UC-NRLF

B M mi Tfl3

liiiifttiitiiifti*i**tt% SI » s » tV*V«

m

1. >'

. I

V

" (»K

-^

•0. \v}M

.V

UNIVERSITY OF CALIFORNIA

SAN FRANCISCO

LIBRARY

Digitized by the Internet Archive

in 2007 with funding from

IVIicrosoft Corporation

http://www.archive.org/details/elementsofcomparOOwagnrich

BOOKS PUBLISHED BY J. S. REDFIELD.

MEDICAI. BOOKS.

RUDOLPH WAGNER, M.D.,

PBOFESSOB OF COMPARATIVE ANATOMY AND PHYSIOLOOY IN THE UNIVERSITY OF
GOTTINGEN, ETC., ETC.

ELEMENTS OF THE

COMPARATIVE ANATOMY

OFTHE VERTEBRATE ANIMALS.

EDITED BY ALBERT TULK.

In one vol. 8vo. Price $1 50.

"Professor Wagner of Gottingen ranks among the first Comparative Anatomists of the
age ; I entertain the highest opinion of his work, and am happy to learn, it is about to be
issued from the American press.

" The subject is one of utility, and has always claimed the attention of the Physiologist.
It is beginning to awaken a lively interest among the scientific men of our own country.

" W. PARKER, M.D., &c.

" 754 Broadway, Oct. 12, 164t."

* * * * <4 1 have looked over Wagner's Comparative Anatomy, and it strikes me as ad-
mirably fulfilling what the title indicates— that of affording a brief but distinct and compre-
hensive outline of the subject. I think too, that by this publication, you are conferring a
benefit upon medical men, and especially upon students who wish to obtain a general knowl-
edge of the subject, without being obliged to purchase the English works, such as Grant,
Jones, Owen, &c., which are all of them expensive books. *****

"R. WATTS, Jr.

" College of Physicians and Surgeons, N. Y."

I J. P. MAYGRIER, M.D.

JcJU PROFESSOR OF OBSTETRICS AND DISEASES OF WOMEN AND CHILDREN AT PARIS, &C.

i MIDWIFERY ILLUSTRATED,

g' WITH TWO HUNDRED ILLUSTRATIONS.

H Translated from the French,

BY A. SIDNEY DOANE, A.M., M.D.
In one vol. 8vo. Price Five Dollars.
" The splendid Illustrations of Midwifery given in Maygrier's large work are admirable in
their execution, and essentially useful both to the Practitioner and Student of Obstetrics.
Dr. Doane, in making a translation of this work, and giving to tiie American public an edition
of these fine engravings, will essentially serve the cause of medicine ; and 1 do not hesitate
to recommend tlie work. " EDWARD DEL AFIELD, M.D.,

Professor of Obstetrics and Diseases of Women and
Children, University of State of New York."
" I AM of opinion that the translation of M. Maygrier's Midwifery, as prepared by Dr. Doane,
will be a most valuable acquisition to Students and Practitioners of Medicine.

" ALEXANDER F. STEVENS, M.D."

WILLIAM BUCHAN, M.D.
A TREATISE ON THE

PREVENTION AND CURE OF DISEASES,

BY REGIMEN AND SIMPLE MEDICINES.

REVISED AND ENLARGED WITH THE ADDITION OF

A VEGETABLE MATERIA MEDICA,

Pointiiig out the virtues, preparations, and doses, of our most valuable native
medicinal plants, and an outline of
ANATOMY AND PHYSIOL9GY.
BY J. G. NORWOOD, M.D.
In one volume, 8vo. Price Four Dollars.
As health is the most precious of all things, and is the foundation of all happiness, the
science of protecting life is the noblest of all, and most worthy the attention of all man-
kind."— Hoffman.

<8

I

BOOKS PUBLISHED BY J. S. REDFIELD.
J. G. A. LUGOL,

PHYSICIAN TO THE HOSPITAL ST. LOUIS, &C., &C.

RESEARCHES AND OBSERVATIONS ON

SCROFULOUS DISEASES;

Translated from the French,

BY A. SIDNEY DOANE, A.M., M.D.

One vol. 12mo. Price One Dollar.

" This is a work of great value to the members of the medical profession, and to the great
number of sufferers by an insidious and most widely-extended disease."— iV. Y. Tribune.

" It is the most complete work we know of on Scrofulous diseases."— Morning News.

" M. Lugol has presented us an admirable treatise on Scrofulous Diseases, adapted to the
comprehension of all reflecting persons. Not only will enlightened parents derive from
it much useful instruction, but the medical professon will assent to the statement that
Lugol's Researches contain a very luminous exhibition of the subject to wtiich it relates." —
Christian Intelligencer.

" It is a very satisfactory and necessary book for all who would understand how to avoid
the various ills of Scrofula."— jEyenin^ Mirror.

" Dr. Lugol has shed great light upon a subject of peculiar interest, both to parents and
their children." — N. Y. Evening Post.

" Dr. Doane has wisely selected tliis volume for transfer into our language. The insidious
character of Scrofula, the multiplied phases that it assumes, its diversified causes and exhi-
bitions, according to the state of the subject whom it affects, and its wide-spread evils, ren-
der a luminous and skilful development of this malady a public benefit."— jIot. Republican.

P. H. RICORD,M.D.,

SURGEON OF THE VENEREAL HOSPITAL OF PARIS, CLINICAL PROFESSOR OF SPECIAL
PATHOLOGY, &C.

PRACTICAL TREATISE

ON VENEREAL DISEASES;

OR CRITICAL AND EXPERIMENTAL RESEARCHES ON INOCULATION

APPLIED TO THE STUDY OF THESE AFFECTIONS, WITH A

THERAPEUTICAL SUMMARY AND SPECIAL FORMULARY.

Translated from the French,

BY A. SIDNEY DOANE, A.M., M.D.

In one volume, 8vo. Price $1 50.

" The subscriber is personally acquainted with Dr. Ricord, and has seen much of his practice,

not only in his Hospital, but in private, and can bear testimony to his merits as a Practitioner,

and also to the value of his " Practical Treatise on Venereal Diseases," now about to be

translated for the general use of the Profession in this country. The present translation is

offered to subscribers at less cost than the French edition at Paris.

" VALENTINE MOTT, M.D., Professor of Surgery."
" The work of Ricord is one of the very best which have been published on Venereal Dis-
eases, and I think that a good English translation will prove of great service to the Profes-
sion. "J. KEARNEY RODGERS, M.D."

" I HAVE seen Dr. Ricord in his Hospital, and have been very much interested in watching
his experiments and his practice. I regard the result of his labors of more importance than
an)rthing which has appeared since the days of Hunter, and it gives me great pleasure to
know that so valuable a work ^s his " Practical Treatise on Venereal Diseases" is to be
presented to the Profession in the English language.

" WILLARD PARKER, M.D.,
" Professor of Surgery and Surgical Anatomy."
" M. Ricokd's •' Practical Treatise on Venereal Diseases" is a substantial addition to our
stock of sound professional knowledge. The reprint of his book in this country' will do vast
good, and none need doubt that the task will be ably performed by his American editor.

"JOHN W. FRANCIS, M.D.,
" Late Professor of Obstetrics in the
College of Physicians and Surgeons."
" M. Ricord's Treatise on Venereal Diseases is generally acknowledged, to be one of the
most valuable on the subject which has ever appeared. I doubt not that every subscriber
will be fully repaid for the small expense he wUl incur, by the large amount of original
and useful information which he will receive. " ALFRED C. POST, M.D.,

" Professor of Surgery."

^

ELEMENTS

COMPAEATIYE ANATOMY

OF THE

VERTEBRATE ANIMALSi

DESIGNED ESPECIALLY FOR

THE USE OF STUDENTS

RUDOLPH I WAGNER, M. D.

PROFESSOR OF COMPARATIVE ANATOMY AND PHYSIOLOGY IN THE UNIVERSITY OF
QOTTINQEN, ETC., ETC.

EDITED FROM THE GERMAN,

BY ALFRED TULK,

MEMBER OF THE ROYAL COLLEGE OF SURGEONS OF ENGLAND.

NEW YORK:

J. S. REDFIELD, CLINTON HALL

CORNER OF NASSAU AND BEEKMAN STREETS.

1845.

ADVERTISEMENT.

The want of some good elementary work in our own lan-
guage, at least of one that, within a small compass and rea-
sonable price, should express the amount of our knowledge
upon the Anatomy of the several classes of Vertebrate Animals,
was the chief inducement to my undertaking the translation
of the present work, in the selection of which I was encour-
aged by the very favorable light in which Dr. Rudolph
Wagner had been already made known to the Medical Pro-
fession through his " Elements of Physiology," so ably edited
by Dr. Willis. The thorough practical knowledge which
he possesses of his subject, combined with the clearness and
brevity of his style, render indeed his works the very best in-
troductions that are extant to the sciences of Physiology and
Comparative Anatomy.

" The Lehrbuch der Zootomie," of Dr. Wagner, having
lately arrived at a second edition in Germany, has given the
Author an opportunity of thoroughly remodelling the work,
and introducing those improvements which time, experience,
and more extended knowledge, have suggested to him. It is
from this amended edition that I have worked, and finding
the original so complete, I have neither added nor taken any-
thing away from it, but have been content with doing my best

VI ADVERTISEMENT.

to clothe it in an English dress, an attempt in which I trust my
labors may not be wholly without success.

The insertion at the end of each Class, of a List of the prin-
cipal works that treat of its anatomy, instead of in the form
of foot-notes, may be regarded as a somewhat novel feature in
a scientific work in this country ; it is highly important, how-
ever, that we should become acquainted with the literature of
a subject in order duly to appreciate its value and progress
up to the present time ; and I have therefore hoped, by giving
it a prominent position in the book, to call the attention of
the reader more directly to this most useful department of his
studies.

Alfred Tulk.
London^ 1845.

CONTENTS.

Tegumentary System.

Mammalia 1

Aves 65

Reptilia 130

Pisces 183

Osseous System.

Mammalia 5

Aves 68

Reptilia 132

Pisces 187

Muscular System.

Mammalia 18

Aves 82

Reptilia 147

Pisces 204

Nervous System.

Mammalia 22

Aves 86

Reptilia 149

Pisces 207

Electric Organs of Fishes.. 217

Organs of the Senses.

Mammalia 25

Aves 90

Reptilia 152

Pisces 221

Digestive System.

Mammalia 35

Aves 99

Reptilia 160

Pisces 230

Circulatory System.

Mammalia 44

Aves 104

Reptilia 164

Pisces 239

Respiratory System.

Mammalia 47

Aves 107

Reptilia 169

Pisces » 246

Sw^imming-Bladder of

Fishes 250

Urinary Organs

Mammalia 49

Aves 121

Reptilia 174

Pisces 253

Particular Organs of
Secretion.

Mammalia 50

Aves 122

Reptilia 176

Generative System.

Mammalia 52

Aves 123

Reptilia 176

Pisces 256

Bibliography of

Mammalia. 61

Aves 127

Reptilia 180

Pisces 259

Appendix 263

ELEMENTS

OF

COMPARATIVE ANATOMY.

VERTEBRATE ANIMALS.
CLASS L— MAMMALIA.*

TEGUMENTARY SYSTEM.

The Integument of the Mammalia resembles in many respects that
of Man, the chief differences between them occurring in the epi-
dermis and its horny appendages. The fatty tissue beneath the
skin is often developed to a surprising degree, and the corium is
very thick, as appears in all large animals, such as the Elephant,
Rhinoceros, and other Pachydermata. Various kinds of pigment

* Frequent reference being made throughout the text to the several Orders of
Mammalia, a tabular view of the arrangement of that Class is subjoined.
Class MAMMALIA.
Order I.— Quadrumana. — Ex. Chimpanzee, Lemur.
II. — Cheiboftera. — Ex. Bat.

{ Insectivora. — Ex, Hedgehog. Mole, Shrew.
III. Carnivora.< Ferae. — Ex. Bear, Weasel, Cat.
(.Pinnipedia. — Ex. Seal, Morse.

Tir -Kyr <«<,.,«,. ^* ( M. Camivora. — Ex. Opossum.
IV. Marsupiata. J ^ Frugivora.-Ex. Kangaroo.

v. RoDENTiA. — Ex. Squirrel, Rat, Beaver.

(E. Tardigrada.— Ex. Sloth.
VI. Edentata. < E. Ordinaria. — Ex. Armadillo. Ant-eater, Pangolin.
(.E. Monotremata. — Ex. Ornitnoi-ynchus, Echidna.

VII. Pachydermata.— Ex. Elephant, Rhinoceros, Hog.

VIII. SOUDUNGULA. — Ex. HOTSC.

IX. RtrmNANTiA.— Ex. Camd, Giraffe, Ox, Sheep.

Y r^TArr-A 5 ^- ^^''^^'^o''^- — Ex. DMjong.

^*:tacea. ^ Q Ordinaria.— Ex. Whale, Porp(yise.

1

2 MAMMALIA.

are frequently found in the epidermis, corium. and Malpighian layer.
The Cetacea approach the fishes in the texture of their corium,
which is composed of an interlacement of very loose fibres, the in-
tervals between which are filled with fluid fat. The pigmentary
layer in this order is remarkably dense, often several lines in thick-
ness, and lies directly beneath a thin, usually smooth and hairless
epidermis. The layers of the epidermis frequently attain a consid-
erable thickness, and form what are called callosities. In many of
the Rodentia and Carnivora, and in the Camels, these callosities are
developed into thick pads under the feet ; in the Apes they form
the cushions upon the buttocks. In the huge Pachydermata a
similar structure prevails in connexion with the whole epidermis.
True scales are met with in the tail of many animals, as in the
Beaver. A horny tissue, consisting of coarse fibres, is exhibited
in the structure of nails and claws, but more especially in that of
hoofs and horns. Thus the horn of the Rhinoceros consists of cor-
neous fibres, likie bristles, which haA-^e coalesced so as to form a hol-
low cone ; the individual fibres, however, have a fine cellular texture
like hairs.

The most common of the horny covering of the Mammalia occurs
in the form of hairs. A distinction of these can be made, as in the
feathers of birds, into woolly hairs corresponding to down, and ordi-
nary hair or fur. The first are very soft and slender, frequently
curled, and are situated next the skin. The second kind are longer,
stiffer, usually running to a fine point, and may be developed into
bristles, vibrissae, and spines. The spinous hairs are mixed with
the others ; they are coarser, more rigid, and generally slender at
the base, bulge out externally. The fine silken sort of hairs are
the connecting link with wool. The roots, follicles, and stems of
hairs, have the same structure in the mammiferous class of animals
as in Man. The follicles of the hairs are, however, very large in
the vibrissas of the upper lip and corners of the mouth in some
Mammalia, as the Seal, where they receive nervous twigs of consid-
erable size.

The minute structure of hair presents great differences, accord-
ing to the class, order, genus, and species, to which the animal
belongs. In difl?erent parts of the body even the hairs have not the
same structure. They consist, as in Man, of cells, and are invested
by a thin cellular layer of epithelium. As a general rule, we can
distinguish a cortical and a medullary substance, which exhibit
differences in the color, thickness, form, and size of their cells

TEGUMENTARY SYSTEM. 3

The two are often very distinct, so that, as in the spines of the
hedgehog, a canal is found internally, separated by transverse parti-
tions into cellular intervals. Sometimes, on the contrary, particularly
in the cervine Ruminantia (the Roe), the cortical substance appears
entirely wanting, and the hair is made up throughout of coarser cells.
The cortical substance is generally coarser and harder than the me-
dullary, but frequently passes insensibly into it. The latter is in many
cases wanting, as almost always in the hair of the human head, where
epithelium and cortical substance are alone found, while in other sit-
uations, as upon the chin, the eyelashes, eyebrows, nose, axillae, and
pubis, the hairs possess a medullary centre. Most hairs are not
round, but compressed upon one or two sides, so as to present a
transversely oval section (Dasyprocta), or one that is kidney-shaped
(Giraffa), or that is quadrangular (Histrix Javan.), or irregularly an-
gular (Auchenia Llama).

The hairs upon their external surface are for the most part smooth
and even, as in Man, or they exhibit slight lateral projections, as in
the Squirrel, or they are knotty, as in the Bear, or provided with
pointed processes like the teeth of a saw, which in some cases
(Mygale) stand out only upon one side, in others (Pteropus) upon
both, or they are furnished with thorn-shaped processes, as in the
Cheiroptera. They are rarely found channelled, as is the case in
the two-toed Sloth, by rounded longitudinal ridges and intervening
grooves. The gray and grayish- white hairs of such animals as the
Mole and Mouse, exhibit a variegated appearance, like the down of
Birds. They are annulated with black at regular intervals, where
the hair is either transparent, or else surrounded by more delicately
marked rings. The spines of the Hedgehog and Porcupine do not
essentially differ in structure from hair, they only seem to contain
more of the same materials. Their epithelium is very much de-
veloped, and the cortical substance consists of small, elongated cells,
and is of a horny consistency. The medullary tube is very spa-
cious, and contains two kinds of cells. In the different species of
the genus Erinaceus, we perceive differences in the form and size
of these internal cells. In bristles, e. g. of the Hog, there is founds
a very small compressed medullary tube, and in the cortical sub-
stance a very ample cellular structure. In the several orders of
Mammalia, very great differences occur, so that they can scarcely
be said to have anything in common. Thus all the Apes have three
substances, which vary much, however, in their relative preportions.
In the Carnivora the cortical substance appears always to predomi-

4 MAMMALIA.

nate very much over the medullary, while in the Antilopes, Musk-
deer, and Goats, among the Ruminantia, the very large celled me-
dullary substance is developed almost to the exclusion of the corti-
cal part. The greatest and most remarkable peculiarities both of
the whole internal and external structure occur in the Edentata, as
has been already mentioned, e. g. in Bradypus didactylus. In Myr-
mecophaga jubata we find very greatly elongated cortical cells, and
the epithelial layer of an exceedingly compact texture. In the Or-
nithorynchus, the spiny hairs have a broad rudder-shaped end ; they
are somewhat serrated, inferiorly near to the bulb, but at the apex
quite entire. Still more remarkable are the fir-cone shaped scales
of the Pangolin, and the coat of mail of the Armadillo. Here
indeed true tegumentary bones occur, as in the Chelonia and many
Fishes.

The cetacea are an exception to the rest of the Mammalia as
regards their outer coverings, since their skin is destitute of hair ;
yet in the Whales there are short bristles growing from the in-
tegument of the upper and lower lip. The epidermis and its
lower layers (Malpighian ret^) are very thick, and provided with
numerous pigmentary cells. The corium consists of layers of white,
tough fibres, which form a network having a large quantity of fat
interposed between them, while the fatty tissue in the interior of the
body, as around the kidneys, where it is very much developed
in other animals, is wanting- The papillary bodies are greatly de-
veloped.

Sudoriparous glands occur in the integument of many animals,
though they have been hitherto most closely investigated in the do-
mestic kinds. They are everywhere distributed in the integument
of the Horse, which perspires profusely and from every part ; they
are generally largest in the skin of the sexual organs. They are no
less numerous, though much smaller, in horned cattle ; more con-
spicuous in the Sheep and Pig. The small sudoriparous glands of
the Dog and Cat are with difficulty detected ; it is only in the skin
of the nose, and especially in that of the elastic footrpads, that they
are manifestly larger.

OSSEOUS SYSTEM.

OSSEOUS SYSTEM,

The type in the Skeleton of the mamraiferous animal is that of
the Vertebrata generally, and of Man in particular. It nevertheless
presents remarkable varieties of form in the class, which, however,
are all easily understood, when they are regarded either as modifica-
tions of the human skeleton, or are viewed in relation with the ele-
ment in which the animals live. The Cetacea and Edentata are
farthest removed from the human type, then the Cheiroptera, Rumi-
nantia, Pachydermata, Marsupiata, and some Insectivora, still less
the Rodentia and Carnivora, and least of all the Quadrumana. Ac-
cording as the animals live in water and move by swimming, or in-
habit cavities dug in the earth, or are organized for running or flying,
or can use the extremities for seizing and tearing, will the skeleton
be modified throughout, and the extremities, along with the bony
arches which support them, be lengthened, shortened, or otherwise
altered, until at length a very evident relationship is established with
Fishes, Amphibia, and Birds.

The Cranmm of the Mammalia, as regards the number and ar-
rangement of its individual bones, agrees in all points with that
of Man, and possesses certain peculiarities which distinguish it from
the two next classes of Birds and Amphibia. The lower jaw al-
ways articulates by a single more or less convex condyle, with the
skull ; and the intermediate bone, called os quadratum, which is
present in the other Vertebrata, is here absent. The facial bones
are immovably connected to each other, while those of the cranium
form a rounded skull, which is developed in ah inverse ratio to the
former. The sutures of the bones of the skull generally remain visi-
ble throughout life, though with age, and in particular orders, they
exhibit a tendency to become obliterated. The occipital bone is
constantly, as in Man, articulated by means of two condyles with
the atlas, and is divided in the embryo into a basilar, two condy-
loid, and a posterior portion, all of which remain permanently de-
tached in the lower classes of Vertebrata. The foramen magnum
is usually situated quite at the back part of the skull, and in a posi-
tion more or less perpendicular. It is only among a few of the
Apes, and especially the young animals, that it approaches the hori-
zontal direction which it has in Man, by being advanced more
toward the sinciput. It is frequently small, and more or less tri-
angular or quadrangular, as in the Pachydermata, sometimes, as

6 MAMMALIA.

in the Cheiroptera, it is remarkably large. Near to, or immediately
above it, there occasionally occur, as in Phoca, small persistent fon-
tanelles. The sphenoid hone coalesces with the occipital at an early
period, has a pair of great wings, much smaller however than in
Man, while the lesser wings are often very conspicuous. The
pterygoid processes of the sphenoid sometimes remain separated
throughout life (Monotremata). In some Cetacea, and in Myrme-
cophega, they coalesce with the surface of the palatal bones. The
temporal bone has a tympanic attached to the petrous portion, either
by suture or ligament. This bony piece exhibits great differences
in the several orders. In the Cetacea it is large, harder than
ivory, and completely detached from the temporal. In some Apes
and Makis, but especially in the Carnivora, as the Cat, and in
many Rodentia, as in Dipus, it presents the form of a large, thin
walled, bony ampulla. The squamous portion is for the most part
low and depressed, and the mastoid process is generally very slightly
developed, and is wanting in many Edentata, Pachydermata, and
Cetacea. The styloid process is usually a separate ossicle, which,
as regards its development, belongs rather to the lingual bones ;
in Man it coalesces at a late period with the temporal bone. The
temporal bone consists originally in the foetus of four pieces —
the squamous, the tympanic, the petrous, and mastoid portions.
The parietal bones are usually small and insignificant, flat, and
united together at an early period in many orders, as in the Soli-
dungula, Ruminantia, most of the Rodentia, the Carnivora, and in
Manatus halicore. Between them and the expanded portion of
the occipital there is developed a small ossicle, which, in Man and
the Apes, coalesces at an early stage of foetal existence with that
bone. The interparietal is met with in many Rodentia, Marsupiata,
and in Hyrax, and sometimes, though then as an abnormal produc-
tion, in Man.. The frontal bone is but slightly arched, and con-
sists originally of two lateral portions, which in Man coalesce at an
early period, but not unfrequently remain distinct. In the Apes,
Cherioptera, Rhinoceros,/ and Elephant, we meet with only a single
frontal bone, which, in the horned animals, is provided with large
bony processes.

The nasal bones, as a rule, are double, as in Man, and mostly
very long. They are very small in the Apes, Avhere they are not
unfrequently joined into a single small bone, as in the Orang-utang,
and many other genera, though not in all, e. g. most of the Ameri-
can species ; the same arrangement occurs abnormally in some races

OSSEOUS SYSTEM. 7

of Man, as the Bushmen-Hottentots. The nasal bones are very
long and conspicuous in the Solidungula and Ruminantia, and of re-
markable length in the Porcupine. The Cetacea, as the Narwhal,
have a pair of very small, rounded, and somewhat asymmetrical nasal
bones, situated far back. The lacrymal bone appears to be very
rarely wanting, as in the Seal and Walrus, or to become confluent
with adjacent bones, as in the Ornithorynchus and Echidna. It ex-
ists only as a small imperforate plate in Manatus and Halicore,
while in the rest of the Cetacea it is merely an appendage of the
frontal bone. In the Solidungula and Ruminantia it is very large,
and is frequently, as in the Stags, provided with a deep pit or
groove for the reception of the sebaceous sacs. The malar bone is
very seldom wanting, as in Manis ; but it is very small, thin, and
flattened in the ordinary Cetacea. In Myrmecophaga it presents
the form of a small thin scale, which is, as in the Tardigrada and
in Centetes, not united by a complete zygomatic arch with the tem-
|)oral bone. In the Sloths it gives off" both above and below a free
and pointed process of considerable size. In the Carnivora it is
very much developed, and forms a very strong arch, convex exter-
nally. Its frontal process seldom reaches the bone of that name,
and it is only in the Solidungula, Ruminantia, and Makis, that the
union takes place between them so as to complete the ring of the
orbit externally. It is only in the Apes that an inner plate is devel-
oped like that of Man, which circumscribes completely the orbit and
zygomatic groove. The palatal bones are small in Man and in the
Apes, and most conspicuous in the Carnivora. The vomer is gen-
erally present, and is sometimes, especially in the Cetacea and Ru-
minantia, a perpendicular plate of considerable size. Numerous
differences are exhibited by the superior and intermaxillary bones.
The intermaxillary, which, in Man, is found only in the earliest
foetal period, occurs in all the Mammalia, and supports the incisive
teeth, except when it is devoid of teeth, as in the Ruminantia.
It is, therefore, particularly conspicuous in animals provided with
large incisors, as in the Rodentia and the Elephant, where it ex-
tends far backward, abutting against the nasal bones and vomer,
and more rarely still against the frontal or the malar and lacrymal
bones. It is very seldom, as in the Ornithorynchus and Unau (two-
toed Sloth), divided again upon each side into two portions. In
mattj-^^jeiroptera the intermaxillaries are separated by a remarka-
ble intervalTtr^o^ jjjj^lg ^^^^ ^^^-^^ other, as in the malformation
called cleft palate mlXXatrv^ /iiie longer jaw consists in the Apes,

8 MAMMALIA. *

Cheiroptera, Solidungula, and Pachydermata, and some few genera
from tlie other orders, of a single piece, as in Man, both halves hav-
ing become united in the median line at an early period before or
after birth. In other animals both the halves remain permanently
separated, and are held together only by ligamentous fibres. The
lower jaw is in its simplest condition in Baleena, where it resem-
bles a rounded arched rib. In the Dolphin it is somewhat deeper,
and provided with a small coronoid process. The ascending ramus
of the jaw, which is more or less conspicuous in the higher orders
of Mammalia, is frequently altogether wanting, as in Orycteropus.
The Carnivora have a strong and broad, the Kuminantia, as the
Camel, a long and small, coronoid process. The lower border of
the symphysis is in Man alone curved forward and upward, in all
.the Apes it slopes downward and backward. Many Mammalia,
such as the Carnivora and Rodentia, have a process directed back-
ward from the angle of the jaw, a structure which is very generally
met with in Birds. The form of the articulating condyle is subject
to great diversities, which usually characterize entire orders. Thus
it is very small, and plays freely in all directions within a shallow
glenoid cavity in the Ruminantia ; it is much elongated transversely,
and locked in a deep cavity of a corresponding form in the Car-
nivora so as to admit of no lateral motion ; it is lengthened out
from back to front, and chiefly moveable in this direction in the
Rodentia.

Viewed as a whole, the form of the skull departs most from that
of Man in the lowest orders. Thus in the Cetacea the jaws are
generally lengthened out in the shape of a snout ; and the cranial
bones are imited merely by squamous sutures. A want of lateral
symmetry occurs also in this order. In the Physeter the right
nasal orifice is much the larger, the nasal partition is pushed to the
left side, and the nasal bones lie rather behind than by the side of
each other. In the Dolphin this asymmetrical condition is extended
to other bones, namely, the intermaxillaries. In the Narwhal the
lower jaw itself is asymmetrical, the left half like the correspond-
ing half of the upper jaw being the larger and broader. The skull
of the Monotremata ( Ornithorynchus, Echidna) is very bird-like
through the early coalescence of its bones, and the snout-shaped
jaws. In the higher orders the facial and maxillary bones con-
stantly retreat farther backward. In the Horse the facinl_> fom
times larger than the cranial portion of thp _cth^Mr^S:i[>Toponion
exactly the reverse of that oi: Man. Ttie depressions within the

• OSSEOUS SYSTEM. 9

cranial cavity for the lodgement of the cerebrum and cerebellum are
in many Mammalia, e. g. the Dolphin, Horse, Seal, Cat, &c., sepa-
rated by a bony tentorium prolonged inward from the posterior part
of the parietal bones. A bony falx, as in the Ornithorynchus is sel-
dom met with. The openings for the nerves exhibit various rela-
lions, those which are separated in Man sometimes coalescing into
single apertures, others, on the contrary, remaining distinct, as the
foramina incisiva. These intermaxillary apertures are particularly
lai^e in the Ruminantia, the Ornithorynchus, &c., but small in the
Apes, and completely absent in the Cetacea.

Ihe comparison of the form of the skull of the higher Apes with
that of Man is a subject of much interest. Young Orang-utangs
and Chimpanzees, like all young animals, have a very rounded form
of skull ; and owing to the slight development of the jaws, the
relation of the cranial to the facial portion approximates more
closely to that of the human subject ; but, as they grow up, very
strong muscular ridges are developed from the skull, and the pro-
portion of these parts then becomes equal. The cranium of a full
grown Orang-utang nearly equals that of Man in size, but the ca-
pacity of its cavity is considerably less. The skull of the Chim-
panzee ranks next to the human cranium, and there are even forms
of the latter, as of persons born deficient in brain and intellect,
which shik to the same proportions as those of the Chimpanzee.
The distinguishing osteological characters in the skull of the Orangs
(S. satyrus and troglodytes) from that of Man are as follows : There
is a remarkable interval betw^^en the canine and incisor teeth in the
upper, and between th.» canine and molar teeth in the lower jaw ;
the original develi^pment of the intermaxillaries is much more
conspicuous, o^xd the foramina incisiva are removed farther back
from the incisor teeth ; the foramen magnum, which in Man falls
immediately behind a median line drawn transversely across the
base of the skull, lies much further back and is more slanting ; the
articulating condyles of the occipital are smaller ; the petrous bone
and the jaws are much more strongly developed ; the nasal bones
are flattened and blended together ; the mastoid and styloid pro-
cesses of the temporal, and the crista' galli of the ethmoid are
wanting.

The Vertebral Column exhibits great constancy in the number
of vertebrae in its cervical region. There are most generally seven ;
Manatus and Rytina have six, the three-toed Sloth has nine cervical
vertebrae, both of these being very rare exceptions. The cervical

10 MAMMALIA.

vertebrae are generally broad and shallow, very long in some Rumi-
nantia, as the Giraffe, very short, thin, lamellated, and partly anchy-
losed together by their bodies and arches, in the Cetacea, as the
Dolphin and Whale. A fusion and partial anchylosis occur also in
some Edentata, e. g, the Armadilloes, Dasypus, and Chlamyphorus.
The atlas is often very large, and the second cervical vertebra has
very generally a processus dentatus. The average number of the
dorsal vertebrae is, as in Man, 12. Most Apes have from 12 to 14';
the Cheiroptera most frequently 11 ; the Camivora usually 13; the
Ruminantia, Edentata, and Pachydermata 15 to 20 ; the Cetacea,

11 to 18 ; the greatest number, 23, occurs in the two-toed Sloth.
The spinous processes are for the most part straight and frequently
very long, as in the Solipedia, Ruminantia, Pachydermata, for the
attachment of the ligamentum nuchae, and form what is called the
withers. In the higher Apes they stand obliquely, as in M^n, and
cover each other like tiles. They are seldom wanting as, i?i Chei-
roptera and some Insectivora. The lumbar vertebrae are generally
the largest, and in a few instances have inferior spinous processes,
€. g. the Hare. Their number is from 3 to 7 ; seldom more. The
Anthropoid Apes have mostly 4, the rest of the Mammalia usually
more than 5 ; the smallest number is 2 (Myrmecophaga didacty-
la), the highest 9 (Loris). In the Solidungula, more rarely in
the Pachydermata and Ryminantia, the transverse processes of
the most inferior lumbar vertebise are united by ligaments or blended
together, a condition which sometimes occurs abnormally in Man.
The sacrum, as a rule, is very narrow, straight, and composed
of from 2 to 5 vertebrae united together ; the Monotreraata, the
Loris, and most of the Marsupiata, have only a, the Mole has 6.
It consists in the Orangs of 4 united vertebrae (iti most dther
Apes of 3), and is in them broad like the human sacmm, and
slightly concave. In the Ornithorynchus, the sacral vertebree, re-
main permanently separated. The sacrum is exceedingly broad
and anchylosed inferiorly to the pelvis in Dasypus. Caudal verte-
brae are very generally present, but, as in Man, {hey are reduced
in some of the higher Apes to 4 or 5 aborted vertebrae. They are
usually very numerous — 20 or 30, and in some E>lentata even 40,
and beyond that number. The first caudal vertebrae are very simi-
lar in form to true vertebrae ; they have the usual processes, and
very generally inferior spinous processes also. Toward the end
of the tail they always dwindle gradually in size, lose their pro-
cesses, and become simple ossicles, resembling the phalanges of the

OSSEOUS SYSTEM. 11

fingers. A universal characteristic of the vertebrae of a mammifer-
ous animal is this : the anterior and posterior surfaces of their
bodies are either flat or slightly concave, and collected together by-
ligament. It is rare for the cervical vertebrae to have, as in the
Horse, an articulating cavity posteriorly, and in front a very convex
head.

The Ribs correspond in number with that of the dorsal vertebrae.
They are for the most part long, flat, and sometimes very broad
from before backward, as in some Edentata, e. g. Myrmecophaga
didactyla, where they are in contact in that direction, and even
overlap each other like tiles, so as to form a kind of coat of mail ;
occasionally, however, they are very small and rounded, as in Mana-
tus. The ribs are mostly connected, as in Man, with two vertebrae,
and their transverse processes ; in the Monotremata, however, they
articulate only with the vertebral bodies. In the Cetacea the pos-
terior ribs hang down from the transverse processes alone. In front,
the ribs are furnished with their costal cartilages, which in some
orders, as the Edentata (also in the Cheiroptera and Cetacea), have
a great tendency to become soon converted into bone, and thus into
a series of sternal ribs, as is constantly the case in birds. The num-
ber of true ribs (those which are attached to the sternum) is usually
greater than that of the false, though the Cetacea have far more of
the latter ; the Whales have in fact only one or two true ribs. The
Seals, on the contrary, have the greatest number of true ribs. In the
Monotremata, the anterior rib-bones are attached by distinct capsular
joints to the sternum, and the last costal cartilages are expanded into
broad thin plates.

The Sternum is very generally divided into three portions, the
middle one of which, or the body, in place of being represented by
a single piece, as in the adult human subject, usually consists of
as many pieces as there are true ribs present. In most cases even
in the Cetacea, the sternum is broad and compressed from before
backward, but more rarely in the lateral direction ; it is very short
in the Cetacea, very long in the Carnivora and Edentata. The
manubrium sterni presents considerable differences, but generally
receives the clavicles, when present, and the first two ribs. It is
very broad and conspicuous in the Edentata, and in the Cheiroptera
and Monotremata is prolonged into a transverse process, so that it
has the form of a T. In the Cheiroptera, the Armadilloes, and the
Mole, there is a crest upon the antero-inferior surface of the manu-
brium for the attachment of the large and powerfully developed pec-

12 MAMMALIA.

toral muscle. In the Elephant and Horse, the whole sternum is
very much compressed latterly. The ensiform process is frequently
short and pointed, sometimes, however, it is very long, and expanded
behind into a thin cartilaginous disc, as in Myrmecophaga, Dasypus,
Manis, and some Rodentia ; in some Edentata it extends nearly to
the pelvis. In the Ant-eaters the anomaly is exhibited of the costal
cartilages passing between two portions of the sternum so as to meet
and become united from opposite sides. In the Monotremata the
manubrium and body of the sternum are united by a capsular articu-
lation. Many of the pieces of the body of the sternum frequently
coalesce, as in the Horse and Elephant.

The Scapular Arch presents very many differences. A Scapula is
generally present ; it is very broad even in the Cetacea, and has for
the most part a spine, though that may be but slightly developed, as
well as a coracoid process. The latter, which is wanting in Phoca,
is very long, on the contrary, in the Cheiroptera. The scapula
is remarkably long and narrow in the Mole, and its form is simi-
lar though of smaller proportion in the other Insectivora, as Sorex.
It is small also in the Ruminantia, throughout which order the
acromion is wanting along with the clavicles. In many Rodentia
a hook-shaped process arises from the spine posteriorly, as in Le-
pus. The broadest and most peculiar shaped scapula is seen in the
Edentata. In the Cheiroptera its form approximates the human,
frequently more so than that of the Apes, where it is, as in the
Chimpanzee, longer, and the neck, as in the Orang-utang, usually
very broad.

The Clavicle is completely wanting in the Cetacea, Ruminantia,
Solidungula, Pachydermata, and some of the Rodentia and Carniv-
era, as Phoca, Ursus, Nasua ; it is found very small, flat, and simply
imbedded in the flesh in the Dog and Hyena, but larger in the
Badger, Otter, and Cat, where it is represented by a sickle-shaped
rib-like bone. It is present in the Marsupiata and Insectivora.
Among the latter the Mole has a very remarkably formed, short,
quadrangular clavicle provided with a joint for articulation with the
humerus. In some Rodentia it is small, connected merely with the
sternum, and does not extend as far as the scapula. In the Chei-
roptera it is very large and strongly arched. In the 'Quadrumana it
agrees for the most part in form with that of Man, though it is pro-
portionately thicker and stronger, as in the Orangs.

The Humerus is in general a rounded and long bony tube, but
exhibits most remarkable differences. In swimming and fossorial

OSSEOUS SYSTEM. 13

animals it is very short, as in the true Cetacea, and in many of the
digging and aquatic Mammalia, On this account it frequently
obtains quite a peculiar breadth, being provided with singular pro-
cesses or inequalities of surface for the attachment of muscles, as
in the Mole and Monotremata. It is on the other hand longest and
thinnest in the Cheiroptera, and in all the Apes, especially the Gib-
bons, Orang-utang, &c. It is much longer in the very anthropoid
Chimpanzee, than in Man. The inferior articulating extremity is
formed into one or two pulley-like surfaces for connexion with the
bones of the fore-arm. The olecranal fossa is perforated in differ-
ent Apes, Carnivora, and Rodentia. There occurs also frequently
in these orders, as also in many Edentata and Marsupiata, an open-
ing in the internal condyle for the passage of the median nerve and
brachial artery. The structure of the scapular and humeral bones
in the Monotremata — Ornithorynchus, and Echidna, is of a very
opposite character, the scapular arch in them being arranged ac-
cording to the type of the Saurians. The scapula is long and sabre-
shaped, and, with a peculiar piece situated more inferiorly, and
connected with the sternum, which corresponds completely with the
coraco-clavicular bone in Birds, forms an articulating cavity for the
humerus. The thin anterior clavicle, corresponding to the furcular
bone, unites with that of the opposite side, and is firmly supported
by the anterior border of the T-shaped manubrium sterni. Beside
these, there lies upon each side a peculiar quadrangular bone be-
tween the manubrium and the coracoid, which reminds us of a sim-
ilar structure in the Lizards.

Still greater differences are met with in the bones of the Fore'
arm and Hand, especially the latter. The element in which the
animals live, whether air or water, upon or beneath the surface
of the earth, has a special influence upon these parts, which are
further modified by particular wants and modes of existence.
In general, we find two bones in the fore-arm, which admit of a
greater degree of rotation in the Quadrumana, the Carnivora, and
Marsupiata, than in the remaining classes. This motion is however
less even in the higher Apes, than in Man, and pronation and su-
pination are much more limited. The ulna is constantly longer than
the radius, and provided with an olecranon of variable size, which
is all but absent in the true Cetacea, where the two short bones
of the fore-arm lie immovably behind each other, and are very
flat like the whole extremity, which is constructed after the fashion
of a fin. Even in the Rodentia and Insectivora, the radius which

14 MAMMALIA.

lies anteriorly is very slightly moveable. In the Mole it gives
off superiorly and anteriorly a free hook-shaped process. In the
Edentata in particular, the ulna is very long, and its large olecranon
often provided with hook-shaped processes. In the Seals both bones
of the fore-arm, as well as the humerus, are bent in a peculiar man-
ner in the form of an S. In those herbivorous quadrupeds which
are organized for rapid motion, both bones lie behind each other,
are immoveably united, and more or less anchylosed. The latter is
the case in some Pachydermata, such as Dycotyles and Hippopota-
mus, but not in the Elephant. In the Horse the ulna has an olecra-
non of considerable size, but which soon becomes thinner and blends
with the very upper portion of the radius, far from its inferior ex-
tremity, so that the latter bone is the main support of the leg. The
construction is similar in the Cheiroptera, where the perfectly rudi-
mentary, short and spine-shaped ulna frequently has appended to it a
discoid olecranon, comparable to a patella, as in Pteropus, Nycteris,
Rhinolophus,*&c.

The Carpus always consists of several small variously shaped
bones ranged in a double row, the number of which varies between
5 and 11 ; very frequently there are 8, as in Man, or 7, 9, or 10, as
in the Apes. The first or posterior row exhibits in the Rodentia,
Carnivora, and Marsupiata a tendency to a reduction of the num-
ber (4), by the first two bones uniting so as to form a scapho-
lunar bone, as in the Hedgehog, while the anterior row is increased
to 5, by the interposition of an additional ossicle between the
scaphoid, os magnum, and cuneiform bones. The pisiform bone
is frequently of considerable size, and serves as a point of attach-
ment to a flexor muscle of the hand. The Whales have only from
3 to 5 dice-shaped carpal bones lying between thick tendons and
masses of ligament. In the very broad hand of the Mole, there is
superadded to its internal border an 1 1th very large and sickle-shaped
bone.

The Metacarpus consists for the most part of five elongated
bones, which dwindle down to four and three in the Rhinoceros,
and in the Ruminantia and the Horse to a single bone, though in
the latter animal there are two shorter styloid appendages, which
are the rudiments of two of the lateral metacarpal bones. Five
fingers are usually met with, whereof the thumb is frequently rudi-
mentary, and consists only of a single small bone, which is also
occasionally wanting. The Ruminantia have generally two fingers ;
the hinder claws, however, and their small phalangeal bones.

OSSEOUS SYSTEM. 15

ate to be viewed as farther rudiments of phalanges. The number of
phalanges in a finger is seldom diminished to two (which is the usual
number in the thumb), or increased to 6 or 11 in the longest finger,
as in the Cetacea, where the Whale has 5 to 6, and there are even
more in the Dolphin. In the Solidungula, and also in the Ruminan-
tia, the posterior phalanx of the finger is called the fetlock, the middle
the coronary, and the anterior which supports the nail or hoof, the
coffin bone.

