and precision to carelessness, this little book is in- I have ever seen. — Peninsular Journal ofMtdicint.
valuable.— N. H. Journal of Medicine.

WALSHE (W. H.), M. D.,

Professor of the Principles and Practice of Medicine in University College, London, &c.

A PRACTICAL TREATISE ON DISEASES OF THE LUNGS; including

the Principles of Physical Diagnosis. Third American, from the third revised and much en-
larged London edition. In one vol. octavo, of 468 pages, extra cloth. $2 25.
The present edition has been carefully revised and much enlarged, and may be said in the main
lo be rewritten. Descriptions of several diseases, previously omitted, are now introduced; an
effort has been made to bring the description of anatomical characters to the level of the wants of
the practical physician ; and the diagnosis and prognosis of each complaint are more completely
considered. The sections on TREATMENT and the Appendix have, especially, been largely ex-
tended.— Author's Preface.

BY THE SAME AUTHOR.

A PRACTICAL TREATISE ON THE DISEASES OF THE HEART AND

GREAT VESSELS, including the Principles of Physical Diagnosis. Third American, from the

third revised and much enlarged London edition. In one handsome octavo volume of 420 pages,

extra cloth. $2 25.

The present edition has been carefully revised ; much new matter has been added, and the entire
work in a measure remodelled. Numerous facts and discussions, more or less completely novel,
will be found in the description of ttte principles of physical diagnosis ; but the chief additions have
been made in the practical portions of the book. Several affections, of which little or no account
had been given in the previous editions, are now treated of in detail. — Author's Preface.

30

BLANCHARD & LEA'S MEDICAL

New and much enlarged edition.

WATSON (THOMAS), M. D., &c.,

Late Physician to the Middlesex Hospital, &c.

LECTURES ON THE PRINCIPLES AND PRACTICE OF PHYSIC.

Delivered at King's College, London. A new American, from the last revised and enlarged

English edition, with Additions, by D. FRANCIS CONDIE, M. D., author of " A Practical Treatise

on the Diseases of Children," &c. With one hundred and eighty.five illustrations on wood. In

one very large and handsome volume, imperial octavo, of over 1200 closely printed pages in

small type; extra cloth, $4 75; strongly bound in leather, with raised bands, $5 50.

That the bigh reputation of this work might be fully maintained, the author has subjected it to a

thorough revision ; every portion has been examined with the aid of the most recent researches

in pathology, and the results of modern investigations in both theoretical and practical subjects

have been carefully weighed and embodied throughout its pages. The watchful scrutiny of the

editor has likewise introduced whatever possesses immediate importance to the American physician

in relation to diseases incident to our climate which are little known in England, as well as those

points in which experience here has led to different modes of practice ; and he has also added largely

to the series of illustrations, believing that in this manner valuable assistance may be conveyed to

the student in elucidating the text. The work will, therefore, be found thoroughly on a level with

the most advanced state of medical science on both sides of the Atlantic.

The additions which the work has received are shown by the fact that notwithstanding an en-
largement in the size of the page, more than two hundred additional pages have been necessary
to accommodate the two large volumes of the London edition (which sells at ten dollars), within
the compass of a single volume, and in its present form it contains the matter of at least three
ordinary octavos. Believing it to be a work which should lie on the table of every physician, and
be in the hands of every student, the publishers have put it at a price within the reach of all, making-
it one of the cheapest books as yet presented to the American profession, while at the same time
the beauty of its mechanical execution renders it an exceedingly attractive volume.

The fourth edition now appears, so carefully re-
vised, as to add considerably to the value of a book
already acknowledged, wherever the English lan-
guage is read, to be beyond all comparison the best
systematic work on the Principles and Practice of
Physic in the whole range of medical literature.
Every lecture contains proof of the extreme anxiety
of the author to keep pace with the advancing know-
ledge of the day One scarcely knows whether
to admire most the pure, simple, forcible English —
the vast amount of useful practical information
condensed into the Lectures — or the manly, kind-
hearted, unassuming character of the lecturer shin-
ing through his work. — Land. Med. Times.