Between the metacarpus and the first row of phalanges are sit-
uated very generally certain sesamoid bones, called in the Horse
splint-bones. Others also lie between the first and second row of
phalanges, but are often wanting. Sesamoid bones lie between the
nail bones and middle phalanges, and are called in the Horse, Ru-
minantia, and Pachydermata, shuttle-bones. Where only one toe is
present, as in the Horse, the shuttle is single, but the splint-bone
double. The Edentata, e. g. Dasypus, Myrmecophaga, exhibit most
extraordinary proportions in the relative size of their different fingers.
In the Sloths the metacarpal bones are united together posteriorly,
and also with the front row of phalangeal bones. The fingers of the
Apes even of the higher species are distinguished from those of
Man by their length and slenderness, and the greater shortness of
the thumb, so that a perfect hand is found only in the human sub-
ject, theirs being more adapted for clasping trees in the act of
climbing. As a rule in the Cheiroptera, the thumb only is free, and
supports a claw, though this is the case sometimes with the index
finger ; the remaining slender, wire-like metacarpal and phalangeal
bones lie within the alary membrane.

The Pelvis of the Mammalia is never so broad as in the human
subject, and its lateral walls are always smaller, flatter, and longer.
The iliac bones are broadest and most depressed in the Tardigrada,
the higher Apes, and the Elephant. In the rest of the Apes, the
Makis, and Carnivora, the iliac bones are much smaller and longer,
and the pelvis, owing to the backward recession of the pubic articu-
lation, are very oblique and narrow. The pelvis is much elongated
in the Cheiroptera, and especially in many of the Insectivora, where
it is either connected only at the pubic articulation by a small liga-
ment, or, as in the Mole and Shrew, is open in the form of a gap.
In many Cheiroptera it is completely open like that of the Bird.
The pubic articulation is frequently very deep ; it is formed also
by the ischia, and is very often converted into bone. In the Ar-
madilloes, as Dasypus, the ischia with the pubis are very broad,

16 MAMMALIA.

and united to 7 or 8 sacral vertebrae. In the Apes with tuberosities,
the ischia are broad and flat inferiorly, as if cut off. The spine of
the ischium occurs only in the Apes. On the other hand, in some
Cheiroptera and Edentata, the spines of the ischia coalesce posteri-
orly, or with the sacral and caudal bones, so that the sciatic notch
is always converted into a true foramen. The foramen ovale is
often very large, and occasionally, as in Phoca, the two bones en-
closing it are very much elongated. The acetabulum has almost
always a bottom, and frequently a depression for the insertion of the
ligamentum teres, which latter is, however, completely wanting even
in the higher Apes. The acetabulum is very seldom perforated, as
in Echidna (and in all Birds). In the Ai, which has such an un-
seemly gait, the acetabulum is very small and shallow. From the
anterior or upper border of the pubic bones there frequently arises
a pointed spine-shaped eminence [eminantia ilio-pectinea)^ which is
the first indication of a marsupial bone, e. g. in Vespertilio spec-
trum. In the Monotremata and Marsupiata there is constantly
placed in the same situation the marsupial bone, an elongated cylin-
drical and triangular bone, the free point of which is directed for-
ward. It may be regarded as formed by a partial ossification of
the fibres of the external sheath of the abdominal muscles. The
pelvic bones are very simple in the Cetacea, and appear sometimes
to be entirely wanting, as in Manatus. In the Dolphins they con-
sist of two simple elongated bones lying near the anal and genera-
tive organs, which converge together from opposite sides, or else, as
in many Whales, are connected by a transverse piece, this rudi-
mentary form of pelvis frequently resembling the hyoid bone of Man ;
in the Dugong a small V-shaped bone is the representative of the
pelvis.

The Posterior Extremities exhibit a great general resemblance to
the anterior. The femur preserves the human type in the different
orders more than the humerus. The trochanter major is often very
large, and extends beyond the head of the bone ; the internal tro-
chanter is occasionally wanting, and in a number of animals, e. g.
Castor, Dasypus, Equus, but in the Rhinoceros especially, we meet
besides with a strong process more or less in the middle, resembling
a third trochanter. In the Cheiroptera the head of the straight
femur lies in a peculiar manner between the two trochanters, which
are of equal height. The femur is short in the Solipedia and Ru-
minantia, and particularly so in the Seals. In the leg, the tibia is
always the principal bone and the main support of the femur. The

OSSEOUS SYSTEM. 17

fibula presents many varieties, and is often very rudimentary. The
two bones lie near to each other, but distinct in the Apes, Car-
nivora, and Marsupiata. The fibula is generally very strong and
thick in the Edentata, especially the Monotrcmata, where it far ex-
ceeds the tibia in length, by a strong process projecting from it supe-
riorly. In Orycteropus it has coalesced with the tibia superiorly ;
in the Sloths it reaches beyond the tibia inferiorly, and forms an ar-
ticulating surface for the astragalus. In the Rodentia, e. g. Dipus,
but especially in the Insectivora, as Talpa, .Sorex, the fibula is in-
dicated bolow by a distinct line marking where it has coalesced,
frequently beyond its lower half, with the tibia, while a complete
vspace remains between the two bones above. In most Cheiroptera,
the fibula is reduced to a thin fibro-cartilage, which most frequently
does not reach the end of the tibia. In the Horse it exists merely
as a short, slender, style-shaped appendage of the tibia. It is for
the most part rudimentary in the Ruminantia, where it is repre-
sented by a small quadrangular bone, lying inferiorly against the
outer side of the end of the tibia. A patella is very generally met
with, and is perhaps only wanting in some Marsupiata. It is par-
ticularly large in the Edentata and Pachydermata, and small in the
Apes. The average number of the bones of the tarsus is seven,
as in Man, in the higher orders of Quadrumana, Carnivora, and
Marsupiata. The smallest number is found in the Ruminantia j
which, as a rule, have five, the astragalus and scaphoid having
coalesced : the Giraffe has only a single scaphoid, and -altogether but
four tarsal bones. The Camels and Solidungula have six (there be-
ing two scaphoids) ; the Edentata have mostly seven or eight. In
the Ai the Anterior bones of the tarsus have coalesced mutually, and
with the metacarpal bones. In the Cheiroptera the os calcis sup-
ports a long slender thread-like bone, like a spur, which bounds the
alary membrane posteriorly. The os calcis has generally a long
process in the Mammalia for the attachment of the tendo-AchiUis ;
and there is frequently developed in the substance of the latter be-
hind this bone a sesamoid ossicle, or kind of petalla, to the calcane-
um. The metatarsus is very similar to the metacarpus, consisting in
the Ruminantia of a single bone, divided, however, internally into
'two cavities, and having, as in the metacarpus, its original separa-
tion marked out by an external elongated longitudinal ridge j there
are also, as appears especially in several Cervine animals, two style-
shaped bones loosely connected with the metatarsal bone inferiorly,
and which support the phalanges of the spur or dew-claws. The

2

18 MAMMALIA.

metatarsal bones of the principal toes in the leaping animals are
long, and partly united together, e. g. in the Kangaroo, Pedetes,
Dipus, where three toes have only a single metatarsal of remarkable
length terminating in three articular heads. The single metatarsal
of the Solidungula has only a single articular head, but two style-
shaped and very slender adjacent bones. Most of the remaining or-
ders have the number of toes from 3 to 4 ; the Quadrumana, Chei-
roptera, and most Carnivora, have 5. The number of toes is the
same as the fingers, only the great toe corresponding to the thumb is
frequently rudimentary, and has only one joint, or is wanting alto-
gether, while the remaining toes have generally three phalanges
each. In the Apes the metatarsal and phalangeal bones are much
slenderer than in Man.

MUSCULAR SYSTEM.

The several orders and genera of Mammalia present the greatest
diversities in reference to the muscles of the extremities. In the
greater number of cases, especially as regards the higher orders, the
muscular system may be referred to the human type. While, how-
ever, the thin flat muscles which lie beneath, and serve to corrugate
the integument, are very slightly developed in Man, and are limited
to particular situations (M. frontales, occipitales, platysma-myoides,
&;c.), they occur in the Mammalia as muscular layers spreading over
the whole face, shoulder, and abdomen. In many cases they coa-
lesce more or less together, and in those animals particularly which
can roll themselves up in a ball, they form a very large thick fleshy
lamina, which can be drawn like a cap over the whole back, sides,
and part of the extremities, e. g. in the Porcupine and Hedgehog, in
which last the tegumentary muscle is short, hood-shaped, very thick,
and separable into two layers.

The muscular system of the Apes, even of the highest, exhibits
many departures from that of Man. The muscles of the extremities
are arranged according to a more analogous type. The individual
mobility of the fingers is much more limited in them than in
Man, and this is particidarly the case with the thumb. The short
extensor of the thumb is wanting ; the flexor brevis is blended
with the adductor ; the flexor longus pollicis is not a distinct
muscle, but only a tendon of the flexor digitorum communis pro-
fundus ; the extensor longus pollicis forms a common muscle with
that of the index and middle fingers. The want of a distinct ex-

MUSCULAR SYSTEM. 19

tensor proprius digiti indicis is the more remarkable, as, through
this, the Apes are deprived of the power of mimicking the action
of pointing, and the index must always in their case be extended
along with the rest of the fingers. The foot of the Apes is, as
regards its muscular movements, more like the hand ; its interossei
muscles are arranged like those of the same name in the human
hand, and enable the toes to spread and approximate, in their
chief movement, the act of climbing. There is found further, in the
foot of the Apes, an abductor longus pollicis and minimi digiti.
Other arrangements of the muscular system in the Apes depend
upon their incapability of maintaining the erect posture. Certain
flexor muscles of the legs, as the biceps, sartorius, gracilis, semiten-
dinosus, are invariably inserted very low down into the leg, so that
the knee always appears bent in front, and the limb can not be com-
pletely extended. The rotator muscles of the femur, such as those
of the buttocks, are much more feebly developed in the Apes, than
in Man. The abdominal muscles are, on the contrary, much
stronger in the Apes, in order to sustain more easily the weight of
the viscera, in progressing upon all fours, and the femoral and
inguinal rings have much wider openings. The scapula of the Apes
has much stronger and more powerful muscles than that of Man, to
prevent its luxation ; and it is furnished with a peculiar protractor
muscle, which is wanting in Man. The cervical muscles are in
like manner much stronger, and implanted higher np upon the
cranium, to prevent the head sinking downward. The latissimus
dorsi gives off a singular muscular slip, which is attached by tendon
to the olecranon process, and is especially developed in the long-
armed Apes, where it serves to sling the whole arm very rapidly
and powerfully forward, a movement which is of the greatest im-
portance for dexterously grasping remote branches while in the act
of climbing. The tailed Apes, those even provided with a short
stump, e. g. Inuus ecaudatus, have a caudal muscle very highly de-
veloped, and divided into many bundles, which act as elevators, later-
alizers, and depressors of the tail. In the prehensile-tailed Apes,
the tail serves even as a fifth hand, and the flexor muscles are
hence very much developed. In Man the facial fnuscles are much
more separated, and subdivided into a greater number of fasciculi
than in the Apes, whence arises that manifold power of expression,
which serves as a reflex of the internal workings of the mind. The
Apes have only a pair of strong muscular masses which surround the

22 MAMMAWA.

NERVOUS Si'STEM.

The corerings of the brain and spinal-cord agree in general, in so
far as the arachnoid and pia mater with its net-work of vessels are
concerned, with those of Man. The dura mater usually forms a falx,
which extends deeply between the hemispheres. As a general
rule, the tentorium cerebelli is present, but the falx minor is nearly
always wanting, on account of the large yermiform lobe of the cere-
bellum projecting beyond its hemispheres. The tentorium is in many
Mammalia supported by a bony plate springing from the internal
surface of the skull, and is particularly strong in the Cat, and other
Ferae, but feeble in the Horse, Dolphin, and some of the Apes. An
osseous plate is seldom found in the falx, as in many Birds ; but it
occurs in the Ornithorynchus. Between the laminae of the dura
mater are found the venous sinuses.

The spinal cord of the Mammalia extends considerably lower
than in Man ; as a rule, it reaches as far as the sacrum, though
in the Cetacea it appears to terminate higher up. The nerves
themselves of the Cauda equina pass out through the openings
of the most complete of the caudal vertebrae. Of the two enlarge-
ments upon the cord, the posterior is wanting where there is imper-
fect development of the hinder extremities, as in the Cetacea ;
and sometimes the two enlargements coalesce so as to form a single
one of very considerable size. The central canal which is present
in the foetus of Man (perhaps also in the adult) appears in very
many of the Mammalia to exist during their whole life ; at all
events, the fourth ventricle is more or less deeply prolonged into the
spinal marrow. The brain is developed in the lowest degree, and
is truly bird-like in the Ornithorynchus, where the pons is very
small, and there is only a rudiment of the corpus callosum present,
as in the Marsupiata, while the hemispheres of the cerebellum
appear more as appendages, or lateral extensions, of the very greatly
developed vermiform lobe ; the corpora quadrigemina form only a
pair of ganglia, the posterior pair being scarcely visible ; the optic
thalami coalesce in the middle by a very strong commissura mollis,
and the hemispheres are without convolutions. In the Rodentia,
Marsupiata, and Edentata, the vermiform portion of the cerebel-
lum is so considerable, that the hemispheres appear to recede
very much ; they are already more developed in the Ruminantia
and Pachydermata, and are still more highly organized in the Car-

NERVOUS SYSTEM. 23

nivora, the Dolphin and most Apes. It is in this order of progres-
sion also that the number of lamellae and lobuli of the cerebellum
are developed, and that the ramifications of the arbor vitae and
the corpora rhomboidea within the olivary bodies, which form
indistinct external projections, become manifest. Above all we
meet with a pons Varolii, the size of which increases in the order
above given. One peculiar organ of the Mammalia, which does
not occur in Man, is the part called trapezium, a quadrangular
elevated layer of transverse medullary fibres, which lies close
behind the pons near to the pyramidal bodies, and abuts against the
origin of the auditory and facial nerves. The corpora quadrigemina
are usually very conspicuous, and very frequently provided with
an internal cavity ; they lie partly, as in the Marsupiata, the Eden-
tata, the Cheiroptera, and most Rodentia, perfectly free, and are
not reached by the hemispheres ; they are smallest in the Apes.
In the Carnivora, the posterior pair is as a rule the largest, in the
Ruminantia and Solipedia, the anterior. The thalami optici increase
in size inversely, in the ascending series of animals. The corpus
striatum is conspicuous, especially in the lower orders, and between
it and the optic thalamus there very generally occurs the broad and
often band-shaped stria cornea.

In the cerebrum are found nearly all the parts of the human brain
repeated with certain modifications. The corpus callosum is very
rudimentary in the Marsupiata, and generally diminutive in the
Rodentia, Edentata, and Cheiroptera, where it extends but a very
little distance posteriorly. The corpora albicantia form as a rule
only a single mass, though sometimes, as in the higher Apes, they
are separated ; indications of their division are also found in the
Dog and other Carnivora. The pineal gland is always present,
varying in form and size, and, in those animals which have the cor-
pora quadrigemina uncovered, lies also for the most part freely ex-
posed, as, for example, in many of the Rodentia and Edentata. The
pituitary gland is of very considerable size, and situated upon a slen-
der infundibulum. The hemispheres exhibit the greatest number
of differences. The posterior lobes are either all but wanting, or so
very much shortened, that the cerebellum remains quite uncovered,
as in the Marsupiata, Rodentia, Edentata, and Cheiroptera. The
hemispheres are moreover quite flat, or have only a very few shal-
low depressions, as in Lepus and Cavia ; in the Insectivora also, as
Sorex, Talpa, Erinaceus, they are often altogether without sulci, and
in the Carnivora they frequently exhibit nothing more than a few

22 MAMMAUA.

NERVOUS SYSTEM.

The coverings of the brain and spinal-cord agree in general, in so
far as the arachnoid and pia mater with its net-work of vessels are
concerned, with those of Man. The dura mater usually forms a falx,
which extends deeply between the hemispheres. As a general
rule, the tentorium cerebelli is present, but the falx minor is nearly
always wanting, on account of the large vermiform lobe of the cere-
bellum projecting beyond its hemispheres. The tentorium is in many
Mammalia supported by a bony plate springing from the internal
surface of the skull, and is particularly strong in the Cat, and other
Ferae, but feeble in the Horse, Dolphin, and some of the Apes. An
osseous plate is seldom found in the falx, as in many Birds ; but it
occurs in the Ornithorynchus. Between the laminae of the dura
mater are found the venous sinuses.

The spinal cord of the Mammalia extends considerably lower
than in Man ; as a rule, it reaches as far as the sacrum, though
in the Cetacea it appears to terminate higher up. The nerves
themselves of the Cauda equina pass out through the openings
of the most complete of the caudal vertebrae. Of the two enlarge-
ments upon the cord, the posterior is wanting where there is imper-
fect development of the hinder extremities, as in the Cetacea ;
and sometimes the two enlargements coalesce so as to form a single
one of very considerable size. The central canal which is present
in the foetus of Man (perhaps also in the adult) appears in very
many of the Mammalia to exist during their whole life ; at all
events, the fourth ventricle is more or less deeply prolonged into the
spinal marrow. The brain is developed in the lowest degree, and
is truly bird-like in the Ornithorynchus, where the pons is very
small, and there is only a rudiment of the corpus callosum present,
as in the Marsupiata, while the hemispheres of the cerebellum
appear more as appendages, or lateral extensions, of the very greatly
developed vermiform lobe ; the corpora quadrigemina form only a
pair of ganglia, the posterior pair being scarcely visible ; the optic
thalami coalesce in the middle by a very strong commissura mollis,
and the hemispheres are without convolutions. In the Rodentia,
Marsupiata, and Edentata, the vermiform portion of the cerebel-
lum is so considerable, that the hemispheres appear to recede
very much; they are already more developed in the Ruminantia
and Pachydermata, and are still more highly organized in the Car-

NERVOUS SYSTEM. 23

nivora, the Dolphin and most Apes. It is in this order of progres-
sion also that the number of lamellae and lobuli of the cerebellum
are developed, and that the ramifications of the arbor vitae and
the corpora rhomboidea within the olivary bodies, which form
indistinct external projections, become manifest. Above all we
meet with a pons Varolii, the size of which increases in the order
above given. One peculiar organ of the Mammalia, which does
not occur in Man, is the part called trapezium, a quadrangular
elevated layer of transverse medullary fibres, which lies close
behind the pons near to the pyramidal bodies, and abuts against the
origin of the auditory and facial nerves. The corpora quadrigemina
are usually very conspicuous, and very frequently provided with
an internal cavity ; they lie partly, as in the Marsupiata, the Eden-
tata, the Cheiroptera, and most Rodentia, perfectly free, and are
not reached by the hemispheres ; they are smallest in the Apes.
In the Carnivora, the posterior pair is as a rule the largest, in the
Ruminantia and Solipedia, the anterior. The thalami optici increase
in size inversely, in the ascending series of animals. The corpus
striatum is conspicuous, especially in the lower orders, and between
it and the optic thalamus there very generally occurs the broad and
often band-shaped stria cornea.

In the cerebrum are found nearly all the parts of the human brain
repeated with certain modifications. The corpus callosum is very
rudimentary in the Marsupiata, and generally diminutive in the
Rodentia, Edentata, and Cheiroptera, where it extends but a very
little distance posteriorly. The corpora albicantia form as a rule
only a single mass, though sometimes, as in the higher Apes, they
are separated ; indications of their division are also found in the
Dog and other Carnivora. The pineal gland is always present,
varying in form and size, and, in those animals which have the cor-
pora quadrigemina uncovered, lies also for the most part freely ex-
posed, as, for example, in many of the Rodentia and Edentata. The
pituitary gland is of very considerable size, and situated upon a slen-
der infundibulum. The hemispheres exhibit the greatest number
of differences. The posterior lobes are either all but wanting, or so
very much shortened, that the cerebellum remains quite uncovered,
as in the Marsupiata, Rodentia, Edentata, and Cheiroptera. The
hemispheres are moreover quite flat, or have only a very few shal-
low depressions, as in Lepus and Cavia ; in the Insectivora also, as
Sorex, Talpa, Erinaceus, they are often altogether without sulci, and
in the Carnivora they frequently exhibit nothing more than a few

24 MAMMALIA.

shallow grooves. In the small Monkeys with claws, as Midas, they
are nearly quite flat. In the Dog, the Otter, and the Seal, among
the Carnivora, the convolutions are far more numerous than in the
Feline tribes, as is the case also in the Horse and the Ruminant.
The Elephant is remarkable for a well-developed cerebrum, provid-
ed with numerous deep furrows. In the ordinary Apes the furrows
are fewer in number than in the last-named orders, and are defi-
cient in symmetry upon the two sides. The grooves are still more
numerous in the brain of the Dolphin, which is so remarkable for its
rounded form. The ventricles and choroid plexuses resemble those
of Man ; yet it is usually only the anterior and middle or descending
cornu of the lateral ventricle which is developed, the posterior oc-
curring in those orders only where the posterior cerebral lobes are
present. The lesser pes hippocampi is almost always wanting^
while the cornu Ammonis with the corpus fimbriatum is usually
found very large, e. g. in the Rodentia. In like manner the fornix
and septum lucidum are met with. The concretions of the pineal
body are wanting. The lateral ventricles communicate in those
orders which are furnished with conspicuous mammillary processes
or ganglia for the olfactory nerves, namely, in the Rodentia, Rumi-
nantia, Pachydermata, Edentata, Marsupiata, and Ferae. These
ganglia form triangular, obtuse projections beneath the anterior lobes
of the cerebrum.

The brain of the highest Apes, as the Orang-utang and Chim-
panzee, approximates more to that of the human subject ; it differs
however in the very inferior proportional development of its hemis-
pheres (the convolutions of which are at the same time more numer-
ous and asymmetrical than in the rest of the Apes), as opposed to the
cerebellum, which is still however covered by the posterior lobes of
the cerebrum in old animals, as in Apes generally, e. g. Celeus capu-
cinus. The digital impressions upon the cornu Ammonis occur only
in the higher Apes. The brain of the Chimpanzee is more anthro-
poid than that of the Asiatic Orang-utang.

The nerves arise and are distributed after the human type, frora
which the olfactory pair exhibit the most departures. They are
probably entirely wanting in the Cetacea, as the Dolphin, or are
present only as very fine thread-like rudiments. In other animals
they form, on the contrary, large hollow clavate organs, provided
with numerous ganglia, which proceed from the mammillary pro-
cesses. They are smaller and correspond with the human form in
the Apes. The animals which have very small rudimentary eyes,

ORGANS OF VISION. 3d

such as the Mole, have very delicate optic nerves. The fifth pair
is frequently very much developed ; the infra-orbital branch in par-
ticular is often of remarkable size, particularly in those animals that
are provided with a snout, or with large vibrissas upon the upper* lip,
to the follicles of which, it gives considerable branches.

ORGANS OF THE SENSES.

Organs of Vision.

It is only in the Apes that the eye is situated, as in Man, in a
complete bony cavity closed both from without and within ; in all
the rest of the Mammalia, and also in the Makis, the orbital and
zygomatic spaces blend upon the sides of the skull. Both spaces
are nevertheless separated by a peculiar membrane, which is called
the orbital membrane, and was formerly regarded incorrectly as
muscular ; it arises from the periosteum, lines the orbits funnel-wise,
and consists partly of elastic tissue. It seems to act as an antag-
onist to the retractor muscle of the globe of the eye, protruding oi
pushing the eyeball forward so soon as the action of that muscle
ceases.

In other respects the Mammalia in general exhibit the greatest
conformity in the structure of the eye with that of Man. Yet there
are some species among the Insectivora and Rodentia, for example
the Talpa caeca, Spalax typhlus, Chrysocloris, living under ground,
in which the eye is very rudimentary, and nearly closed by the skin,
so that they possess an extremely imperfect sense of vision. The
globe of the eye is here very small, but appears to contain all
its principal parts. In the Mammalia the transverse diameter of
the eyeball is generally the largest, as in the Whale, tl]e Walrus,
and the Seal ; the sclerotic is of enormous thickness in the Whales,
and in the Ornithorynchus it is enclosed by a bony plate. In the
Apes and in Man the longitudinal axis of the eye exceeds the trans-
verse in diameter. The cornea is flat in the aquatic Mammalia.
Between the sclerotic and choroid lies as usual the pigmentary layer.
In addition to this there occurs in many Mammalia a membrane
composed of an interlacement of delicate fibres, and having a metallic
brilliancy, called the tapetum. In the Ruminantia, Solidungula
and Pachydermata, it has a variegated lustre of blended green and

26 MAMMALIA.

blue ; in the Carnivora and Whales a silvery or mother-of-pearl
tint. The form of the pupil varies frequently in one and the same
genus ; thus the Wolf and Dog have a round, the Fox a perpendic-
ular slit-shaped pupil. In the Solidungula and Ruminantia there
project from the uvea upon the border of the pupil, tuft-shaped flakes
of pigment, called the racemiform or sponge-like bodies.

The lens is, in some Rodentia, but particularly in aquatic animals,
such as the Cetacea and Seals, very convex and spherical. The
macula lutea of the retina appears, with the exception of the Apes,
to occur only in the human subject. The number and mode of
attachment of the muscles of the eye are the same as in Man. The
tendon, however, of the superior oblique appears to be wanting to
the Cetacea. With the exception of the Apes, all the Mammalia
appear also to have an additional muscle, the suspensory or retractor.
This is a quadrifid muscle embracing the optic nerve, the portions
of which sometimes coalesce, as in the Ruminantia, into a single
infundibuliform muscle. It is fixed to the sclerotic behind the
cornea.

The eyebrows and eyelashes occur only in a few Mammalia,
the latter being wanting in the smaller kinds. The eyelids have
the usual cartilages and muscles, and the lower lid is moveable.
The third eyelid, called also the haw or nictitating membrane,
has a single triangular cartilage, and is met with in nearly all
the Mammalia, with the exception of the true Cetacea ; it contains
muscular fibres, and is drawn like a curtain over the front of the
eye, so soon as the retractor muscle acts upon the latter. The Apes
have, like Man, no haw, but only a rudiment of it, the plica semi-
lunaris, in the inner angle of the eye. In the Ornithorynchus, and
Echidna, the eye is closed by a single circular eyelid, with a small
round opening in it. Meibomian glands and a caruncula lacrymalis
are frequently present ; the last, however, is wanting where the
haw is much developed. The lacrymal gland with its apparatus
appears to be wanting only in the Cetacea ; it is often very large,
and in addition to it, there is found in all animals provided with
a third eyelid, as the Hare, the Harderian gland (which occurs
generally in Birds) well developed, two or three ducts from it opening
beneath a fold of the inner surface of that lid. The mechanism for
moving the nictitating membrane is not the same as in Birds. It
seems to be drawn forward the more the retractor muscle acts, when
the eye by being pulled back presses within the orbit against the
posterior termination of the cartilage of the nictitating membrane,

ORGAN OF HEARING. 27

and at the same time favors the escape of the secretion from
the Harderian gland.

Organ of Hearing.

The most important part of the organ of Hearing, the labyrinth,
exhibits throughout the Mammalia in general a complete agreement
with the human structure. It is completely imbedded in the dense
osseous substance of the temporal bone, and in the foetus only is
surrounded by loose bony tissue. The direction of the semicircular
canals and the vestibule are in their number and shuation, their
histological elements, and otolithic concretions, with slight variations,
similar to those of the human subject. In some instances, as in
the Ornithorynchus and the Mole, where the semicircular canals
are very large, they project internally into the cranial cavity.
Recent accurate investigations concerning the labyrinth show also
that in the individual genera and orders of Mammalia a number of
minor but very interesting differences occur. The least variations
occur in the vestibule of the labyrinth (which is, however, all but
wanting in the Whales) ; the greatest in the semicircular canals.
In the Cats, the Cheiroptera, and Viverridae, these canals form the
segment of a circle, in the Horse they exhibit a parabolic curve, in
the Camels, Goats, and in Myrmecophaga jubata, they form a por-
tion of an ellipse, frequently also of a spiral, as in the Antilopes
and some Edentata. In the Whales they are very small, smaller
than in the Field-mouse, and form a segment of a circle of scarcely
90°. The Dromedary has the largest canals, and next to them,
some Seals. In many, though not in all of the Mammalia, the
canals open by five orifices into the vestibule. The ampullae
also in size and situation present numerous differences ; there are
nearly always, however, three ampullae present, but only two in the
Sloths, none being met with upon the external canal. Of all the parts
of the labyrinth, the cochlea varies most, namely, in the number of
its coils. In the Whales and Dolphins, it has only 1-^ turns, though
it is very large, being thus in remarkable contrast with the small
canals ; in Delphinus delphis it is larger than in the largest terres-
trial mammal, and the spires lie upon one level. In the Hedgehog
also the small cochlea makes only 1-^ turns, but is more conical;
in the Seals, 2 coils are met with, as likewise in the Chamois. Most
Ruminantia, the Horse, and many of the Edentata, have not quite
2-J coils, which is the case too in Man, in the Apes, and Cheiroptera.

28 MAMMALIA.

Bears, Cats, Dogs, and probably the Carnivora in general, have three
complete coils ; the Pig, the Squirrel, and other Rodentia, have
nearly 4 ; in Caelogenys Paca nearly 5 turns are met with ; in the
Ornithorynchus and Echidna, on the contrary, the cochlea has only a
half coil, and rather represents a semilunar cone, comparable to
the cochlea of a Bird ; it has, however, a modiolus and two scalse.
The size and form of the two fenestrse vary remarkably ; in the
Seal, for example, the foramen rotundum is three times larger than
the f. ovale. The tympanic cavity offers in the class Mammalia the
greatest differences of all. In Man, and in the Apes, it is completely
concealed in the petrous bone ; in the remaining orders, on the con-
trary, we find a peculiar tympanic bone which exhibits great diver-
sities in the several orders. In the Cetacea it is large, and hard as
ivory, remains completely separated from the much smaller petrous
bone, and like it, is only united by ligament to the skull. In the
Ruminantia, the tympanum is angular and irregular, in the Ox very
cellular, and the Sheep and Goat spacious and devoid of cells. The
Horse and Pig have a cellular tympanum. In many Rodentia
and Carnivora, where it usually swells out into a bony bulla (very
large in Dipus), the tympanum remains at least a very long time
separated, or is united by means of a suture, which sometimes
disappears at a later period ; externally there is often appended or
united to the tympanum a bony tympanic ring, which is not always
complete above. The tympanic cavity extends occasionally into the
other cavities of adjacent bones, e. g. in the Sloth, into the zygo-
matic arch. The membrana tympani" is (except in the Cetacea)
drawn in a somevi'hat funnel-shape inward, lies sometimes, as in
the Mole, nearly horizontal, or approximates that position, as in
many Carnivora and Edentata, while elsewhere it stands more
perpendicularly, as in Man. The Eustachian tube is partly bony,
partly cartilaginous, and always opens by a peculiar orifice behind
the nasal passages within the fauces. In the Horse and x\ss the
Eustachian tube, upon either side, is always united with a mem-
branous oviform purse or air-sac, which lies within the fauces,
beneath the occipital bone, and is formed of mucous membrane, the
sacs of either side being contiguous. The three auditory ossicles
can in general be distinguished, namely, the malleus, the incus,
with the OS orbiculare and the stapes, and although their forms un-
dergo considerable changes, we frequently recognise in them the
human type, as in the Apes of the Old World. In those of the
New World their form varies more ; the opening into the stapes for

ORGAN OF HEARING. t^a

example, being vory small. The three ossicles can still be recog-
nised in the Rodentia, e. g. the Squirrel. The handle of the malleus
is especially subject to variation ; in the Carnivora it is very long,
in the Sloth broad with a projecting ridge ; in the Rodentia it is fre-
quently formed like the blade of a knife. In Chrysocloris a peculiar
clavate bone is found lying between the malleus and incus. , Small
ariimals not unfrequently possess very clumsily shaped ossicles, as
is the case in a remarkable degree in the malleus of the Hedge-
hog. The stapes exhibits very interesting modifications of form.
Without bearing any relation to the position of the animal in
the system, it presents, for example, in the higher Apes, the
Elephant, Mole, Hedgehog, Ox, only slight variations from the
human form, its opening being larger or smaller, its branches
equal or imequal. In some Rodentia and Insectivora, as in the
Squirrel, the Marmot, the Mole, a branch of the carotid, namely,
the trunk of the arteria opthalmica and maxillaris, and in Chei-
roptera, the art. raeningea media, pass through the stapes and
the tympanic cavity ; the artery between the branches of the stapes
is surrounded by a bony tube which serves as a kind of bolt
(pessulus) upon which the stapes rides, and is thus prevented
from entering too far into thfe very large foramen ovale. In the
Seal and other animals the branches of the stapes are very thick,
and the opening therefore very small ; the latter indeed disappears
completely in the Walrus, the Dolphin and the Whale. Imperfo-
rate and rod-shaped, the stapes of the Ornithorynchus resembles
the columella of Birds, and a similar transition of form is shown in
the Sloth and Kangaroo, and, as appears from recent researches,
in the Marsupiata generally. The muscles of the ossicles appear
to be always two in number, as in Man, the tensor tympani and sta-
pedius. In the Horse and Ox, there is frequently found a sesamoid
bone in the stapedius muscle. The cells which in Man are found
in the Mastoid process of the temporal bone, are present also in the
Apes, but they frequently disappear along with that process, which
is often represented by an apophysis of the occipital bone ; in some
instances, however, small cells extend also into the squamous and
even the jugal portions of the temporal.

External to the merabrana tympani there lies in nearly all the
Mammalia, excepting the Cetacea, the bony meatus, which differs in
length, width, and direction. Attached to it is a trumpet-shaped
cartilage, the concha of the ear, which is wanting only in a few
Mammalia, namely, such as live in water or under the earth, as in

30 MAMMALIA.

the Cetacea, the Walrus, many Seals, the Mole, Ornithorynchus
and Pangolins. The ears are, on the contrary, in the African Ele-
phant, very large pendulous flaps ; they are much smaller in the
Asiatic species ; they are largest of all in many Cheiroptera, c. g.
Plecotus auritus, where they are nearly as long as the body, and the
tragus also is greatly developed, exhibiting manifold forms through-
out this order, in which the ears are very membranous. Hanging
ears appear to occur in the Dogs, Pigs, and Goats, only when domes-
ticated. In Man the cartilage of the ear consists only of one piece,
while in most Mammalia three can be distinguished. The concha
is the largest cartilage, and trumpet-shaped. Above the anterior
part of the convex surface of the concha lies the cartilago scuti-
formis, which merely serves as a surface of attachment to several
muscles, but does not contribute to the formation of the concha.
The cartilago annularis lies over the external auditory meatus in
the lower curve of the concha, to which it is united by ligament,
and completes the meatus. While in Man the muscles of the
external ear are only feebly developed, and that organ can be but
slightly moved, very numerous muscles turn the ear of the Mam-
malia in all directions. In the Horse there are enumerated seven-
teen separate muscles, of which'the depressor, adductor, and rotator,
are in particular wanting in man. In many diving animals pecu-
liar valve-shaped projections are found, by which the external meatus
is closed and protected against the entrance of water ; thus, for
example, the narrow tortuous meatus of the Ornithorynchus has
a valve externally, and in the Water-shrew the antitragus can
close the external meatus at will. The external meatus is lined
with a delicate skin, and contains the secretory sacs of the cerumen,
which are not even wanting in the Cetacea. This last-named
order presents further peculiarities, which here require notice. The
tympanic cavity exhibits a very peculiar formation in the large
sinuses, which are appended to it, and penetrate partly into bony
cavities, which have been regarded as receptacles for large blood-
vessels, but are in truth auditory sinuses, which extend partly into
the cranial bones, and, partly enclosed by a peculiar smooth and
shining membrane, stretch over them. The completely membranous
and never cartilaginous Eustachian tube extends from a large mem-
branous sinus, with which the bony tympanic cavity is continuous,
inward and upward, to open upon the external side, very high
up in the bony nasal cavity. The internal lining of this tube
forms several crescentic valves, which can not however completely

ORGANS OF SMELL. 31

close its cavity. Of the three ossicles, that which corresponds to
the malleus is nearly triangular, departing very much from its usual
form, and being provided with a long pointed process. The stapes
has only a very fine opening, or is solid. The external meatus is
not formed of bone, and is excessively narrow and tortuous. The
external opening of the ear is so small, that it is scarcely visible.

Organs of Smell.

All Mammalia, with the exception of the Cetacea, have an eth-
moid bone, often of great breadth, the cribriform plate perforated
with numerous holes, and the ethmoidal labyrinth well developed.
In the Apes the ethmoid is narrower than in Man, the crista galli
is wanting (even in the Orang-utang), and it exhibits few openings.
It is larger and very much perforated in the Pachydermata, the
Ruminantia, and especially in the Carnivora. Of the three tur-
binated bones, the inferior is in particular frequently developed
to a surprising degree, and consists of a pair of much convoluted
laminae, as in the Ruminantia, some Rodentia and Pachydermata.
Other Rodentia, as the Hare, Beaver, Squirrel, have more the
complex structure of the Carnivora, in which the nasal cavity,
though spacious in animals generally, is the largest of all, The
turbinated bone is here divided into a number of jagged lateral
lamina), so that, on a transverse section, it seems like a branching
tree. The nasal sinuses are generally present, but exhibit great
differences in the separate orders and genera, and are least de-
veloped in the Rodentia and Cetacea. The frontal sinuses are
sometimes remarkably large, the wide intercommunicating bony
cells penetrating even into the temporal and occipital bones, while
in many animals, as the Marten, the Badger, the Rhinoceros, they
are entirely wanting. In the Ruminantia they enter the frontal
prominences upon which the horns are situated. The superior
maxillary cavities are small in the Apes, and disappear entirely in
the Carnivora, Edentata, and Rodentia ; in the Pachydermata they
are of moderate size ; they are very large in the Horse, and in the
Ruminantia. The sphenoidal sinus is enormously developed in the
Elephant, and extends even into the alary processes of that bone ;
yet the frontal sinuses are here wanting. The nose is formed, as
in Man, partly of cartilage ; its muscles are often powerfully de-
veloped, and there is a special dilator. There is found very gene-
rally also, as in Birds, a peculiar nasal gland, which is, however,

33 MAMMALIA.

«

frequently wanting ; it always lies upon the external wall of th^
nasal cavity, and where there is an antrum, it is contained within
the cavity, and its duct terminates at the anterior extremity of the
inferior meatus. In animals provided with a snout, the nasajl.^
cartilages are lengthened out to a tube, which is covered with mus-"
cles that move it in many directions. Frequently, as in the Hog
and the Mole, there lies near to the root and in the substance of
the snout a peculiar bone. . Internally the snout is divided into a
double tube, and the whole structure is particularly remarkable in
the Elephant, where it forms that highly developed organ of touch
and prehension, the proboscis, which is lined internally with a dry
epithelium ; its two tubes are contracted in the vicinity of the inter-
maxillary bones, by which the ingress of water when sucked up is
prevented ; it consists of very numerous longitudinally arranged
muscular bundles, with tendinous contracted portions, which, when
they act, shorten the proboscis, while their antagonists are trans-
verse or oblique bundles, imbedded in a net-work of adipose tissue.
In all, there are reckoned about 50,000 to 40,000 bundles. Special
elevators and depressors arise from the frontal and superior max-
illary bones. In the Mole, there lie upon each side of the- snout
four muscles, which arise from the upper jaw, and are attached by
their tendons to the nasal tube, like ropes to a mast. In many
Cheiroptera, as Rhinolophus, Phyllostoma, peculiar appendages,
partly cartilaginous, partly membranous, and of very singular forms,
are developed upon the nose. Diving animals have occasionally
valves by which the nasal passages can be closed internally, as in
the Ornithorynchus, where the small round nasal openings lie at
the base of the snout. The seals have an annular sphincter muscle
round the nostrils. In the male of Phoca cristata, the Cystophora
borealis, the nose is not developed into a snout, but presents itself
as a large niusculo-membranous bag, into which the animal can
introduce air.

The nose of the Cetacea departs from the type of the rest of the
Mammalia, and is developed into the blowing canal, while it takes
a perpendicular direction, and terminates superiorly in front of the
fore-head, as the blow-hole. The bony nasal cavity is therefore
extremely simple. It consists, for example, in the Dolphin and in
the Narwhal, of a simple smooth bony canal upon either side,
without sinuses or turbinated bones. The nasal or spouting
opening is single in the Spermaceti Whale, the Narwhal and the
Dolphin; the Whales (Balaina) have two nasal openings, and

ORGFANS OF TASTE. _ 33

true ethmoidal cells appear to be met with here, which are wanting
in the rest of the typical Whales.

In the Dolphins, the spouting apparatus has been accurately de-
scribed. Behind the velum palati the inferior part of the nasal canal,
which is here single, can be shut off from the pharynx by a strong
circular muscle (Muse, pharyngo-palatinus v. constrictor isthmi
faucium superior). Further, superiorly above and behind the bony
palate, the nasal canal is as usual divided by a septum, and each
of the two passages thus formed receives the Eustachian tube of
its side, and terminates, as the external nasal aperture, upon the
skull in front of the forehead. The blowing apparatus with its pe-
culiar cavities here lies upon the bones. The nasal canal passes
immediately into two anterior and two posterior cavities, lying one
over the other ; the covering of these is formed by a couple of pro-
jecting folds or valves, one arising from the anterior, one from the
posterior wall, and which leave between them a narrow transverse
fold. Above the valves there lies a simple flask-shaped cavity, the
neck of which passes into the external blow-hole, which communi-
cates upon either side in front and externally with the double Tapa-
cious and rounded spouting sacs, each of which presents upon its
basis strong parallel rib-shaped elevations (plications of its fibrous
coat) ; all the parts of this external apparatus are lined with a hard,
dry epithelium, and are formed of a thin fibrous tissue. The whole
apparatus is surrounded by muscles which lie beneath the integu-
ment and fat, and form several layers which probably dilate the blow-
hole.

Organs of Taste.

Tne tongue in the Mammalia, as in Man, serves as an instru-
ment of taste ; in relation, however, to size, form, structure, and
development of epithelium, degree of mobility, (fee, it exhibits great
difierences. In the true Cetacea it is but slightly moveable, flat,
depressed, smooth and without gustatory papillae ; this is the case
also in the Dugongand Sea-cow (Manatus). In maAy Edentata, e.g.
Myrmecophaga, Manis, and such like, it is very long and vermiform,
smooth and viscous. In the Ornithorynchus it is covered in front
with large, hard, horny spines, behind with soft villi ; in the Cats
among the Carnivora, with very pointed horny spines, capable of
tearing ; among the Cheiroptera, at least in Pteropus, partlyv with
similar trident-shaped corneous spines, as sheaths to the papillae.
Most animals have a soft tongue covered with papillae, of which

3

34 MAMMALIA.

the papillas vallatae, in number, position, and size, are subject to
the greatest variations. In the Apes the tongue is most like the
human organ ; they have from 3 — 4 — 7 cup-shaped papillae (p. cir-
cumvallatae) ranged in the form of a triangle, or the letter Y ; there
are found mostly but 2 or 3, as in the Cheiroptera, in the Horse,
Dog, and other Garni vora ; sometimes, however, 10 or more occur.
Great and interesting varieties are here exhibited, which have not
been followed out so closely as they deserve, since they certainly
stand in connexion with the sense of taste, and it is in the
papillae vallatae that the glosso-pharyngeal nerve ramifies in particu-
lar. Further examples of such varieties may be here adduced.
While in Hyaena striata, and Viverra zibetha, there are only two
such papillae upon the root of the tongue, and in the Cats, eight dis-
posed in two rows, e. g. the Lyon and Lynx ; there are found in Ur-
sus arctos as many as 20 arranged in an arciform manner in two rows,
the posterior of which is formed of smaller papillae ; 15 in one row
are found in Ursus Americanus. Among the Rodentia, Dasyprocta
Aguti has a pair of peculiarly large, much elongated papillae. The
Goat has 30, 15 upon each side, forming two rows ; the Stag has
20 similarly disposed papillae. The 10 to 12 papillae vallatae in the
Camel, in which the papillae filiformes also are very long and thick
at their roots, are very singularly formed, being large and unequally
notched like molar-teeth, and surrounded by a deep fossa. There
rarely lies beneath the tongue a second accessory organ, as in the
Bear, or sometimes even a third.

In addition to the tongue there occur in the Mammalia very pe-
culiar organs, probably connected indirectly with the nutritive
instincts, and thus with the sense of taste, and which combine the
nasal with the oral cavity. These are the Stenonian ducts and
Jacobson's organs, so called after their discoverers. The latter
sometimes occur when the first are wanting ; though the reverse is
more frequently the case. The ducts of Steno are those canals,
nearly filled with dense cellular tissue, lined with mucous membrane,
and frequently surrounded by cartilaginous sheaths, which lie near to
each other, separated by a partition in the intermaxillary bone, behind
the incisive teeth ; in the skeleton they pass out by the foramina in-
cisiva, which coalesce in Man into a common hole. The naso-pala-
tine nerve of Scarpa enters here, and ramifies upon the nasal septum
and mucous membrane of the palate. The Jacobsonian organ is
particularly developed in the Ruminantia, as in the Stag and Ox,
where the trumpet-shaped tubes are above four inches long, and ex-

ORGANS OF TOUCH— DIGESTIVE SYSTEM. 35

tend anteriorly over the Stenonian canals, to the posterior border of
the vomer. The Carnivora and Rodentia have in part only the Ste-
nonian canals, while even these are wanting in the Horse.

Organs of Touch.

The tips of the fingers are alone specially constructed as organs
of touch in Man ; still, many Apes, as Cebus Azarae, possess a fine
tactile sense in these parts. In the rest of the Mammalia, the up-
per lip, the nose, and snout, especially the bristles or vibrissce seat-
ed upon the upper lip and at the angles of the mouth, the follicles of
which often receive very large twigs from the infra-orbital branch
of the fifth pair, serve chiefly as organs of touch. In the common
Otter the vibrissas of the angle of the mouth receive twigs from the
alveolar branch of the third division of the fifth pair, and in the
Seals, the numerous ramifications of the infra-orbital form an
areolar plexus, before they enter the follices of the hairs of the
beard.

DIGESTIVE SYSTEM.

The organs of mastication, namely, the Teeth, present in the Mam-
malia remarkable difl^erences in number, form, and structure, which
stand in such close relation with the whole economy, mode of life
and form of the animal, that its place in the system can, as a rule,
be determined from a few fragments of the teeth. In some genera
of the lowest orders, e. g. Manis, Myrmecophaga, and Echidna,
the teeth are completely wanting. In others, as in the Whales,
their place is occupied by mere horny laminae, called whale-bone.
^The teeth occur invariably only in the intermaxillary upper and
lower jaw-bones, and are generally implanted in sockets. As a rule,
there are two sets of teeth, which succeed each other, the milk teeth
and the permanent teeth, and these, as in Man, are divided into
molar, canine, and incisor teeth, the first of these being the most uni-
versally present. Three kinds of teeth may be distinguished, 1st,
Simple teeth, denies simplices, in which the crown, as in man, is sim-
ply covered over with enamel. This is the case in the higher orders,
the Apes, the Cheiroptera, Carnivora, Marsiipiata, and many Ro-
dentia, viz., the Mice, Marmots, Sic. 2d, Enamel-folded teeth,
denies complicati, where the enamel is inflected into the dental sub-
stance, a form met with in many Rodentia, as Myoxus, Castor, and

36 MAMMALIA.

Hystrix. Sd, Compound teeth, denies compositi, in which each molar
tooth consists of separate laminje covered with enamel, and united
by means of a softer intervening substance, called crusta, petrosa, or
cementum. This structure is most clearly and strikingly displayed
in the large molars of the elephant, but it occurs also in the Horse,
the Ruminantia, and many Rodentia, as the Hare, the Field-mouse
(Arvicola), and the Guinea-pig.

The diversities in the form and arrangement of the teeth are so
great, that scarcely anything general can be said about them. It
is the special province of zoology to set forth these specialities, and
we shall therefore here give only a few of the prominent examples.
Thus in the Narwhal a very peculiar formation and asymmetrical
arrangement of the teeth occurs. There is usually found only upon
one side of the upper jaw a very long spear-shaped projecting tusk,
while that of the other side remains quite rudimentary, and is prob-
ably a mere deciduous tooth ; the rest of the teeth are want-
ing. Hyperoodon has only some small teeth in the lower jaw. The
Dolphins have a great many, often 200, mostly pointed teeth, in
both jaws. The graminivorous Cetacea, Halicore and Manatus, have
merely molar teeth with flat crowns ; in the first the incisor teeth
in the upper jaw are developed into long deflexed tusks. In the
Ruminantia generally the superior incisor teeth are wanting in the
intermaxillary bone, which in the Camels only supports a pair of
incisors resembling canines. The canine teeth, with the exception
of the Musk-deer and the Camel, are also wanting in the Rumi-
nantia. In the Horse the males only have canines, but here also
they are frequently undeveloped. Among the Pachydermata the
canines are wanting in the Rhinoceros, in the Hyrax, which has
rodent-shaped incisors, and in the Elephant, in which incisor teeth
are also wanting in the lower jaw, while those in the intermaxillary
project as long tusks. The* Ornithorynchus has, upon the whole,
above and below, four singular horny molar teeth. The incisors are
wanting in all the Edentata, Dasypus sexcinctus only having two
upper ones ; the canines also are wanting in nearly all, and the
molar teeth easily fall out. The Rodentia always have two long
chisel-shaped incisors, covered only upon their anterior surface with
enamel, continually growing from behind, and implanted in very
long deep maxillary sockets ; behind the superior pair in Lepus
and Lagomys two lesser ones are found. The canines are here
wanting without any exception, and we therefore meet with a great
interval between the incisor and molar teeth. The herbivorous

DIGESTIVE SYSTEM. 37

Marsupiata approximate the Rodentia in the absence of canine
teeth, and in having sometimes, as in Phascolomys, two incisors both
above and below. The carnivorous Marsupiata, as Didelphis, cor-
respond in the structure of their teeth with the Carnivora, whose
molars are always furnished with more or less pointed, and frequent-
ly, as in Phoca, many jagged crowns. The more purely carnivor-
ous the animal, and the more it feeds* upon living prey, the less nu-
merous are the molars, one of which, the Ingest, constitutes what is
called the carnivorous tooth. The canines here become large tusks
or fangs. The Cats serve as an example, in which, through the pro-
digious development of the canines, conspicuous intervals arise in
the dental series. The Walrus has also very large canines (tusks).
The Cheiroptera and insectivorous Ferse, as the Hedgehog and Mole,
have broader molars, but with very pointed serrse ; they are similar
also in the Lemurs, the Makis and Loris ; in the Cheiroptera the
superior incisors are very small, and easily fall out. Among the
Apes, those of the Old World have the same number of molars as
Man (20) ; those of the New World have 24. They never how-
ever stand in old animals (even in the Orang-utang and Chimpan-
zee) in an uninterrupted row, but there are always, on account of
the enormous development of the canines, conspicuous spaces in
front of the molar teeth. In Man alone the teeth stand in one con-
tinuous unbroken row, and it seldom happens, save in the Negro
races, that small intervals remain between the incisor and canine
teeth of the upper jaw. It is only in an extinct race of Pachyder-
mata, Anoplotherium, that all the teeth form an unbroken series, as
in Man.

As concerns the microscopic structure of the teeth, their tubuli
and enamel, &c., we are hardly prepared at present to offer any
generalizations, and recourse must be had therefore to the most
recent works of micrographers upon this subject. The manifold
external forms and arrangements of the teeth are figured in zoologi-
cal books.

The form of the Lips is very various. Thus many Ruminantia,
like the Ox, or the Sea-cow (Manati), have a thick, moist, hairless
upper lip, while in the Ornithorynchus hard horny kind of lips,
shaped like the bill of a duck, occur. Many genera possess what
are called cheek-pouches, that is, purse-shaped sacs, usually internal,
seldom external, when they are always small, as in Gailogenys and
Askomys. The Apes of the Old World, with the exception of the
highest genera, have mostly small cheek-pouches ; d' kewise some

38 MAMMALIA.

Cheiroptera. They are very large in the Hamster and other Ro-
dentia, where they extend deeply down the neck, and are compres-
sed by peculiar tegumentary muscles which arise from the spinous
processes of the vertebrae, being detached from the trapezius mus-
cle. The cavity of the mouth is usually smooth internally ; some-
times, however, as in the Ruminantia, it is beset with hard tubercles,
which are very hard and horny on the palate of Echidna. The pal-
ate is frequently providad with deep transverse furrows and pro-
jecting elevations. Some Rodentia, such as the Beaver and Hare,
have a spot upon the inner surface of the cheek beset with hairs.
The velum palati is more or less scooped out into a semilunar form ;
the uvula is wanting in nearly all animals, even in the Makis ; and
in the Apes where it occurs, it is smaller than in Man. In the
Elephant the velum palati is very long ; as also in the Cetacea,
where it is drawn very far back. The mucous glands are more or
less developed; in the zygomatic groove in the cheek, they not
unfrequently form a ragged conglomerate gland (glandula buccalis),
with several excretory ducts, which sometimes extends even into the
orbit and zygomatic fossa. The tonsils are generally met with ;
they are largest in rapacious and carnivorous animals, as in the
Bears and Cats ; they are, on the contrary, very small in the
Mustelidae ; in the Rodentia they are most feebly developed, and ex-
hibit in general great diversities in the several orders. In the Apes
even they are different. In the Lion and some other Cats, each ton-
sil forms a sac, in which the fluid secreted accumulates. A peculiar
formation occurs in the Camel ; there is here found a singular de-
velopment of the velum palati, which is called the bursa faucium,
as a moveable duplication of the velum containing many glands,
which occurs in its full development pnly in the male, and in the
rutting season swells out so much as to protrude from between the
teeth.

The Tongue has already been considered as the organ of taste.
In some animals, as the Dog and Cat, there is found in its middle
line covered by flesh a band-shaped fibro-cartilage, called the worm.
The lingual or hyoid bone is generally present, but exhibits very
diversified forms. It is in its simplest condition in the scaly animals,
as the Manis, where it forms only a slender arch, and exhibits no
traces of peculiar cornua. It is of considerable size, and pro-
vided with two cornua in the Ornithorynchus and Echidna ; in the
latter the posterior cornu consists of three pieces. In the Cetacea,
as the Dolphin, the body of the lingual bone is flat, and there are

DIGESTIVE SYSTEM. 39

two pairs of tolerably conspicuous cornua. In the Ruminantia, the
body represents a small bow, and the anterior cornua are united
with a very long styloid process, a peculiar bone in itself. The
structure in the Horse is similar, only the body is larger, and the
anterior cornua consist of single pieces ; in both orders, as in the
Pachydermata, the posterior cornua are anchylosed to the body, and
very short, as in the Elephant and Rhinoceros especially. The pos-
terior cornua are generally the longest in the Rodentia, and particu-
larly in the Marsupiata, among which they are least in Didelphis,
and their pieces are elongated and slender, as is also the case in the
Carnivora. In most Apes the anterior cornua are elongated, or as
long as the posterior, and simple. In the Orangs the anterior cornua
are small, as in Man, in whom they are very small, and far surpassed
in size by the posterior pair. In the howling Apes (Mycetes), the
body is expanded into a very large, thin-walled, bony bladder, in
which the voice formed in the windpipe resounds, and is thus ren-
dered so remarkably loud.

The manducatory, lingual, and hyoid muscles present themselves
generally in the Mammalia, as in Man, with, however, a number
of minor differences. Thus it is only in the higher orders that the
digastric muscle is truly double-bellied, and is, even in the Apes,
not generall}^ perforated by the stylo-hyoideus. The omo-hyoideus
is very frequently wanting, next to it, the stylo-glossus, and stylo-
hyoideus. As a rule, there is developed a peculiar masto-hyoid
muscle, which draws the styloid bones powerfully backward.

The Oesophagus is short and very wide in the Cetacea, so also in
the Carnivora and Makis. It is otherwise, as a rule, long and nar-
row, and in many Rodentia, as the Hamster, passes far beyond the
slit in the diaphragm. It has frequently a thick epithelium, and its
inner surface is longitudinally plicated, but it is rarely, as in Didelphis,
provided at its inferior extremity with valvular spiral folds : as a rule,
it passes to the stomach without any valve. In the Horse, however,
there is developed a more or less large sickle-shaped fold, which can
close the cardia, and prevent the return of food, so that the Horse
can not vomit.

The Stomach exhibits remarkable diversities. In the greatei
number of Mammalia it is simple, as in Man and in most Apes,
where it is, however, mostly rounder than in Man, and in the Makis,
has a considerable ccecal dilatation. The slender Apes (Semno-
pithecus) form a striking exception ; here the left half forms a
large cavity many times constricted, while the right is long, narrow,

40 MAMMALIA.

and intestiniform, and puckered up by a pair of strong muscular
bands, like the human colon. In Mycetes, also, at least in several
species, the stomach is divided into two portions by a constric-
tion. The stomach is always simple, and mostly very rounded (as
in the Cats), in the Carnivora and Cheiroptera, least of all in the
true insectivorous Bats, and in the insectivora among the Ferae,
e. g. Centenes. In many of the Vampires it is elongated and coni-
cal, with a small cardiac coecum. In the fructivorus Cheiroptera
(Pteropus) the stomach is very long, and intestiniform with a very
considerable ccecum, and has a transverse position, while in the
Walrus the very much elongated stomach is without a coecal pouch,
and lies perpendicularly within the abdomen. Very many differen-
ces are exhibited by the Rodentia, among which indeed most of the
genera haA^e a simple cylindrical stomach, with a tolerably large cce-
cum. The stomach, however, is frequently, even when it has no
visible, or but an insignificant constriction externally, divided within
into two very distinct portions, as in Meriones. In the cardiac half
the epithelium is continued from the oesophagus, while the pyloric is
thickly beset with glands, and coated over with a soft mucous mem-
brane ; in the Beaver it has a very dense glandular layer. Fre-
quently as in the Hamster, the division into two halves is very
striking externally. There is seldom found a long glandular proven-
triculus, separated, as in Birds, by a constriction from the wide
muscular stomach, as in the Red-dormouse (Myoxus avellanarius),
but not in M. glis and nitela. In the Lemming, and in most of the
Musk-rats (Hypudasus. s. Arvicola), the second or pyloric division
itself is divided again into several (3) sacs or portions. The stom-
ach is simple in most Edentata (even in the Ornithorynchus), and
almost without a coecum. The squamigerous Edentata (Manis)
have a thick glandular layer in the left portion. Among the Mar-
supiata the stomach is simple in the carnivorous kinds ; in the Kan-
garoo it divides into a left, middle, and right portion, and is very in-
testiniform. Also in the Pachydermata there occurs a complex
stomach, as in the Peccari, while in the Elephant and Rhinoceros it
is simple, and double in the Tapir and Hyrax. In the Horse, the
stomach is simple externally ; the oesophagus, however, enters the
middle of the lesser curvature, and the cardiac and pyloric portions
are differently constructed. The sloth has a twisted intestiniform,
subdivided stomach ; and in the Manati and Dugong the stomach has
even two pedunculated coecal pouches in the middle.

Still more peculiar is the stomach of the Ruminantia, in which order

DIGESTIVE SYSTEM. 41

it first merits the special name of a Compound stomach, from its being
divided into four different cavities. The Sheep will serve best as a
type of this structure, which, however, does not differ essentially in
the Ox, Goat, &c. The first stomach is called the paunch [rumen
s. inghivics) ; it is the largest, situated most to the left side, and
usually projects below into a pair of blind appendages ; its inner sur-
face presents very prominent, conical, and hard papillae. The sec-
ond stomach, the honeij-comh [reticulum s. ollula) lies more in front,
above and to the right of the paunch, is small and round, and has a
similar hard epithelium upon the mucous membrane, the projecting
folds of which unite to form hexagonal cells, which are beset with
small pointed warts. The third, likewise small, placed more supe-
riorly, and to the right behind the liver, is called the psalterium or
many j^lies [omasus), the internal lining membrane of which forms
numerous deep folds, lying iipon each other like the leaves of a book,
and beset with small hard tubercles. To this succeeds the fourth stom-
ach, named rennet [abo?nasus), of larger size than the two prece-
ding, elongated, and terminating in the duodenum, and provided with
a velvety mucous membrane disposed in several longitudinal folds.
The oesophagus enters to the right far into the paunch, but in such
a manner, that what is called the oesophageal groove passes at the
same time through the honey-comb into the third stomach, or
many-plies. This groove consists of two longitudinal ridges of
muscle and mucous membrane, which commence from the paunch
as thin folds, and form in the reticulum two thicker lips, having be-
tween them a groove, which, by the approximation of its edges, can
be converted into a canal. The food first reaches the paunch by
the usual route, and is then regurgitated bit by bit from it back
again through the reticulum into the gullet, and so into the mouth,
where having been rechewed, it is swallowed and conveyed within
the closed groove, between the folds of the psalterium, whence it
advances into the fourth stomach. Fluids are conveyed directly
through the oesophageal groove into the rennet. In the Camel and
Llama the construction is essentially the same, but with some modi-
fi.cations. The paunch, and also the reticulum, have here a great
number of peculiar shaped cells ; the psalterium is very small, and
nearly free from folds, and the rennet intestiniform. The cells are
indicated externally as bladder-like elevations, arranged in groups.
In the Cetacea (and what is remarkable, in the carnivorous kinds)
compound stomachs also occur, the structure of which is best known
in the Dolphuas. Four stomachs are found ; the first, lying to the

42 MAMMALIA.

right, has the largest circumference, corresponds with the paunch,
and is very much corrugated internally. The second is smaller,
and communicates with the very extremity of the a^sophagus by a
large round opening. The third stomach is the smallest, while the
fourth, next in size to the first, is intestiniform, very long and
curved, and opens by a very small pyloric orifice into the in-
testine.

The Intestinal canal is in general portioned off by means of a
valve into an anterior longer small intestine, and a posterior shorter
or large intestine. In the genuine Cetacea (not in Manatus and
Halicore) no limitation is found between small and large intestine,
and the coecum is wanting, as also in the Cheiroptera, many Car-
nivora (e. g. Ursus, Mustela), and in the Insectivora, while it is
very seldom wanting in the Rodentia. The coecum, elsewhere
pretty generally present, is very short in the rest of the Carnivora,
namely, in the Cats ; it is conspicuous in the Ruminantia, still more
so in the Horse, and especially in most of the Rodentia, e. g. Mus
Cricetus, Cavia, Castor, and Lagomys, where it exceeds the stomach
many times in size — in the Hare from 8 to 10 times. There rarely
occur, as in most Birds, two small coeca, e. g. in Myrmecophaga and
Hyrax. A vermiform appendix occurs in the Orangs and Gib-
bons, and rarely here and there throughout the other orders, as in
Lagomys. In the Cetacea the duodenum commences by a bladder-
like enlargement, which was once falsely regarded as a portion of
the stomach. The clusters of Peyer's glands are, as a rule, consid-
erably developed. The mesentery is usually longer than in Man,
even in the Apes. A small and large omentum, traversed by ele-
gantly disposed streaks of fat (as in the Otter), is regularly present.
The insertion of the great omentum departs most from that of the
human adultj and resembles more that of the foetus. Frequently,
as in the Rodentia, lumbar omenta occur, which penetrate partly
into the inguinal canal, and are to be regarded as elongations of the
peritoneal or vaginal coat of the testicle. In the female (as the Rat),
the lumbar omenta are elongations of the round ligaments of the
uterus. In the Ruminantia the great omentum forms a veil over
the compound stomach ; in the Carnivora it lies around the intes-
tines. The intestinal villi are exceedingly large in the Rhinoceros,
and very conspicuous in the Rodentia, and also in the Makis ; they
are larger in the Apes than in Man, and small in the Ruminantia.
The length of the intestinal canal is most considerable in the latter,
and is in proportion to the length of the body as 15 or 20 to 1 ; in

DIGESTIVE SYSTEM. 43

the Sheep even as 28 to 1 ; in most Carnivora, it is as 4 to 1 ; and
in the Cheiroptera, as 3 to 1. Many animals, as the Cetacea, the
Ornithorynchus, and the Mole, seem to have mere longitudinal folds
upon the mucous membrane, but no villi.

Of the Salivary glands the three pairs of the human subject are
generally present, yet they are wanting completely in the Cetacea.
The Dugong (Halicore) alone has a very large parotid, which on the
other hand is wanting along with the sublingual gland in the Seals.
These glands are also partly wanting in the Monotremata. In gen-
eral the salivary glands are largely developed in the Ruminantia,
Pachydermata, and Rodentia, moderately so in the Quadrumana, and
less in the Carnivora. In many Carnivora, as in the Dog, and in
many Rodentia, as the Squirrel, and also in the Makis, the submaxil-
lary glands are larger than, frequently as large again as the parotids.
This is especially the case in the Beaver, where the two coalesce
posteriorly in the nape of the neck, and form a large mass. The
Edentata, also, especially the Kangaroo and Opossum, as likewise
the Cheiroptera, have large salivary glands, with the exception of the
sublingual, which, in the last-named order, is very slightly developed ;
in the Dog and Cat it is also very small. The submaxillary gland
is very large in Myrmecophaga and Orycteropus.

The Liver of the Mammalia is fashioned after the human type ; it
is usually divided into two principal lobes, and is frequently more
deeply bisected. In the Cetacea its two lateral lobes are very feebly
indicated; in the Ruminantia there is found a third smaller lobe.
The liver is three-lobed in the Hog and some Rodentia ; most of the
Rodentia, Marsupiata, and Apes, have, however, from 4 to 6, the Car-
nivora still more, 6 to 8 lobes, as the Dog, Cat, and Bear. The
liver of the Orang is like that of Man.

The Gall-bladder is usually present, though it is also frequently
wanting, as, for example, in the true Cetacea, many Ruminantia
(Camel, Goat), the Horse, and most Pachydermata (though not in
the Hog), and several of the Rodentia, as the Hamster, the 'Mouse,
and in the Sloth among the Edentata. A biliary duct always passes
to the intestine, into which, or into the gall-bladder, the excretory
ducts of the liver pour their secretion. The pancreatic duct often
joins just before it enters the intestine the termination of the biliary
duct, which is in this situation frequently expanded in the shape of a
bladder, as in the Elephant, the Kangaroo, the Otter, the Seal, &c.
A remarkable peculiarity is possessed by the Orycteropus, in which
two separate gall-bladders occur, united by a common peritoneal

44 MAMMALIA.

covering ; each of these is continued into a tortuous cystic duct, which
unites with three ducts from the liver into a common excretory-
canal.

The Spleen is always present, but varies in form and size in the.
several orders. Thus it is, in general, elongated and small in the
Ruminantia, Carnivora, and Makis ; short, broad, and flat, in the
Apes ; largest, in relation to the liver, in Man. The Cetacea here
also exhibit a striking anomaly, the Dolphins having from 5 to 6 les-
ser spleens, lying near to the larger one, which is always proportion-
ally but slightly developed. In Man also there occurs in rare cases
an abnormal subdivision of this organ.

The Pancreas is, for the most part, formed of two, and rarely of
three, principal lobes. It has one or two excretory ducts, which
last number occurs also not unfrequently in Man. When it is sim-
ple, as in all the Apes, the Ruminantia, and most Carnivora and Ro-
dentia, it usually falls, as has been mentioned above, into the
biliary duct, but if a second one is present, as in the Horse, Hog,
Otter, and Beaver, it enters by itself farther behind into the duo-
denum.

ORGANS OF CIRCULATION.

The Heart consists, as in Man and Birds, of two perfectly dis-
tinct auriculo-ventricular chambers. It is surrounded by a peri-
cardium, the lower part of which is not generally united with the
diaphragm, as is the case in Man and the Orang, and is frequently,
as in the Hedgehog, remarkably thin and delicate. The form of
the heart is, in general, more rounded and not so elongated as in
Man. In the Cetacea it is very broad and flat. In the herbivo-
rous Cetacea (Halicore and Manatus) the heart is cleft in a pecu-
liar manner, the division into two ventricles being indicated exter-
nally by a deep fissure in its apex. The foramen ovale is, as in
Man, always closed, and only open as an accidental abnormal con-
dition. The internal arrangement of the muscles and valves exhib-
its several trifling varieties ; thus the Eustachian valve is wanting
in many genera, while on the contrary in the Elephant it is very
large and spirally twisted. In the Ornithorynchus the fleshy condi-
tion of the valves (valv. tricuspidales) in the right heart reminds us
of that in Birds. In some herbivorous Mammalia, as in the Ox,
Sheep, Hog, and Goat, there is found as a normal formation, in the
septum ventriculorum, below the origin of the aorta, a cruciform

uilGANS OF CIRCULATION. 4^

ossification called the bone of the heart. The heart lies, for the
most part, in the median line, parallel with the sternum, rarely having
its apex, as in Man, directed to the left, though this is the case in the
Apes, the Sloth, and the Mole, and also in a less degree in some other
animals, as the Seal.

The Aorta gives off first from its root the two coronary arteries,
rarely only a single one, as in the Elephant. The origin of the
vessels from the arch of the aorta exhibits, as is well known, fre-
quent varieties in Man, several of which occur as normal states in the
genera and orders of Mammalia. In the Horse and the Ruminan-
tia tbe aorta divides at once at its origin into an anterior trunk,
or arteria innominata, which gives '>fF both carotid and subclavian
arteries, and a posterior trunk for the thoracic and abdominal aorta.
In most of the Carnivora, Rodentia, Marsupiata, and in the Hog,
Ant-eater and Pangolin, the left subclavian artery is distinct from tho
innominata, and proceeds by itself from the arch. In the Dolphin
and Cheiroptera, at least in VespertiJio murinus, two arteriae innomi-
natas arise, and give off each a carotid and subclavian upon either
side. The human arrangement, namely, with three main trunks,
of which the innominata gives off the right common carotid and
subclavian arteries, occurs partly in the Apes, Carnivora, some
Rodentia and most Edentata. It is very rarely, as in the Ele-
phant, that both the carotids are given off from a single common
trunk, situated in the middle between the two subclavian arteries.
Sometimes, as in some diving animals, as the Seals aYrd Narwhal,
the aorta forms near to its exit from the heart a sac-like expan-
sion. The subdivisions of the arterial system exhibit a host
of minor differences, which can not be entered upon further here.
It is only worthy of remark, that in some animals, as the Sloth and
Loris, which are remarkable for the slowness of their movements,
that the arteries of the arm and leg divide at the commencement
of the extrernities into several (3) main tnmks, two of which rami-
fy again into a number of finer anastomosing filaments (retia mi-
rabilia), which wind around the middle branch. Large arterial retia
mirabilia occur within the skull of the Ruminantia, and are situated
within the cavernous sinus, and extend even to the vertebral artery.
The Cetacea have many arterial plexuses in different situations — in
connexion with the intercostal and thoracic arteries in the cavity of
the thorax, and upon both sides of the vertebral column from the
psoas muscle to the neck.

The Pulmonary artery, in its mode of origin and the number of its

46 MAMMALIA.

valves, agrees for the most part with that of Man, though there
sometimes occurs, as in the aorta, a sacciform expansion of its com-
mencement, e. g. in the Narwhal, and in a less degree in many of
the Dolphins also. The number of pulmonary veins varies consider-
ably, and there frequently occur upon one side a greater number than
upon the other (3+2), a circumstance chiefly occasioned by the
number of the lobes of the lung.

Valves occur in the Veins of the body, and frequently, even as in
the Ox, in the portal veins, where they are wanting in Man. The
trunk of the superior vena cava is very frequently double, in indi-
vidual animals from all the orders, as in the common Bat, Hedge-
hog, Squirrel, Ornithorynchus, Elephant ; as a rule, however, it is
single, as in the Apes, Ruminantia, most Carnivora, &c. The
inferior vena cava is commonly dilated in diving animals, previous
to entering the heart, and while ypt within the liver, as in the Seals ;
in a less degree also in the Dolphin and Otter, still less so in the
Beaver and Ornithorynchus j in these it forms a true sinus, like
that of Fishes. This large size of the veins, in relation to that of
the arteries, exerts unquestionably an important influence upon the
circulation and the process of diving ; and the discovery is a re-
markable one, of a peculiar annular muscle, about an inch in
breadth, which is met with in the Seals on the trunk of the inferior
\'ena cava, above the diaphragm and venous sac, and which can
cut off* the retui:n of blood to the heart. In the Cetacea remarkably
developed venous plexuses occur ; one of these lies, e. g. in the canal
formed by the inferior spinous processes of the tail ; another much
more conspicuous (plexus iliacus) lies between the psoas muscle and
the peritoneum.

The absorbent vessels exhibit in general the same conditions as
in Man, in reference to the chyliferous ducts. The lymphatic
glands of the mesentery are usually less numerous, and more
blended together, than in Man. They sometimes form only a
single mass lying at the root of the mesentery, called the Pancreas
Asellii (as in the Dog and the Carnivora generally), near to which,
however, some smaller lymphatic glands usually occur. This me-
senteric gland is most conspicuous in the Cetacea, where the lym-
phatic vessels are very much developed.

The Blood of Mammalia very uniformly presents small, round,
disc-shaped corpuscles, very similar to, but m9stly somewhat
smaller than in Man ; this is especially the case in the Ruminantia.
The largest animals, as the Elephant, have still very small cor-

ORGANS OF VOICE AND RESPIRATION. 47

puscles. In the Apes they appear of the same size as in Man.
There is a remarkable exception to the form of these corpuscles in
the Camels and Llamas, where they are somewhat elliptical.

ORGANS OF VOICE AND RESPIRATION.

The larynx, trachea, and lungs, in the Mammalia, are fashioned
after the type of the same organs in Man. In the larynx the same
cartilages are met with as in Man, though the relations of their
separate parts are frequently changed. In the Cetacea the larynx
is very small, especially the thyroid and cricoid cartilages ; on the
contrary, the arytenoid cartilages and the epiglottis are very long,
and reach as far as into the nasal cavity. The thyroid cartilage
is very anomalous in form, and there are no chordae vocales,
since neither the Dolphins nor Whales have been heard to utter
any sound. In the Pachydermata also the larynx is small, espe-
cially its arytenoid cartilages. The thyroid cartilage is long and
deep, but narrow in the Ruminantia, and for the most part also in
the Edentata. The Rodentia have a conspicuous larynx, and in
the Carnivora especially, the cricoid cartilage is very large, often
three times greater than the thyroid. The Cheiroptera are dis-
tinguished by their very small epiglottis. The lateral ventricles of
the larynx, and with them the anterior chordae vocales, are fre-
quently wanting, as in the Ox, Sheep, Musk-deer, Armadillo, and
Pangolin. In several Mammalia, as in the Apes (but not the Ma-
kis), and many Carnivora (e. g. Ursus, Canis), the two cuneiform or
Wrisbergian cartilages (cartilagines cuneiformes), which lie in the
fold of membrane between the arytenoid cartilages and the epiglottis,
are considerably developed, while in man they are wanting, or very
minute. Peculiar sesamoid cartilages rest, in some Mammalia, as
the Ornithorynchus, the genera Mustela, Didelphis, &;c., upon the
posterior border of the arytenoid cartilages. There occurs a smaller
azygos interarticular cartilage (c. interarticularis) in many Mam-
malia, as the Hedgehog (where it is very conspicuous), and also
in the Hog, Dog, &c., situated in the middle between the two
arytenoid cartilages upon the upper border of the cricoid. The
human larynx is distinguished from that of the Apes, in particular
by the greater shallowness of the thyroid cartilage, the greater de-
velopment of the arytenoids, the lesser size of the lateral ventricles,
the absence or slight development of the Wrisbergian cartilages, and
the greater degree of hardness and frequent ossification of the carti-

48 MAMMALIA.

lages, especially in the male sex, as well as by a greater sexual dif-
ference, the female larynx being softer in its cartilages, smaller, and
less prominent.

Singular varieties have still to be mentioned in the structure of
the larynx in some Mammalia, namely, among the Apes. In the
Sapajous the cavity of the larynx above the inferior chordae vocales
is lengthened out into a bent tube, the anterior wall of which is
formed by the thyroid cartilage, the superior by the epiglottis, the
posterior and inferior wall again by the adjacent prominences of the
cuneiform cartilages. Still more striking is the arranoement in the
Howling Apes, where membranes, bones, and cartilages, both of the
larynx and os hyoides concur to form the lateral laryngeal sacs or
apparatus of resonance, by which the volume of their voice is pro-
digiously increased. Even in the Orang-utang and Chimpanzee the
lateral ventricles of the laryngeal cavity are lengthened out into mem-
branous sacs, which extend forward beneath the body of the hyoid
bone. Similar sacs also occur in other Apes, as in the common
Inuus ecaudatus, where there is, however, only one" which opens by
a small simple orifice beneath the epiglottis above the lateral ventri-
cles. There is a remarkable valve, found hitherto only in the Mar-
mots, which, directed downward, can fill up and close the whole
breadth of the larynx.

There is very generally situated upon and beneath the larynx in
the Mammalia a Thyroid gland. It consists in a great number of
two completely separated lateral lobes, and, as a rule, is double. In
many Apes both lobes are more separated than in Man, but usually
united by a ligament. Both halves of the gland lie very far apart in
the Otter, where they are situated upon the sides of the larynx, and
are in contact with the sub-maxillary glands. In the Cetacea, on the
contrary, the flat or heart-shaped thyroid gland is not separated into
two lobes, and lies transversely over the trachea.

The Trachea in the Cetacea is extremely short, on account of
the shortness of the neck, and, at the same time, very wide ; the
cartilaginous rings are very closely approximated together, and in
the Whales not closed anteriorly, so that here it is membranous.
In the herbivorous Cetacea it is not divided into separate rings or
arches, but is wound about by a spiral band of cartilage. In the
Horse and some Ruminantia it consists of complete rings, while in
a large number of animals it is perfectly membranous behind, as ap-
pears to be particularly the case in the Rodentia. The number of
rings varies remarkably, and is determined by the length of the

URINARY ORGANS. 49

trachea and neck. While the Cetacea have only from 7 to 13, the
Carnivora have mostly from 30 to 40, and even more rings ; there
occur from 60 to 100 in the Rmninantia, and in the Camels even 110
rings ; their nmnber varies, however, in individuals of the same
species. In Man we find from 17 to 20 imperfect rings. The
trachea is almost always straight, i. e., it passes without any con-
tortions to the lungs ; in the Sloth (Bradypus tridactylus) alone, it
makes, as in many Birds, a bend forward and downward before
dividing into the bronchi. The trachei usually divides, as in Man,
into two main bronchial trunks ; occasionally, however,, as in the
Ruminantia and the Hog, it divides into three, which is also the case
in the true Cetacea. The third supernumerary bronchus is always
smaller, arises anteriorly, and passes to the right lung. The bron-
chial rings are in one case to be traced, quite complete, far into the
lung, in others they soon disappear.

The Lungs are sometimes quite simple and undivided upon each
side, as in the Horse, Elephant, and Rhinoceros. The number of
the lobes, is, however, commonly greater than in Man, four or even
five (as in Hamster and Marmot) being found upon the right, two to
three upon the left. The right lung is usually larger, sometimes
double the size of the left, as in the Musk-deer. The lungs of all
Mammalia, as in Man, have terminal cells which are situated at the
extremities of the bronchi, and appear to be in the whole class near-
ly of the same size — from -g^th to ^th of a line.

The Mammalia, like Man, have a Thymus gland, which is formed
toward the end of fcetal existence, and attains its greatest develop-
ment during the period of lactation ; it afterward usually disappears
by degrees, though sometimes it is persistent. It lies in the antero-
superior part of the cavity of the chest, usually consists of two main
lobes, and agrees in structure with that of the human thymus. All
diving animals, the Beaver, Seal, Otter, and Cetacea, exhibit a very
large thymus gland which exists throughout life, and which frequent-
ly extends from the thoracic cavity, along the trachea, up both sides
of the neck, as is the case in the Ruminantia.

URINARY ORGANS.

In the internal structure of the Kidneys, in reference to their
vascular system, their Malpighian bodies, the infundibuliform struc-
ture of the urinary canals, &c., the Mammalia agree with Man.
The kidneys in most of the Carnivora are much rounded ; in the

4

50 MAMMALIA.

Dugong, on the contrary, they are greatly elongated ; occasionally
they appear incompletely lobed (in many Cats and Weasels), as in
the newly-born infant. In some animals, particularly those that live
in water, each kidney is divided into several, often into many lobuli.
In the Ox, there are found 20 free, rounded lobuli, about 12 in the
Otter, and from 40 to 50 in the Bear. The kidney is divided into
from 70 to 100 or more lobules in the Seals, and its surface has in
consequence a tessellated aspect. In the true Cetacea the kidneys
have a racemiform appearance ; in the Dolphins 200 separate lo-
bules can be counted. Each lobule is provided with a papilla, and
there is here found no pelvis, but an excretory duct proceeds from
each lobule, so that the ureter is composed of branched tubes, like
the ducts of other glands. Most of the remaining animals, namely,
all Apes, even the Orangs, most Rodentia, Camivora, and Edentata,
have only a single papilla, into which all the renal tubuli open. The
urinary bladder is particularly large in the Herbivora (as in the
Horse), smaller, rounded and muscular in the Camivora, thick-walled,
elongated, and very small in the Cetacea, whore the ureters also are
exceedingly short.

The Renal capsules are generally present, and always larger in the
foetal than in the adult animal. They are flat, and like those of Man,
in the Quadrumana ; very large in most Rodentia, and very small in
the Cetacea, even in their foetus.

SPECIAL SECRETING ORGANS.

Besides the organs of secretion which are necessary for the gen-
eral animal economy, there occur in separate families, genera and
species, particular secretions, which always serve a special purpose
in connexion with the peculiar structure and mode of life of the ani-
mal to which they belong.

Thus several of the Sebaceous follicles of the skin are developed in
many animals into compound follicles and true glands, which secrete
a strong smelling sebaceous or unctuous Huid.

A group of such sebaceous sacs lies in the Stags and Antilopes in
a cavity of the lacrymal bone beneath the eye, which secrete what
are called the " tears of the Stag."

The peculiar smell which emanates from the Cheiroptera depends,
for the most part, upon a considerable flat and yellow colored
gland, which in Vespertilio murinus, noctula, &c., lies upon both
sides of the upper jaw, between the eye and nose. Similar, only

SPECIAL SECRETING ORGANS. 51

less developed, sacs are found in some other animals, e. g., Arctomys,
Lutra, &LC.

In the Shrew-mice, at least the larger species, there occurs upon
the side of the body, opposite to the anterior feet, a layer of glands,
which secrete a fetid fluid.

In the genera nearly allied to the Shrew-mice, namely, Myogale,
and Macroscelides, a layer of separate caecal sacs, or pyriform pouch-
es, lies upon the under side of the tail. The secretion of these glands
is very strong in Moschus.

In the Peccari (Dicotyles torquatus) there lies upon the back in
the crupper a gland opening externally, and giving exit to a strong
smelling secretion ; it consists of a sac with thick walls, into which
blind cells open. A glandular organ, probably similar, has been
recently found in the Stag, surrounding the eight basal caudal
vertebrae.

A considerable gland, 6 to 8 inches broad, lies, in the Elephant,
beneath the integument in the neighborhood of the temple. It
opens by a narrow excretory duct between the ear and eye, and
secretes in the male, during the rutting season, an adhesive fetid
moisture.

In the Carnivora and Rodentia, Anal sacs or glands are very
frequently fo«nd ; and their secretion appears always to possess a
strong odor. Such simple sacs, consisting of many coats, and
covered with a muscular layer to press out their contents, are
found in Mustela, Lutra, Arctomys, Dasyprocta, &c. ; in the Civet
(Viverra zibetha), and in the Beaver, they are provided with thick
glandular walls. In the Hyaena there is only a single pouch which
opens by a transverse slit above the anus ; it contains, however, sev-
eral conspicuous sacs, which consist of blind follicles grouped together
like a bunch of grapes.

The peculiar Preputial glands, which frequently occur, as in
some Rodentia and Carnivora, near to the anal sacs, appear to be
less generally distributed. Conspicuous but simple sacs are found
in the preputium in Mas, Cricetus and Lepus. In the Beaver and
Civet they are found along with the anal sacs, and yield the casto-
reum and civet-musk. The sacs in the Civet are double, but en-
closed in a common pouch, which opens between the anus and sexual
organs. Small follicles are situated in its thick walls. Such sacs are
also met with in the Ruminantia, namely, the Antilopes. The most
remarkable instance, however, occurs in the Musk-deer, where the
musk pouch is an organ of secretion opening into the prepuce, though

62 MAMMALIA.

it lies as a simple azygos pouch, provided internally with small de-
pressions, between the umbilicus and the glans penis.

In many Ruminantia, such as the Sheep, Doe, Elk, and Rein-
deer, we frequently find over the hoofs, both in the fore and hind
feet, or only in the one set, a membranous pouch of considerable
size, beset with follicles, which secrete a fatty odorous substance,
which is poured out upon the anterior surface of the hoof above
its cleft.

A most peculiar gland, probahly a Poison gland (and in this case
it would be, as such, the only example in a mammiferous animal),
occurs in the male Ornithorynchus. It is a considerable triangular
gland, which lies upon the outer side of the leg. A long excretory
duct runs beneath the integument to the inner side of the heel as fal
as the astragalus, where it forms a sacculate dilatation at the base of
the horny spur, and opens' at length by a canal traversing the lattei
to its apex.

SEXUAL ORGANS.

The sexual organs of the Mammalia and the organs of lactation,
which must be here considered also, differ very much from those of
the other Vertebrata. They repeat with certain modifications the
human type of formation.

The Ovaries are, as a rule, rounded or oviform bodies, as in Man,
in which are imbedded in a more or less dense fibrous stroma the
Graafian follicles. In each of the latter there lies one small ovule
(very rarely two), scarcely visible by the naked eye, which includes
a germinal vesicle with a single germinal spot. If the stroma is in
small quantity, the follicles frequently appear pedunculated, and thus
the ovarium obtains a more clustered appearance, as is the case in the
Mole and Ornithorynchus.