Thus these admirable volumes come before the
profession in their fourth edition, abounding in those
distinguished attributes of moderation, judgment,
erudite cultivation, clearness, and eloquence, with
which they were from the first invested, but yet
richer than before in the results of more prolonged
observation, and in the able appreciation of the

latest advances in

pathology
id medical

and medicine by one

of the most profound medical thinkers of the day.—
London Lancet.

The lecturer's skill, his wisdom, his learning, are
equalled by the ease of his graceful diction, his elo-
quence, and the far1 higher qualities of candor, of
courtesy? of modesty, and of generous appreciation
of merit in others.— N. A. Med. -C hir Review.

Watson's unrivalled, perhaps unapproachable
work on Practice — the copious additions made to
which (the fourth edition) have given it all the no-
velty and much, of the interest of a new book.—
Charleston Med. Journal.

Lecturers, practitioners, and students of medicine
will equally hail the reappearance of the work of
Dr. Watson in the form of a new — a fourth — edition.
We merely do justice to our own feelings, and, we
are sure, of the whole profession, if we thanK him
for having, in the trouble and turmoil of a large
practice, made leisure to supply the hiatus caused
by the exhaustion of the third edition. For Dr.
Watson has not merely caused the lectures to be
reprinted, but scattered through the whole work we
find additions or alterations which prove that the
author has in every way sought to bring up his teach-
ing to the level of ihe most recent acquisitions in
science. — Brit, and For. Medico-C hir. Review.

New and much enlarged edition.

WILSON (ERASMUS), F. R. S.

A SYSTEM OF HUMAN ANATOMY, General and Special. A new and re-

vised American, from the last and enlarged English Edition. Edited by W. H. GOBRECHT, M. D.,
Professor of Anatomy in the Pennsylvania Medical College, &c. Illustrated with three hundred
and ninety-seven engravings on wood. In one large and exquisitely printed octavo volume, oi
over 600 large pages; extra cloth, $3 50; leather, $4 00.

The publishers trust that the well earned reputation so long enjoyed by this work will be more
than maintained by the present edition. Besides a very thorough revision by the author, it has been
most carefully examined by the editor, and the efforts of both have been directed to introducing
everything which increased experience in its use has suggested as desirable to render it a complete
text-book for those seeking to obtain or to renew an acquaintance with Human Anatomy. The
amount of additions which it has thus received may be estimated from the fact that the present
edition contains over one-fourth more matter than the last, rendering a smaller type and an enlarged
page requisite to keep the volume within a convenient size. The editor has exercised the utmost
caution to obtain entire accuracy in the text, and has largely increased the number of illustra-
tions, of which there are about one hundred and fifty more in this edition than in. the last, thus
bringing distinctly before the eye of the student everything of interest or importance.

It may be recommended to the student as no less beauty of its mechanical execution, and the clear
distinguished by its accuracy and clearness of de-
scription than by its typographical elegance. The
wood-cuts are exquisite.— Brit, and For. Medical
Review .

An elegant edition of one of the most useful and
accurate systems of anatomical science which has
been issued from the press The illustrations are
really beautiful. In its style the work is extremely
concise and intelligible. No one can possibly take
up this volume without being struck with the grout

ness of the descriptions which it contains is equally
evident. Let students, by all means examine tne
claims of this work on their notice, before they pur-
chase a text-book of the vitally important science
which this volume so fully and easily unfolds. —
Lancet.

We regard it as the best system now extant for
students.— Western Lancet.

It therefore receives ourhighestcommendation. —
Southern Med. and Surg. Journal.

AND SCIENTIFIC PUBLICATIONS.