The Fallopian tubes or Oviducts usually commence, as in Man,
by a free opening into the abdominal cavity, and are usually sur-
rounded by a puckered border of folds, forming what are called the
fimbriae. In many Carnivora, e. g. Canis, Felis, Phocha, Mustela,
Lutra, the peritoneal covering of the oviducts is continued to the
ovary, which it loosely invests, after the manner of the testicle, with
a kind of tunica vaginalis. In some animals, as the Dog and Cat,
a small opening remains in this sac, communicating with the abdom-
inal cavity ; in others the sac is completely closed, and in these last,

SEXUAL ORGANS. 53

what is called extra-uterine or abdominal pregnancy, which some-
times occurs in the human subject, can not take place.

The Uterus exhibits great varieties. It is Simple, uterus simplex^
and of a triangular, oval, or round form, according with the human
type, while the two oviducts enter its cavity at right angles upon
either side of the fundus. This is the case principally in the Apes
and Cheiroptera. The uterus is Two-horned, utertis bicornis, in the
Ruminantia, Pachydermata, Solipedia, and Cetacea, and in a less
degree also in the Makis. The body is here prolonged into a pair
of thick and crooked cornua, which pass into the very narrow and
much-contorted Fallopian tubes. The uterus is called Divided, ute-
rus divisus, where it has only a very short body, as in most Car-
nivora, Edentata, and most Rodentia, which speedily divides both ex-
ternally and internally, and is continuous with the straight or slightly
twisted oviducts. The uterus is actually Double, uterus duplex s.
biforis, in some of the Edentata, and in most Rodentia, as the
Mouse and Hare. Each Fallopian tube passes above into an intes-
tiniform uterus, which has two completely distinct openings lying
near to each other within the vagina. The structure is still more
anomalous in the Ornithorynchus ; the oviducts are here not com-
pletely separated, but each has inferiorly an expansion, like the ovi-^
ducts of Birds, and opens by itself into the cloaca ; between the two
apertures lies that of the urinary bladder.

The uterus of the Marsupiata is very peculiar, and exhibits in the
several genera varieties which, however, are not very remarkable, so
that its structure in the Kangaroo may serve as an example. The
oviducts are at their abdominal extremity surrounded with a folded
crown of fimbrias, and each, very delicate at its commencement, ex-
pands into an elongated uterus, in which the small embryos are de-
veloped, and attached by a short umbilical cord. Both uteri open
into the vagina, which is likewise double, and very peculiarly formed,
as it frequently forms a coecal sac, which is often divided by a sep-
tum, into the commencement of which the uteri open. From this
arise superiorly the vaginal canals, two handle-shaped and intes-
tiniform membranous tubes, frequently contorted, which coalesce in
front of the external sexual opening, or kind of cloaca. Through
these the small and still imperfectly developed foetus unquestionably
reaches the exterior, and is conveyed by a process not yet known
into the pouch.

The Vagina of the Mammalia seldom presents transverse rugae,
but usually slight longitudinal folds. At its termination, frequently

54 MAMMALIA.

also in its middle, but rarely posteriorly, there is often found, as in
the Horse, the Ruminantia, Carnivora, and Apes, a fold or septum,
in one case strong, in another merely rudimentary, which corresponds
to the hymen of the human female, but is never so peculiarly devel-
oped as in the latter.

The Clitoris appears to be generally present, and occurs also in
the Monotremata and Cetacea. It is usually situated far forward,
consists of cellular tissue, and is provided with a glans, and pre-
puce. It is very much developed in the Rodentia, Carnivora, and
Apes, and in them contains not unfrequently a cartilage or bone
analogous to that of the penis. Thus there is found a small bone in
the domestic Cat, which is larger in other species of the Feline
race, and in the Otter, Bear, Marmot, &c., but is apparently fre-
quently wanting in the Apes. A clitoris, on the contrary, of unusual
size occurs in the Spider-monkeys (Ateles), being from two to three
inches long, and provided with a glans and conspicuous prepuce,
upon the under surface of which a groove runs from the orifice of
the bladder, along which the urine flows. In the Marsupiata, the
clitoris is split like the glans of the male, and there project from it
two folds forming a groove for the passage of the urine, or, as in
the Lemming, the Makis, and Loris, the clitoris is actually perfo-
rated, and thus attains the highest grade of analogy with the male
penis. The spongy bodies and arterise helicinee are frequently
wanting, and the body is filled with fat, so that even in the Spider-
monkeys, it is probably incapable of erection. The preputial glands
of the clitoris are occasionally very much developed ; and in some
Carnivora, Marsupiata, Ruminantia, and Rodentia, we also find at
the base of the clitoris more or less distinctly developed Cowper's
glands, which have been lately proved to exist in the human female.
The nymphae or internal labia are wanting ; the external labia are
but slightly developed, and consist only of a pair of hairless pro-
jections, which bound a mostly rounded vaginal orifice ; the mons
veneris is wanting. In some Mammalia, namely, the Horse and
Ruminantia, we find upon either side of that of the urethra the two
orifices of what are called the vaginal canals, which run between
the muscular and mucous membrane to the broad ligaments of the
uterus, but are sometimes entirely closed ; they may probably be re-
garded as the remains bf the excretory ducts of the Wolffian bodies
or false kidneys in the foetus, and thus as a kind of persistent arrest
of formation.

The Mammary glands, which occur in all the Mammalia, are to

SEXUAL ORGANS. 55

be viewed as accessories of the sexual organs. The number, posi-
tion, and external form of the mammae are very different in the sev-
eral orders ; it is the special province of Zoology to describe more
minutely these diversities. Frequently, as in the Hedgehog, Dog,
Hare, and other rodent and carnivorous animals, there occur from 10
to 12 mammae ; the number, however, varies between 2 and 12. It
is only in the higher orders, as in the Apes and Cheiroptera, though
also in the herbivorous Cetacea, that the mammse are present two
in number, as in Man, and situated upon the breast. In the rest of
the Cetacea, indeed, and in the Solipedia, there are found only two
mammae, but they lie far back, near to the anus or the sexual organs.
The Pachydermata and Ruminants have mostly from 2 to 4 upon the
belly. In the Carnivora and Rodentia, the number varies from 4 to
12, and they then lie in two adjacent rows, upon the belly, extend-
ing from the breast to the perineum. The number of the lactic
glands, which are frequently blended together, is indicated externally
by that of the nipples ; these have a soft cuticular covering, are perfo-
rated by the excretory ducts of the glands, and differ in number and
arrangement. In the Cow, the ducts pass into a large simple sinus,
which has only a single papillary opening ; the structure is similar
in the Whale and Dolphin. In the Rabbit and Cat we find 5 small
openings, and ten in the Dog, while in Man from 15 to 20 occur.
The nipples are seldom completely wanting, as they are in the Mono-
tremata, where the young can only suck, by making a kind of fold
of the skin upon the breast by means of their snout. In this order,
however, as in the Cetacea, a peculiar tegumentary muscle occurs,
which can compress the gland, and so spurt, as it were, the milk into
the young one's mouth. The same arrangement occurs also in the
Marsupiata, so that the fluid necessary for their nourishment can be
supplied to the small and imperfectly developed embryos which hang
on to the elongated nipples. The mamma appears in general to be
a conglomerate gland with arborescently divided excretory ducts,
which terminate in clusters of small bladders like bunches of grapes.
An exception, however, to this is presented by the Monotremata.
Thus in the Ornithorynchus each mammary gland consists of a mass
of coeca of considerable size, and varying in length, and either single
or divided at their extremities, which converge toward the nippleless
external openings.

In the Marsupiata a peculiar external or^an of generation occurs.
There is found, namely, in front of the pelvis, supported by a pair
of peculiar bones, a sac or pouch (in many genera, e. g. in Didelphis,

56 MAMMALIA.

only a pair of lateral tegumentary folds), within which are situated the
mammae and nipples, to which the still slightly developed embryos
attach themselves, and are there completely formed. The pouch is
a duplicature of the external integument, which posteriorly and supe-
riorly stands in connexion with the tendon of the external oblique
muscle of the abdomen. The muscle of the mammary gland, al-
ready mentioned {compressor mammcB), is situated upon the external
oblique muscle, arises from the posterior part of the pelvis, becomes
broader anteriorly, and divides into two slips, between which the
nipples are enclosed. The number of the latter is greater in the
carnivorous than in the herbivorous Marsupiata.

The Male sexual organs, like the female, exhibit considerable di-
versities in the several orders. The Testicles, as in Man, are oval
or rounded, and sometimes much elongated and thin or slender, as
in the Cetacea. They have a tunica vaginalis, but are seldom sit-
uated, as in Man, in a scrotum separated by a partition, this being
the case only in the Apes, several Carnivora, the Ruminantia, and
the Horse. The scrotum usually stands in communication with the
abdominal cavity through an open inguinal canal. In many insectiv-
orous Carnivora and in most Rodentia, the scrotum is all but want-
ing, and the testicles lie in the perineum, as in the Beaver, or within
the abdominal cavity, as in Sorex, Erinaceus, Talpa, Myoxus, and
many others, while in other genera and in the Cheiroptera the tes-
ticles, during the rut at least, glide back into the belly. In the Ce-
tacea and Monotremata, as also in some Pachydermata, e. g. the
Elephant, and indeed, in many Rodentia, the testicles are situated
permanently in the abdomen, upon either side of the rectum, and are
there retained in their place by a mesentery similar to the broad lig-
aments of the uterus. The internal structural arrangement of the
testicle is essentially the same as in Man ; the delicate seminifer-
ous tubes uniting into the seminal duct form an epidydymis. In
many animals a portion of the tunica albuginea is given off as a strip
of various form, which sends laterally ray-shaped fibres between the
lobules of the seminal vessels ; this structure is known by the name
of Corpus Highmori, and is particularly distinct in the Ruminantia,
and also in the Horse and Dog. At the spot where the vasa defer-
entia unite, before the commencement of the urethra, they form not
unfrequently an expansion like the uterus, or a kind of sinus, which
is perhaps to be viewed as a remnant of the sinus urogenitalis in the
foetus.

The testes secrete a white Semen^ the moving elements of which.

SEXUAL ORGANS. 57

called seminal animalcules or spermatozoa, are formed indeed after a
common type, but exhibit numerous shades of difference in the sev-
eral species. They have always, however, like those of the human
subject, a small, thick, more or less clavate, shovel or even sickle-
shaped head, from which extends a long and very slender tail.

The VesiculcB seminales, which are probably to be regarded less
as receptacles for the semen than as organs of secretion, since
they not unfrequently have thick glandular walls, exhibit great
diversities. In the Apes they are commonly more tortuous and
divided, than in Man. In the Makis they form a large coecum with
a simple cavity, and appear to be similar in most Cheiroptera. In
the Carnivora, the Marsupiata, the Monotremata and Cetacea, they
would appear to be wanting, if an expansion which frequently occurs
of the vas deferens be not taken for them. In the Horse three ve-
siculaj seminales are found ; in the Hare there is only a single,
large, glandular bladder present ; they are very large, and provided
with lateral lobes, in the Hog ; those of the Ruminantia are similar
and large. In the Elephant the very large vesiculee seminales appear
to be compressed by a special muscle. There frequently occur dila-
tations of the vasa deferentia, which may be regarded as vesiculae
seminales, as in Dipus.

The Prostate gland presents remarkable diversities. In the
Apes it resembles for the most part that of Man, though in a less
developed condition. In the Cheiroptera it is divided into lesser
lobules. It is distinct and cylindriform in most Carnivora ; it
is frequently, however, but slightly developed, as in the Otter. In
the Horse the gland has two cornua, and consists of large sacs ; in
the Ruminantia and in the Hog it is represented by a very thin
glandular layer ; in the Cetacea it forms a single large mass, which
surrounds the urethra in the form of a ring. The greatest devel-
opment of the prostate is exhibited by many Rodentia and Insec-
tivora. Thus there is found in the hybernating Dormice (Myoxus
for example), a tuft of coecal tubes, or a rounded sac, as in Sorex,
or a large knotty tuft of glands, as in Talpa, Castor, Cricetus. In
Dipus, near a pair of large simple ccecal tubes of unequal size,
there is found a pair of lesser lobed glands. Its development is
perhaps greatest among our indigenous animals in the Hedge-hog,
where the posterior pair always consists of six lobes, with very long
contorted, coecal vessels, united by cellular tissue, the anterior pair
being represented by a tuft of divided coecal canals. The Elephant
has also two pairs of divided vesiculae seminales, and among the Ro-

58 MAMMALIA.

dentia there are animals, as the Rat, in which there are as many as
three pairs of prostate glands.

Conyper'*s glands likewise exhibit remarkable complexities ; and
perhaps in no part of the anatomy of the Mammalia does greater
variety prevail. As a rule, allied genera have them formed alike,
while in one and the same order great diversities occur. In the
Apes these glands are mostly larger than in Man ; in the Cheirop-
tera and Carnivora they are often very conspicuous, as in Sorex,
Hyaena, Viverra, and also in the herbivorous Marsupiata ; they are,
on the contrary, very small in the Dog, Cat, and Fox. They are
very much developed in many Rodentia, as Myoxus and Castor, and
in the Hog, Elephant, and Camel. In Dipus they form a pair of dis-
tinct sacs, and in the Hedge-hog they are long, and contorted. In
the Hedge-hog, the Mole, and Insectivora generally, they are most
conspicuous, and form at times large flat lobed glands, composed of
tufts of delicate ca3cal tubes.

The Penis of the male also exhibits exceedingly great diversities
It is only in the Apes and Cheiroptera that it hangs down freely,
as in Man, from the pubic arch. In the Cats and many Rodentia
it is directed backward. In the Marsupiata the opening of the
prepuce is even surrounded by the sphincter ani muscle, and in the
Beaver it is so drawn back that the entrance into it nearly resem-
bles a vagina. These relations are occasioned by the prepuce or bag
of the penis commonly investing the organ in such a way, that in
its usual position the penis is retracted within it as in a sheath.
This vagina-shaped prepuce opens for the most part behind the um-
bilicus, and when the penis is long, it lies within the sheath with
either a simple or double S-shaped curve ; this is the case to a very
great degree in the Elephant. In the Hog there lies internally, upon
each side of the prepuce, a small folded ccecal pouch, which is apt to
retain some of the urine as it escapes, and in which calculi easily
form. Animals having the penis directed backward micturate also
in that direction, but during copulation, when it is erected, the pe-
nis stands forward. The suspensory ligament arising from the pubic
arch is in man and most Mammalia feebly developed ; but in large
animals, as the Pachydermata and Solipedia, it is very strong and
remarkable, in order to support the great weight of the penis. In the
orders just mentioned, as also in most Ruminantia and Carnivora,
the prepuce is drawn back from over the penis by a pair of retractor
muscles, which arise from the abdomino-tegumentary muscles ; while
by another pair of retractors arising from the first caudal vertebrae

SEXUAL ORGANS. 59

and the sphincter ani, the penis is withdrawn into the prepuce.
There usually occurs, as in man, a corpus spongiosum, perforated by
a single urethral canal, and two corpora cavernosa divided by a sep-
tum. This last is frequently wanting in the Ruminantia and Cetacea.
In the Kangaroo the corpora cavernosa of the penis and urethra are
blended, and it is here, as in the Marsupiata generally, that the penis
is bifid at the end, corresponding with the double vagina of the female;
the urethra opens in the angle of the fissure, though each apex of the
divided glans is perforated by an opening for the semen. In the
Monotremata also, the penis is perforated by an urethra, though
the seminal canal is, at least in the Ornithorynchus, separated from
the urethra, and gives off two lateral canals for each half of the
glans, which open upon the spines of the latter, by four fine
canals.

There is scarcely an organ throughout the class Mammalia, with
the exception of the teeth, which in the orders, genera, and even
species, exhibits such great and striking varieties as the Glans of
the penis. In some animals, as the Ruminantia, the Hog, and some
of the Carnivora, it might almost be said to be wanting ; for the
slightly developed spongy body of the urethra running to a thin
point anteriorly, the extremity of the urethra or penis can only be
improperly called a glans. It is seldom soft and spongy, as in Man,
but is often covered with hard and pointed epithelial structures. In
some Apes it is mushroom-shaped, even somewhat split, and occa-
sionally provided with horny spines, which are also found in the
Cheiroptera. In the Shrews the glans is hard, horny, and tubercu-
lar, and it is similar in the Hedgehog, being here divided into three
lamelliform lobes; in the Hyajna it is a broad knob; in the Bear
and Dog it is elongated and club-shaped, but smooth ; while in the
Cat it is beset with spines directed backward ; it is deeply slit in the
Marsupiata, and furnished in the Guinea-pig with scales and two
horny hooks, and in Dipus with two long soft spines ; in the Hare it
is small, thin, and pointed ; in Dasyprocta it supports serrato-dentated
plates ; in Castor it is provided with rough tubercles, in the Ham-
sters with hairs, in Phascolomys, &c., with spines. In the Horse it
is bulbous anteriorly, and has a groove inferiorly, where the urethra
terminates, and posteriorly a ridge ; in the Rhinoceros it is bell op
mushroom-shaped, with a pedicle ; in Delphinus delphis it is tongue-
shaped, and in the rest of the Cetacea for the most part acutely coni-
cal ; in the Ornithorynchus its form is particularly singular ; it is
very large, four-sided, divided into two halves, and thickly beset with

60 MAMMALIA.

spines ; in Echidna it is divided into four rounded, perforated extrem-
ities, beset with small tubercles.

The Bone of the penis, which principally belongs to the glans, is
met with in many animals, namely, in the Apes, Cheiroptera, Car-
nivora (even in the Seal and Walrus), many Rodentia, and some
Cetacea, as in the Whales (though its existence has been disputed
by other writers), but not in the Pachydermata and Ruminantia. In
Man, to wit, in the Negro race, where the penis is very largely de-
veloped, there frequently occurs a small prismatic cartilage from one
to two lines in length, as a rudiment of this bone. The bone usually
arises at the end of the fibrous septum, and advances toward the
glans, the tendinous fibres of the septum being attached internally
to its periosteum. Among the Apes, where the bone of the penis is
often very large, it appears to be entirely wanting in the Orangs. In
the Fox and in the Dog-kind it is large, and hollowed out inferiorly
in the form of a groove ; it is very small and thin in the Cat, curved
in the shape of a hook anteriorly in Mustela, and bent in the form
of the letter S in the Rackoon ; it is terminated anteriorly by two
rounded bodies in the Otter, has a small but broad shovel-shaped
extremity in the Squirrel, and is deeply slit in the Marsupiata. This
bone serves obviously to increase the rigidity of the penis during the
act of copulation, which, as is known, is in many animals a pain-
ful operation. The penis has the usual muscles {m. m. ischio-caver'
nasi and bulbo-cavernosi), and in many animals where the penis is sit-
uated in the direction backward, there is found a pair of muscles often
thick-bellied (m. pubcf-cavernosi) arising from the pubis, the tendons
of which are attached to the dorsum of the penis, and seem to
be instrumental, during copulation, in giving the penis an anterior
direction.

The same diversity, which is observed in the Mammalia in ref-
erence to the form of the internal and external sexual organs, is
met with in the foetal envelopes, e. g. in the allantois, the umbil-
ical vesicle and placenta. The latter exhibits great diversities,
which are frequently characteristic of whole genera and families.
Thus, the true Carnivora, such as the Cats, Dogs, Seals, &;c.,
have a girdle or band-shaped placenta, so that the membranes
of the ovum are free at both of its ends or poles. On the
border of this annular placenta, there often appear, as in the Dog,
beautiful green pigmentary deposites. In the Ruminantia the pla-
centa is divided into a great number of distinct round or but-
ton-shaped cotyledons, which are distributed over the whole ovum

SEXUAL ORGANS. 61

and uterus, being separated by considerable intervals. In many Ro-
dentia, a single rounded placenta is indeed present, but it is divided
into several lobes, as occurs occasionally also in Man. In the Apes
the placenta consists of two adjacent divisions. In the Hog the whole
surface of the chorion performs the function of a placenta. There is
no vestige of a placenta in the Marsupiata, which is probably the
case also in the Monotremata.

In Birds and Amphibia, there is found what is called the cloaca,
or the termination in a common opening of the urinary and sexual
organs. In the Mammalia this structure occurs only in the Mar-
supiata and Monotremata. The closest relation of the cloaca to that
of Birds is presented by the latter order, where it is provided, as in
them, with powerful muscles.

REFERENCES

TO

WORKS UPON THE ANATOMY OF THE MAMMALIA, WHICH MAY BE
MOST ADVANTAGEOUSLY CONSULTED IN THE PERUSAL OF THE
TEXT.

General WbrJcs upon Comparative Anatomy.

Cuvier, Lemons d' Anatomic Comparee, 2rde edit- 1835, et seq.

The treatises upon the Anatomy of the several Orders of Mammalia, in
Todd's Cyclopoedia.

Meckel, System der vergleichenden Anatomic, 1821, translated into
French by MM. Riester and Sanson, 1828.

Carus, Introduction to Comparative Anatomy, translated from the Ger-
man by R. T. Gore, 1827.

Blumenbach, Manual of Comparative Anatomy, translated by W. Law-
rence, 1827.

Gurlt, Handbuch der vergleichenden Anatomic der Haussaiigethierci 2
Anfl. Berlin. 1833.

Schreber's Saiigethiere, continued by J. A. Wagner, Professor in Mu-
nich, 1839.

Jones, Animal Kingdom, 1841.

Grant, Outlines of Comparative Anatomy, 1835.

R. Wagner's Icones Zootomica;, 1841, and Carus and Otto's Erlaii-
terungstafeln, 1826.

Tegumentary System.
Flourens, Anatomie Generale de la Peau, Archives du Museum, tom.
3, 1843.

62 BIBLIOGRAPHY.

Eble, die Lehre von den Haaren, Wien, 1831.

Heusinger, System der Histologic, Eisenach, 1824, 2tes Heft. 4to.

Erdl, Ueber den feineren Ban der Haare, in den Abhandlungen der
matliematisch-phjsikalisch Klasse der Alvademie der Wissenschaften zu
Miinchen, Band 3-

Gurlt, Op. Cit. und Hertwig's Magazin fiir die gesammte Thierheil-
kunde, Band. 1, S. 194, Tab. H. HI. (Upon the Sudoriparous Glands.)

Osseous System.

Blainville's Osteographie Comparee, Par. fol. (not yet completed).

Pander und D'Alton, Vergleichende Osteologie, 96 Tafeln, Bonn,
1821—31.

Cuvier, Recherches sur les Ossemens Fossiles, Par. 1834.

Hallman, Vergleichende Osteologie des Schlafebeins, Hannov. 1837.

Leuckart, Untersuchungen liber das Zwischenkieferbein, Stuttg. 1840.

Owen, Upon the Osteology of the Orang, Transactions of Zoological
Society, vols. 1, 2.

Spix, Cephalogenesis, Miinchen, 1842. (Beautiful Plates of the Skulls
of different Animals.)

Oken, Ueber die Bedeutung der Schiidelknochen, 1807.

Vrolick, Ueber den Bau des Schimpanzee, Amsterdam, 1842.

Owen, Osteology of Marsupiata, with Plates, Transactions of Zoologi-
cal Society, vol. 2, p. 379.

Muscular System.

"Wagner's Supplementband zu Schreber's Naturgeschichte der Saiige-
thiere, 1840, contains an interesting comparison of the muscular system
of the Apes with that of Man.

The Myology of the Apes is treated of by Ernst Burdach in the 9ten
Berichte der Anatomischen Anstalt zu Konisberg, 1839.

Ilg's Monographe der SehnenroUen, Prag. 1824,

Ilai)p, Die Cetaceen zoologisch-anatomisch dargestellt, 1837, contains
a description of the muscular system of the Cetacea, particularly of Del-
phinus phocajna. Consult also Stannius, Erster Bericht des zootomisch-
physiologischen Instituts in Rostock, 1840.

S. Meckel, Ornithorynchi paradoxi descriptio anatomica. Lips. 1826, fol.

Nervous System.

Tiedemann, Icones Cerebri simiarum et quorundam animalium rarior-
ujn, Heidelb. 1821.

Tiedemann, Das Hirn des Negers mit dem des Europaers und Orang-
Utangs verglichen, Heidelb. 1837, 4to.

Leuret, Anatomic Comparee du Systeme Nerveux, Paris, 1829, an.
atlas in folio,

Vrolik, Recherches Anatomiques sur le Chimpanzee.

Swan, Illustrations of Comparative Anatomy of Nervous System,
1835-6.

BIBLIOGRAPHY.

63

Longet, Anat. et Phys. du Systeme Nerveux de rHomme et des Ani-
maux Vertebres, Paris, 1842.
Rapp, Die verrichtungen des fiinften Nervenpaars, Leipz. 1832, 4to.

Organs of the Senses.

Soeramerring, De oculorura sectione horizontale, Getting. 1818, fol.
contains excellent illustrations of sections of the eyes of Mammalia.

Bendz, Die Orbitalhaut bey den Haussaiigethieren, Miiller's Archiv.
1841.

Hyrtl, Ueber das Knocherne Labyrinth der Saugethiere in den medi-
cinischen Jahrbuchern des ostereichischen Staates, 1843. (52 genera in-
vestigated.)

Hagenbach, Die Paukenhohle der Saugethiere, Leipz. 1835, 4to.

Berthold in Miiller's Archiv 1838 (upon the ossicle in the stapedius
muscle of many Mammaha).

Hannover, De cartiiaginibus, musculis, nervis auris externse atque de
nexu nervi vagi et facialis, Havnioe, 1839, 4to (numerous details relative
to the external ear).

V. Baer, Isis, 182G (upon the spouting apparatus of the Dolphin).

Jacobson and Cuvier in Ann. du Museum d'Hist. Nat. vol. 3 8, p. 412.

Organs of Digestion.

Mulder in van der Hoeven's Tijdschrift voor naturlijke geschiedenis en
physiologic. Band 2 (interesting details relative to the teeth of the
Narwhal).

Owen's Odontography, or a Treatise on the Comparative Anatomy of
the Teeth, Part I. Lond. 1840.

Erdl, Untersuchungen iiber den Bau der Zahne bei den Wirbelthieren,
insbesondre den Nagem, Abhandl. der physikal Klasse der Akademie de
Wissenschaft in Miinchen, Band 3.

Retzius, Mikroskopiska undersokningar ofver Tandernes, etc. in K. V.
A. Handlingar for 1836, translated in Miiller's Archiv C 1837.

Fr. Cuvier, Des dents des Mammiferes, Paris, 1825 ; and Blainville,
Osteographie Comparee.

Rapp, Ueber die Tohsillen der Thiere, Muller's Archiv 1839.

Grundler in A. Wagner's Continuation von Schreber's Saiigethiem,
Band 5, S. 1728 (detailed description of bursa faucium).

Retzius in Muller's Archiv f. 1841 (upon the structure of the stomach
in the Lemminfr and Field-mouse).

Leuckart in Muller's Archiv f. 1843, uber den Mangel des dritten
Magens bei Moschus Javanicus.

Hennecke, de functionibus omentorum, Gotting. 183G, 4to.

Duvernoy in Ann. des Sciences Naturelles, 1835 (upon the lobes of the
liver in Mammalia).

H. F. Jaeger, Anatomische Untersuchungen des Orycteropus capensis,
Stuttgart, 1837, 4to.

64

BIBLIOGRAPHY.

Organs of Circulation.

Burow, Gefiiss-system der Robben in Miiller's Archiv f. 1838.

Breschet, Histoire Anatomique et Physiologique d'un organe de nature
vasculaire decouvert dans les Cetaces, Paris, 1836, 4to.

Von Baer in den Nov. Act. Pliys. Med. Acad. Leopoldin, torn. 17,
Tab. XXXIX. (description, with beautiful figures, of the ihac plexus of
the Cetacea).

Mandl, Anatomic Microscopique, Paris, 1838 — 43.

R. Wagner, Beitrage zur vergleichenden Physiologic, Heft. 2, Tab. I.

Gulliver in appendix to Gerber's General Anatomy, 1842 (elaborate
researches on the blood) .

Organs of Voice and Respiration.

Wolff, De organo vocis mammalium. Berol, 1812, 4to.

Brandt, Obs. Anat. de mammalium quorundam praesertim quadrumano-
rum vocis instrumento, Berol, 1826, 4to.

Joh. Miiller's Schrift iiber die Compensation der physischen Kriifte am
menschlichen Stimmorgan. Berlin, 1839, fig. 23, 24.

Organs, of Secretion.

Joh. Miiller, De Glandularum secementium structura penitiori. Lips.
1829, fol.

Rapp, in Miiller's Archiv f. 1839.

Brandt und Ratzeburg, Medicinische Zoologie, Band 1, Tab. II. IV.
VIII. ('figures and descriptions of the pouches of Musk-deer, Civet, and
Beaver).

Organs of Generation.

Wharton Jones, on the Ovum of Man and Mammifera, 1843.

R. Wagner's Ic. Physiol. Tab. IL fig. 9. Tab. VI. fig. 1, and Elements
of Physiology, Part I., translated by Robert Willis, M.D. 1841.

Fugger, Diss, de singulari clitoridis in simiis generis Atelis magnitudine,
Berol, 1835, 4to. ^

Morgan in Linnaean Transactions, vol. 16, upon the structure of the
pouch in the Kangaroo.

Treviranus, Beobachtungen aus der Zootomieund Physiologic, Heft I,
1839.

TEGUMENTARY SYSTEM. <S5

CLASS II. AVES.— BIRDS.*

TEGUMENTARY SYSTEM.

As the body of the Mammalia is very generally covered with hair
80 that of Birds is clothed with feathers, which belong, like it to
the epidermic structures. The skin of the Mammalia is much
stronger than that of Birds, for although the larger Wading, Aquatic
Birds and the Ostriches, have a thick hide, yet the corium is
in general throughout the class thin, transparent, and very highly
vascular, from the large follicles of the feathers which penetrate
into the subcutaneous cellular tissue being supplied by numer-
ous vessels. The epidermis is exceedingly delicate upon those
parts of the body where feathers are met with, but dry and con-
stantly desquamating. In featherless parts, as upon the head and neck
of many Birds, it becomes very much thickened, and forms callosi-
ties, wattles, and combs, in which, in addition to the cellular,
what are called the erectile and elastic tissues are often devel-
oped, while at the same time red and blue pigmentary cells occur
beneath the epithelium. Beneath the integument are found, as in
Man, the subcutaneous mucous crypts, which are particularly con-
spicuous, as^ in Aquatic birds, upon the joints of the posterior ex-
tremities. Upon the toes and feet there occur plates and scales of
horny tissue, and both the toes and beak are invested by laminiform
horny sheaths, which may be completely detached from the bony

* Class AVES.

Order I AcciPiTRmK .; Rapapfs $ Diurnae.— Ex. Ea^le, Falcon, Vulture.
uratr i. AcciPixRmA s. Uapaces ^ Nocturnse.— Ex. Owls.

J Ex. All true singing Birds and those which, having no song,
yet possess a complicated interior larynx, as the SpaiTow,
Rook, Shrike, fyc.

{Ex. Woodpecker, Cuckoo, Parrot, Toucan, with those gen-
era which, though related by external characters to the
singing Birds, are devoid of a muscular vocal appara-
tusy viz., Alcedo, Upupa, Merops, Cypselus, Trochilus, ^c,
and constitute the subdivision Picaria?.

IV. Galling. — Ex. Pheasant, Turkey, Partridge, Pigeon.
V. Brevipet^es or Struthiokid.^. ^^^^.j^^*^^''^'^' Ccssatmry, Emeu, Ap-

VI. GRALi/r:. — ^Ex. Bustard, Heron, Snipe, Flamingo.
VII. Palmipedes.— Ex. Divers, Albatross, Pelican, Goose.

5

€6 AVES.

Structures beneath. Occasionally the feathers assume a hair-like
character, as upon the eyelids and base of the bill, e. g. in the Ra-
ven. It is very rarely that true hairs resembling bristles are met
with, as upon the neck of the Turkey.

The epidermic plant-like horny structures of Birds, the Feathers,
are divided into Down-feathers and Contour or Quill-feathers. The
first are delicately soft and flexible, mostly of a gray or grayish-yel-
low color, and lie beneath obscured by the quill-feathers. There are
feathers which are entirely downy, but each quill-feather, even the
large primaries of the wing, has some strips of down at its com-
mencement. The feathers of the neck and trunk form in most Birds
circumscribed patches (ptert/la), which are distinctly defined by
means either of intervals naked or beset with down.

In a perfectly formed Feather, the following parts may be distin-
guished. 1st. The stem {scapus), which forms the principal part of
the feather ; it is cylindrical or fusiform, and is prolonged inferiorly
into the transparent hollow part, the quill (calamus)^ by which it is
attached to the skin. Within the quill is found what is called the
pith, which consists of membranous cones arranged one upon the
other. Externally, vi^here the vane or beard of the feather commen-
ces, the stem becomes medullary, and is then called the Shaft (ra-
chis). This shaft, over the back of which the quill is continued as
a horny investment, is almost always quadrangular, and rarely quite
flat, as in Aptenodytes. The inferior surface of the shaft, namely,
that which is turned toward the body of the bird, is hollowed out
into a groove, and is depressed at the commencement of the quill
into an umbilical fossa, near or from which the accessory plume
(hyporhachis) arises. This resembles the main shaft, in giving off
a bilinear series of barbs, and the two together form an apparently
double feather. It is wanting in the primary feathers of the wing
and tail. It frequently supports merely downy barbs, as in the Gal-
linae, and is occasionally reduced to a single barb, or is wanting al-
together, as in the Owls, many Picariee (Alcedo, Upupa), and Ducks,
&c. From either side of the main and accessory plumes arise
the Barbs which form the vane (yexillum) of the feather. They are
small lancet-shaped lamellae, varying in form, length, and thickness,
in different Birds. In like manner, from either side of the barbs,
proceed the Barbules (radii), which are much more numerous and
complex in their structure than the barbs. Occasionally, like as in
a tripinnate leaf, the barbules are provided again with smaller
accessory barbules, constituting a third series. The barbules are

TEGUMENTAIIY SYSTEM. 67

called, in accordance with their form and function, either cilia or
hamuli. The former, where they occur, as in the feathers of the
Goose, are the most numerous of all the parts of the feather, and
proceed with the hooklets only from the foremost series of barbs ;
they are situated only upon the upper edge of the barb, and stand
either in a double or only a single row. In the barbs of downy
feathers small nodules appear to supply the place of the cilia. The
cilia, like the hooklets, can only be seen with a magnifying power.
The hooklets form likewise lateral processes of the barbs, but are
found only upon their anterior series and upon the inferior side of
each barb. They differ from the cilia by the hook-shaped curve of
their extremities, the hooklets of an anterior series of barbs catching
upon those of the one behind it, so that in this way the barbs are
held fast. This arrangement is of importance for the flight of the
bird, as by means of it the barbs of the feather are prevented from
being torn asunder by the air, which would necessarily injure the
power of flight.

The Contour-feathers are, as a rule, formed in the manner *bove
stated, and have a perfectly-formed and stiff shaft. Their structure
is most complete in the primaries of the wing, and the remigial feath-
ers of the tail. The cilia and hooklets, however, are occasionally
wanting, as in the Ostrich and Nandou (Rhea) ; and in other birds,
as in the Cassowary, the barbs are absent. At the extremity of the
bristles at the angle of the mouth, and upon the chin, and the
eyelashes, the barbs are also wanting, or there is found only a
membranous projection in place of a vane. The remarkably long
spurs of the wing in the Indian Cassowary are shafts without any
barbs.

The Doion-feathers pass occasionally into quill-feathers ; although
they mostly lie concealed, yet they frequently form large freely ex-
posed masses, as upon the neck of many of the Vultures. A down-
feather frequently stands in the middle between four quill-feathers,
and forms with them a quincunctial figure. The true down feath-
ers exhibit an articulated structure, and appear like so many cones
inserted in each other, and exhibit under the microscope, when they
are of a gray color, a particolored appearance like that of the gray
hairs of the Mouse, &c. The broader nodules are black, the inter-
vals between them transparent and colorless. The down-feathers of
nestling and young birds have very delicate barbs, and none, or only
very small, nodose dilatations.

The Plume-feathers (filo-plumae) differ very strikingly from the

68 AVES.

tv\'0 kinds already named, by a very slender stiff stem and a mar-
rowless, transparent, very slender shaft, with very fine round barbs,
not provided with ciliary, nor connected by hook-shaped, barbules.
The barbs are occasionally entirely wanting and then these feathers
resemble hairs. They occur in all birds, but are often easily over-
looked ; they are always associated with the quill-feathers, so that
Upon the head, neck, and trunk, one or two filamentary feathers stand
quite near to each of the quill-feathers, and appear to proceed along
with them from the same tegumentary capsule. It is more rare to
find, as in the Herons and birds of the duck-kind, several, even so
many as ten, filamentary feathers near to each quill-feather.

OSSEOUS SYSTEM.

The Skeleton of Birds presents a remarkable contrast to that of
the other Vertebrata, while, at the same time, nearly all its forms
throughout the class are characterized by a great uniformity.

Oge special peculiarity is met with in the internal structure of the
bones,. which are more or less hollow internally, devoid of mar-
row, and permeated by air. For the latter purpose many of them
are provided with openings, which stand in relation to certain air-
cells of the body (which will be described in treating of the respira-
tory organs), and are filled from tliem with air. As a general
rule, the capacity and extent of these openings throughout the skel-
eton depends upon the size of the bird, and its powers of flight.
Small, thouo-h very rapidly flying birds, have few hollow bones : in
large and very high flying species, they are, on the other hand, most
numerous. In many Birds, all or nearly all the bones are solid. In
several of the bones, there is a predominant tendency over others to
this hollow structure, as is found most frequently the case in the
humerus, cranium, and sternum, but more rarely in the femur, and
very rarely in the bones situated below the elbow and knee-joints.
The bones are filled through one or many openings, which occupy
different situations, according to the genera and species. Thus the
small Passerine birds, many small Grallae and Palmipedes, as the
Snipes, Terns, Moor-hens, <fcc., have no bones for the reception of
air, except some of the cranial, which are always filled with air
from the nose. The most complete want of pneumatic permeability
in the bones is at present to be observed in the Apteryx of New
Zealand, a bird belonging to the order Brevipennes, and which is
destitute also of air-cells. In some of the larger Passerine birds, as

OSSEOUS SYSTEM. 69

the Crows, Shrikes, the humerus is the least hollow. The femur
is far more generally filled with medullary tissue, but in the Diurnal
birds of Prey it is permeated by air as well as the sternum, verte-
brae, ribs, and pelvic bones. In the Owls, the femora of which con-
tain marrow, the cranium is very much elevated by the large and
wide air-cells of the diploe. In the Pelicans very many of the bones
receiA'e air. The air openings are developed to the greatest extent,
however, in the genus Buceros, where, in addition to the cranial and
Maxillary bones, the cervical vertebra?, the pelvis, the caudal verte-
brae (but not the sternum and ribs), and all the bones of the extremi-
ties, even to the phalanges and toes, are permeated with air. As re-
gards their situation, the air-openings are frequently characteristic of
different genera. Thus, e. g. in the Vulture and Falcon, the air
opening in the femur is placed anteriorly and superiorly beneath its
head, as is also the case in the Stork and Picariae, but in the Ostrich,
the Blackbird, and Thrush, it is situated posteriorly; in Buceros
melanoleucos there are two pneumatic openings, one superiorly and
in front of the femur, the second inferiorly and posteriorly. The Os-
trich has the humerus permeable to the air ; in the Cassowary, how-
ever, it is full of marrow, which is the case also in most of the Scan-
sores, Gallinae, Grallse, and Palmipedes. In the Pelican, the Pea-
cock, Bustard, this bone is again found permeable to air. In young
birds those bones which at a later period admit air, are filled with
marrow, which first of all becomes gradually absorbed. Those bones
in the birds' skeleton which convey air differ at the first glance from
the rest by their greater whiteness, and more compact cancellated
structure ; they contain also more earthy constituents.

The Cranium of Birds is peculiar in the early union of its sepa-
rate bones and the complete obliteration of their connecting sutures,
so that a complete bony case is formed, which encloses the brain
and leaves free only the occipital foramen and the openings for the
exit of the nerves. In very young birds, however, the several
bones and their sutures may be distinguished. The occipital bone
consists, as in most Amphibia, of four primary elements, the body,
the two condyloid, and the superior occipital. The articulating
condyle consists of a single round tubercle. The foramen magnum
is sometimes perpepdicular, as in the Gallinae, Grallse, and Palmi-
pedes, e. g. the Goose, but more frequently horizontal, in which
case the posterior part of the skull projects in a vaulted form be-
hind it, as in the Rapaces and Passeres, the Woodpeckers, and
many of the Grallatorial birds. In the Snipe especially it lies very

70 AVES.

far forward and horizontal, so that the cranium is very much
rounded. In the Rapaces, Passeres, and Scansores, as also in
many of the Grallae and Brevipennes, the cranium exhibits, par-
ticularly upon its back part, very smooth convexities, and is devoid
of those singular muscular ridges which occasionally, as in the
Gulls and Herons, form high ridges corresponding in situation with
the direction of the lamboidal suture, and to which the muscles of
the neck are attached. Young birds have a rounder form of skull
than adults. There is found not un frequently situated above the
foramen magnum, and chiefly in the superior portion of the occipi-
tal bone, a considerable opening or fontanelle, filled up only by
ligaments, e. g. in many Grallae and Palmipedes, as the Goose,
Duck, Crane, Snipe, Flamingo, Spoonbill, and Ibis, while this
structure is often wanting in very closely-allied genera. In the
Cormorant (Carbo), at least in the larger species of that genus,
there is situated loosely upon the posterior surface of the occipital
bone, to which it is attached merely by ligament, a long pyramidal
and accessory bone, directed straight backward. In the sphenoid
bone we distihguish a mostly narrow body (spine-shaped anteriorly)
directed forward, as also the alae majores, which confluent with
it at an early period, are perforated by the openings for the fifth
pair of nerves, and give off in the direction outward and downward
a peculiar hook-shaped process, or postero-superior jugal pro-
cessf This process is occasionally very strongly hook-shaped, as
in Buceros. It coalesces occasionally, as in the Gallin2e, with an
inferior process of the same name, coming from the temporal bone,
so that an aperture is thus formed between them. In the Parrots it
is developed to the greatest degree, and projects far forward, so
that in many of the species it coalesces with the lacrymal bone, and
forms an arch beneath the orbits ; this occurs also in Scolopax rus-
ticola. A peculiar pair of distinct and mostly narrow style-shaped
bones converging together anteriorly, which articulate in front with
the palate bones, behind with the ossa quadrata, and often, by
means of a third joint in the middle, with the body of the sphe-
noid, may be regarded as the inferior wings of that bone. These
inferior wings, called by other writers ossa communicantia, exhibit
in other respects many diversities. They are short, and thick in the
Gallinee, most frequently long and style-shaped, as in the Rapaces,
and Passeres, and most of the Grallae, Palmipedes, and Picariae. In
the Woodpeckers they support superiorly a free process. Their third
■ broad articulation provided with a smooth cartilage occurs, e. g. in

OSSEOUS SYSTEM. 7l

the Owls, the Pigeons, Snipes, Goatsuckers, and birds of the Duck
kind, and contributes to the movement of the superior maxillary arch.
The temporal bone consists of a cranial portion which encloses the
organ of hearing, and is formed by the early coalescence of the pe-
trous, squamous, and mastoid portions ; the squamous frequently gives
off an inferior spine-shaped zygomatic process, not connected, how-
ever, with the jugal bone ; the mastoid process is but slighty devel-
oped, and there is moreover an articular portion, the tympanic or os
quadratum. This bone, which is free, and wanting in the Mamma-
lia, occurs constantly in the other Vertebrata, where it often con-
sists of several portions ; it very generally projects superiorly into
two processes, the posterior one of which, the largest, articulates by
a rounded head with the cranium, while the anterior remains free.
Inferiorly it articulates with the lower jaw, inferiorly and externally
with the jugal bone, inferiorly and posteriorly with the lower wings
of the sphenoid. Laterally, and in the direction inward, the os
quadratum gives off a peculiar tympanic process, which helps to
form the posterior wall of the tympanic cavity, and partakes in the
movement of the upper jaw. This process exhibits no inconsider-
able differences in the several orders. The parietal bone, origi-
nally consisting of two halves, abuts anteriorly against the frontal,
which is also double in early life. The latter has often concave de-
pressions or deep grooves, as in the Gulls and many other Aquatic
birds, for the reception of the nasal glands, which here he upon the
edge of the orbital cavity. The ethmoid is occasionally present only
as a single perpendicular plate, which, with the sphenoid, forms
either the closed or more or less perforated partition of the orbits.
This partition is frequently, in nearly allied birds, completely bony,
as in the Stork, or very perforated and membranous, as in the Heron.
The ethmoid, however, frequently exhibits traces of lateral portions,
as in the Passeres, e. g. Corvus, the Rapaces, and many Scansores,
where they are more strongly developed, and abut against the lacry-
mal bone.

As regards the Facial bones, an intermaxillary bone of mostly
large size and single (rarely, as in the Gallinse and Snipes, of small
or minute size), forms the principal part of the upper bill, and
exhibits great diversities of form. Superiorly and posteriorly it is
slit for the reception of the nasal cavities, and sends usually a long,
narrow, flattened process between the nasal bones. In the Parrots
the intermaxillary bone is merely united by ligament to the skull,
and is therefore very moveable, while in other cases the union is

72 AVES.

usually effected by means of a bony suture. The superior maxil-
laries, which are generally small, and removed quite to the sides of
the upper mandible, are united posteriorly by a slender flattened
jugal process to the bone of that name, so as to form a jugal arch.
The nasal bones are flat and mostly of considerable size, lie in front
of the frontals, and give off frequently two processes directed for-
ward, as in the Gallinae, where they are very deeply excavated so as
to present the form of an arch. By means of this excavation in tho
bones, the nasal foramina coalesce posteriorly. Near to and exter-
nally to the nasal and frontal bones, upon the anterior edge of the
orbital cavity, are situated the lacrymal bones, for the most part sep-
arate, and exhibiting great varieties in their degree of develop-
ment, but which are, as a rule, however, very large, and project in-
feriorly into a hook-shaped process. In the Woodpeckers and Par-
rots they are very firmly blended with the skull ; they are very
small in the Gallinae, while, on the contrary, in the Spoon-bill, Al-
batross, and other birds, they abut against the jugal arch, and are
united to it by a ligament which is frequently ossified. In the Par-
rots and Snipes the lacrymal bone forms a ring around the orbit
after it has united with the jugal process of the sphenoid bone.
The lacrymal bone is very much developed in the Diurnal birds of
Prey, where it helps to form the roof of the orbit, and supports ex-
ternally the OS superciliare, which occurs even in the . Ostriches.
The palatal bones exhibit important diversities. They are in
general two elongated slender bones, which are moveably united,
partly together, and partly with the sphenoid (rarely by means of
a suture), but are firmly anchylosed in front with the superior max-
illary bones. They are flat, broad, and horizontal, in the Birds of
Prey ; particularly broad in Caprimulgus ; narrow and not united in
the Passeres, with but few exceptions, such as Loxia coccothraustes,
where they are placed vertically, as in the Parrots ; they are very
narrow, especially in front, in the Gallinae ; wedge-shaped and hol-
lowed out into the form of a groove in many Grallae and Palmi-
pedes, as the Storks and Herons, and anchylosed so as to form a
short tube along with the vomer in Buceros ; in the Goose they are
perpendicular, and so also in the Parrots, where however they con-
sist of much broader laminae^ with a strong free process given ofT
posteriorly and inferiorly ; in the Brevipennes they are anchylosed
by suture with the Sphenoid. Between them lies the vomer, which
is wanting in the Parrots and Gallinae, but which is most strongly
developed in the Palmipedes, and is generally represented by a

OSSEOUS SYSTEM. 73

.perpendicular bony plate. The jugal bone, which is throughout the
class very long, slender, and flattened, consists of two pieces, and
is united posteriorly to the os quadratum by iibro-cartilage, anteriorly
with the jugal process of the superior maxillary by suture, forming
nearly always a straight bridge of bone parallel with the lower jaw.
It is only in the Goatsucker (Caprimulgus) that the jugal bone is
arched in the direction outward to conform with the similarly pro-
jecting posterior piece of the lower jaw. In other instances the
zygomatic arch is very short and strong, as in Buceros, or very slen-
der, as in the Snipes.

The Lower Jaw consists of a single anterior and five pairs of pos-
terior pieces, perfectly analogous to those in the lower jaw of the
Amphibia. They soon, however, coalesce, the anterior pretty firmly,
the posterior pieces completely. Instead of the articulating condyle,
there is found, as in all the Yertebrata below the Mammalia, an ar-
ticulating cavity for the reception of the os quadratum, and which
gives oflT internally and superiorly a kind of coronoid process, and in
the direction backward a frequently long and very much developed
process, as is seen particularly in the Gallinae, e. g. the Grouse. Mi-
nor differences also frequently occur ; thus in Cypselus the lower
jaw is in the form of a very narrow and slender arch, while in the
Parrots it is formed of deep perpendicular bony walls ; in both the
processes are wanting. In the Crow and most Passeres the poste-
rior half of the lower jaw is perforated by a large opening. It is re-
markable that in birds the whole apparatus of the superior maxilla
(supporting the upper Mandible) admits generally of a slight, occa-
sionally even a considerable degree of motion, in the direction up-
ward and forward, which is effected by ihe moveable connexion pos-
teriorly of the palatal, sphenoid, jugal, and quadratal bones.

The different portions of the Vertebral Column in birds exhibit
several peculiar and remarkable arrangements. The number of the
vertebrae not only varies very considerably in the orders, butialso
among the genera and species^ and even in individuals of thie same
species ; the Swan, for example, has generally 23, but frequently
also 24, cervical vertebrae. The relative numbers of the vertebrae
are, however, in general more constant than in the Amphibia. The
cervical vertebrae are always more numerous than in the Mammalia ;
as a rule, there are from 11 — 12 (rarely only 9 or 10), as in most
Rapaces, Passeres, and Scansores birds; 13 — 15 in the Gallinae,
16 — 19 in the long-necked Grallas and Palmipedes, as in the Stork,
Crane, Heron, and also in the Ostrich and Cassowary ; 23 — 24, as in

74 AVES.

the Swan, being the highest number. The atlas is depressed and
ring-shaped, and generally articulates by its capsular surface with
the single condyle of the occipital bone, so that the head can be
freely rotated in a circle upon this joint, and directed completely
backward. In the Ostrich and Penguin a pair of smaller lateral
articulating surfaces are met with, which are directly confluent with
the central articulating cavity of the atlas, and receive two corres-
ponding divisions of the tubercle of the occiput, formed by the lateral
portions of that bone. The second cervical vertebra is deeper, and
has a processus dentatus ; its body is united to the atlas by a single
synovial capsule ; an annular and a straight check ligament are met
with binding the processus dentatus to the atlas and tubercle of the
occipital bone. In Buceros the two superior cervical vertebrae are
blendid together and united into one. The rest of the cervical ver-
tebrae have oblique, transverse, and slightly-developed spinous pro-
cesses, namely, upon the middle part of the neck, and the most pos-
terior have also occasionally inferior spinous processes. The trans-
verse processes are very thick and strong, and have a double root,
so that they form a ring, and in the entire skeleton an interrupted
canal, within which the vertebral vessels and the cervical portion of
the sympathetic nerve are lodged. The bodies of these vertebrae
are very moveable upon each other, concave on their superior sur-
face, convex posteriorly, and are united by free capsular ligaments,
with only very thin intervening cartilages. The superior can be
moved usually more freely in the direction forward, the middle more
backward, and the inferior again forward, whence is produced the
peculiar sigmoid curve of the neck which is visible in the skele-
tons of most Birds. The spinal canal is of various form and width
in the several divisions of the cervical vertebrae, a condition which,
in long-necked Birds, has especial reference to the great degree
of mobility in the neck ; the roots of the spinous processes are also
united, for greater security during the numerous movements of the
vertebrae, by elastic ligaments, an arrangement which, along with
the preceding one, is plainly for the purpose of protecting the spinal
cord during the extensive inflections of the neck. The number of
dorsal vertebrae is in general less, and subject to fewer varieties ;
there are mostly found from 7 — 9, rarely 10, as in the Ostrich, Cas-
Bowary, Goose, and still more rarely 11, as in the Swan and some
Ducks. They are but slightly moveable, and are often, especially
the hindermost, completely anchylosed together and to the sacrum.
This normal state of anchylosis, like that of the sacral vertebrae, was

OSSEOUS SYSTEM. 75

here necessary, from the posterior extremities being brought behind
the centre of gravity of the body. With this view the superior spi-
nous processes are not unfrequently blended together so as to form
a continuous ridge, and in the Flamingo, even the second to the fifth
dorsal vertebrae are completely fused together, and their transverse
and spinous processes have coalesced into a single plate of bone.
The bodies relatively to those of the cervical vertebra? are short,
and more or less strongly compressed laterally, in the Penguins
being quite crest-shaped, while on the contrary they are very broad
in the Ostrich. The anterior usually support strong elongated,
and, as in Eudytes and other birds, disjoined inferior spinous pro-
cesses for the attachment of the recti antici majores muscles. The
lumbar vertebrae are anchylosed with the sacrum and pelvis to form
a single lumbo-sacral bone. The portions however which belong
to the several bodies can be more or less clearly distinguished.
The lumbo-sacral bone is mostly composed of from 9 to 10, or even
more, as 15 vertebrae (many Grallatorial and several Gallinaceous
birds), rarely of 17 (as in the Ostrich), or 19 (Cassowary). The
caudal series of vertebra? exhibits slight differences ; the vertebrae
are here very moveable and few in number, and have for the most
part considerable transverse and superior, as frequently also inferior
spinous, processes. They are hollow even to the last, and form the
canal for the spinal marrow. The last carodal vertebra is always of
a peculiar shape, and has mostly a strong share-shaped spinous pro-
cess arising from it, upon which the remigial feathers of the tail are
supported. This process is absent however in birds which have a
rudimentary tail, as the Struthionidae and Penguins ; on the contrary,
in some of the Scansorial birds where the tail serves as an instru-
ment of support in the act of climbing, as in the Woodpeckers and
Tree-creepers, the body of the last caudal vertebra is very broad, and
supports a peculiar flattened and concave plate.

The number of the Ribs varies in accordance with that of the dor-
sal vertebrae. They always articulate by means of a small head with
the body of a single vertebra near to its anterior border, and with
the corresponding transverse process by their tubercle. Anteriorly
there are situated mostly two, rarely, as in the Cassowary, four false
ribs, generally small, and running to a point, which do not reach the
sternum. The succeeding true ribs are always laterally compressed
and very flat, with the exception of the last rib and the one before
it ; from about their middle there proceeds a strong and elongated
process, which is very seldom moveably united to the rib, as in the

76 AVES.

Cassowary, and which directed backward rests upon the rib imme-
diately behind that from which it springs. These processes are
rarely wanting entirely, or so slightly developed, as in the Emeu of
New Holland, that they can scarcely be perceived. The last, also
the second, as in the Ostrich, but more rarely the three last ribs, as
in Rhea, do not reach the sternum, and correspond thus with the
false ribs in the human subject. The true ribs are united to the
sternum by peculiar long bones corresponding to the cartilages of the
ribs. These, called sterno-costal bones, are moveably articulated
both with the ribs and the lateral borders of the sternum, and are
united at both ends by capsular ligaments.

The Sternum is, of all the bones in Birds, that which exhibits the
most numerous and striking variations, being formed upon a very
special and definite type, which departs widely from that of the rest
of the Vertebraia. It is in general of considerable breadth, and of an
elongated quadrangular form, and upon its anterior surface there is
found arising from the median line a very strongly developed crest
or keel, which is wanting only in the Brevipennes or Struthious
birds, and which serves for the attachment of the great pectoral
muscle. The development of this crest generally stands in direct
relation with the powers of flight of the Bird, and it is accordingly
most large and projecting in the Humming-birds, which though the
smallest in size, are the most rapid flyers. High-flying Birds, such
as the typical Birds of Prey, have a broader sternum, the pos-
terior margin of which is uninterrupted by notches, as in birds of
feeble flight. Anteriorly, the sternum is united with the coracoid
bones, upon either side by a pair of very elongated articulating
surfaces. Between them is usually situated a single median and
often small process, while a similar one projects upon either side from
the outer edge of the coracoid articulation. The greatest number
of varieties are met with in the posterior border of the sternsm, and
which are frequently employed as characteristics of whole families
and genera. There occur here one or several notches (excisur<B
obturatorice) closed only by tendinous membrane, which are either
bounded by long narrow abdominal processes externally, or consti-
tute true openings. As regards the diversities which the sternum
presents in the several orders, it is short and broad, almost entirely
flat or slightly concave in the Brevipennes, with two short abdominal
processes in the Ostrich and in the Apteryx, in which last it is per-
forated in the middle by two openings ; in the Cassowary it is
somewhat roof-shaped. Next to the Humming-birds, the keel is

OSSEOUS SYSTEM. 77

Strongest in the Pigeons, Swifts (Cypselus), and the Pratincoles (Gla-
reola). The keel is very broad in the Crane, from its being hollowed
out to receive a convolution of the trachea. The anterior median
process is mostly furcate in the Passerine birds and also in the Par-
rots, but it is small and undivided in the Rapaces. The sternum is
without any openings upon its posterior edge in Trochilus, Cypselus,
and the Brevipennes. A pair of slight notches is found in Carbo,
Caprimulgus, Podiceps. The Diurnal birds of Prey have simply a
pair of round openings, which in old individuals occasionally dis-
appear. Most Parrots and the Picariae have similar openings, but
a sternum of smaller size. The Passeres have a pair of simple but
often deep incisures, which are still more strongly developed in many
Grallse and Palmipedes. In the Owls there are two small notches
and processes upon either side of the middle of the posterior border,
as also in many Scansores and Picariae, and many of the Grallse and
Palmipedes, where they are often larger. The Gallinae have four
very deep notches, especially the internal pair, and very long abdom-
inal processes, so that their sternum contains the least extent of bone.
In the Pigeons the sternum is similar in character, though the exter-
nal notch is larger. In the Divers (Colymbus) the middle posterior
portion of the sternum is very long.

The Scapular Arch of birds consists of a narrow, somewhat
curved, and long scapula, which covers the ribs posteriorly from
above, and is united anteriorly by fibro-cartilage with the coracoid
bone. The latter, which has been called also the posterior clavi-
cular bone, but which is regarded by some anatomists as an in-
creased development of the coracoid process of the scapula, becomes
broader inferiorly toward the sternum, and is united to the anterior
edge of that bone by a tense capsular ligament. There is found
very generally a second anterior V-shaped clavicular bone, com-
monly called the " merry-thought" bone {furcula), the prongs of
which converging downward and backward, are, with scarcely
any exception, blended together, and frequently project into a pro-
cess, which is United by ligament to the anterior apex of the sternal
keel ; more rarely a joint is formed in this situation which subse-
quently becomes obliterated by the formation of bony tissue. All
these bones exhibit, with the exception of the Struthious birds, no
very remarkable differences. In the Penguin, however, the sca-
pula is very straight, and unusually broad at its posterior extrem-
ity ; in the Woodpeckers it is bent behind in the form of a hook.
The furcula is, in the Diurnal birds of Prey, very much divaricated.

78 AVES.

in other words, strongly arched, its branches standing wide apart
from each other; in the Owls the branches are thinner, and the
whole furcula more Y-shaped ; this being the case in a still greater
degree in the Gallinae, where the process at the angle of union of
the branches is of very considerable size. In the Cuckoo the furcula
articulates with the keel of the sternum ; in the Stork and Heron
these parts are firmly united by syndesmosis, and in the Crane
by actual coalition. In some Owls, Parrots, and in the Rhamphas-
lidiae, the two branches are not united, and in some New Holland
Parrots (Pezoporus) the furcula is either entirely wanting, or in a
very rudimentary condition. The Brevipennes present peculiar
modifications of the scapular arch, for in them the scapula is very
narrow and small, the furcula is wanting or coalesces with the cora-
coid bones, which in the Ostrich are each perforated by a single large
opening, and in the Cassowary are represented by naiTow bony plates.
In the Emeu a rudiment of the furcula is always present, and appears
in the Indian Cassowary as a mere hook-shaped process. The fur-
cula is entirely wanting in the Apteryx.

The Humerus articulates by its broad head with the shoulder-
joint, to which it is attached by a loose capsular ligament and
several strong fibrous bands ; this articulating surface is commonly
formed by the coracoid bone and scapula. The humerus is iH
many of those small birds which are considered powerful fliers, as
the Swift (Cypselus), Humming-bird, very short and broad, pro-
vided with processes, and in some degree resembles the scapula of
the Mole. In the Penguin it is, in common with all the bones of
the arm, quite thin and flattened ; it is very large in the great
Birds of Prey, as Gypaetus, in the Ostrich at least it is much longer
than the bones of the fore-arm, but is small and rudimentary in the
Emeu. The two bones of the fore-arm are generally the longest in
large Birds of powerful flight. The ulna, which is of considerable
size and thickness, has usually a short olecranon at its proximal
extremity, while near to and in front of it lies the far more slender
radius. To these bones succeed two short bones, particularly large
in the Penguin, very rarely wanting, as in the Emeu and Apteryx^
and which represent the bones of the carpus. The metacarpus is
always composed of a single bone, which consists however primarily
in nearly all birds of two distinct pieces, which at a later period in
their existence blend so completely together at their extremities,
that a large elongated space is left between them. The principal
bone is that which, corresponding in position to the radius, is turned

OSSEOUS SYSTEM. 79

mostly directly forward, and forms the metacarpal bone of the middle
finger; the smaller bone directed backward supports on its apex
the little finger, while at the base and from the radial side of the
middle metacarpal, a strong process is met with, which supports the
thumb, and forms the rudiment also of its carpal bone. The thumb
itself mostly consists of an elongated phalanx of considerable size,
which supports the spurious alule or winglet; not unfrequently,
however, as in the Ostrich, the Duck, and Swift, it supports a ter-
minal phalanx provided with a horny covering. The thumb is
wanting in the Penguin. The middle finger is the longest, and con-
sists for the most part of two, more rarely, as in many Palmi-
pedes, the Ostrich, and Emeu, of three joints ; in the last-named
bird a strong nail is met with upon the distal phalanx ; the first
phalanx is a tolerably broad bone. The little finger has in all cases
probably only one phalanx. In this manner the hand of the Bird,
without overstraining the homologies of its constituent parts, may
be readily compared with that of the Mammalia. In some Birdss
which are possessed of great powers, of flight, e. g. Cypselus and the
Humming-bird, the portion which forms the hand is the largest in the
whole skeleton of the arm. In the Penguin, also, the case is very
similar, only the bones here are all situated in a rudimentary wing
which has been converted into a paddle, and are therefore completely
flattened, reminding us of the like condition of the anterior extremi-
ties in the Dolphin. In the Apteryx the hand is still more simple
than in cases where it exhibits only a single three-jointed digit, for
there a solitary phalanx, provided with a claw, is supported by tne
small metacarpal bone, and forms what is called the spur of the wing.
The horny spur in Palamedea, Parra, Charadrius spinosus, and other
birds, is firmly implanted upon a long process of the rudimentary
metacarpal bone of the thumb.

As regards the movement of the anterior extremities in the bird,
the arm is found placed in the position of pronation, and the hand
is not capable of true flexion and extension, but merely of abduction
and adduction, so that the rowing movement of the wings through
the air in flight may be performed in the most eflicient manner.
The curves also of the articulating surface of the distal end of the
humerus, upon which the radius and ulna move, are so diflTerently
arranged, that the two bones of the fore-arm, if flexed and extended
upon each other in the longitudinal direction, would be inevitably
dislocated. The radius acts in flexion by being pushed forward
upon the corresponding small bone of the carpus, by which move-

do

AVES.

merit the hand becomes more strongly bent, or cirawn much more
toward the fore-arm. A peculiar arrangement of ligaments gives to
the arm the necessary degree of security during these complicated
movements.

The Pelvis of Birds is completely closed posteriorly throu^'^h the
union into one of the mostly elongated iliac bones with the lumbo-
sacral bone, but open in front, through the very general want of
union of the pubic bones. The iliac bones are also frequently an-
chylosed to the last ribs and the dorsal vertebra?. The ischium is a
small perpendicular plate of bone extending in the direction down-
ward, and united to the iliac bones, so that the ischiatic notch is
converted into a large foramen situated behind the acetabulum.
The pubic bones are very thin, narrow, and rib-like, run parallel
with the lower border of the ischia, and are usually united with
them over a greater or lesser interval by a narrow ligament, so that
between the two, as in most Passeres and Palmipedes, an often
small but occasionally double obturator foramen is left. Frequent
ly, as in the Birds of Prey, this pubo-ischiadic symphysis is ossified,
so that both bones are united by a broad bridge ; in other birds, on
the contrary, as the Stork and Ibis, the two bones are not immedi-
ately in contact, but separated by a tendinous membrane. A part
of the pubis however extends beyond this symphysis ; the extremi-
ties of the pubis usually diverge strongly, as in many Grallae and
Palmipedes, but they are often expanded and converge considerably,
as in the Diurnal birds of Prey, the Swan, and the Diving birds.
A true pubic symphysis occurs however in the Ostrich, in which bird
alone the pelvis is therefore closed in front. The acetabulum for
articulation with the head of the thigh-bone, is always completely
perforated, the bottom of its cavity internally being merely closed
by ligament. Lesser peculiarities are exhibited in the conformation
of the pelvis by the different orders. In the Penguin however a
singular anomaly occurs, namely, that the hip-bones are not anchy-
losed to the vertebral column, but are rendered to a certain degree
moveable by ligamentous union ; a condition of parts which must
tend to increase the waddling unsteady gait of this bird upon its
hinder extremities, placed, as they are, so far back beneath the body.

The Femur is constantly smaller than the bones below it which
constitute the leg, and is easily distinguished from that of the
Mammalia by a groove upon the tuberosity of its external condyle,
which is converted into a pulley for receiving the articulating head
of the fibula. Upon its head there is a groove for the insertion of

OSSEOUS SYSTEM. 81

a very strong ligamentum teres. The Tibia is always a strong and
very elongated bone, and is characterized in particular by a bony
bridge which proceeds obliquely from its lower end to the external
maleolus, and beneath which the tendon of the extensor communis
digitorum passes. Superiorly the tibia is prolonged into a crest-
shaped process projecting in the direction upward and forward,
above or behind which there lies, as in Aptenodytes, an often large
and misshapen patella. In some Palmipedes (Podiceps, Eudytes),
this process of the tibia is long, conical, and terminates in a point,
and in the latter genus where the patella is wanting, it exceeds
even the femur in length. In Podiceps a smaller, similarly formed
patella lies behind the process. In the Ostrich two patellas con-
stantly occur, situated one above the other. The Fibula is always
very slender, applies itself inferiorly to the tibia, to which it is partly
united, and is frequently continued below into a mere fibro-carti-
lage. The metatarsal or tarso-metatarsal bone very strikingly re-
minds us through its simple condition of an analogous structure in
the Ruminantia and Solipedia. It is strong and of very great length,
projecting inferiorly into three trochlear heads for the three toes,
and is frequently present, especially in the Wading-birds, as the
principal bone of the leg exceeding remarkably the bones above it in
length ; toward its distal extremity a very small adjacent bone is
found provided with an articulating head for the great toe when that
is present ; it is fixed to the tarso-metatarsal only by a ligament. In
the Penguin the latter bone is unusually short and broad, and parti-
tioned by deep longitudinal grooves and interspaces, so that its origi-
nal division into three metatarsal bones becomes thereby indicated,
most birds have four toes, and in that case the large, posterior or
inner toe has constantly two, the next to it, three, the middle and
longest four, and the external toe five, phalanges. When the
great toe is wanting, the remaining digits preserve generally the
above number of plialanges, though several departures from this rule
occur, as in Caprimulgus, where the external toe has four joints,
while in Cypselus all the toes, with the exception of the great toe,
have three.

In Birds there occur more generally than in the other classes of
Vertebrate animals, regular ossifications or sesamoid bones in sev-
eral of the ligaments and muscular tendons, the presence and func-
tional conditions of which frequently characterize whole families
and orders. Thus in most birds the lower jaw obtains its supply
of air from the tympanic cavity by a membranous tube, which, placed

6

82 AVES.

close behind the os quadratum, passes internally thence into the
pneumatic opening in the posterior part of the lower jaw. Now in
the Passerine birds this tube is very generally surrounded by a bony
sheath [siphonium Nitzch), which is absent in the remaining orders ;
in the larger species, such as Corvus, which are provided with a
muscular vocal apparatus, this sheath of bone is very large and con-
spicuous. Another ossicle which constantly occurs in the Rapaces,
Passeres, and Scansores, is called the humero-capsular, from its
being situated within the articulating capsule of the shoulder,
•where it plays by means of a surface invested with cartilage upon
the upper part of the head of the humerus. Frequently among
the Passeres, as in Cypselus, a kind of patella is found in the
tendon of the long extensor of the arm, behind the olecranon ; it
is even double in Aptenodytes, where two large patelliform bones
are met with. Two other sesamoid bones {epicarpium and hypocar-
pium) are situated on the carpus, which serves as a point of attach-
ment to the primaries of the wing. Two ossicles (ossa palato man-
dibularia) are occasionally situated upon the upper edge of the lower
jaw, as in Fulica. In the ligament which passes from the jugai
bone to the lower jaw, one or two ossicles are situated in many
birds. Some others occur also in the lower extremities, as in many
Mammalia.

MUSCULAR SYSTEM.

The muscles of Birds exhibit in general, in conformity with the
whole organization of this class, fewer diversities of importance than
those in the Mammalia and Amphibia. The muscles of most Birds
are remarkable for their deep red color and the density of their tex-
ture. In the herbivorous birds the muscles are of a paler color, and
softer, and their intervening cellular tissue contains a greater quan-
tity of fat, so that the flesh is also more palatable as an article of
food. The mechanical arrangement and position of the muscles is
specially adapted to the performance of the function of flight ; the
fleshy parts of the muscles, or their bellies, are very short and thick,
and concentrated upon the trunk, so as not to encumber the limbs,
the muscles of which lie as much as possible upon the body, and
are extended into long tendons, which exhibit a peculiar disposition,
especially in the posterior extremities, to become ossified to a con-
siderable extent.

The tegumentary muscles which contract the skin are very ex-

MUSCULAR SYSTEM. 83

tensively developed in the present class, as also the muscles which
bristle up the feathers upon the neck and head particularly of those
birds, where they arise in tufts. In the Gallinse a peculiar tegu-
mentary njuscle supports the crop as it hangs down in the neck.
The strongest tegumentary muscles occur in the Apteryx, in which
several distinct layers and fasciculi may be distinguished ; a pro-
vision very necessary to this bird, which scratches deep in the earth,
and must therefore shake its feathers with considerable force to
dislodge the dirt from them. In addition to these muscles in birds,
there are strips appropriated to the feathers, which becoming de-
tached from the tegumentary muscles, form a sheath around the
quill part of each feather where it projects into the skin. They
are wanting generally to the down-feathers, and are in the others
easily overlooked on account of their small size in most birds. In
the larger birds, however, as some of the Palmipedes, e. g. the
Pelican, Goose, and Duck, they are very much developed, each
feather receiving four, more rarely five, small muscular fasciculi,
which can move the feather in all directions, so that in Sula and
Anas, where about 3,000 quill-feathers are reckoned upon the body,
the number of these muscles amounts to 12,000. The muscles of the
great primaries of the wing are the largest. No muscles are found
upon the face of birds, the greatest part of which is covered by
horny substance. The temporal, masseteric and pterygoid muscles,
as well as the depressor of the lower mandible, are strongly devel-
oped, and so arranged, that in acting, they effect at the same time
the movement of the upper maxillary arch and tympanic bones. It
is rare for an asymmetrical disposition of these muscles to occur, as
in the singular cross-bill of the Loxia curvirostra, in which the mus-
cles of the jaws are more strongly developed upon one side than the
other, but always upon that toward which the apex of the lower jaw
is turned up in a state of rest.

As might be anticipated from the great degree of motion and
flexibility of the neck, and the consequent freedom with which the
head can be turned in all directions, the muscles of the neck and
its nape exhibit numerous subdivisions, and are powerfully developed.
The neck, especially when long, can be contorted like the body of a
serpent in the most varied manner, a condition which was essen-
tial to birds, from their jaws having to serve principally as instru-
ments of prehension. The fixed and partly anchylosed condition
of the vertebrae of the trunk afford a strong immoveable point of
attachment to part of the cervical muscles ; while the muscles of

84 AVES.

the dorsal and lumbar region are, on the contrary, less distinct and
much more feebly developed.

The muscles which correspond to the rectus capitis anticus major
et minor lateralis, trachelo-mastoidcus, complexus, hiventer cervicis
(the last, however, being wanting in the Herons), are very large and
powerful.

From the tail serving in Birds, as a very moveable rudder to
steer their course through the air, the muscles which are found up-
on the caudal portion of the vertebral column are very strong and
distinct, and arise from the pelvic and lumbo-sacral bones, which
afford them a fixed point of attachment. By these muscles the
tail itself is elevated, depressed, and lateralized, and by means of
other very powerful fasciculi, which are attached to the proximal
ends of the remigial feathers, these also can be expanded or approxi-
mated.

A great portion of those muscles which lie immediately upon the
trunk, namely, the costal and abdominal muscles (m. m. intcrcostales
externi et intcrni, serratus anticus major, latissijnas dorsi, m. rec-
tus externvs, intcrnus transversus abdominis), are but slightly de-
veloped, and of a very flattened form. The abdominal muscles,
which, though broad and weak are however constantly present, form
«nly a thin covering over the viscera, which are protected for the
greatest extent by the large and expanded sternum ; they have no
transverse tendinous intersections, but are united in the middle by a
broad white line Qinea alba). The rectus muscle of the abdomen
frequently does not pass to the pubis, but blends with its fellow of the
opposite side in the sphincter of the anus.

The diaphragm, which is most developed in the Ostrich, is repre-
sented by small muscular fasciculi, which usually arise by digitations
from the four middle sternal ribs, and are attached to a thin tendinous
aponeurosis, which is spread over the inner and inferior surface of
the lungs.

The pectoral muscles are enormously developed, more especially
the pectoralis major, the fleshy mass of which in certain instances
weighs as much as all the rest of the muscles put together. It
arises from the keel and posterior and external part of the lower
surface of the sternum, and from the furcular bones, and is inserted
into the humerus, and serves to depress forcibly the latter bone, so
as to produce the downward stroke of the wing in flight. Beneath
it there lies a second muscle or pectoralis minor, and beneath that
again a third. In the Ostrich the origin of the pectoralis major iss

MUSCULAR SYSTEM. 85

limited to a smaller proportional extent, namely, about one eighth of
the anterior and outer part of the ^ternum ; it is inserted by a
feeble tendon into the crest of the humerus, which it moves in the
direction forward. In the Penguin and some other Palmipedes the
second pectoral muscle is actually the largest and strongest of the
three, and extends over the whole length of the sternum ; the pec-
toraJis tertius s. coraco-hrachialis inferior is here, also (and panic*
ularly in the Gallinac), strongly developed ; it acts likewise as a de-
pressor of the humerus, and thus these muscles become in birds
which, like the Penguin, use their wings only as fins, no less import-
ant agents in the performance of that function, than in the ordinary
one of flight. The muscles of the shoulder are more feebly de-
veloped ; the deltoid is divided into several portions ; the rest may be
easily distinguished as the analogues of the trapezius, rhomboideuSy
supra spinatus, infraspinatus and suhscapularis of the human sub-
ject. The extensors of the alary membrane (m. rn. extensores pUccB
alaris anterioris) present a peculiar structure ; they consist of sev-
eral short muscular bellies, which arise from the furcular, coracoid
and humeral bones, and give off long slender tendons, one of which,
composed partly of elastic tissue, runs along the free anterior border
of the aponeurotic expansion of the wing, and is inserted into that
portion of it which covers the radial side of the carpal bones. A
similar tendon, only feebler and shorter, lies in the posterior part of
the alary expansion {?n. tensor plica alaris posterioris), and is given
off by a muscle arising from the ribs ; it is inserted by an aponeurosis
into the fascia of the fore-arm.

Birds have in general two flexor muscles of the fore-arm, of which
the biceps is strongly developed, and a single extensor ; they have
also pronators and supinators, but their action is limited to inflexion
and extension of the fore-arm. Long narrow-bellied muscles with
thin tendons are also met with, which adduct and abduct the hand,
as well as move the phalanges of the digits ; they have received
the names oi m. m. extensores et flexores carpi s. metacarpi radiales et
ulnares (Jongus et brevis), m.m. extensores, flexores ^ abductores, adduc-
tores pollicis et digiti medii, &c. The last muscles act only as ex-
tensors and abductors.

The muscles of the pelvis are very slightly developed, and there
are none which might correspond to the psoas, obturator extemus
and quadratus lumborum muscles ; tbe other muscles here situated
may be compared with the iliacus, obturator internus and pectincRus,
In the posterior extremities, from their having to support the entire

86 AVES.

weight of the body, the extensors obtain a manifest preponderance
of size over their opponent flexors, and all take their origin high up
upon the pelvis. Two glutaei muscles (m. gluteeus major ct minor)
may be distinguished, the first of these being of tolerably large size,
and filling up the external concave surface of the ilium ; there
frequently occurs also a third glutaeus muscle. Of the gemelli
muscles the superior one is present. The adductor and flexor mas-
cles, viz., the rectus femoris, the sartorius which is often wanting
e. g. in the Herons, the m. gracilis, hiceps femoris and also the tensor
vagizKB, admit of being readily referred to their respective analogues
in Man.

Such is also the case with the remaining flexor and extensor mus-
cles of the leg and toes, in which a gastrocnemius, tibialis anticus^
peroncBus, fiexcr digitorum longus perforatus et perforans, can be dis-
tinguished, along with special adductors and abductors of the toes.
The fleshy portions of all these muscles are situated high up, arising
from the proximal end of the tibia, or even from the femur, and arc
continued over the rest of the leg, in the form of very long tendons.
They exhibit modifications in the foot according as the great toe is
present or absent, or there is a fifth toe developed, or in relation to
the whole foot, as it may be adapted either for swimming or climb-
ing, &c.

The methods by which the actions of swimming and flying are
performed are subjects belonging rather to the pliysiology and natural
history of birds, and can not therefore be further inquired into in the
present work.

NERVOUS SYSTEM.

The same coverings or membranes can be distinguished in the
Brain of birds as are met with in that of the human subject. The
dura mater, which is of a tough consistence, gives off" ja feebly de-
veloped falx, prolonged from a bony ridge upon the internal surface
of the cranial cavity, between the two cerebral hemispheres. A
strong fold of this membrane forms also a tentorium between the
cerebrum and cerebellum ; and the vascular plexuses of the pia mater
are remarkably developed.

The Hemispheres form a pair of nervous masses usually of the
shape which their name implies, but which are, in some cases, as
in the Grallae, Palmipedes, and also in the Parrots, more elon-
gated longitudinally, than laterally expanded, as in the Birds of

NERVOUS SYSTEM. 87

Prey, while they present in the Pigeons and Passeres a toler-
ably uniform and rounded aspect. Their surface is either quite
smooth, or exhibits only simple inflexions, or several shallow depres-
sions, as in the Parrots. They appear to terminate abruptly be-
hind, so as to. leave the small cerebellum completely uncovered.
The cerebellum, as it is called, would seem to correspond rather
with the vermiform process of that organ in the Mammalia, here
increased in size, and its hemispheres, to a pair of lateral projec-
tions or appendages of the same. This process is divided into a
considerable number of lamellae (20 to 30), which vary in different
genera. A longitudinal section exposes in its interior the arbor
vitae, the ramifications of which vary numerically according to the
genera, they being 9 in Lanius, 11 in the Falcon ; the corpora den-
tata cerebelli are, however, wanting. There is no distinct connect-
ing commissure to the lateral lobes, or pons, its place being supplied
only by some transversal medullary fibres. The corpora quadri-
gemina are represented by a single pair of convex eminences, pre-
senting externally no indicatipns of a further division, and which,
placed tolerably apart from each other, are interposed between the
cerebral hemispheres and cerebellum. They are composed exter-
nally of white or medullary substance, but have internally a large
nucleus of gray matter, enclosing a small cavity or ventricle.
The thalami optici of smaller size are partly united with these bige-
minal bodies, and partly lodged within the hemispheres of the
cerebrum. The corpora striata form a pair of large ganglia. Su-
periorly and posteriorly, in the angle between the cerebellum and
its two hemispheres, the pineal gland is situated as a tongue-shaped
lobule, in general placed quite superficially, though its position in
the Owls is deeper. It is easily removed along with the dura
mater in stripping off that membrane. The pituitary body lies in
a depression of the sella turcica of the sphenoid bone, and is of
considerable size. Of the commissures, the great or corpus callo-
sum is extremely short and small, and the part corresponding with
the fornix is in an equally .rudimentary condition. These parts have
in fact all but coalesced with the anterior commissure, from which
a radiated expansion of medullary fibres may be seen, upon drawing
the hemispheres asunder, to be prolonged into their substance.
Several streaks of gray and white matter lying further back behind
this, correspond to the commissura mollis and posterior, which over-
lie the large valvula cerebelli. The ventricles of the brain are essen-
tially the same as in the Mammalia, only the lateral ventricles have

oo AVES.

coalesced into one with the third ventricle, and are prolonged for-
ward into the olfactory ganglia or mammillary processes, as in most
of the Mammalia. The fourth ventricle communicates as a narrow
slit with the stem of the arbor vitee, and in the direction forward with
the aqueduct of Sylvius.

The Spinal Cord is connected to the brain through the interven-
tion of a well-developed medulla oblongata ; it is cylindrical through-
out, has an anterior and posterior tissure,*and a narrow central
canal which extends throughout its entire length. There is a
swelling upon the anterior extremity of the cord corresponding with
the origin of the brachial plexus of nerves ; another of larger size
is situated within the lumbo-sacral bone, and accords with the origin
of the nerves to the posterior extremities, while at its commence-
ment the lateral columns of the spinal marrow diverge so much as
to form a kind of groove, termed from its figure the rhomboidal sinus,
and which, communicating with the median canal of the cord, is
covered by a very soft gelatinous transparent substance, consisting
of an assemblage of delicate white cells permeated by blood-vessels.
The spinal cord then becomes narrower and is prolonged into the
canals of the caudal vertebrae.

The twelve cerebral pairs of nerves in the class of Birds can be
readily referred to their types in the human subject. The nerves
of smell take their origin from a special swelling or olfactory gang-
lion. The optic nerves are always of very large size and cylindri-
cal, and form a complete union or chiasma, which consists in gene-
ral of eight nervous fibrils, that decussate each other. The fifth pair
is very conspicuous, and the larger or sensitive root has a Gasserian
ganglion upon it. Its first or ophthalmic division combines with
a branch from the oculo-motor, or third pair of nerves, to form a
large ciliary ganglion, from which is given off directly the ciliary
nerve supplying minute filaments to the iris. No connexion of this
nerve with the sympathetic has been observed ; a fact which is the
more interesting, from the relation which it probably bears to the
voluntary power possessed by Birds over the movements of their
iris. From the ophthalmic division of the fifth a branch proceeds
also to the Harderian gland, another to the nasal organs, while a
third ramifies upon the beak, so that this nerve is more extensively
distributed than in the Mammalia. The second division or supe-
rior maxillary nerve is particularly large in the Ducks and Geese,
and ramifies in the upper mandible beneath its marginal lamellee
and the mucous lining of the palate ; branches also arise from it to

NERVOUS SYSTEM. 89

supply the eyelids and lacrymal gland. The course of the inferior
maxillary or third branch of the fifth is very simple, entering the
canal of the lower jaw, and ramifying, as may be most distinctly
seen in the Duck, beneath the horny texture of the mandible ; it
gives off no gustatory branch to the tongue. The small root of the
trigeminal nerve passes over the ganglion, and distributes twigs, as
in the Mammalia, to the manducatory and hyoid muscles. The
third, fourth, and sixtn nerves correspond with those of the Mam-
malia, and supply the muscles of the eye ; their mode of origin
from the brain is the same as in Man, and their cerebral roots ad-
mit of being easily traced. The large muscles of the nictitating
membrane are supplied in birds by nerves from the sixth pair, or
abducens. The seventh pair, or portio dura, is, as might be pre-
mised from the absence of facial muscles, only feebly developed, and
as usual united with the portio mollis or auditory nerve. The
eighth, or glosso-pharyngeal, is more remarkable, and differs in
several important relations from the same nerve in Man and the
Mammalia. It is more intimately united than in them both in its
origin and course with the nervus vagus, and gives off, in common
with the latter, several branches to the pharynx and upper part of
the larynx, parts which in the Mammalia are supplied from the ner-
vus vagus only. The most important branch however of the
eighth is the largest, which is distributed to the tongue, and may be
traced in birds of a delicate sense of taste into the papillae of that
organ, serving unquestionably in such cases to the exercise of the
gustatory function. At all events, this nerve, as well as the vagus,
is of a mixed character, being both motor and sensitive. The va-
gus gives branches to the muscles of the tongue, descends the neck
by the side of the jugular vein, and forms plexuses, from which
branches proceed to the pharynx, lungs, stomach, and proventriculus,
while recurrent branches are distributed to the muscles of the inferior
larnyx. The nervus accessorius soon unites within the cranium with
the vagus. The hypoglossal nerve, or ninth pair, arises by two roots,
and gives branches to the muscles of the tongue, which are particu-
larly developed in the Woodpeckers, and others of large size, to the
sterno-tracheal muscles.

The brachial plexus is formed in birds by the two last cervical and
two first dorsal nerves. The nerves of the lower extremity proceed
from an anterior and posterior plexus, that of the lumbo-sacral nerves
forming the ischiatic nerve. The number of spinal nerves generally
corresponds with that of the vertebrae.