31

WILSON (ERASMUS), F. R. S.
ON DISEASES OF THE SKIN. Fifth American, from the Fifth enlarged

London edition. In one handsome octavo volume, of nearly 700 large pages, with illustrations

on wood, extra cloth. $3 25. (Now Ready, May, 1863.)

This classical work, which for twenty years has occupied the position of the leading authority
in the English language on its important subject, has just received a thorough revision at the hands
of the author, and is now presented as embodying the results of the latest investigations and expe-
rience on all matters connected with diseases of the skin. The increase in the size of the work
shows the industry of the author, and his determination that it shall maintain the position which it
has acquired as thoroughly on a level with the most advanced condition of medical science.
f the last edition are appended.

No matter what other treatises may be in the libra-
ry of the medical attendant, he needs the clear and
suggestive counsels of Wilson, who is thoroughly
posted up on all subjects connected with cutaneous
pathology. We have, it is very true, other valuable
works on the maladies that invade the skin; but,
compared with the volume under consideration, they
are certainly to be regarded as inferior lights in guid-
ing the judgment of the medical man.— Boston Med.
and Surg. Journal, Oct. 1857.

The author adopts a simple and entertaining style.
He strives to clear away the complications of his
subject, and has thus produced a book filled with a
vast amount of information, in a form so agreeable
as to make it pleasant reading, even to the uninitiated.
More especially does it deserve our praise because of
its beautiful and complete atlas, which the American
publishers have successfully imitated from the origi-
nal plates. We pronounce them by far the best imi-
tations of nature yet published in our country. With
the text-book and atlas at hand, the diagnosis is ren-
dered easy and accurate, and the practitioner feels
himself safe in his treatment. We will add that this
work, although it must have been very expensive to
the publishers, is not high priced. There is no rea-
son, then, to prevent every physician from obtaining
a work of such importance, and one which will save
him both labor and perplexity.— Fa. Med. Journal.

As a practical guide to the classification, diagnosis,
and treatment of the diseases of the skin, the book is
complete. We know nothing, considered in this as-
pect, better in our language ; it is a safe authority on
all the ordinary matters which, in this range of dis-
eases, engage the practitioner's attention, and pos-
sesses the high quality — unknown, we believe, to
every older manual, of being on a level with science's
high-water mark : a sound book of practice. — London
Med. Times.

A few notices of the last edition are appended.

The writings of Wilson, upondiseasesof the skin,
are by far the most scientific and practical that
have ever been presented to the medical world on
this subject. The present edition is a great improve-
ment on all its predecessors. To dwell upon all the
great merits and high claims of the work before us,
seriatim, would indeed be an agreeable service ; it
would be a mental homage which we could freely
offer, but we should thus occupy an undue amount
of space in this Journal. We will, however, look
at some of the more salient points with which it
abounds, and which make itincompara oiy superior to
all other treatises on the subject of dennatology. No
mere speculative views are allowed a place in this
volume, which, without a doubt. will, for a very long
period, be acknowledged as the chief standard work
on dermatology. The principles of an enlightened
and rational tnerapeia are introduced on every ap-
propriate occasion. — Am. Jour. Med Science.

When the first edition of this work appeared;
about fourteen years ago, Mr. Erasmus \Vilson had
already given some years to the study of Diseases
of the Skin, and he then expressed his intention of
devoting his future life to the elucidation of this
branch of Medical Science. In the present edition
Mr. Wilson presents us with the results of his ma-
tured experience, and we have now before us not
merely a reprint of his former publications, but an
entirely new and rewritten volume. Thus, the whole
history of the diseases affecting the skin, whether
they originate in that structure or are the mere mani-
festations of derangement of internal, organs, is
brought under notice, and the book includes a mass
of information which is spread over a great part of
the domain of Medical and Surgical Pathology. We
can safely recommend it to the profession as the
best work on the subject now in existence in the En-
glish language. — London Med. Times and Gazette.