90 AVES.

Communications may be traced between the cranial portion of the
Sympathetic system and most of the cerebral nerves. The superior
cervical ganglion is of considerable sizei The remainder of the main
trunk of the sympathetic then enters the uppermost cervicle verte-
brae by the canal formed by their double transverse processes,
communicates with the corresponding spinal nerves in that situation,
and forms ganglia upon the vertebral vessels. It next issues from
this canal, and is continued over the brachiaPplexus, to which other
ganglia developed in its course are very firmly attached, and at
length enters the thoracic cavity, where it becomes of very large
size and forms a ganglion in front of the head of each rib ; two
nervous filaments from each ganglion, one passing above, the other
below the neck of the rib, serve to bring into communication contig-
uous ganglia. The branches from the thoracic ganglia give off the
splanchnic nerve, which forms an aganglionic caeliac plexus accom-
panying the gastric and intestinal arteries, but passing chiefly to the
muscular parietes of the gizzard and to the liver. The nerve is then
prolonged to the caudal vertebrae, where it terminates in a series of
small ganglia.

ORGANS OF THE SENSES.

Organs of Vision.

All Birds, without exception, are provided with a perfect and well-
developed visual apparatus. The eyes are always of great size,
being largest and most prominent in the Owls, flattened and smallest
relatively to the size of the head in the Natatores. They are but
slightly moveable, and are situated in orbitar cavities circumscribed
superiorly and laterally by bone, which are separated in the
cranium from each other by a thin osseous plate, frequently perfo-
rated to such an extent as to leave only an intervening membranous
partition. The globe of the eye, the form and component parts of
which may be recognised upon a perpendicular section, is convex
posteriorly, more flattened in front, or, as in the Owls, elongated into
a round cylinder, and in such cases provided with a very prominent
cornea. The very dense and tough sclerotic coat is supported by a
series of bony plates interposed between its two fibrous layers, and
united so as to form a continuous circular chaplet embracing the
posterior part of the eyeball as far forward as the margin of the
cornea ; their number consists mostly of 12 — 15, and they partially

ORGANS OF VISION. 91

overlap each other so as to admit of a slight degree -of motion.
These osseous plates are most largely developed in the Owls, as the
horned species or Hibous, where they form a cup-shaped ring of
remarkable depth, and are usually as long as they are broad. The
cornea is in general highly convex, to the greatest degree in the
Birds of Prey, and least in the Natatores. The anterior chamber
of the eye is very large, and contains an abundant quantity of
aqueous humor, so that the iris is very far removed from the cornea.
The choroid is provided upon both its surfaces, especially the inter-
nal or retinad, with a dense and black layer of pigment. It is
attached in front and externally to the sclerotica by a dense white
ciliary ligament or zone, from which fasciculi proceed to the iris and
largely plicated ciliary processes. These fasciculi, like the fibres
of the iris, exhibit under the microscope the transverse striae so
characteristic of voluntary muscular tissue. Between the folds of
the ciliary ligament is situated the canal of Fontana. The iris
presents numerous shades of color, but is never of a metallic hue ;
the yellow color of the iris, e. g. in the Owls, being due to the pres-
ence of distinct racemoid follicles or cells which contain a fluid fat.
The pupil, which can be voluntarily contracted and dilated by the
movements of the iris, is always round. The optic nerve perforates
the posterior part of the globe of the eye by a slightly excentric elon-
gated fissure. The retina presents a well-developed papillary or
nervous layer, and the vitreous humor, which is in considerable
quantity, exists in a semi-fluid condition. The variously-shaped but
never spherical lens is generally more convex upon its posterior
surface.

A peculiar mechanism is met with in the eye of birds, which
has been called the pecten or marsupium. This organ, which is
more or less quadrangular, and varies in length and breadth, con-
sists of a plicated membrane invested like the choroid (from which
it is a production corresponding in structure) with a layer of black
pigment, and projects forward from the fissure of entrance of the
optic nerve into the vitreous humor, frequently, though not always,
reaching as far forward through the apex of its longest fold, as
the posterior surface of the capsule of the lens. It is very richly
supplied with blood, by an arterial plexus given off from a ra-
muscule of the ophthalmic artery, which corresponds to the arteria
centralis retinae. The form and number of the plications of the
marsupium vary remarkably in the several genera and species,
and even in individuals of the latter. In thtf Ostrich and Casso-

92 AVES.

wary the folds are acutely angular like those of a fan, though in
other cases they are generally rounded off. Nocturnal birds have
in general the fewest number of folds, e. g. the Owls from 5 to 6,
the Goatsuckers 5. In the greater proportion of birds from 14 to 15
occur. The folds are most numerous in the Passeres, where they
amount from 16 to 18, and 22, or even 28, as in Corvus. In Diurnal
birds of Prey, there are from 14 to 16 ; in the Gallinse 16 to 18, and
in most Palmipedes only 9 to 12. The pecten in the Ostrich is pro-
vided with 15 or 16, in the Cassowary with 4 or 5, and with 18 folds
in the Humming-bird.

The function of the marsupium is unknown. It can not in any
way contribute, as has been suggested by some anatomists, by the
alternate contraction and dilatation of an erectile tissue to alter and
adjust the focal distance of the lens within the eye ; this power, which
is possessed to a considerable extent by birds, being probably ef-
fected by the conjoined action of the muscular and very mobile
structures of the iris and ciliary ligament, by which the position of
the lens may be shifted. The whole form of the eyeball is very
admirably adapted for the exercise of this function, through the large
size of its anterior chamber, and the quantity of aqueous humor con-
tained therein.

A remarkable exception to the great uniformity of structure which
the eye exhibits throughout the present class, is furnished by that
singular bird of New Zealand, the Apteryx australis. The marsu-
pium is here entirely wanting (and so far as is known this is the
only instance of the absence of that organ among Birds), a condition
which may be probably associated with the perfectly nocturnal habits
of this species, and its limited range of locomotion. The optic nerve
enters the eye by a small round opening, and the globe of the eye is
in proportion to that of other birds of very small dimensions ; the lens
also is small, and very convex.

The eye of Birds is moved by four recti and two oblique muscles ;
the trochlea or pulley for the tendon of the superior oblique muscle
is however wanting, and all the muscles are proportionally very short.
All birds have three eyelids ; a superior which is the shortest ;
an inferior the largest and most moveable palpebra, provided with
a tarsal cartilage, and a third situated in the anterior angle of the
eye, which is very moveable, and called the nictitating membrane.
The orbicularis palpebrarum muscle, which is most strongly de-
veloped in the Apteryx, is inserted into the tarsal cartilage, and
when it acts draws tlfe lower eyelid in the direction upward. The

ORGANS OF HEARING. 93

levator palpebrac siiperioris arises from the roof of the orbit, and is
inserted near the external canthus of the lid. Both the upper and
lower eyelids are provided with short feather-like bristles, as eye-
lashes. The nictitating membrane can be swept by a very peculiar
mechanism over the whole anterior surface of the eye. The muscu-
lar structures by which this is effected may be best studied in the
eye of the Owl. A very broad, flat, thin, and quadrate muscle (m.
quadratus mcmb, nictitantis) is situated upon the back part of the
globe of the eye, and arises from the superior and posterior margins
of the sclerotica. Its fibres descend toward the entrance of the optic
nerve, and terminate in a free concave tendinous canal. A second
muscle {m. pyramidalis memb. nictitantis) has a short narrow belly
which arises from the inner or nasal aspect of the eyeball, and gives
off a long slender tendon, which, as it turns round the optic nerve,
passes through the canal formed by the tendon of the quadratus, and
is inserted into the lower margin of the third eyelid, which by the
contraction of this muscle is drawn like a curtain in front of the
globe of the eye. In the Owls a small ossicle {ossiculum tuherculare)
is situated upon the inferior surface of the bony ring of the sclerotica,
to support the long tendon of the pyramidalis muscle.

Birds have very generally a lacrymal gland situated in the posterior
angle of the eye, two excretory ducts, and a membranous lacrymal
canal leading into the nasal passages. The Harderian gland, which
has been already alluded to (p. 2C) as occurring in many Mammalia,
is much more largely developed in Birds than the lacrymal gland,
and especially in the order Palmipedes, as the Goose and Pelican.
It is situated upon the anterior or internal angle of the eye, and
through an excretory duct which opens upon the inner surface of the
nictitating membrane, pours out a viscid secretion to moisten and
lubricate the latter.

Organs of Hearing.

The Organs of Hearing in Birds admit of being easily demonstra-
ted, from the very superficial position which the labyrinth occupies
in relation to the bones of the cranium.

An external ear or auricle is wanting, and it is only a {e\v spe-
cies, such as the Owls, which have a large membranous crescentic
fold or auditory conch, provided with tufts of short feathers, and
which can be used as a valve. The largest ear-conch is met with
among our indigenous Owls in the long-tufted Hibou (strix otus)»

94 AVES.

The external auditory meatus is short, and completely formed by
bone posteriorly, where it forms a conchiform expansion. The mera-
brana tympani large and consisting of several lamellce, is directed ob-
liquely backward and inward, and differs in form from that of the
Mammalia, by being stretched so as to be convex or infundibuliform ex-
ternally toward the meatus, instead of internally, as in the human
subject. The tympanic cavity is spacious and irregular, and re-
ceives the orifices of the two mostly osseous Eustachian canals
which nearly coalesce together at their faucial extremity into a com-
mon opening. Other small apertures conduct from this cavity into
the osseous cells of the surrounding bones, which correspond to the
cells of the mastoid process, and occasionally extend over the whole
cranium. The walls of the tympanic cavity are not truly closed, but
communicate directly with all the cranial bones, and even with the os
^uadratum.

A veritable chain of auditory ossicles may be distinguished, one
of which is style-shaped and bony, while the two others remain in a
cartilaginous condition. The external of these cartilages, corre-
sponding to the malleus, is mostly of a triangular shape, perforate,
and provided frequently with a long process, abuts against the mem-
brana tympani. The second internal but smaller cartilage may be
frequently detached from the malleus, which it serves to unite with
the stapes or columella ; it may be regarded as the rudiment of the
incus. The principal bone is the long styliform analogue of the
stapes, the columella or bacillus ; its base expands into a broad oval
plate which is lodged in the foramen ovale, and through this the son-
orous impressions are transmitted to the aqueous fluid of the laby-
rinth. More frequently the columella is found to be broader inferi-
orly, and by being provided with two crura, to assume its character-
istic stirrup-like figure, as is the case in the Pelican, Raven, &c.,
where it resembles the stapes of many of the Mammalia, e. g. the
Kangaroo.

Only a single muscle can be detected for moving the auditory os-
sicles ; this would seem to correspond to the laxator rather than the
tensor tympani, the nominally implied action of the latter muscle
upon the membrana tympani being usually effected by the elasticity
of the malieal cartilage. The muscle in question arises from the
posterior part of the tympanic cavity, and is inserted into the malieal
cartilage, expanding also in a tendinous manner upon the membrana
tympani.

The Labyrinth consists of very compact bony parietes, but ia

ORGANS OF HEARING. 95

surrounded by a very loose osseous tissue, so that it may be readily
exposed for examination. The vestibule is very small, while on
the other hand the semicircular canals are large and vary in size ;
being slender, elevated and broad in the Rapacious and Passerine
birds, but depressed and thick in most of the Grallae, Palmipedes,
and Gallinae. The vertical canal from the depth of its arc is appa-
rent at once within the cranial cavity, without any previous prepara-
tion, and is directed inward and forward. The two others, which
are directed externally and posteriorly, cross each other completely ;
the external or horizontal canal being the smallest. In the direc-
tion forward there projects a slightly-curved osseous cone, with the
concavity directed downward, inward, and somewhat backward,
which represents the cochlea, although it is not spirally twisted like
that organ. The foramen rotundum, which is small and closed by
a kind of secondary tympanic membrane, is here met with, and serves
to bring the cochlea and vestibule into functional communication
with each other. The foramen ovale is in Birds also round, but
larger than the f. rotundum, and is closed by the basi-opercular plate
of the columella.

A mucous membrane is found lining the bony labyrinth ; the tubes
of the semicircular canals dilate into ampullae, the external of which
is the least developed, while the anterior and posterior are supported
by a cruciform septum, and it is upon the bulging prominence of this
septum that the auditory nerve expands. These dilatations are visi-
ble at once upon opening the cavity of the labyrinth. The cochlea
contains internally, as in the squamigerous Amphibia, two curved
cartilaginous lamella3 of a triangular form, united by a delicate
membrane ; upon this lies another plicated and very highly vascu-
lar membrane, which gives off a sacciform expansion, called the
Utricle (lagena), into the round terminal dilatation of the conical
cochlea. One of these cartilaginous lamellae (the vestibular) is
fringed with dento; a processes, the number of which differs in the
several genera. The other or tympanic cartilage is situated in the
direction backward, and faces the foramen rotundum. A branch
of the auditory nerve enters the cochlea upon the external side of
one of these cartilages, expands and perforates it by numerous fila-
ments, which are distributed upon the membrane connecting the two
cartilages, and analogous to that covering the lamina spiralis in the
higher animals ; a branch is also given to the utricle. • In the
membranous sac of the vestibule, which is double, being divided by
a thin septum, pulverulent masses of crystallized phosphate of lime

96 AVES.

(otoliths) are found, as in Man and Mammalia. The diversities pre-
sented by the auditory apparatus in the several orders and genera'can
not be entered upon in a work like the present. The Struthious
birds appear to agree essentially with the other members of the class
in their organs of hearing, only their conical cochlea is the smallest
in size in proportion to the other parts.

Organs of Smell.

The ethmoid bone in Birds forms an osseous plate of considerable
size (frequently interrupted by an aperture closed with membrane),
which is interposed between the orbitar cavities, and presents
generally rudiments of lateral parts. This bony septum is completed
in front by cartilage. The nasal cavity is remarkably large ; a
proper external moveable nose is, however, wanting, and the nostrils
are situated upon the upper mandible near to the base of the bill,
being wide and distinctly visible ; but in rare instances, as in the
Booby (Sula alba), they are so narrow that they have been errone-
ously believed to be wanting altogether. Cartilaginous but immove-
able nasal alae are for the most part present, and occasionally, as in
the Albatross, Petrel, and Puffin, elongated into a tube which may
be regarded as an external nasal organ. The nostrils vary in form
and size, and are frequently, as in the Raven, protected with feather-
like bristles. The two nostrils are separated from each other by a
septum, which is wanting however in many birds, e. g. the Gallinazo
(Cathartes), so that they intercommunicate from either side. The
posterior nasal orifices {choaneB) are two long narrow fissures fre-
quently coalescing into one, at the commencement of which in the
palate are usually found some epithelial papilla?. Within each
nasal cavity are situated three cartilaginous, rarely partly ossified,
turbinated bones ; the superior of these is formed by a simple
spheroidal or bell-shaped inflexion of the lateral cartilaginous pa-
rietes of the nasal cavity ; the inferior frequently consists of a
small curved plate provided with lateral projections, which adheres
to the septum narium and is often largely developed, as in the Snipe,
where it is represented by a falciform lamina. The middle one,
which is the largest in size, is to be regarded as a true turbinated
bone, being constantly a perfectly convoluted cartilagino-membran-
ous plate varying in its degree of development. Among birds of
the Duck kind, its convolution makes two and a half turns, in the
Gallinse only one and a half ; accessory nasal cavities or sinuses are

ORGANS OF TASTE. 97

rarely met with, though in Anas clangula true frontal sinuses are
found extending over the whole upper part of the cranium. The
nasal cavities are lined by a very vascular mucous membrane. The
olfactory nerve ramifies in a radiated manner upon the septum narium
and superior turbinated bone only, the two inferior ossa turbinata
receiving filaments from the fifth pair.

A peculiar Nasal Gland for lubricating the surface of the pitui-
tary membrane of the nose is very generally found, being rarely
wanting, as in the Pigeon, Cuckoo, and Woodcock, and is often very
largely developed. It exhibits very great diversities throughout the
orders and genera ; in many Birds, as the Palmipedes, e. g. Eudytes,
Alca, Diomedea, and in Charadrius, it lies in a deep coecal depression
upon the frontal bone, which is narrower and flatter in the Gulls and
Puflins. The gland is of a crescentic shape in most Birds, as the
Passeres, Gallinae, Owls, many of the Grallae and Palmipedes, and
situated in depressions above the obtuse supra-orbital ridge ; in the
Bustard it is placed near to the superior turbinated bone ; in the
Rapacious and some of the Wading-birds, as the Heron, it is lodged
in the upper part of the orbit, but very rarely, as in the Woodpeckers,
in its lower part beneath the eyeball. The two nasal glands often
form, as in Charadrius, large cushions upon the forehead, and in
these cases the excretory duct perforates the groove of the frontal
bone anteriorly, and is continued onward upon the external wall
of the nasal cavity. The Ostriches have a nasal gland, but only
slightly developed.

Organs of Taste.

Covered for the most part by a hard and dense epithelium,
and having only upon its root some softer sensitive papillae supplied
by branches of the glosso-pharyngeal nerve, the Tongue is obviously
but ill adapted to serve as a very refined instrument of taste ; still
however the extent to which this function is enjoyed varies in many
Birds.

Setting aside, as belonging rather to the special province of Orni-
thology, a detailed description of the great diversities of form and
structure which this organ presents in the several genera of Birds,
we shall be content with only noticing here some of its most striking
modifications. It is of moderately large size, but hard and horny
in the Rapaces, Corvidae, &c. ; short, thick, subcylindrical, and soft
in the Parrots, where alone it is frequently provided with small soft

7

98 AVES.

and filamentary papillae. Other Parrots, as the Lorikeets (Tricho-
glossus), are furnished with an extensile tongue terminated by a pen-
cil of hairs (whence the generic name), adapting them admirably
for feeding upon the nectar of flowers. In the Woodpeckers the
tongue is very long, slender, and vermiform, and beset with small
retroverted hooks. In the Humming-birds it is also very long and,
as in many other birds, deeply slit at the apex, but each half is in
them hollowed out into the form of a groove, so that the two divi-
sions when approximated form a tube, which serves as a syphon for
pumping up the nectar from the flowers. The tongue is in the
Flamingo exceedingly large, angularly curved, and fleshy, or rather
provided with an abundant cellular and adipose tissue (upon which
account it was esteemed by the Roman emperors as a savory arti-
cle of food), and its upper surface is covered with recurved spinous
papillae. It is, on the contrary, extremely small and rudimentary
in the Picariae and Auks, and even more so in the Pelican and Gan-
net (Sula), where in fact the styliform and slightly curved hyoid
cartilage covered by the mucous membrane of the mouth is all that
can be detected, so that a proper tongue may be said to be completely
wanting. In the Tenuirostral and Passerine birds generally, the
greater part of the gustatory organ is horny with acute lateral mar-
gins. Frequently, as in the Toucans (Ramphastos), it is comb or
brush-shaped upon either side, from being provided with horny frin-
ges. There is found within the substance of the tongue posteriorly
a usually double, rarely single, cartilaginous or frequently osseous
body [os linguale, ossa entoglossa Nitzcli), which abuts against the
hyoid bone, and forms at the same time the apicial portion of its
body. In the two-toed Ostrich (Struthio camelus) this lingual ossicle
coalesces with the hyoid bone, and in many Birds consists of an ante-
rior and posterior division.

The Os hyoides consists of an elongated and narrow body, which
usually extends posteriorly into a short pointed, or longer filamen-
tary cartilaginous portion, and has upon the middle of its sides or
more posteriorly a pair of articulating surfaces for the lesser cornua.
These are often very long, and formed of an anterior thicker osseous,
and a posterior slenderer piece, which is more or less cartilaginous,
and terminates in a filamentary manner. In the Woodpeckers and
also in the Humming-birds peculiar modifications are exhibited in
the arrangement of the above parts ; in them the cornua of the os
hyoides are exceedingly long and slender, and continued round the
skull beneath the skin to the base of the upper mandible, where their

DIGESTIVE SYSTEM. 99

extremity is inserted in a groove above the nasal apertures; by this
contrivance the tongue admits of being projected far out of the mouth
to nearly the length of the body, and thus constitutes a most efficient
implement for either spearing rapidly their insect food, as is the case
with the Woodpeckers, or, as in the Humming-bird, for probing in
search of nectar to the bottom of tubular flowers.

The tongue, together with the hyoid bone that supports it, is
moved by- three to four pairs of muscles, which correspond to the
genio- stylo- and sterno-hyoid muscles in Man ; besides which
there is an additional pair of very short muscles. All these are
remarkably developed in the Woodpecker ; where we meet also
with a singular pair of muscles, called cerato-tracheal, which arise
from the trachea about half an inch beneath the superior larynx, wind
several times spirally around it, and are inserted into the terminal
portion of the hyoid cornua ; they serve chiefly to forcibly retract the
tongue. The most complicated condition of lingual muscles occurs
in the Parrots, from their being the only Birds that truly chew their
food. The usual number of muscles is here increased ; the most im-
portant being the mylogJossus, which retracts and bends the tongue
in the direction downward.

Organs of Touch.

The tongue serves frequently in Birds for an organ of touch, as
in the Woodpeckers, where it is darted into the chinks and holes in
the bark of trees in search of the larvae of insects. Many Nata-
tores, e. g. the Ducks and Geese, and the Flamingo among the GralljB,
hsf\'e the upper mandible soft and profusely supplied with nerves
from branches of the fifth pair, so that they possess a delicate tac-
tile sensibility in that part which enables them in stirring up the
mud with the bill in quest of food to appreciate more readily its
presence. An apparatus of touch is also developed at the apex of
the Snipe's bill, which is provided for that purpose with numerous
osseo-cellular depressions.

DIGESTIVE SYSTEM.

The superior, inferior, and intermaxillary bones of the Bird are
generally invested by horny sheaths, which form in the several
orders and families a beak of very varied character, the modifications
in the structure of which are commonly depicted in Zoological works.

100 AVES.

It is in the Parrot-tribe alone that the horny mandibles perform the
functions of a proper instrument of mastication ; for, as a rule, they
are adapted only for seizing and retaining the food within their grasp..
The peculiar degree of mobility of which the superior maxillary arch
is capable in Birds, has been already alluded to in speaking of their
skeleton. The jaws are moved by several muscles (see Muscular
System) analogous to those of the Mammalia.

In place of the velum palati, we find near to the opening of the
posterior nares within the faucial cavity-, tubercular elevations of epi-
thelium, or dentated ridges similar to those upon the root of the tongue
and the margins of the glottis, and behind these are situated glan-
dular follicles, which have been regarded by some as analogous to
the amygdalcE or tonsils. These follicles are frequently aggregated
into a thick glandular layer, provided with numerous excretory open-
ings, as in the Birds of Prey, while in others of the class Aves e. g.
^the Cormorant (Carbo) they are altogether wanting.

The CEsophagus is always very muscular, slightly plicated inter-
nally, and iexpands in many Birds usually below its middle and in
front into a sacciform pouch called the crop, craw, or ingluvies.
This is commonly of a thin membranous texture, provided internally
with small mucous glands, and when distended with food hangs down
in the neck in front and between the branches of the furcula, and, as
in the Gallinae, is there supported by a special muscle. The crop is
found in all the Diurnal birds of Prey, but it is only feebly indicated
in the nocturnal Rapaces or Owls ; it is of large size in the Parrots,
particularly so in the Gallinae and Pigeons, and more rarely in the
Grallae and Palmipedes, as in the Flamingo (Phaenicopterus). The
craw is extremely large in the Pigeons, and during the period *of
incubation obtains in both sexes a remarkable degree of vascularity,
its lining membrane becoming, at the same time, developed into a
network of folds and cells, which form two large laminiform layerSj
that secrete and pour out into the crop a creamy or lacteal fluid ;
with, this alone, discharged from the crop of the parents, the young
are at first fed, but at a later period of their existence it is mingled
with grain, that has been macerated in the ingluvial secretion.
The craw is generally wanting in the Struthionidge, with the excep-
tion of the Cassowary, and also in the Scansores and Passeres,
where the oesophagus is frequently much expanded and even wider
than the proventriculus. In rare instances, as in the Pelican, there
occurs an additional expansion of the gullet which is situated between
the rami of the lower jaw, and being provided with muscular arches.

DIGESTIVE SYSTEM. 101

serv^es as a bag for carrying food. It may be compared to the cheek
pouches of the Rodentia. A very singular peculiarity occurs in Pala-
medea cornuta, which consists in the presence of a craw-like dilata-
tion between the proventriculus and gizzard.

At the extremity of the gullet there is found very generally occur-
ring throughout the class of Birds a lEirst division of the stomach,
called the proventriculus or bulbus glandulosus, the walls of which, as
the latter name implies, are thickly studded with a layer of simple or
divided glandular follicles, that pour out their secretion by separate
mouths upon the internal surface of the stomach. The proventricu-
lus is in general, e. g. in the Gallinae, Geese, and Ducks of a smaller
size than their very largely-developed gizzard, but frequently the re-
verse is the case to a striking degree, as in the genus Thalassodroma
or Storm-petrel, and the Puffin. In the Pigeons long slender strips
of glands are sent upward from the proventriculus over the oesopha-
gus as far as the crop, and between these the oesophagus is thin and
membranous. More rarely, as in the Northern Divers, the com-
mencement of the proventriculus is indicated by a narrow chaplet of
glandular follicles situated at the termination of the gullet, or it is
not recognisable externally by any expansion, as in Euphone vio-
lacea ; its cavity, however, is provided throughout its entire extent
with follicles. The gastric follicles are usually simple coeca of very
small size, as in the carnivorous Birds, and frequently also in the
granivorous Birds, as the Peacock and Cassowary, but they are lar-
ger and divided at the extremity in the Common Fowl, or even
slightly racemoid, as in the Ostrich. The proventriculus is dis-
tinctly separated by a constriction from the gizzard in all cases
where the latter is very fleshy, but when it is more membranous,
both stomachs communicate with each other by a wide aperture.

The second fleshy muscular stomach or Gizzard is very highly
developed in the Granivorous birds, as in the Fowls and Pigeons,
and also in many Grallae and Palmipedes, as the Swan, Goose, Duck,
Coot, and Flamingo. The thick muscular layers upon either side
are here divided in the middle by a tendinous disc, into two
halves. The cavity of the gizzard is of but small extent, owing to
the projection internally of its strong muscular parietes, and is in-
vested by a hard, pergamentaceous or even horny epithelium, which
can be readily detached. Occasionally corneous tubercles project
from the epithelium, as in the Puffin. The gizzard is frequently also
of very small size, not very muscular, and provided only with a flat
thin disc of radiating tendinous fibres. In the Pelican and Gannet

102 AVES.

the oesophagus is much wider than the gizzard ; the latter is very
thin and membranous, as in the Divers. It is very rarely, as in
Euphone violacea, that all traces of a muscular stomach or gizzard
are wanting. On the contrary, there occurs occasionally, as in the
Herons and Pelican, though not in the genus Sula, so nearly allied
to the latter, a third always smaller gastro-pyloric dilatation, which is
tolerably distinct, and conducts by a narrow pyloric opening into the
duodenum.

The Intestinal Canal always makes a number of convolutions
upon itself that are retained in their place by mesenteric folds of
peritoneum ; the latter membrane does not, however, develop true
omenta. The duodenum forms at its commencement a long loop,
within which the pancreatic gland is situated, while the small intes-
tine is continued at its lower extremity into a large intestine not
much wider, but shorter, and passing downward in front of the ver-
tebral column, its commencement being usually indicated by a sym-
metrical pair of short or longer coeca coli. The large intestine ter-
minates by opening into a wide sacciform or rather bladder-shaped
compartment of the urethro-sexual cavity, the cloaca. The villi of
the small intestine are generally much elongated, and extend also
occasionally as far as the extremities of the coeca, e. g. in Fulica, but
this is not the case in the Gallinae and Owls. The villi are, how-
ever, frequently wanting, or rather, there occur instead zigzag folds
of the lining membrane, as in Corvus, Euphone, Turdus, and perhaps
in the Passeres generally.

Many varieties occur in reference to the two coeca just alluded to.
They are, for example, completely wanting in nearly all the Scan-
sores and Picariae, as Picus, Psittacus, Rhamphastos, Alcedo, Upupa,
Cypselus ; they are very short in the Pigeons, Owls, most Passeres,
and many Grallse, e. g. the Stork and Spoon-bill, somewhat longer
generally in the Diurnal birds of Prey, while they attain, on the
other hand, a considerable development in most of the Natatores,
as the Geese, Ducks, &;c., where they are frequently also asymmet-
rical, being longer upon one side than the other. The coeca are of
surprising length and width in the Gallinae, as in Tetrao, where they
each measure a yard in length ; in the Ostrich the coeca are upward
of two feet long, provided internally with a spiral valve, and blend,
at their inferior extremity, into a single cavity ; the large intestine
is here also, as an exception, much longer than the small intestine.
It is very rarely that, as in the Mammalia, a single, and in such

DIGESTIVE SYSTEM. 103

cases invariably shorter, coecum is present, as in the whole genus of
Herons.

There is not unfrequently found, about the middle of the small in-
testine, a small coecum or diverticulum, which indicates the former
place of entrance of the vitelline duct into the intestine. This per-
sistent remnant of an embryonic structure is remarkably constant and
normal in many of the Grallae and Palmipedes,, as the Goose, while it
is scarcely ever to be perceived in the orders Rapaces, Passeres, and
Scansores.

The whole intestinal canal is of very variable length, being
scarcely dpuble as long as the body in Mormon fratercula, while in
the Penguin it is fifteen times its length.

The Salivary Glands vary greatly in number and development
throughout the several orders and even genera of birds, in accord-
ance with their mode of life. In general four pairs of these glands
are to be met with, namely, a pair of sublingual glands situated upon
either side beneath the tongue, two submaxillary glands divided
each into an anterior and posterior, which lie the one behind the
other, and open by special ducts in front of the lingual organ, and a
gland that may be compared to the parotid, which is placed close
beneath the skin upon the angle of the mouth, and frequently extends
into the orbitar cavity. Occasionally one or the other pair of the
above glands are wanting, and in Sula, Carbo, Phoenicopterus, they
appear to be all of them absent, or, as in the Grallae and Palmipedes
generally are but slightly developed. In the Geese and Ducks all
the pairs, however, are met with, and in the Goose the sublingual
gland is of particularly large size. The Herons possess only the
sublingual gland. In the Watercoot (Fulica), and still more so in
Hirundo esculenta, the parotid gland is very much developed, and
in the latter bird its secretion serves for the preparation of their edi-
ble nests ; in the Rapaces, Passeres, and Gallinae, the salivary glands
are generally all present. In the Woodpecker and Wryneck (Yunx)
the anterior and posterior submaxillary glands are constantly blended
into a large, white, and flattened gland, which secretes a very vis-
cous salivary fluid.

The Liwr, which is of a brownish red color, is divided always
into two halves or lobes, of equal or else very unequal size. In the
Rapaces, many Grallse and Palmipedes, both lobes of the liver are
of equal magnitude, while in the Passeres the left lobe is generally
much smaller than the right. The Gall-bladder is absent only in
a few genera, as in the Ostrich, the Pigeons, and many of (though

104 AVES.

not all) the Parrots, As a rule, two hepatic ducts are met with (in
the Ostrich however there is only one, and a single cystic duct),
which open generally -near to (more rarely apart from each other,
as in the Pigeons) the extremity of the duodenal loop. Other
slight varieties occur in these parts, thus the gall-bladder is very
long and intestinoid in the Toucan, and in the Flamingo the short
hepatic duct dilates into a bladder-like receptacle after its exit from
the liver.

The Spleen is in general small and exhibits manifold diversities
of form, being elongated and cylindrical in the Passeres and in
Rhamphastos, disc-shaped in the Bustard, rounded and broad in
many Palmipedes. It is unusually small in the Cuckoo. In the
Struthionidac a small accessory spleen is frequently observed.

The Pancreas is almost always a gland of considerable size, in-
variably lodged within the loop formed by the duodenum and of a
white or yellowish white color ; it is small and single in the Heron
and Cuckoo, and frequently double, consisting of two lobes united by
a very slender isthmoid portion, as in the Gallinse, Pigeons, many
Rapacious and Natatorial birds ; it is even tri-lobed, as in the
Woodpecker. It has mostly two, though frequently three excretory
ducts, as in the Rapaces, Pigeons, Ducks, &c., but more rarely only
a single one, as in the Ostrich and Cassowary.

ORGANS OF CIRCULATION.

The Heart of birds is highly muscular, and of very large size in
proportion to the bulk of the body. It presents but a few trifling
diversities of form, such as being more elongated than usual in the
Passeres and Grallae, or broader, as in the Parrots. The whole
organ is situated, enveloped by a thin pericardium, in the middle
line of the body resting upon the sternum, its apex being directed
straight backward, and lodged between the two lobes of the liver.
It consists of two auricular and two ventricular chambers, which
are not however portioned off, as in the Mammalia, by a well-deflned
circular groove, nor are the appendices of the auricles so distinct.
The cavity of the right ventricle is wider, but its walls are much
thinner and shorter than the left, so that the apex of the heart is
formed by the left ventricle alone, which is mnch stronger, being
furnished with walls three times as thick as those of the right.
The usual valves are found in front of the openings of the venae
cavae into the right auricle, and between the latter and the right

ORGANS OF CIRCULATION. 105

ventricle there is found a peculiar valve of very great strength, and
formed of longitudinal muscular bundles, which pass obliquely from
the right wall of the ventricle to the interventricular septum, and
serves obviously to bring into forcible approximation the opposite
parietes of the ventricle, and thus to drive out the blood more effectu-
ally into the pulmonary artery. The septum ventriculorum is directed
convexly toward the right, concavely toward the left ventricle. In
the inter-auricular septum the fossa ovalis is found always completely
closed, and surrounded by a strong muscular ring (annulus ovalis).
The left auricle is smaller, but more muscular than the right, and the
openings within it of the two pulmonary veins are commonly provided
■with valves. Three semilunar valves, provided in the middle of their
margin with a small ossified nodule, are found at the commencement
of the ptilmonary artery and aorta.

The trunk of the systemic circulation, the Aorta, is extremely
short ; from its root two coronary arteries arise to be distributed to
the heart, and it then divides at once into three main branches,
one of which forms the descending aorta ; the two others, a right
and left arteria innominata, giving off their corresponding carotid
and subclavian arteries. The carotids, which are of small propor-
tional size, exhibit many remarkable varieties, that are frequently
characteristic of the several orders. As a general rule, in the Ra-
paces, Gallinae, most of the Grallae and Palmipedes, the Ostrich, and
a few Scansorial birds, e. g. Kakadus, Psittacus builarius, passe-
rinus, &c., the two carotids traverse the canal formed by the trans-
verse processes of the cervical vertebrae. On the other hand, in all
the Passeres without exception, and many Scansores, e. g. Picus,
Sitta, Merops, and some of the Parrot-tribe, as also the genus Podi-
ceps, and the Rhea or American Ostrich, there is only a single, and
that the left, carotid present ; it is much more rare, as in the Fla-
mingo and Pelican, for the right carotid to exist and the left be
absent. In a few instances the two carotids adhere so closely to-
gether as to appear like a single trunk, as in the Bittern. A lesser
degree of v,ariety is found in most of the Parrots where both the caro-
tids are present, but the left mounts upward, without entering the
canal of the cervical vertebrae, by the side of the jugular vein. The
subclavian artery runs beneath the furcular bones in the direction
outward, gives off the brachial artery to the wing, and a still larger
thoracic artery to the pectoralis major muscle. The descending
aorta curves over the left instead of the right bronchus, as in
Mammalia, passes along and in front of the vertebral column be-

106 AVES.

tween the two lungs, and gives off large visceral trunks within the
thoracico-abdominal cavity to the stomach, liver, spleen, and mesen-
tery, a superior and inferior artery passing transversely to the
kidneys, and a small anterior or femoral with a much larger poste-
rior ischiadic artery to the leg ; the aorta is then continued along the
spine, as the arteria sacra media, and gives branches to the contents
of the pelvis. Several of the arteries, as the anterior tibial in the
Goose, Heron, and Crested Grebe, form here and there beautiful retia
mirabilia or vascular plexuses.

The Veins of the body, as in Mammalia, have but few valves.
The blood of the superior half of the body is poured into the right
auricular sinus from the two distinct mouths of a pair of superior
vense cavae. They are formed by the junction of a jugular and
subclavian vein, of which the right jugular is generally tliree to
four times thicker and stronger than the left. The inferior or pos-
terior vena cava collects the blood from the posterior moiety of the
.body, and receives especially the large renal veins. The inferior
vena cava is very broad, especially in the Diving-birds. The Pul-
monary artery ^ single at its commencement, divides into two main
trunks for the two lungs ; in a similar manner, also, the pulmonary
veins enter the left auricular sinus by a single trunk. The vena
porta receives principally the blood from the viscera, but some also
from a large branch of the caudal vein and the veins of the poste-
rior extremities. The blood of Birds has the highest temperature
of all the Vertebrate animals (about 110® Fahr.), and the blood cor-
puscles are always of an elliptical form, and of very uniform diame-
ter, throughout all the orders.

The Chyliferous or Lymphatic Vessels are numerous, and pro-
vided with valves, but do not form any conglobate glands upon the
mesentery, though in the neck these glands often occur, and are of
considerable size, as in the Heron, where there are from five to six
pairs. A receptaculum chyli is situated upon the origin of the
coeliac artery, and the lymph of the body, as well as the chyle, is col-
lected into two lymphatic trunks, which enter the angles formed by
the junction of the superior vense cavae with the jugular and subcla-
vian veins. Lymphatic hearts have not as yet been satisfactorily
demonstrated to exist jn Birds ; still, however, in the Cassowary a
lymphatic sinus has been found, situated beneath the integument,
upon the transverse processes of the second sacral vertebra, and
which, reasoning from the analogy of its position with that of the
Frog, may perhaps be regarded as a lymph-propelling organ.

ORGANS OF VOICE AND RESPIRATION. 107

ORGANS OF VOICE AND RESPIRATION.

The air during the act of inspiration in Birds passes through the
nasal openings to the Rima glattidis, the opening and closing of
which aperture may be very well observed in the expanded mouths
of young birds while they are being fed. The rima glottidis forms
a longitudinal fissure in the superior larynx, and is generally
provided with pointed or obtuse epithelial papillae more or less
strongly developed, and frequently arranged in rows that would ap-
pear in some measure to supply the place of the epiglottis, which is
wanting in the present class ; they offer varieties in the several
genera, and are wanting only in the Struthionidae. Occasionally
there is found behind the tongue a membranous valve-like fold, as in
many Ducks and in the Ostrich ; in some cases this fold has a me-
dian lappet, as in Scolopax gallinula, while a thicker dentated fold is
found as a rudiment of the epiglottis in Fulica atra. A true epi-
glottic cartilage appended to the superior border of the thyroid car-
tilage occurs however in a few Birds, as the Swan and some other
Natatores and Grallae.

The Superior Larynx consists of several cartilaginous pieces,
which admit of being compared with analogous parts in the human
subject, and are constantly ossified in adult Birds. The largest of
these pieces is a single bony plate, which forms the anterior part of
the larynx, and abuts posteriorly and inferiorly against two lesser
elongated and narrow cartilaginous pieces, not united in the median
line, which appear at first sight in adult Birds to be separated from
the anterior bony plate, but are blended with it at an early period
in young birds. These three bony pieces are the conjoined repre-
sentatives of the thyroid cartilage ; the anterior plate is usually in-
terrupted by several transverse intervals, that indicate its original
formation from the coalescence of a short series of tracheal rings,
these last being distinctly perceptible in many cases. Two to four of
these rings are generally to be recognised, except in the Parrots,
where there is no visible trace of their fusion. Posteriorly and
internally the thyroid plate presents a more or less elevated ridge,
dividing incompletely the cavity of the superior larynx into two
symmetrico-lateral halves. Another process {processus epiglotti-
cus Henle) arises from it superiorly, and in many Birds, as Larus,
Alca, from its soft and slender condition approaches in character to
the epiglottis of the mammiferous animal. Posteriorly, between

108 • AVES.

and above the two posterior thyroid pieces, there is situated a small
rounded, cordiform or quadrangular plate, which must be viewed as
the cricoid cartilage. In the Cassowary and Parrot, the posterior
surface of the cricoid cartilage lies perfectly free, but is partly con-
cealed in many Birds, as the Gallinazo, and in others can not be seen
upon an external view of the larynx. The narrow elongato-triangular
arytenoid cartilages are somewhat similar to those of the Mammalia,
and bound the fissure of the glottis.

Three pairs of Laryngeal Muscles varying only in their size may
be distinguished in all Birds. Upon the anterior surface of the
thyroid cartilage there is situated, particularly in the Rapaces, a
strong muscular fasciculus, which arises from the lingual bone, de-
scends the trachea to a greater or less distance, and is attached to
the inferior margin of the thyroid cartilage ; it serves to draw up
the larynx as well as the trachea, and correspond thus in action with
the hyo-thyreoideus and crico-thyreoideus muscles of the higher ani-
mals. A thyrio arytcenoideus posticus, the function of which is to
open the rima glottidis, is situated upon the uppermost part of the
dorsal surface of the larynx, takes a broad origin from the lower mar-
gin of the lateral posterior pieces of the thyroid cartilage, and passes
to the extreme apex of the arytenoids. Upon removing this pair a
broader thinner muscle will be brought into view, which constantly
arises from the superior margin of the arytenoid cartilage and unites
posteriorly and anteriorly with that of the opposite side. It acts as a
sphincter contracting the fissure of the glottis, and is called thyreoi-
deus lateralis s. compressor laryngis. There are no chordae vocales
in the superior larynx.

The Trachea of Birds is usually of great length, and consists of a
large number of rings, the fewest 20 to 70 occurring in the Passeres,
while among the Grallae and Natatores the Ducks present above
100, the Heron, Pelican, and Ostrich, above 200, and the Crane and
Flamingo the surprising number of upward of 300 rings. These
rings are for the most part complete, approximated very closely to-
gether and remain often partly membranous as in Tetrao. In many
Birds the rings, at least at their commencement, are fissured, e. g. in
the Woodpecker. In the Scansores and Picariae, many Gallinae,
Rapaces and Grallae, the rings continue cartilaginous throughout
the whole of their existence, while in the majority of cases, as in
the Passeres, the Ostrich, many Grallae and Natatores, they are
completely ossified, so that the trachea becomes a hard cylindrical
tube, as in the Goose. The trachea generally descends straight

ORGANS OF VOICE AND RESPIRATION. 109

down the neck from the superior to the inferior larnyx, and then
divides at the commencement of the thoracic cavity into two bron-
chi. It is very rare for the trachea to divide higher up, namely, in
the neck, as in the Humming-bird. The bronchial tubes are mostly
short, and usually narrower than the trachea, though occasionally
they are wider and dilated at their origin, as in the Pelican and
Merganser. They are usually composed of a series of half-ringa
completed by an elastic membrane ; more rarely, as in the Stork,- of
perfect rings which are occasionally continued some distance into
the lungs.

Two pairs of muscles are generally found which draw down the
trachea, one of which is frequently arrested in its development, or
wanting altogether. The superficial pair, which is partieularly
well-developed in the Natatores, as the Merganser and Duck, but ab-
sent in the smaller birds, e. g. the Passeres, Scansores, and Picariae,
lie upon the sides of the whole length of the trachea, and arise from
the upper part of the inferior larynx, and the internal surface of
the furcula, whence their name of m. cleido or ypsilo-tracheales.
The second pair, which are generally present, yet appear to be
wanting along with the first in the Parrots, are called the m. sterno-
iracheales, arise from the external part of the anterior margin of the
sternum, are attached likewise to the lateral surfaces of the trachea
and the upper part of the inferior larynx, and ascend more or less
upward covered by the preceding pair of muscles. In the Pigeons
the last two mUscles or sterno-tracheales arise as usual from the ster-
num, but pass both asymmetrically to the right side of the trachea.