* ALSO, NOW READY,

A SERIES OF PLATES ILLUSTRATING WILSON ON DISEASES OF

THE SKIN; consisting of twenty beautifully executed plates, of which thirteen are exquisitely
colored, presenting the Normal Anatomy and Pathology of the Skin, and containing accurate re-
presentations of about one hundred varieties of disease, most of them the size of nature. Price
in cloth. $4.50.
In beauty of drawing and accuracy and finish of coloring these plates will be found equal to

anything of the kind as yet issued in this country. The value of the new edition is enhanced by

an'additional colored plate.

We have already expressed our high appreciation
of Mr. Wilson's treatise on Diseases of the Skin.
The plates are comprised in a separate volume,
which we counsel all those who possess the text to
purchase. It is a beautiful specimen of color print-
ing, and the representations of the various forms of
skin disease are as faithful as is possible in plates
of the size. — Boston Med. and Surg. Journal. April
8, 185d.

The plates by which this edition is accompanied
leave nothing to be desired, so far as excellence of
delineation and perfect accuracy of illustration are
concerned. — Medico-Chirurgical Review.

Of these plates it is impossible to speak too highly.
The representations of the various forms of cutane-
ous disease are singularly accurate, and the color-
ing exceeds almost anything we have met with. —
British and Foreign Medical Review.

ALSO, the TEXT and PLATES done up in one handsome volume, extra cloth, price $7 50.

BY THE SAME AUTHOR.

THE DISSECTOR'S MANUAL; or, Practical and Surgical Anatomy. Third

American, from the last revised and enlarged English edition. Modified and rearranged, by
WILLIAM HUNT, M. D., Demonstrator of Anatomy in the University ot Pennsylvania. In one
large and handsome royal 12mo. volume, extra-cloth, of 582 pages, with 154 illustrations, $2 00.

BY THE SAME AUTHOR.

ON CONSTITUTIONAL AND HEREDITARY SYPHILIS, AND ON

SYPHILITIC ERUPTIONS. In one small octavo volume, extra cloth, beautifully printed, with
four exquisite colored plates, presenting more than thirty varieties of syphilitic eruptions. $2 25,

BY THE SAME AUTHOR.

HEALTHY SKIN; A Popular Treatise on the Skin and Hair, their Preserva-
tion and Management. Second American, from the fourth London edition. One neat volume,
royal 12mo., extra cloth, of about 300 pages, with numerous illustrations. $1 00; paper cover,
75 cents.

BLANCHARD & LEA'S MEDICAL PUBLICATIONS.

WINSLOW (FORBES), M. D., D. C. L., &c.
ON OBSCURE DISEASES OF THE BRAIN AND DISORDERS OF THE

MIND; their incipient Symptom?, Pathology, Diagnosis, Treatment, and Prophylaxis. In one
handsome octavo volume, of nearly 600 page;*, extra cloth. $3 00.

We close this brief and necessarily very imperfect
notice of Dr. Winslow's great and classical work,
by expressing our conviction that it is long since BO
important and beautifully written a volume has is-
sued from the British medical press.— Dublin Med.
Press, July 25, 1860.

We honestly believe this to be the best book of the
season.— Ranking* s Abstract, July, 1860.

The latter portion of Dr. Winslow's work is ex-
clusively devoted to the consideration of Cerebral

Pathology. It completely exhausts the subject, in
the same manner as the previous seventeen chapters
relating to morbid psychical phenomena left nothing
unnoticed in reference to the mental symptoms pre-
monitory of cerebral disease. It is impossible to
overrate the benefits likely to resulc from a general
perusal of Dr. Winslow's valuaole and deeply in-
teresting work. — London Lancet, June 23, 1860.

It contains an immense mass of information.

Brit, and For. Med.-Chir. Review, Oct. I860.

WEST (CHARLES), M. D.,

Accoucheur to and Lecturer on Midwifery at St. Bartholomew's Hospital, Physician to the Hospital for

Sick Children, &c.

LECTURES ON THE DISEASES OF WOMEN? Second American, from the

second London edition. In one handsome octavo volume, extra cloth, of about 500 pages ;
price $2 50.

*** Gentlemen who received the first portion, as issued in the "Medical News and Library," can
now complete their copies by procuring Part II, being page 309 to end, with Index, Title matter,
&c., 8vo., cloth, price $1.

We mustnow conclude this hastily written sketch
with the confident assurance to our readers that the
work will well repay perusal. The conscientious,
painstaking, practical physician is apparent on every
page N. Y. Journal of Medicine.

We know of no treatise of the kind so complete
and yet so compact.— Chicago Med. Jour.

A fairer, more honest, more earnest, and more re-
liable investigator of the many diseases of women
and children is not to be found in any country.—
Southern Med. and Surg. Journal.

We have to say of it, briefly and decidedly, that
it is the best work on the subject in any language ;
and that it stamps Dr. West as the facile princeps
of British obstetric authors. — Edinb. Med. Journ.

We gladly recommend his Lectures as in the high-
est degree, instructive to all who are interested ia
obstetric practice. — London Lancet.

Happy in his simplicity of manner, and moderate
in his expression of opinion, the author is a sound
reasoner and a good practitioner, and his book IB
worthy of the handsome garb in which it has ap-
peared .— Virginia Med. Journal.

We must take leave of Dr. West's very useful
work, with our commendation ol the clearness of
its style, and the intustry and sobriety of judgment
of which it gives evidence.— London Med Times.

Sound judgment and good sense pervade every
chapter of the book. From its perusal we have de-
rived unmixed satisfaction. — Dublin Quart. Jour*.

BY THE SAME AUTHOR.

LECTURES ON THE DISEASES OF INFANCY AND CHILDHOOD.

Third American, from the fourth enlarged and improved London edition. In one handsome
octavo volume, extra cloth, of about six hundred and fifty pages. $2 75.

The three former editions of the work now before
us have placed the author in the foremost rank of
those physicians who have devoted special attention
to the diseases of early life. We attempt no ana-
lysis of this editionrbut may refer the reader to some
<»t the chapters to which the largest additions have
been made— those on Diphtheria, Disorders of the
Mind, and Idiocy, for instance — as a prooi that the
work is really a new edition j not a mere reprint.
la its pretent shape it will be lound of the greatest
possible service in the every-day practice of nine-
teuths of the profession. — Med. Times and Gazette,
London, Dec. 10, 1859.

All things considered, this book of Dr. West is
by far the best treatise in our language upon such
modifications of morbid action and disease as are
witnessed when we have to deal with infancy and
childhood. It is true that it confines itself to such
disorders as come wichin the province of the phy-
sician, and even with respect to these it is unequal
ita regards minuteness ot consideration, and some

diseases it omits to notice altogether. But those
who know anything of the present condition ot
paediatrics will readily admit chat it would be next
to impossible to effect more, or effect it better, than
the accoucheur of St. Bartholomew's has done in a
single volume. The lecture (XVI.) upon Disorders
of the Mind in children is an admirable specimen of
.the value of the later information convejed in the
Lectures of Dr. Charles West.— London Lancet.
Oct. 22, 1859.

Since the appearance of the first edition, about
eleven years ago, the experience of the author has
doubled; so that, whereas the lectures at first were
founded on six hundred observations, and one hun-
dred and eighty dissections made among nearly four-
teen tliousand children, they now embody tiie results
of nine hundred observations, and two Hundred and
eighty-eightpost- mortem examinations made among
nearly thirty thousand children, who, during the
past twetty years, have been under his care. —
British, Med. Journal, Oct. 1, 1859.

BY THE SAME AUTHOR.

AN ENQUIRY INTO THE PATHOLOGICAL IMPORTANCE OF ULCEB-

ATION OF THE OS UTERI. In one neat octavo volume, extra cloth. $1 00.

WHITEHEAD ON THE CAUSES AND TREAT-

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