In addition to the normal peculiarities of structure already
noticed, the trachea exhibits singular dilatations and convolutions,
which appear however to occur only in some orders, as the Nata-
tores, Grallae, and Gallinae, and what is remarkable, are frequently
absent in closely allied genera, or even species of the same genus,
and often constitute characteristic sexual distinctions, occurring in
many cases only in the male, and being either entirely absent, or
exhibited under a lesser degree and with particular modifications
in the female, or else being met with in the same conditions in both
sexes.

Claiming our attention in the first place are those elongated dila-
tations which are situated commonly about the middle of the trachea,
and provided with cartilaginous and bony rings ; they are usually
single, but are double in the Dralve and male Merganser. Anas
leucocephala and Mergus serrator have a single dilatation of the

110 AVES.

trachea, which is more strongly developed in Anas fusca and in
Clangula. Feeble traces of a double widening of the tube occur in
Anas crecca and tadorna ; there are elongated dilatations in Anas
rufina, glacialis and Mergus merganser, and a single one in Pala-
medea cornuta. In the Emeu a peculiar structure is observed, for
in that bird an elongated slit, several inches long, is found above the
bifurcation of the trachea, and communicates with a large cellular
air-sac situated in the neck.

In other Birds from the orders just mentioned convolutions occur
of the lower part of the trachea, and are situated either free beneath
the integument at the commencement of the thoracic cavity, or
are enclosed to a greater or less degree of depth within the sternal
keel. Thus in Platalea, Penelope, the Cock of the Woods, the
Corn-crake, and some Pheasants, especially in the males of these
species, and in Anas semipalmata (where it makes the most com-
plex convolutions of all), the trachea descends beneath the skin to
beneath the level of the anterior border of the sternum, ascends and
having made a second curve upon itself, bifurcates into the bronchi
for the lungs. In both the male and female of Grus virgo and
cinerea, with however certain sexual modifications, the trachea
penetrates the keel of the sternum, is enclosed within it as in a bony
capsule, and there makes several spiral convolutions upon itself
which extend in the male as far as the posterior extremity of the
keel. In both the sexes of Cygnus musicus and Bewickii, a loop-
shaped coil of the trachea lies within the keel of the sternum ;
in the Black Swan however this structure is more feebly developed,
and does not exist at all in the mute Swan (Cygnus o\or). It is
most strongly indicated in the Trumpeter Swan (C. buccinator),
where the tracheal convolution descends as deeply as in the male
Crane. In Numida cristata a coil of the trachea is situated between
the shafts of the furcular bone. A well-marked sexual difference
is observable in the Black Stork, where in the male the bronchi,
long and having complete-rings, are always curved in the shape of
the letter S ; this is the case also, though in a lesser or scarcely
noticeable degree, in the male of the White Stork. A peculiar con-
dition of the trachea is met with in the Penguin, by the ridge upon
the inner wall of the thyroid cartilage forming a septum, which is
prolonged throughout the whole of that tube. A similar structure
is found at the inferior extremity of the trachea in Procellaria gla-
cialis.

The existence of an Inferior or Bronchial Larynx, in which the

ORGANS OF VOICE AND RESPIUATION, HI

voice is produced, constitutes a special peculiarity of the class of
Birds. It is situated in the upper part of the thoracic cavity at
the extremity of the trachea, where that divides into the two bron-
chi. The length of the inferior larynx is mostly greatest from be-
fore backward, and its interior forms a quadrangular cavity, which
is generally divided inferiorly (at its outlet) by a cross-hone pas-
sing from, before backward, into two lateral halves, that receive the
two openings of the bronchi, which are to be viewed as forming a
double rima glottidis. The cross bone consists of the last tracheal
ring increased in size, or else of several rings which have be-
come firm and rigid, approximated and even blended together, so
as to form a firm bony drum of variable size. The commencement
of the bronchial tubes is also to be regarded as forming part of the
inferior laryngeal apparatus, since their first rings and the mem-
branes which unite them must exert the greatest influence upon the
production of the voice.

As might be expected from the great variety of character which
the voice of Birds presents, the structure of the inferior larynx in the
several genera and species offers for our study a very extensive series
of modifications. In some cases this larynx appears to be entirely
absent, there being neither expansions of the trachea nor vibratory
membranes to produce, by combining in action with the lingual ap-
paratus, any kind of sound, so that voice may be said to be totally
deficient. These conditions are exemplified in both the Black and
White Stork. The rings are very soft and cartilaginous through-
out the whole extent of the trachea, and there are no indications
whatever of a larynx at its bifurcation ; and as little of an internal
and external tympanic membrane, or even of a single pair of mus-
cles. The bronchi are long, and formed, like the trachea, of nume-
rous (about 50) entire rings, the intervals between which are car-
tilaginous, so that the bronchi form soft but elastic cylindrical tubes,
which become membranous so soon as they enter the substance of
the lungs. The storks, as is known, with the exception of a clat-
tering noise produced by the bill, give utterance to no distinct tone,
but only a feeble hiss. The muscles of the inferior larnyx are want-
ing in the Struthious birds, several Grallae and Natatores, and in
the Gallinse and Owls; the bronchi are partially surrounded by
segments of rings, and completed by membrane on their internal
side.

From the preceding examples we pass to those Birds, as the true
Vultures, which have been also stated, though incorrectly, to possess

112 AVES.

no inferior larynx. It is true that in the Viiltur cinereus and fulvus
as also in Gypaetos, there can not be found, as in many other Birds,
any coalescence of the lower tracheal rings, or an external tympani-
form membrane, but between the demi-rings of the bronchi (which
appear, however, in the American Vulture or Gallinazo to be almost
complete) there is situated the internal tympaniform membrane,
■while a single pair of muscles placed externally at the extremity of
the trachea, serves to elevate slightly the bronchi upon either side,
shorten the trachea, and thus expand the two bronchio-glottidean
fissures. This pair of muscles acts moreover as an antagonist to the
sterno-tracheales.

In the majority of those Birds which are capable of uttering
sounds membranes are found situated both exteriorly and internally
to the inferior larynx. There arises from the cross-bone a thin mem-
branous slightly elastic and easily lacerable membrane, which com-
pletes the bronchi upon their internal aspect. The extent of this
membrane is greater or less in proportion to that of the segment
formed by the imperfect bronchial rings ; the first two or three of
these are usually very slightly curved, and in the form only of a
small semicircle ; the membrane completing the rings is therefore
largest in this situation, and fully merits its appellation of membrana
tympaniformis interna. In some Birds, as in several Ducks, espe-
cially the Mergansers, large flat cartilaginous discs are situated in
this tympanic membrane, or, as in Fulica, thick cordiform cushions
of cellular tissue, either of which structures must exert an indubitable
influence upon the formation of the voice. There is generally found
a membrana tympaniformis externa presenting the form of a fenes-
troid oval membrane placed between the cross-bone or the low^ermost
tracheal ring and the most superior of the bronchial semicircular
cartilages.

This external fenestra or membrane may be wanting and still the
inner one present and the trachea form an osseous drum, as in the
Ducks and Mergansers. Or else the hard rings of the trachea may
lie closely approximated and invested by fibro-cartilage, beneath
which is situated the external ovale membrane, as in the Flamingo.
No important change however can be effected in the relative degree
of tension of the two membranes in cases where a single pair of
muscles is present, and attached high up to the border of a drum
formed of immoveable rings, whereas when inserted in the upper-
most bronchial rings, a far greater share of mobility is attainable by
the membranes.

ORGANS OF VOICE AND RESPIRATION. 113

Such a single pair of muscles (m. m. broncho-tracheales) occur
in the Rapaces, some Scansores and Picarioc, c. g. Picus, Cypselus,
Caprimulgus, and, though but feebly developed, in the Cuckoo ; also
in the Pigeons (which have a large external membranous fenestra),
and many Grallee and Natatores, while it is absent in other Scan-
sores and Picariae, e. g. Alcedo, Upupa, other Grallse, and Natatores,
as Hoematopus, Anser, Anas, Mergus, and in the Brevipennes and
Gallinae. This single pair of muscles often ascends high up close to
the sterno-tracheal muscles, draws the bronchi in the direction out-
ward and thus expands their glottidean fissures.

Two special muscles of the larynx do not appear to occur in these
cases, to which succeeds the peculiar structure of that organ in the
Parrots, where it has three strong pairs of muscles, but the sterno-
tracheales are absent. The inferior glottis is single and narrow
in the Parrots, from the inferior partition or cross-bone being
wanting. The structure of their larynx is as follows : the tra-i
chea passes into a short tympanum, and beneath this there is con-
stantly situated a semilunar ossified cartilage [cart, semilunaris),
having its concavity directed downward, and between its border
which excavated in a crescentic form is curved upward, and the first
bronchial demi-ring, is situated the external tympaniform mem-
brane. The superior semilunar pieces can be moved inward and
outward upon the tympanum, or raised and depressed like a pair
of valves, and the membrane follows these movements. Of the
three muscles, that which is situated most deeply is the shortest ;
it arises from the upper part of the tympanum, and is inserted by
its whole breadth to the upper semilunar cartilage which is move-
able like a valve. This is the m. abductor cart, semilunaris, and
while this muscle elevates the corresponding semilunar bone, it
draws also the membrane outward, and thus widens the opening
of the glottis. Above this is situated another longer muscle, which
arises close to it, and passing in a bridge-like manner over the tym-
paniform membrane, is inserted into the uppermost bronchial ring ;
it elevates the bronchus of the corresponding side, by which move-
ment the two membranes approximate, come nearly in contact in
the middle line, and thus narrow the fissure of the glottis. Above
this short levator bronchi, is situated another, the levator longus,
which has the same function, though at the same time its muscular
belly arises higher up and is continued into a long tendon which, run-
ning over that of the former muscle, is occasionally inserted into
the anterior side of the fifth to the seventh, or often the third to the

8

114 AVES.

fifth bronchial ring. Upon the internal side of the tympsiniform
membrane, which is thrown into vibrations during the passage of the
air from the kings, there is placed a strip of membrane, which also
vibrates and may be regarded as corresponding to the ligamentum
vocale externum of the Singing-birds.

The structure of the inferior larynx is still more complicated in
the Singing-birds, and those birds generally which are provided with
what is called a true muscular vocal apparatus^ among these
the Ravens being included, from the power they possess, like the
Parrots, of imitating the human voice. Although a number of
slight varieties occur in the different genera and species, which
stand in direct relation with the degree of complexity of their song,
still, however, a great general conformity may be perceived in the
structure of the singing app;iratus, it, as a rule, being formed of
five well-developed pairs of muscles. In the Nightingale and other
small Singing-birds, this muscular apparatus is indeed very power-
fully developed, but on account of its small size, the student will do
best to select a larger bird, as the Raven or Rook, for the purposes
of examination.

The trachea here consists of a short bony tympanum or dnira,
constituting its inferior extremity, and usually formed by the early
coalescence of three rings. The tympanum is divided as usual infe-
riorly by a transverse or cross bone. From the superior border of
this, a membranous semilunar fold [memhrana semilunaris Savart)
rises to about a line in height, as in the Rook ; its dimensions, how-
ever, are very various, and in birds of accomplished song, or such
as can learn to speak, it is more largely developed. In other Pas-
seres, as in the Sparrow, Haw-grosbeak, &c., these membranes are
of course wanting. From these observations it may be inferred that
this membrane is of essential importance to the production of song
or the power of uttering articulate sounds, since when it is absent or
slightly developed, the voice is feeble or has but little variety of
tone. The first three bronchial demi-rings exhibit also remarkable
peculiarities. The first or uppermost ring is thicker in the middle
than at the extremities ; at the posterior end inferiorly it be-
comes broader, and curves in such a manner backward and in-
ward, as to form the posterior and internal wall of the bronchial
portion of the inferior larynx ; below it passes into an acute angle,
which forms the point of support of the internal lip of the glottis.
The second bronchial demi-ring is more moveable than the first,
especially in the direction outward and upward. The third demi-

ORGANS OF VOICE AND RESPIRATION. 115

ring is nearly straight, and between it and the second demi-ring
there is a triangular membranous fenestra, and between the first
and second bronchial demi-ring an oval memhrana tympaniformis
externa. Upon its inner surface there is found a remarkable fold
of the mucous membrane, consisting of tolerably thick and elastic
tissue ; it forms a true vocal chord, ligamentum vocale externum,
which always forms the external lip or wall of the glottidean fissure.
This membrane or fold is thrown into vibrations during the passage
of the air from the lungs. Besides this the memhrana tympani-
formis interna is found as usual completing the inner side of the
bronchi, and is in continuous connexion with the memhrana semi-
lunaris of the cross-bone. A small pliant cartilage {cartilago ary-
tmnoidea Savart) is situated in the upper part of this membrane, is
in connexion with the second arch of bone, and exhibits manifold
diversities.

Two anterior and three posterior pairs of muscles may be distin-
guished as belonging to the inferior larynx. In front, a long elevator
muscle {m. levator anterior longus) arises tolerably high up from
the trachea, and is firmly attached to the second bronchial demi-ring,
the anterior extremity of which it draws upward and outward, and so
widens the larynx. In like manner the transverse elevator {m. le-
vator anterior transversus) arises in front, but obliquely, from the ex-
ternal part of the superior border of the tympanum ; it proceeds in
the direction forward, and is attached by its inferior extremity to the
anterior part of the second and third bronchial demi-rings, and to
their interjacent membrane ; elevating and drawing these parts also
in the direction outward. By both, of these muscles, as well as by
the m. depressor trachem s. sterno-trachealis, which arises externally
from the tympanum and passes forward to the border of the sternum,
the tavity of the inferior larynx is shortened and dilated. The
memhrana semilunaris and the ligamentum vocale externum will be
also synchronously stretched in a variety of ways by the action of
these muscles, joined to that of the three posterior pairs, the descrip-
tion of which will now occupy our attention. The posterior long
elevator (m. levator posterior longus) arises high up behind the
corresponding anterior elevator muscle, and is inserted posteriorly
into the extremities of the second bronchial demi-ring which it draws
upward, and at the same time rotates the third. The posterior
short elevator (m. levator posterior) is partly covered by the former
muscle, but is situated more in the direction backward and inward,
and at its origin from the upper part of the tympaaum abuts closely

lie AVES.

against its fellow of the opposite side, and is attached higher up to
the posterior extremity of the first bronchial arch, which it serves to
elevate. The fifth pair of muscles is situated between the posterior
long, and .the anterior transverser, elevator, and is called the oblique
elevator (m. ohliqxius posterior s. rotator posterior) ; it arises exter-
nally from the superior border of the tympanum by a short and thick
muscular belly, passes obliquely backward, and is inserted into the
posterior extremities and lower border of the second bony arch, which
it rotates and draws in the direction outward.

The voice of Birds appears like that of the human subject to be
produced by the combined vibrations of the laryngeal membranes
and the tongue. The flute-like tones of the Singing-birds are doubt-
less accomplished by a vibration of the whole column of air while
passing through the trachea. Where all the membranes are absent
and the bronchial rings complete, the voice is also deficient, as in
the Stork.

In addition to the already recorded peculiarities in the anatomy
of the inferior larynx, there occur in many Birds expansions of the
tympanum or apparatus of resonance which strengthen the tone of
their voice. To these belong the large bladder-like dilatations and
expansions of the tympanum met with hitherto only in the Natatores,
as the Drakes and Ganders. These expansions, which have been
called the labyrinth, are peculiar from their occurring only in the
male and never in the female sex, and in being asymmetrical or of
unequal dimensions upon the two sides, the left being always con-
siderably larger than the right ; as a rule, this structure is found upon
the left side, it being very rare for the right tympanum to be the
largest.

In the Ducks the labyrinth consists for the most part of round
bony ampullae about the size of a pea in the lesser species, as Anas
crecca, still smaller in A. clypeata, but much more developed in the
larger species. More rarely there occurs a double irregular labyrinth
larger upon the right side than the left, as in Anas tadorna. These
ampullae are wanting in the Dipper (Hydrobates), and both sexes
are alike in this respect. Other Ducks, as Anas marila, fuligula,
glacialis, leucophthalmos, have a perforate labyrinth : the enlarge-
ment is here more angular, and partly provided with membranous
fenestrae. This also is generally the case in the male Mergansers,
where the labyrinth in M. merganser attains its highest grade of
development. The larynx here forms a thick-walled and hard bony
expansion nearly one and a half inches in length, having an uneven

ORGANS OF VOICE ^ND RESPIRATION. 117

tubercular surface, and an irregular triangular form. Upon the left
the labyrinth has the form of a somewhat irregular tetrahedron, from
the basal surface of which the left bronchus arises, its three sides
being occupied by oval membranous fenestras. The membranes are
stretched within arched bony frames, so that the whole resembles a
lantern. In the female the inferior larynx forms only the usual bony
tympanum, but is still somewhat asymmetrical in form. This laby-
rinth obviously acts in modulating and strengthening the voice, and
reminds us of that bony dilatation of the os hyoides constituting an
apparatus of resonance in the Howling-apes, as has been already
described under the head of the Respiratory Organs in Mammalia.
The male Ducks have, as is well known, a stronger voice than the
females, and can even produce a considerable variety of tones.
Among the more remarkable diversities of the inferior larnyx, one in
particular deserves to be here indicated. In Sula-alba (at least in
the male) the trachea is formed as usual, and the bronchi are com-
posed of half-rings, but there invariably projects in the direction out-
ward from between the first and second bronchial demi-ring a
yellowish body, tolerably hard and solid, of the size of a pea, and
which contains fibres and a great quantity of adipose-cells ; with its
basis is connected the strong inferior larynx, and by means of this
arrangement the bronchi admit of being drawn much apart from each
other. This body does not appear to be a gland, for no excretory
duct can be detected.

As regards the immediate organs of respiration, the Lungs, they
are in Birds, as in Mammalia, invariably two in number, but propor-
tionally of very small extent to what they are in the latter class.
They are flattened, irregularly triangular, and attached posteriorly
to the vertebrae and ribs (from the heads of which last they receive
deep permanent impressions) by cellular tissue. They are of a bright
florid red color, invested in front only by the pleura, and made up
of a loose parenchymatous tissue. They are of largest proportional
size in the Singing-birds, but are destitute of lobes throughout the
whole class, and exhibit great uniformity of character. The bronchi
as soon as they have entered the lungs form always a wide vesicular
cavity, perforated by a number of apertures. It is only anteriorly
and posteriorly that there are some imperfect cartilaginous arches,
and there are here found between the fifth to the sixth most anterior
cartilaginous demi-rings, four or five oval apertures, which are kept
open by the cartilages already named, and their mutual lateral
connexions ; they lead into larger superficial membranous tubes,

118 AVES.

which traverse the internal and inferior side of the lungs ; behind
these openings are situated others for the superficial tubes, and lesser
ones for the deeper. The superficial tubes pass almost completely
round the lung upon every side, and their external walls are very
thin and transparent. The deeper tubes resemble cylindrical pipes,
traverse the lungs in many directions, and are nearly straight and
parallel to each other ; they are the most numerous, aiMl open in
such a manner into the superficial tubes, that they pass from the
upper to the under siie of the lungs, and communicate laterally with
each other. From their walls being thick and remaining constantly
patulous, and from those of the superficial tubes into which they open
being transparent, the lungs of Birds acquire the perforated tubular
appearance which they present. The parietes of the tubes and
canals are covered with a most beautiful and delicate network of
small cavities and cells, with intervening septa mostly of an hexago-
nal form, and within the meshes lie other still smaller open cells.
The cells of the lungs in Birds are therefore never terminal cells, as
in the Mammalia, but open parietal cells from -Jth to ^^^th of a line in
diameter, upon which the vessels expand and thus come into contact
with the air. All the cells and tubes of the lungs communicate
naturally with each other, so that the lungs can be perfectly inflated
from any one point.

Upon the surface of the lungs near to their posterior margin and
upon the inner side, there is observed, upon stripping off the pleura
in this situation, openings from five to seven in number, by means of
which the bronchi are brought into communication with the peculiar
Air-cells of the Bird. These highly remarkable receptacles for the
atmospheric fluid are membranous, being formed by reflected prolon-
gations of the pleura and peritoneum, and surround all the viscera.
These cells may be distinguished in general into the following prin-
cipal divisions, which are separated by membranous partitions, and
for the major part transmit air. \st^ The two empty lateral cells
which descend beneath the sternum as far as the pelvis, divide
again into an anterior and posterior, or frequently even into three
cells, and enclose no viscera. In the Passeres the two anterior
lateral cells coalesce into one, and communicate with the bronchial
cells. 2d, the two cells which enclose the lobes of the liver, do
not communicate with any air-opening, and therefore receive no
air, and merely result from the subdivision of the remaining air-
cells. Zd, An intestinal cell, also conveying no air, which includes
the intestinal canal, and is divided by the mesentery into two

ORGANS OF VOICE AND RESPIRATION 119

halves. 4th, A cell for the heart. 5th, A cell situated in front of
the breast for the bronchi, which it surrounds, together with the
inferior larynx. A still greater extension of the air-cells occurs in
some Birds. Thus, the Roller (Coracias) is provided with a pair
of large air-cells beneath the skin of the head and neck, and .these
communicate with the nasal cavity, but not with the trachea. The
distribution of air throughout the body is nowhere more extensive
than in the Booby (Sula) and the Pelican. In these genera the
lateral cells of the trunk are uncommonly large, and separated by
two partitions into three large chambers, from the most anterior of
which the air gets beneath the axilla under the integument, and
fdls the space upon th^ breast and belly from the furcular to the
pubic bones. Several larger and various smaller cells are also met
with, and the fat, which is generally abundant in such situations,
is here wanting. The air-cell above the great pectoral muscle and
on the inferior part of the neck is particularly large, and the deli-
cate cellular tissue here forms partitions including cells several lines
in diameter, which are continued almost beneath the epidermic layer
of the skin as far as the quills of the contour-feathers, but not into
their interior. These cellular air spaces are further distributed
beneath the short investing feathers of the wing, and between the
quills of the great primaries. Upon the middle and upper part of
the body tegumentary air-cells do not exist ; and upon the head
there is found beneath the crisp-feathers covering the occipital re-
gion, only a single solitary cell partitioned off into some small spaces.
The communication which exists between the pneumatic cells of
Birds and the interior of many of their bones, the latter being for
this purpose devoid of medullary tissue, and thus rendered permea-
ble to air, has been already mentioned'-in treating of the skeleton.
The Apteryx offers a striking contrast to the Pelican in being en-
tirely devoid of air-cells, and is hitherto the only known exception
of this kind among Birds. This extensive distribution of the at-
mospheric air throughout the body of Birds contributes obviously,
by highly oxygenating the blood, to increase the general activity of
their arterial system, conditions which are manifested in the greater
number of its pulsations within a given time, and its more elevated tem-
perature (107° to 1 lO'^ Fahr.), as contrasted with that of the Mammalia.
The mechanism of the function of respiration, according to the
recent special researches of Dr. Edward Weber, is performed in the
following manner. The ramifications of the bronchi with the net-
work of tubes they form within the lung are during inspiration

120 AVES.

drawn apart by means of the expansions of the ribs, to which the
lung is firmly fixed, and the contraction of those fasciculi of the
diaphragm that are inserted upon the free surface of the lung. By
this action not only are the tubes expanded and lengthened out, but
in like manner also the interspaces included between them. The
air must of necessity therefore penetrate and distend the terminal
bronchial raftiifications situated between these interspaces. The
lungs derive their supply of air, which they receive by the process
just mentioned, partly from the trachea and partly from the air-
sacs, the latter forming pneumatic reservoirs, from and into which
the lungs both inspire and expire. Now as each of these reservoirs
is in communication with the bronchus through a wide tube, the air
they contain is always in a respirable condition, for while the thorax
is being expanded that portion also of the pneumatic sac which lies
concealed beneath it is expanded also, and sucks in the air upon the
one hand through the trunk of the trachea, upon the other, from
that part of the air-sac that projects out of the cavity of the thorax,
and which may accordingly be seen to collapse during the act of
inspiration. When, however, the capacity of the thorax becomes
narrowed during expiration, that portion of the air-sac covered by
it is compressed and drives out its contained air upon the one hand
into the tracheal trunk, upon the other into the projecting part of the
air-sac which is then observed to dilate. There appears, moreover,
to exist a special provision whereby, when the wings are elevated
during flight, and their pressure is consequently removed from the
great pneumatic sacs situated in the axilla and between the pectoral
muscles, that the sacs become distended with air, which, when the
"wings are depressed, is driven out of them into the lungs, so that a
bird, such as the Lark, while mounting perpendicularly upward to a
great altitude in the air, is still enabled to sing without at the same
time getting out of breath.

A pair of small glandular bodies devoid of excretory ducts occur
in Birds, and from the situation they occupy may be regarded as
Thyroid glands. They are very generally of a rounded form and of
a reddish color, richly supplied with vessels, and lie upon either side
of the lower part of the trachea, where they are more or less attached
by cellular tissue and an arterial ramuscule to the carotid, or else to
the jugular vein. Immediately beneath and united to them, there are
found in many Birds small corpuscles of a denser texture, and whitish
or yellowish color. Both thyroid glands are separated from each
other in the middle line by a wide interval.

URINAEY ORGANS. 121

URINARY ORGANS.

The Kidneys in the Bird are very large and impacted within deep
depressions in the pelvis, which they completely fill up ; they com-
mence immediately beneath the lungs, and like those organs, they
retain the impressions of- the lowermost ribs, but particularly of the
transverse processes of the sacral bone. They almost invariably
consist of three principal lobes, of which the middle one is generally
the smallest, the anterior frequently the largest, as in the Rapaces,
but in other cases, as the Pelican, the posterior lobe. In the Ra-
paces, Gallinse, and Columbidae, they are separated from each other
by a wide interval, in which the aorta passes, and do not occupy
the whole extent of the cavity of the sacrum, part of it being
occupied by air-cells. In other Birds, as the Passeres, they
come in contact in the median line, and even coalesce in several
species, e. g. Lanius Excubitor, and more rarely in Ardea cinerea.
The kidneys form, however, as a rule one blended mass in the Loons
(Colymbus s. Podiceps). In the Coot (Fulica atra) the kidneys
are divided on their postero-superior surface into a great number
(about 60) small lobules, which are only loosely connected together
by cellular tissue. The kidneys are of a brown color, and friable
texture ; the delicate urinary canals give off short lateral branches,
presenting thus a pinnatifid appearance, and do not terminate upon
conical papillae. The urine of Birds is very rich in earthy constit-
uents, and contains but little water, so that the kidneys frequently
appear, after death, as if injected from a deposite of urate of
ammonia having taken place and filled their tubes. In the Stru-
thious birds papillae and calyces are met with in the kidneys, and
in the Ostrich a true renal pelvis. Several excretory ducts gener-
ally proceed from the kidneys to form the ureters, which descend
along the anterior surface of the kidneys, and terminate by perfora-
ting the cloaca posteriorly and superiorly. A proper urinary bladder
is absent, though the ureters in many Birds open into a distinct pouch-
shaped dilatation of the. cloaca, bounded above and below by a valvu-
lar fold, separating it on the one hand from the urethro-sexual cavity,
on the other from the orifice of the rectum, and which is by many
writers viewed as a rudimentary urinary bladder ; this structure is
most strongly developed in the Ostrich.

A pair of yellow or orange colored Suprarenal Capsules^ of the
shape of millet-seeds, flat and usually of small size, are constantly

122 AVES.

found, situated on the mesial line of the anterior extremity of the
kidneys, are in contact externally with the large vascular trunks, and
are partly covered by the testes and ovaria.

PARTICULAR ORGANS OF SECRETION.

Particular glandular organs are found very generally distributed
in the region of the tail and cloaca ; but really specific secretions,
such as occur so frequently in several of the orders and genera of
Mammalia, do not appear to occur in Birds.

A peculiar gland, which is called the Glandula Uropygii, exists
very commonly throughout the class, and secretes an oily fluid of a
whitish or yellowish color, having occasionally a musky odor,
and which is applied by the bill to anoint the feathers, so as to
prevent their getting wet. It is situated above the last caudal
vertebrae upon the quills of the remigial feathers of the tail, and
consists properly of two distinct glands, which are either united in
the median line, or frequently only by their posterior extremities.
They consist internally of close-set elongated coecal tubules, not in-
tercommunicating and opening into a mostly linear cavity of greater
or less size situated in the centre of the gland. A double orifice,
rarely one (or many, as in the Pelican, where twelve apertures are
found arranged in two rows), which opens upon a papilla, and, as
in the Diurnal birds of Prey, the Parrots, Gallinse, and Natatores, is
surrounded by a tuft of small feathers, indicates the outlet of the
excretory duct. The gland itself is usually triangular or cordiform in
the Natatores, as the Ducks, where it is of the largest size, and divi-
ded by a fissure into two clavate lobes. It is very rarely absent, as
in the Brevipennes, e. g. the Bustard, in the Penguin, and some only
of the American Parrots, for others possess it.

Another organ that may be conjectured to be one of secretion
also, is called the Bursa Fahricii. It occurs in nearly all Birds,
being wanting in the Ostrich, probably alone among the Brevipen-
nes, and is situated deep within the pelvis between the ureters and
behind or above the cloaca, in front of the extremity of the sacrum,
and is usually covered by cellular and adipose tissue. It opens
below the two ureters into the cloaca by a considerable orifice, which
is separated by a fold from the urinary compartment of that cavity.
Covered externally by a layer of muscular fibres, it is in some cases
of a thin membranous texture, but in others frequently provided with
a thick layer of small follicles, as is especially the case in the Grallae

ORGANS OF GENERATION. 123

and Natatores. It appears to be very much developed in young
Birds, but dwindles in size so as to be scarcely apparent in adult
age ; slill, however, it exhibits varieties of form and proportions.
Its fuiiclion is not accurately known. At first sight it might be com-
pared to the anal sacs of the Mammalia, while some anatomists on
the contrary regard it as the urinary bladder of the Bird, but both its
position, and the certain fact that urine gets into it only by accident,
militate against this opinion. Furthermore, its equal degree of devel-
opment in both sexes is opposed to the view of its being destined to
receive in the female the seminal fluid of the male, and be thus anal-
ogous to the spermatheca in the female insect.

ORGANS OF GENERATION.

The Generative apparatus in Birds, especially of the female, de-
parts very considerably from its conditions in the Mammalia, and
throughout the whole class exhibits a very close conformity of char-
acter with the type of organization in the inferior Vertebrata.

The Female organs of generation are, as a rule, asymmetrically
disposed, being only fully developed upon the left side. The ovari-
um consists of a small stroma made up of a bed of compact fibres,
in which are situated the very small vitelline vesicles. It is situa-
ted in the lumbar region, and is attached to the superior or anterior
extremity of the left kidney, and partly also to the renal capsule.
The free surface, or that directed toward the abdominal cavity, is
disposed in transverse folds, from beneath which the vitelli gradual-
ly protrude during their growth, so that the ovarium soon assumes
the appearance of a cluster of berries supported upon pedicles or
stalks. The oviduct, spirally contorted like an intestine, and at-
tached to a fold of the mesentery, descends parallel with the left
kidney, and commences by an open funnel-shaped or truncate abdo-
minal ostium, adapted for receiving the ova after they have been
detached from the ovarium. This part is called the infundibulumf
and after being continued into a narrower portion, the oviduct again
expands into a kind of ventricle, within which the vitellus obtains
its complete investiture of albumen, and external to that the calca-
reous shell ; the rest of the tube is termed vagina, and short and
narrow opens upon the left side of the cloaca. The mucous lining
of the oviduct presents well-developed longitudinal folds, and the
whole organ augments in length as well as in capacity during the
period of oviposition. There are only a few Birds that possess a

124 AVES.

clitoris or organ of sexual excitement. These are some of the Ducks,
as Anas clangula, in which the clitoris is upward of half an inch long,
but without any groove. It is of more considerable size, and provi-
ded with a demi-groove like the penis, in the Brevipennes, as the
Ostrich and Cassowary.

Several Birds furnish a remarkable peculiarity, and one which is
interesting in a developmental point of view, namely, in the coexis-
tence along with the left, of the right ovarium either in a rudimen-
tary or completely developed condition. In the earlier stages of
the existence of the embryo within the ovum, it would appear that
the two ovaria and oviducts are in general formed of equal size.
Upon the right side, however, these structures soon cease to grow,
become absorbed, and disappear almost always before the exclusion
of the young bird from the egg. In rare cases, however, as in the
adult Duck and Goose, rudiments of this arrest of structure are to
be seen, and in some Parrots, Eagles, and Vultures also, there con-
stantly occur small rudiments of the right ovarium. The Gos-hawks,
as Falco palumbarius and nisus, and the Harriers (Circus) have al-
ways two ovaria, provided with mature ova at the period of propa-
gation.

As regards the Male organs of generation, the testes of Birds are
always double, and situated like the ovaria behind the lungs against
the renal capsules. They are either of an elongated or rounded
form, and very small during the winter season when the genera-
tive functions are at rest, and in small Birds are then so diminutive
that they are with difficulty discovered. They become however
remarkably turgid at the breeding season, increasing from 20 to 50
times their former size, and are particularly voluminous in some
Birds, as the Fowls and Ducks. They are then rarely of equal but
mostly unequal size, the left being usually the largest. At this period
too of sexual excitement, the contorted seminal vessels are seen very
distinctly through their external transparent tunica albuginea, and
a very beautiful plexus of vessels is expanded over them. From
the seminal vessels proceed the seminal ducts, or vasa deferentia,
which pass in the form of serpentine canals upon the anterior surface
of the kidneys near to the ureters. Occasionally, as in the Passeres,
the seminal ducts form a compLx skein of contortions like a ball of
thread within the pelvis near to the cloaca, into which they open by
a double orifice upon two papilliform projections of the mucous
membrane.

The Spermatozoa or seminal animalcules constituting the moveable

ORGANS OF GENERATION. 125

essential elements of the vivifying fluid in the class of Birds, have
in general an elongated body terminated at one end by a filamentary
appendage or tail. Those of the Passeres, which exhibit some slight
varieties of form in the different genera, are characterized without
exception by a very long body, and a tail spirally contorted after
the fashion of a cork-screw ; they are situated freely in the seminal
excretory duct, but within the testicle itself are found enclosed in long
pyriform cysts.

A true Inlromittent Organ or Penis is vranting to most Birds;
some, however, as the Ostrich, have this part very developed, and
traversed by a groove for the passage of the semen ; it is of smaller
size, tongue-shaped and grooved, as in Crypturus among the Gallinae,
or of a membranous texture and cylindrical, lying in a state of rest
folded upon itself, or spirally twisted within the cloaca, as in the
Drake. According to the recent researches of Joh. Miiller, the varie-
ties in the structure of the penis in Birds may be referred to three
principal types. 1^^, The penis is formed, as has hitherto been ob-
served, only in the Two-toed Ostrich, of two solid fibrous bodies, pro-
vided superiorly with a web of cavernous tissue which is traversed
by a cleft or groove ; a third, more elastic and internally cavernous
body, is situated upon the opposite side, and forms the extremity of
the penis or rudimentary glans. Erection is the result of the dis-
tension of the cavernous tissue. 2d, The glans is wanting and
the penis has a seminal groove imbedded in cavernous tissue, and
also two fibrous bodies. The extremity of the penis with a continu-
ation of its groove is involuted so as to form a sack-like part compar-
able to a prepuce, which can be partially everted and again re-
tracted by an elastic ligament. This structure is met with in the
Cassowary and Three-toed Ostrich or Rhea. 2dly, There is found
a small tongue-shaped rudiment of a penis, surrojmded by a circular
pouch, and either with or without a groove. Examples of this type
are furnished by the Bustard, several of the Gallinae, e. g. Cryp-
turus, Crax, Penelope, and of the Grallae, as the Heron, Stork, and
Flamingo.

Cloaca.

The term Cloaca is applied to the terminal bladder-like expansion
formed by the rectum before terminating in the anus, which occurs
in several Mammalia, as the Marsupials and Monotremes, as well as

126 AVES.

in Birds and Amphibia, and is the common cavity receiving the ori-
fices of the intestinal, sexual, and urinary organs.

In Birds the cloaca usually forms a very wide vesicular dilatation,
a continuation properly of the intestinal tube, nearly as long as it is
broad, and invested externally to a considerable extent by peritoneum
and lined with mucous membrane, a muscular layer being interposed
between these two. The rectum enters the upper and anterior part
of the cavity, protected by a circular fold, and to the left behind it
the oviducts in the female, or the two vasa deferentia in the male,
terminate from either side upon papilliform eminences, provided with
similar folds ; behind these papillae is found a well-developed plexus
of vessels, or rete mirabile. Between and posterior to the orifices of
the excretory ducts of the sexual organs, those of the ureters are
found in juxtaposition with each other, while behind them is situated
a very prominent circular valve, beneath which the bursa Fabricii
opens directly by a small aperture ; last of all, is the large circular
aperture of the cloaca which at the same time constitutes the external
anal outlet. The 'space between the two circular folds guarding the
urethro-sexual cavity and the rectum, has been regarded as a rudi-
mentary receptacle for the urine. The penis, when present, arises
from the lower wall of the cloaca, where it is either surrounded by
folds, or situated, as in the Ostrich, in a special pouch.

The cloaca is closed by a circular sphincter muscle. From the
longitudinal muscular layer particular fasciculi are developed, or, as
in the large Brevipennes or short-winged birds, muscles of consider-
able size, which are inserted into the ischium and expand or open
the cloaca. Peculiar muscles are connected with those of the cloaca
for moving the penis when present, such as an elevator and retractor
of that organ.

BIBLIOGRAPHY. 127

REFERENCES

TO
THE PRINCIPAL WORKS UPON THE ANATOMY OF BIRDS.

In addition to the list of General Works upon Comparative Anatomy
given at page 61, consult the very excellent article Ayes by Professor
Owen in Todd's Cyclopajdia of Anatomy and Physiology, and that of
Birds by Dr. Macartney in Rees's Cyclopaedia ; also Tiedemann's Hand-
buch der Zoologie, Bd. 2, 1810.

Tegumentary System.

Nitzch's System der Pterylographie, with an Appendix upon the devel-
opment and microscopic structure of Feathers by H. Burmeister. Halle,
1840, 4to, with 10 copper-plate illustrations.

Schreger de bursis mucosis subcutaneis, 1825, fol.

Osseous System.

Nitzch's Osteographische Beitrage zur Naturgeschichte der Vogel.
Halle, 1811, with two copper-plates.

Pander and D'Alton, the Second Part of their " Vergleichenden Osteo-
logie" contains illustrations of the skeletons of Rapacious and Stmthious
Birds.

Brandt, Beitrage zur Kenntniss der Naturgeschichte der Vogel. St.
Petersburg, 1839, 4to, are rich in osteological details.

Platner, Bemerkungen iiber das Quadratbein und die Paukenhohle der
Vogel. Leipzig, 1839, 4to.

Earle, in Philosophical Transactions, 1822.

Berthold, Beitrage zur Anatomic, Zootomie und Physiologic. Gottin-
gen, 1831.

Kuhlmann, Dissertatio de absentia Furculaa in Psittaco pullario. Kiliae,
1842, 8vo.

Owen, Trans, of Zoological Society, vol. 2, monograph upon the Anat-
omy of the Apteryx.

Bergraann, iiber die Bewegungen von radius und Ulna am Vogelfliigel.
Miillefs Archiv. 1839.

Muscular System.

Edward d' Alton de Strigum musculis commentatio. Halae, 1837.

Nitzch, Artikel Dermorhynci in Ersch und Gruber's Encyklopiidiet
Band 24.

Owen, Anatomy of Apteryx, op. cit.

Naumann, Naturgeschichte der Vogel Deutschlands, contains observa-
tions, with figures, upon flight of Birds.

12B BIBLIOGRAPHY.

Nervous System.

A. Meckel, in Fr. Meckel's Archiv. fiir die Physiologic, Band. 2.

Swan, Illustrations of the Comparative Anatomy of the nervous system,
Pan 4.

Thuet, Disquisitiones anatomicse Psittacomm. Turici, 1838, 4to.

Ritzel, Commentatio de nervo trigemino et glosso-pharyngeo avium.
Fuldse, 1843, 8vo.

Schlemm, Observationes neurologicse. Berol, 1834, 4to.

Organs of the Senses.

Soemmerring de oculorum sectione horizontali. Gotting, 1818, fol.

Krohn, in Miiilei*s Archiv. 1837, upon the strijjcture of the Iris.

Huschke, Commentatio de pectinis in oculo avium potestate. Jenae,
1827, 4to.

R. Wagner, Beitrjige zur Anatomic der Vogel in den Abhandlungen der
mathematisch-physikalischen Klasse der bayerischen Akademie. Miin-
chen, 1832, S. 295.

Breschet, Recherches Anatomiques et Physiologiques sur I'organe de
Taudition chez les oiseaux. Par. 1836, fol. 8 plates.

Steifensand, iiber die Ampullen des Gehororgans, MuUer's Archiv. 1835.

Huschke, ia Miiller's Archiv. 1835.

Windischmann, de penitiori auris in amphibiis structura, contains good
illustrations and descriptions of cochlea in the ear of Birds.

Scarpa, Disquisitiones anatomicse de auditu et olfactu. Ticini, 1789.

Nitzch, iiber die Nasendriise in Meckel's Archiv. fiir Physiol. Band. 6.

Huber, de lingua et osse hyoideo pici viridis. Stuttg. 1821.

Duvernoy sur les organes de deglutition de la classe des Oiseaux et
Reptiles, in Mem. de la Soc. d'Hist Nat. de Strasbourg, tom. 1.

Digestive System.
Rapp. iiber die Tonsillen der Vogel, Miiller's Archiv. 1843.
L'Herminier in Annales des Sciences Naturelles, 1837 (on craw of
Palamedea cornuta).

Organs of Circulation.

Nitzch, Observationes de avium arteria carotide. Halse, 1829, 4to.

Barkow, Untersuchungen iiber das Schlagader-system der Vogel, in
Meckel's Archiv. f. Anat. und Physiol. 1819.

Hahn, De arteriis anatis commentatio, Hanov. 1830.

Lauth, sur les vaisseaux lymphatiques des Oiseaux, in Ann. des Scien-
ces Naturelles, 1825.

Weber, in Mayer's Anelekten fiir vergleichende Anatomic, Band S,
Bonn. 1838. (Upon Lymphatic sinus of Cassowary.)
Organs of Voice and Respiration.

Henle, Vergleichend-anatomische Beschreibung des Kehlkopfs. Leip-
zig, 1839. 4to.

BIBLIOGRAPHY. 129

Yarrell, on organs of voice in Birds, Linuaean Transactions, vol. 16.
Observations on trachea of Birds, vol. 15. Ramsey upon tracheae of
Birds, in vol. 4.

Cuvier, in Millin's Magasin Encj^clopedique, vol. 2.

Humboldt, Beobachtungen aus der Zoologie und vergleichenden Ana-
tom\e, Heft. 1.

Savart, in Froriep's Notizen, Band. 16, 1827.

Joh. Miiller's Schrift iiber die Compensation der physischen Kriifte am
menschlichen Stimmorgan mit Bemerkungen iiber die Stimme der Siiuge-
thiere, Vogel, &c., Berl. 1839.

Eyton, monograph of Anatidae, Lond. 1838 (figures of inferior laryngeal
labyrinth).

Retizius, on the cells of the Lungs, in Froriep's Notizen, Bd. 35.

Edward Weber, iiber den Bau der Lungen und den Mechanismus des
Athmens beiden Vogeln. Braunschweig, 1841.

Organs of Secretixm.
Joh. Miiller's de glandularum structure, Lips. 1829, fol.
Nitzch, Pterylographia avium, Heft 1 (upon Uropygial gland).
Huschke, de Bursae Fabricii origine. Jenae, 1838, 4to.
Berthold, in novis actis Leopold Acad. tom. 14.

Organs of Generation,
R. Wagner's Beitrage, &c., supra cit.

Joh. Miiller's Schrift uber zwei verschiedene Typen in dem Baue der
erectilen mannlichen Geschlechts-organe bei den straussartigen Vogeln.
Berlin, 1838.

Geoffroy St. Hilaire, Memoire du Museum d'Hist, Nat. tom. 9 (upon
the Cloaca).

9

130 REPTILIA.

CLASS III.— REPTILIA.*

TEGUMENTARY SYSTEM.

The external coverings of Reptiles have not been so closely inves-
tigated, especially in an histological point of view, as those of Mam-
malia, Birds, and Fishes.

The naked Amphibia, such as the Frogs, have a smooth slippery
skin covered by a tesselated epithelium, which is continually being
shed in large irregular patches, or shreds. The nuclei of the epithe-
lial cells are usually distinctly visible in the layers thus thrown off.
Simple glandular follicles, closely aggregated, and more or less
numerous, with frequently star-shaped or ramified pigmentary cells,
are found beneath this epithelial layer. The skin surrounds but
loosely the muscles of the body, and numerous spaces for lymphatic
vessels are found beneath it. It is exceedingly vascular and richly
supplied with nerves, and is therefore very sensitive, and capable of
producing when irritated the most lively reflex phenomena. The
small slightly-developed glandular follicles of the integument attain
so large a size in the Toads, Frogs, and Newts, as to effect a transi-
tion to the more composite forms of glands. In some instances, as
in Salamandra, Triton cristatus, &c., small pyriform follicles, either
solitary or aggregated, extend over a great part of the back, or form,
as in the Toads and Newts, a large warty protuberance behind the
ear, from which an acrid milky fluid may be readily expressed, the
excretory ducts of the several sacs being readily recognised during
this operation.

• Class REPTILIA.

Sub-Class 1 . Reptilia squamigera.
Order I. Sauria. — Ex. Crocodile, Lizard, Chameleon.
II. Chelonia. — Ex. Tortoise, Turtle.
III. Ophidia. — Ex. Rattlesnake, Boa, Viper.

Sub-Class 2, Reptilia nuda s. Amphibia.

r\,Ac.r. i\T p A ^T, . ^„, A S^- Anoura.— Ex. Toad, Frog.

Order IV. Batrachia. | ^^ Urodela.-Ex. Salaman^.

C Derotrcmata.— Ex. AmpMume, Menopome.
V. IcHTHYODEA.— < Perennibranchiata s. Proteidea.— Ex. Proteus, Siren,
i Axolotl.

TEGUMENT ARY SYSTEM. 131

The transition from the Naked to the Squamigerous Reptiles
appears to be effected by those kinds of Reptiles, as the Chameleon,
that are provided with a thin and delicate epidermis, having be-
neath it soft tubercles or excrescences, endowed with the power to
expand and contract. These tubercles, which are continued also
upon the circular eyelids, are separated from each other by strong
annular layers of fibres, and consist of a bed of fibro-cellular tissue,
within which a double layer of pigmentary cells may be detected.
The most superficial pigmentary cells are black, either small and
rounded, or of larger size and ramified, and beneath them are found
some smaller nucleated cells or spots of a bright red color. The
general appearance of these structures remind us very strikingly
of the chromatophorous cells of the Cephalopoda, and it is probable
that in the living Chameleon the same lively contraction of the
walls of the cells may take place as in the Cuttle-fish ; and to this
property may be owing the well-known power of changing color which
that animal possesses. In specimens preserved in spirits of wine,
these cells may be rendered beautifully distinct by treating the skin
with caustic potash.

The Squamigerous Reptiles exhibit various degrees in the devel-
opment of their epidermic structures, giving rise to those numerous
diversities of form which it is the special province of Zoology to
depict. Frequently, as in the Snakes, in Scincus and other Sau-
rians, scales are found that overlap each other like tiles, as in
Fishes, or are disposed in a quincunctial order, or so as to form
annular bands, as in Ophisaurus. Scutes, provided with tubercles
and spines, are also commonly met with, or large plates containing
bony matter, as in the Crocodiles and Chelonia ; in the latter indeed
they constitute true dermal bones, which coalesce with the skeleton,
and form the dorsal and ventral shields, as will be described more
minutely further on. The laminae or scuta of the epidermis are
formed by the coalescence of horny cells, which may be brought
into view by submitting the scales of a tortoise to the action of
caustic potash.

The scales of the Snakes exhibit under the miscroscope very deli-
cate longitudinal and transverse striae, which are probably caused
by the coalescence of cells. In the parts of the epidermis situated
between the scales, the cellular structure may be often more dis-
tinctly recognised. The epidermis is cast several times during the
year, either piecemeal, or like the exuvia of the caterpillar, in one
entire piece from ofT the whole surface of the body. A kind of

132 REPTILIA.

moult is thus performed, as by Birds, and something analogous
occurs not only in many Saurians, but even in Emys among the
Chelonia. The exuviation usually takes place in spring, but fre-
quently upon the occurrence of a change of weather several times in
the course of the year.

Tegumentary follicles of a particular kind are developed in several
Sauria, as the true Lizards, e. g., Lacerta, but also in Iguana,
Cordylus, Gecko, though they are here fewer in number. In the
above named genera a single row of them provided with from
12 to 20 orifices is found extending from the inguinal region to the
knee-joint. These apertures are placed upon scales of a particular
construction, forming tubercular or bulb-shaped elevations. Each
opening conducts into a sac, the commencement of which is divided
into small coeca.

OSSEOUS SYSTEM.

The remarkable diversities which the Osseous System of the
Reptilia presents throughout the several orders and genera, render its
description by no means easy without entering into very consider-
able detail.

As regards the Cranial bones, the best plan will be to consider
them separately in each of the orders belonging to the two sub-
classes of Reptilia, commencing with the naked Amphibia. The
Ichthyodea or Fish-like Amphibia and the Batrachia agree closely
in the conditions of their skeleton, though that of the former approxi-
mates more closely to Fishes. This is exemplified in the structure
of the occipital bone in the Proteus, where the two lateral occipital
bones do not articulate by condyles with the vertebral column, but
are united firmly by synchondrosis with the first cervical vertebra.
In the Salamanders and Frogs, on the contrary, each of the two
lateral occipitals has an elongated condyloid process, and both abut
against each other superiorly and inferiorly, so as to circumscribe
an interjacent foramen magnum. The body of the sphenoid bone
is of considerable size, forming the basilar surface of the cranium,
and is of a cruciform figure in the Anourous Batrachia, running
to a narrow point anteriorly ; it is broad, however, in the Pipa,
and to a still greater degree in Siren and in Coecilia. In the
direction upward, it supports the alae-majores, which are osseous
only in the Tailed Batrachia, being in the Anoura membranous, and
perforated by a large opening for the passage of the optic nerve.
Each of the inferior wings or alae (processus sphenoidei) is provided

OSSEOUS SYSTEM. 133

in the Frogs with two large processes, one in the direction for-
ward and outward, uniting them with the supra-maxillary,
palatal and nasal bone, and the other, or posterior process, with the
OS quadratum. In the Tailed Batrachia, as the Salamander, the
sphenoidal wings are not united to the supra-maxillaries, but
project forward into a free and pointed process ; in Acholotes they
unite with the vomer, but in the Siren are absent together with
the palatal bones. The temporal bone has only the articulating
portion of the petrous bone developed to form part of the cranium,
and this is let in between the circumjacent bones. The articulating
portion of the temporal, or what is called the os quadratum or tym-
panicum, is freely detached from the petrous, and consists mostly
of one, more rarely as in Proteus, of two pieces. It is united above
to the cranium by a suture, abuts inferiorly against the jugal bone,
and articulates with the lower jaw. The pair of parietal bones are
always distinctly present, but occasionally, as in Hyla and Bombi-
nator, separated by an interval or membranous fontenelle. The
two frontals of considerable size are very distinct in the Tailed and
in the Fish-like Batrachia, but are either absent in the Frogs or
anchylosed with the parietals. In front of the frontals, between
them and the intermaxillaries, certain bones are found, the homo-
logies of which it is by no means easy to determine. A pair of
ossicles placed in this situation in the Frogs and Pipa have been re-
garded by some writers as the nasal, by others as lateral ethmoidal
bones. In the Salamander, a pair of similarly placed, but smaller
bones, separated from each other in the middle line by the principal
frontals, have been regarded as particular bones under the name of
the anterior frontals, if they be not upon the other hand viewed as
ethmoids. A single azygos bone, which in many Batrachia and
also in Coecilia appears as a small plate in front of the parietal and
frontal bones, and usually projects downward in the form of a sep-
tum, may be well considered as a middle ethmoidal. The lacrymal
bones are generally absent. The analogue of the jugal bone is
seldom met with, or is at all events not to be determined with cer-
tainty. In the Frog there lie in front of the apex of the body of
the sphenoid a pair of narrow transversely directed bones, which
are united to the superior maxillary, and by a small ascending
ramus, with the nasal bones j they may be regarded as the palatal
bones. In front of them is situated in the Frog a pair of bones of
considerable size provided with minute teeth, and which are proba-
bly the representatives of the vomerine. On the contrary, in the

134 REPTILIA.

Tailed Batrachia, e. g., Siren, only a single pair of ossicles is found
provided with teeth, and which admit therefore of being taken
either for palatal or vomerine bones. The superior maxillaries are
usually of very large size, being rarely, as in the Siren, in a minute
or rudimentary condition. The intermaxillaries are also consider-
ably developed. The inferior maxilla generally consists of an
anterior piece supporting teeth, and a posterior articular portion of
nearly equal length. A small ossicle is occasionally placed upon
its articulating surface, but is generally anchylosed thereto. A
fourth piece is seldom found in the middle of the lower jaw, as is
the case in the rest of the Amphibia.

The Squamigerous Reptiles are characterized by the greater
extent to which ossification is carried in the several bones com-
posing their skull, many parts that in the naked Amphibia were
only membranous having become in them converted into bone. The
individual bones of the cranium are here also multiplied by division,
as is especially exemplified in those that enter into the construction
of the occipital, sphenoid and parietal. In this respect the present
order of Reptiles seems to be most closely related to the Osseous
Fishes.

In all the three orders composing this sub-class, namely, the
Sauria, Ophidia, and Chelonia, the occipital bone is furnished with
only a single condyle, which articulates with the first cervical ver-
tebra, and is usually formed by the coalescence of three ossicles,
namely, by the body of the occipital bone, which is always present,
and the two lateral occipitals. Between the two last is interposed
the supra-occipital plate completin_§- the foramen magnum from
above ; it is of small size in the Ophidians, but mostly large in the
Chelonia, where it projects backward into a pointed crest. In the
last named order, and in the Crocodiles, a pair of supra-laeral
occipital bones, as in Fishes, are intercalated between the others ;
they abut in the direction outward against the mastoid bone, in-
ternally against the petrous, and assist in forming the bony part of
the organ of hearing. The body of the sphenoid is broad and short
in the Chelonia, very elongated and narrow in the Ophidians,
whereas in most Sauria it projects forward in the form of a style.
The alae majores of the sphenoid are in the Ophidians and Saurians
perfectly membranous. There occurs here, however, a peculiar,
narrow, long and style-shaped bone, usually called the columella
[os tympanicum Bojanus, os suspensorium Nitzch) which ascends
perpendicularly like a small column from the inferior wings of the

OSSEOUS SYSTEM. 135

sphenoid upon either side, and supports the parietal bone, which
rests upon it like the capital upon a pillar. This' columella corre-
sponds acconding to some anatomists with the great wings of the
sphenoid. The inferior wings of the sphenoid are very large in
the Chelonia, and united with the body of the bond, and to each
other in the middle line, by suture ; they represent at the same
time the great alae, and unite in front with the palatal bones. In
most of the Sauria they are narrow and elongated, frequently sup-
port teeth, and are connected by synchondrosis with the body of the
sphenoid ; they are separated from each other, and abut posteriorly
against the os quadratum, and in front, generally by means of two
processes, against the palatal and jugal bones. In the Crocodiles
they are very broad, unite in the middle line by suture, and con-
ceal the body of the sphenoid. In the Ophidia the two wings are
widely separated, very elongated, frequently provided with teeth,
and bifurcate into an internal piece united with the palatal bones,
and which can be regarded as an internal pterygoid process, and an
external corresponding with the external pterygoid, and connected
to the superior maxilla. The first piece extends very far back
posteriorly to the union of the os quadratum with the inferior
maxilla. The last piece is considered by many anatomists as a
particular bone under the name of os transversum. The temporal
bone is divided upon an average in all three orders into four pieces.
In the direction inward and backward is situated the petrous
bone, posteriorly and externally the mastoid, which in the Ophidia
is very much elongated and style-shaped, but shorter in the other
orders ; in front of and in contact with this is generally placed the
squamous element, united in the Chelonia and Sauria by suture
with the parietal and jugal bone, but being quite free in the
Ophidia, and advanced further forward. This piece is however
viewed by many anatomists as a peculiar bone, under the name of
anterior frontal, and being divided in the Tortoise into two pieces ;
the posterior of them has been in like manner termed the posterior
frontal. The right interpretation of these bones has, however, given
rise to much contrariety of opinion, relative to which the reader
must consult and compare the special treatises on the osteology of
the Reptilia. The articulating portion of the temporal, called the
quadratal or tympanic bone, is particularly broad and concave in
the Chelonia so as to be adapted for the reception of the large tym-
panic membrane, and superiorly is united by suture with the
squamous and mastoid elements, while jnferiorly it always projects

136 REPTILIA.

into a rounded condyle for articulation with the inferior maxilla.
This bone is similar in character, only narrower, in the Sauria, still
more elongated in the Ophidia, and in both, especially the latter,
moveably united to the mastoid bone. The pariefMl bone is double
in the Tortoises, but throughout almost all the Ophidia and Sauria,
as in the Crocodiles, and even the anomalous genus, Amphisbaena,
it consists of a single usually insignificant bone. The two frontals
are still smaller, and united by a suture in the Chelonia, Ophidia,
and some Sauria ; the Crocodiles and other Sauria have a single
frontal. A pair of bones situated in front of the frontals, frequently
separated, as in the Ophidia and Crocodiles, by the nasal bones, may
be regarded as ethmoidal, or according to others nasal bones. They
appear to be absent in other Reptilia.

The Facial hones exhibit fewer deviations from their normal
type in the higher Vertebrata, and admit, therefore, for the most
part, of being readily and consistently referred to their analogues in the
human subject. In front of the frontals lie generally a pair of mostly
elongated nasal bones, there being very rarely only a single bone
in their place, as in Monitor niloticus. Between the squamous
element of the temporal and the superior maxilla the jugal bone is
intercalated ; it is of very large size in all the Chelonia and Croco-
diles, and is met with in the rest of the Sauria, but appears to be
absent in the Ophidia, and its place to be supplied by the external
wings of the sphenoid. The palatal bones are very generally
present, situated between the pterygoid processes and the superior
maxilla, and are broad in the Chelonia, very elongated and mostly
furnished with teeth in the Ophidia. Between the superior max-
illary, nasal, ethmoid, and jugal bones, there is introduced, as in the
Crocodile, a bone of tolerably large size, which may be either
regarded as a distinct bone by itself, or from the analogy of its
position, as a lacrymal bone. It would appear to be absent in the re-
maining Reptilia. The vomer is in the majority of instances, as in
the Ophidia and Sauria, of large size and double ; in the Crocodile,
however, it is absent. In the Chelonia this bone is single, and
frequently concealed from beneath by the palatal bones. Those bony
plates, called ossa superciliaria s. squamcs supra-orhitales, which are
placed in the Lizards upon the edge of the frontal bones, and
form the roof of the orbitar cavity, are rather to be considered as
pertaining to the tegumentary skeleton, than as true bones of the
face. The intermaxillary bone is generally small and single in the
Ophidia, Sauria and Matamata Turtle (Chelys) ; but double in the

OSSEOUS SYSTEM. 137

rest of the Chelonia and Crocodiles. Externally and behind the
intermaxillary is placed the superior maxillary bone. This bone
is long, and beset with teeth of equal size in the ordinary Ser-
pents, but very short and thick in the Venomous species, where it
is hollowed out posteriorly, and supports the poison-tooth or fang.
The lower jaw consists generally of two halves, which are com-
pletely anchylosed together to form a continuous arch of bone, with-
out any trace of suture, in the Chelonia ; in the Crocodiles and the
rest of the Sauria, both halves are firmly connected by suture and
synchondrosis ; in the Ophidia, however, they are generally per-
fectly loose, being connected only by an intervening membranous
symphysis, so that they can be separated widely from each other ;
indications of this separation may even be remarked externally in
the groove upon the integument covering the chin. By means of
this structure the mouth can be prodigiously expanded so that the
Serpents can swallow living prey of much larger bulk than them-
selves. Each half of the lower jaw consists regularly in the Che-
lonia, Crocodilia, and most other Sauria, of six bony pieces. The
Serpents have at least five, but the venomous kinds probably only
three pieces. When, however, all six pieces are present, they are
as follows : 1st. Most anteriorly, the large Dental piece (pars
alveolaris) which, with the exception of the Chelonia, supports
teeth. 2d. Posteriorly, the mostly small Articular piece (p. an-
gularts) which, either alone, or in conjunction with No. 4, forms the
concave joint for receiving the quadratal bone. Between these
two terminal pieces, the following, united together by suture,
and separable by maceration, are interposed, namely, 3d, the Ex-
ternal accessory piece (p. complementaris externa) a bony plate,
forming the greatest part of the external and posterior wall of the
inferior maxilla. 4th. The Posterior accessory piece {p. cample-
mentaris posterior), which is situated beneath the former, and
frequently concurs with the articular in forming the cavity for the
OS quadratum. 5th. The Anterior or Internal accessory piece (p^
complementaris anterior), a plate of bone which assists in forming the
inner wall of the lower jaw, and abuts anteriorly against the dental
piece. 6th. The Coronoid piece {p. coronoidea), forming the highest
part in the middle of the lower jaw, and which obviously corresponds
to the coronoid process in Man and the Mammalia.

Associated with the diversified forms of the several classes of
Reptilia, are many peculiar modifications in the structure of the

138 REPTILIA.

cranium, which will not aamit of being included under the general
description already given. Thus, in the Chameleon, long processes
invariably project backward from the temporal and parietal bones,
and unite to form an arch, thereby occasioning a most singular form
of skull. . The serpent-like apodal Saurians, as Pseudopus, Anguis,
have the head constructed completely upon the Saurian type, pre-
senting as in them the same style-shaped bone or columella which
occupies the place of the large alae of the sphenoid. Still more
abnormal are the conditions of the cranium in the Saurian genera,
Amphisboena and Trogonophis, in which, however, the halves of the
lower jaw are firmly consolidated ; and also in those genera of Ser-
pents, which depart most from the Ophidian type, as Rhinophis, Tor-
trix, and particularly Typhlops, where the maxillary and nasal bones
form in front a hollow bony bladder, the pterygoid bones are repre-
sented by long sqiiamoid bones, and the lower jaw, which in the
Rattlesnakes consists of three pieces, appears to be formed of one
piece, and to be edentulous.

The Vertebral Column exhibits remarkable diversities in the several
orders of Reptilia.

The vertebrae of the Icthyic Reptiles (Proteus, Siren, &c.) have
their bodies conically excavated at either end, and the intervals
between them filled up by a gelatinous substance, as in Fishes. The
number of the vertebrae is remarkable in the elongated bodies of the
animals belonging to this order, for 60 are to be counted in the
Proteus, 80 in the Siren, and above 100 in the Amphiuma. The
vertebrae are divided into those of the trunk and tail ; the first of
these presenting distinct and often strongly developed transverse
processes, and for the most part spinous processes also, which
entirely disappear at the extremity of the caudal series. The
number of the vertebrae is also very great in the Tailed Batrachia,
as in the spotted Salamander and Tritons, where there are 15 — 16
in the trunk, 20 — 30 in the tail, the numbers varying somewhat in
difl!erent individuals. The bodies are concave anteriorly, and con-
vex posteriorly ; the reverse of this is, however, the case in the
Tailless Batrachia, as the Frogs. These, as well as the Tree-frogs,
have but very few vertebrae, there being from 8-^9 ; in Pipa there
are only 7, with stout transverse processes, which are especially
long upon the second and third lumbar vertebrae, to which succeeds
the single though large sacral vertebra, the transverse processes
of which are particularly broad. A long style or sabre-shaped bone

OSSEOUS SYSTEM. 139

forming the terminal portion of the vertebral column, and extending
nearly to the pubic symphysis, is to be regarded as a caudal
vertebra.

In the Icthyic Reptiles, as also in the Batrachia, with the ex-
ception of Pipa, the first cervical vertebra or atlas is distinguished
by the absence of transverse processes. It never supports any
costal appendages in the true Frogs, though these are present in
the Icthyic and Tailed Batrachia under the form of small, pointed*
bony processes. The Pipa, among the Anoura, has only upon two
of its vertebrae a pair of cartilagino-membranous appendages. In
Proteus, Amphiuma, and Siren, only from 7 to 8 vertebrae of the
trunk, while in Salamander and Triton, nearly all of them support
ribs. The Sternum is very rudimentary in the Sirens and Tailed
Batrachia, being here reduced to some cartilaginous lines and
laminae. The Toads exhibit the first trafces of a distinct sternum,
which, as a short bony piece, projects in them posteriorly into a car-
tilaginous plate, and abuts against the posterior clavicle. In Pipa,
this cartilaginous plate is very broad. Besides the posterior, the
Frogs have an anterior osseous piece which rests in front upon
the anterior clavicular bone. The Serpentoid genus, Coecilia, which
from its having a scaleless integument, and gills at an early period
of its existence, has been referred by systematists to the Batrachia.
presents a perfect anomaly in the fact that all the vertebrae, with the
exception of the atlas and some few caudal vertebrae, bear short ribs.
The number of its vertebrae is also very great, amounting in Coecilia
lumbricoidea to upward of 200.

The vertebrae of the Ophidia are short and -strong, the bodies
concave anteriorly, and provided behind with a spherical head, arti-
culating in a ball and socket fashion with the vertebra next suc-
ceeding. The vertebrae are united moreover by means of the
anterior and posterior oblique processes, which present eight
articulating surfaces invested by cartilage, and surrounded by
capsular ligaments, sufficiently loose to admit «f a great degree of
mobility, but at the same time of an adequately firm union between
the several bones. Superior spinous processes, short and broad,
are generally met with, and frequently also, inferior spinous pro-
cesses. The first vertebra, or usually the first two vertebrae, belong to
the neck, being destitute of ribs. The succeeding vertebrae, support
large, strong, cylindrical and arched ribs, with short appended costal
cartilages ; they are very moveably attached by concave articulating
heads to the corresponding, smooth, rounded transverse processes of

140 REPTILIA.

the dorsal vertebrae, and are more numerous than those of the
caudal vertebrae. In the true Serpents, there are always above
100 vertebrae, usually above 200, or 300, as in the great Boas, while
the Python presents even 400 and upward, of which the caudal make
up only a fourth to a seventh part of the whole series. No traces of
a sternum are met with in the Ophidia.

In the true Sauria the number of the vertebrae and ribs is also con-
siderable, being greatest in the elongated serpent-like forms of that
order, as Anguis, Pseudopus, Chirotes, Amphisboena, where they
amount from 30 — 60 or 100, while that of the caudal vertebrae,
which at the extremity of the tail become very small and rudimentary,
frequently exceeds 100, as in Lacerta, Monitor, (fee. The bodies
of the vertebrae, like those of the Ophidia, are generally concave
anteriorly, and provided with a hemispherical head posteriorly.
The cervical vertebrae, of which the second has an odontoid process,
are few in number, and generally devoid of ribs, but occasionally
support them ; to these succeed numerous dorsal vertebrae, and more
rarely behind them some lumbar vertebrae, e. g., in Monitor, Lacerta,
Chameleon, Draco ; lastly, a sacrum may be distinguished, usually
consisting of two vertebrae, with long transverse processes that unite
it to the iliac bones ; to the sacrum follow next the numerous caudal
vertebrae, frequently provided at their commencement with superior
and inferior spinous processes. Superior spinous processes are
usually found upon the cervical and caudal vertebrae, and upon the
latter, inferior processes also, forming at their root a hemispherical
canal, within which the aorta passes. Transverse and oblique
processes are likewise met with. The ribs are numerous, and
there are several anterior and posterior ones, as in the Lizards,
which are not connected to the sternum. In the Chameleon, the
broad body part of the sternum is merely cartilaginous, and the
costal cartilages, corresponding with the sternal ribs, coalesce to-
gether in the middle line, so as to form so many intersecting bands.
In the Flying Dragon (Draco viridis), the anterior ribs alone are
united with the sternum ; the posterior, especially the three middle
ones, are very long and straight to support a membranous expansion,
which serves the animal as a parachute, to sail through the air
with from tree to tree. Nearly all the Saurians, with very few ex-
ceptions, such as Amphisbcena, possess a sternum, which occurs,
however, in a rudimentary condition in the other serpentoid genera.
It consists, as is well exemplified by the genera Lacerta, Monitor,
&c., of an anterior slender T-shaped or cruciform bone, which

OSSEOUS SYSTEM. 141

corresponds to the manubrium, and behind this of a very broad,
flat, cartilaginous piece representing the body of the sternum,
whereunto are appended posteriorly two small elongated pieces,
parallel with each other, which, but for their recei^dng some of the
costal cartilages, might be regarded as analogous to the ensiform
cartilage of the Mammalia. The sternum becomes smaller, and
more rudimentary in Chirotes, where the ensiform cartilage is
formed by the uni-perforate plate of the body of the bone. In An-
guis, even this is wanting, and there is only left a thin cartilaginous
plate behind the clavicles ; while in Pseudopus, the T-shaped manu-
brium is present along with it, though furnished with shorter pro-
cesses.

The Crocodiles exhibit in the conditions of their skeleton, as in
other general points of structure, various departures from the type
of the remaining Sauria. The relative number of the vertebrae,
with the exception of the caudal, agrees with that of the human
subject, there being seven cervical, twelve dorsal, and five lumbar.
The atlas is remarkable for consisting of four pieces, and support-
ing, as does also the second cervical vertebra, a moveable bone or
rib of considerable size. The five succeeding vertebrae of the neck,
like the twelve dorsal vertebrae, have their laminae united by
suture to the vertebral bodies, and support also short rib-like ap-
pendages, which are attached, like true ribs, by two crura, or in a
furcate manner to the double (superior and inferior) transverse
processes, and terminate externally by a hammer-shaped head, the
anterior and posterior ends of which lie in such a way upon those
of the adjoining vertebrae, as to limit the movements of the vertebrae
in the lateral direction. This structure explains the fact, why one
can easily escape when pursued, from a Crocodile, by moving in a
circle. The sternum is broad anteriorly, and there projects into a
pointed and free median process, while posteriorly it extends by
means of two long slender pieces (sternal ribs), as far as the pubis.
The part opposite to the lumbar vertebrae supports five pairs of free
costal cartilages, without any vertebral ribs. There are only two
sacral vertebrae, as in the rest of the Sauria, and about forty caudal
vertebrae.

It is in the Chelonia unquestionably that the vertebrae, ribs, and
sternum, present the most abnormal structure, for it is in them that
a coalescence of some of the tegumentary bones takes place with
those of the true skeleton, so as to form the dorsal shield, or cara-
pace, and the ventral or plastron. The cervical vertebrae, eight in

142 REPTILIA.

number, are always freely moveable, and to such a degree in the
Land and Fresh-water Tortoises, that the neck can be retracted be-
neath the carapace. They are similar to those of the Lizards,
and provided with long but very depressed superior and inferior
spinous processes. The odontoid process of the second cervical
vertebra is constituted by a distinct bone. The two sacral, as also
the caudal vertebra?, few in number, are provided with strong
transverse processes. The bodies of the dorsal vertebrae are of
very peculiar construction, being very long and narrow, and anchy-
losed to the dorsal shield, and hollowed out superiorly for the lodge-
ment of the spinal cord. By making a perpendicular section of
young specimens, the bodies may be readily perceived with the
arches alternating with them. A distinct series of bones of a
flattened form may at the same time be seen in the upper part of
the section, to be situated upon the spinous processes ; they form
the middle row of dorsal scutes, and are partially anchylosed
together, and with the ribs, by suture. They belong to the dermo-
skeleton, and in adult animals coalesce completely with the spinous
processes. The lateral parts of the carapace also consist of anchy-
losed ribs and dermal bones. In young specimens the ribs are s^en
to be narrow, and are plainly distinguishable from the dermal bones.
The origin of the rib, or its narrow neck, may be also detected, and
the mode by which the head uniting with the bodies of two verte-
brae, and also with their arches, forms the tuherculum costcB. In
adult specimens of the Land Tortoises, the tegumentary bones are
so strongly anchylosed together, that the two ribs which were
originally distinct, become completely absorbed, and even the costal
necks and heads are represented by only thin bony fibres. Ex-
ternally the carapace is surrounded by a circle of quadrangular, or
elongated bony scutes, which belong entirely to the tegumentary
skeleton, and replace as it were, the costal-cartilages, while they are
in part firmly united to the plastron. This union is effected more-
over by means of a sternum, and several dermal bones anchylosed
to it, as may be also seen in young specimens. The plastron con-
sists of eight pieces united by suture, or by fibro-cartilage, and of a
single piece intercalated between the four anterior ones, and which
may be regarded as a kind of manubrium sterni. In the Land and
River Tortoises, at least in Emys, this piece consists of a large and
entire plate ; in Trionyx, and the Marine Tortoises (e. ^. Chelonia),
it is perforated by irregular apertures, and the anterior pieces con-
cur to form a T-shaped bone, which reminds us of the structure of

OSSEOUS SYSTEM. 143

this part of the sternal apparatus in the Lizards. In Trionyx and
Chelonia, the apices of the ribs are free, and abut against marginal
scutes, which never become anchylosed to them. In Testudo and
Eniys the dorsal scutes are most perfectly developed, but they are all
blended together, and united by suture.

The typical structure of the Scapula and Clavicle is best exem-
plified in the Tailless Batrachia, or the Frogs, whence we will
pass to consider its modifications in the other orders. The Scapula
consists in the Frogs of two bony plates, the superior one of which
rests upon the transverse processes of the anterior vertebra, the
inferior narrower helps to form, along with the two succeeding
bones, the articulating surface for the humerus. The clavicles are
two in number upon either side ; the anterior one is narrow, and
flattened like a scale, the posterior is broader ; they both diverge
from each other in front, and come in contact in the middle line
with their fellows of the opposite side, so that the anterior coalesces
with the anterior, the posterior with the corresponding piece of the
sternum.

Next in order to the above, we have to consider the structure of
these parts in the Chelonia. The Scapula is in them a longer and
narrower bone, slightly and loosely connected superiorly by liga-
mentous bands with the first cervical vertebra, while inferiorly it
is continuous directly with the anterior and also narrow clavicle,
so that the two bones are anchylosed into a single one. The poste-
rior clavicle is mostly broader, and expanded in the form of a shovel
at its free extremity, which is directed backward, while in front it
unites with the two former bones by means of synchondrosis, to form
the articulating cavity for the humerus. The whole of this osseous
girdle is completely covered by the carapace and plastron, and is
therefore not visible externally.

In most of the Sauria, the scapula, as in the Frogs, is formed of
two pieces. The posterior clavicle is very broad, projects into seve-
ral points, which abut against a cartilaginous piece that is united to
the sternum, and a corresponding cartilaginous piece of the other side.
The anterior clavicle is rib-shaped, and does not contribute in any
way to the formation of the shoulder joint. Both the anterior clav-
icles abut against each other in the middle line, and together form
a narrow arch in front of the T-shaped portion of the sternum.
The above arrangement of parts is principally displayed by the
Lacertae, and other closely-allied genera. The Crocodiles have a
single elongated scapula, and also a single, tolerably broad and flat

144 REPTILIA.

clavicular bone, forming, with the preceding, the articulating cavity
for the humerus ; the two clavicles rest upon the supra-lateral bor-
der of the broad sternum. The structure is in a like degree simple
in Chameleon, and also in Chirotes. In Anguis and Pseudopus
there is found beneath the skin a bony girdle, without any further
development of extremities ; in this the anterior flattened clavicles
which converge and come in contact with each other, are distinct,
and in a less degree, may the rudimentary scapula, and still less the
posterior clavicle, be distinguished. In Amphisboena, at least in
Trogonophis Wiegmanni, only a rudiment of the anterior clavicle
is present, so that this animal exhibits the greatest amount of im-
perfection, and, as it were, the last link in the interesting metamor-
phoses of the anterior extremities in the Sauria. While, however,
these subcutaneous rudiments of bones occur in the serpent-like
Sauria, it would appear, at least according to present researches,
that in the Ophidia every trace of anterior extremities has disap-
peared. In the Tailed Batrachia, as the Salamanders and Tritons,
the structure is more simple. The scapulae continue in a more
cartilaginous condition, and instead of the clavicles, there is found
anteriorly, a broad, partly cartilaginous plate, which comes in con-
tact with that of the opposite side. The structure of these parts is
similar in the Icthyic Reptilia ; in Siren, and Proteus, the scapula is
at least osseous inferiorly, but in Amphiuma is reduced to a mere
cartilaginous plate. Every trace of extremities appears to be want-
ing in Coecilia.

In the disposition of their Anterior Extremities, the Reptilia ap-
proximate the Mammalia. The humerus is of moderate length, and
in th« Chelonia very much bent, and twisted in such a manner in
relation to the axilla, that the arched surface looks in the direction
backward j two bones are generally met with in the fore-arm, whereof
the radius is usually placed anteriorly, but in the Chelonia, inter-
nally and posteriorly ; it is only the Tailless Batrachia who have
a single bone to their fore-arm, but even this presents a double
groove indicative of its division into two bones, and possesses inter-
nally a double medullary canal. In many Reptiles a peculiar ossicle
is developed in the extensor tendon of the humerus, above the pro-
jection of the olecranon, and, from its resemblance to the patella, has
been called the patella brachialis. It occurs in many Batrachia and
Sauria, more rarely in the Tortoises, but is wanting in many genera,
and in the Crocodiles. In all Reptiles, the carpus is composed of
a double, more rarely a single or triple, series of small ossicles, which

OSSEOUS SYSTEM. H5

vary in number, and present a merely cartilaginous condition in the
Sirens. To these succeed the metacarpal and phalangeal bones of
the fingers, the latter differing in number and proportion, three in
a row being the usual quantity, though in the Sauria there are from
four to five phalanges upon some of the digits. The Ichlhyic Reptilki
have a few somewhat cartilaginous carpal bones. The Land Tor-
toises appear to have no metacarpal bones ; the phalanges are here
very short, but in the Marine Tortoises very long, and well de-
veloped to sustain the swimming paddles. In the FiH)gs, and Sala-
manders, there are found from 5 — 7, and in the Chelonia and
Sauria mostly 9 — 10 phalanges. The two latter orders have mostly
five, the Batrachia four fingers. There is frequently found how-
ever in the males of the Tailless Batrachia, a special rudimentary
bone, or thumb. In the Sauria the third digit has four, the fourth
five joints, and both of them are very long. The Proteus and
Amphiuma tridactylum, as the name of the latter implies, possess
only three digits, while there are only two in A. didactylum, and one
in Choemasaura.

The greatest resemblance to the Mammalian type, and conse-
quently the most perfect condition of the bones of the Pelvis, is
manifested by the Sauria and Chelonia ; for it is here that we con-
stantly find an ilium united to the sacrum, as well as a pubis and
ischium, all these three bones remaining permanently separated, and
meeting in the acetabulum ; in both orders the ischiac unite in
front, like the pubic bones, thus giving rise to a symphysis^ as in
the latter ; in the Chelonia these two symphyses approximate, so
as to leave an intervening obturator foramen. In the Anourous
Batrachia the pelvis has a V-shaped form ; the two iliac bones are
very long and narrow, form the branches of the letter, and coalesce
within such a narrow space behind with the very small pubic and
ischiac bones, as to leave a bony disc, perforated by the two closely
adjacent acetabula. In the Tailed Batrachia, and the Ichthyic
Reptiles (though in some of the latter, as in Siren, it is wanting),
the ilium is a narrower bone, united by ligament with the vertebral
column ; the pubis and ischium are blended together so as to form
a single plate of considerable size, loosely connected to that of the
other side, and for a great extent cartilaginous, especially in the
Sirens. The rudiments of the pelvis are still further diminished in
the Apodal Sauria, wherein a single bone is all that is invariably
found, situated as in many Ophidia beneath the skin, behind the
rib-bearing vertebrae, and nearest to the anus ; it actually supports

10

146 REP TIL lA.

in several species small osseous rudiments of feet. The structure
of the posterior extremities in Pseudopus, Anguis, and Acontias, is
yery interesting, as exhibiting an advanced condition, for here, in-
deed the single elongated pelvic bones are attached by ligament to
the transverse processes of the last dorsal vertebra ; in Eryx, Boa,
Typhlops, Amphisboena, (fee, a pair of very elongated bones, con-
sisting occasionally of several pieces, lie always free, and at a dis-
tance from the vertebral column, in a parallel position with the rectum.
The Amphisboenas, such as Trogonophis, exhibit the simplest form
of pelvis, since it consists in them of a very small flattened bone,
lying posteriorly beneath the integument, and near to the vertebral
column ; it may be regarded as a rudiment of the ilium. This struc-
ture is rather more complete in Ophisaurus.

The Femur is of large size, and strongly curved in the Chelonia ;
the tibia and fibula are generally met with, with the exception of
the Anourous Batrachia, where only a single bone is found, as in
the fore-arm, presenting marks of division. There is frequently
developed in the extensor tendon of the femoral muscles, in many
Sauria, a patella, and in several Batrachia, as in Pipa, a second
patella occurs, situated behind, between the tibia and tarsal bones.
These last, disposed in three rows, continue partly cartilaginous
in the Tailed Batrachia, and present themselves under similar con-
ditions in the Ichthyic Reptiles ; on the contrary in the Anourous
Batrachia the two tarsal bones, corresponding to the os calcis and
astragalus, are constructed after the type of the crural bones, being
of an elongated form, while in front of them is situated a row of
lesser tarsal ossicles ; in the Chelonia, and Sauria, the small tarsal
bones are disposed in two rows. The metatarsal bones correspond
completely in the several orders with the metacarpals. The num-
ber and form also of the phalanges of the toes correspond, with
some exception, to those of the fingers. The last toe but one is
usually the longest. Several Ophidia, and Apodal Sauria, possess
the rudiment of a single toe, which is even provided with a nail,
as in Pseudopus, where the rudiment is very small, arid turned in the
direction upward. It is more developed in the true Serpents, but it
is only in some genera, as Tortrix, Boa, Python, and also Eryx, in
which this rudiment of a toe supports a strong pointed claw. The
poisonous Snakes, Natterers, &c., appear to be destitute of these
structures. In Siren, and Coecilia, all trace of posterior extremities
is likewise wantinsr.

MUSCULAR SYSTEM. 147

MUSCULAR SYSTEM.

The two sub-classes of Reptilia exhibit, even in the structure and
arrangement of their muscles, certain constant differences.

The muscles of the Squamigerous Reptiles who rank nearest to
Birds and Mammalia, are of a redder color, more isolated and sep-
arated from each other into several bundles, and generally possess
greater energy of action, although those of the Frogs, which are
white, are endowed also with remarkable strength. In the Sirens,
and also in the Tailed Batrachia, the mode of arrangement of the
muscles is analogous to that of Fishes, their body, as in them, being
adapted for swimming. The distinctness and degree of separation
of the muscles increase as we approach the Sauria, in which the
muscles are most readily referred for comparison to those of the
human subject. In other respects such great diversities occur
throughout the class, that it were difficult to give a general de-
scription, without entering into more tedious detail than would be
compatible with the nature and extent of this work, and we must
therefore refer the student to the list of books and illustrations
given at the end of the class, for further information upon this
subject.

The Tegumentary muscles are not always so developed in Rep-
tiles, as in Mammalia and Birds, and are completely wanting, for
example, upon the trunk of the Chelonia. Powerful and distinct
muscles of this kind are found, however, in the Serpents, upon the
ventral scutes, to the number of six pairs to each of the latter, which
by means of their action can be slid one within the other ; tegumenta-
ry muscles occur also in the Batrachia.

The Ichthyic Reptilia, the Water-Newts, and the Tadpoles or
larvae of the Raniform Amphibia, which progress in the water by
inflecting tnmk and tail, possess large laternal masses of muscle
similar to those of Fishes, which cover the whdle back, and are
continued directly into the ventral muscles. The large lateral
muscle always arises from the occipital and temporal bone, and
from the arches and transverse processes of the vertebrae, and is
continued to the end of the caudal portion of the column. It is
usually intersected transversely by as many tendons as there are
vertebrae present. A superior and inferior layer of muscles may be
distinguished, which correspond to the m. sacro-lumbaris, and Ion-
gissimus dorsi. Besides the two oblique muscles of the abdomen, a

148 REPTILIA.

rectus may be distinguished, provided with many transverse tendinous
bands. The muscles of the extremities are more analogous to those
of the higher Reptilia.

In the Frogs the muscles of the back, are much shorter, and the
parallel tendinous intersections are limited, as in man, merely to
the abdominal muscles. The dorsal region in the Frog, particularly
behind the head, is covered chiefly by the powerful muscles of the
scapula, and the very small latissimus dorsi. The temporal muscle
is very developed, and in like manner the strong muscles of the
lower law. The pedoralis major is of very remarkable strength,
and gives oflf narrow strips in the direction forward and backward,
and is also divided into several stout bellies ; beneath it lies the
small pectoral, also of considerable size. The extensors of the
humerus and fore-arm (m. m. deltoideus and triceps brackii) con-
sist of very short, but uncommonly fleshy and strong muscular
bellies. The flexor and extensor muscles of the hand present a
similar character, so that in this respect the organ obtains a form
analogous to that of the human subject. Upon the posterior extrem-
ities, on the contrary, the large glutaei are very different from
those of Man, appearing as short, narrow, and but slightly de-
veloped muscles, adapted to the elongated form of the iliac bones, to
which they are attached. The muscles of the legs, from the hinder
extremities being adapted by their length for leaping and swim-
ming, exhibit forms more analogous to the human structures, this
holding good, both with the extensor and fliexor muscles, as the
m. sartoriuSf adductor magnuSf semitendinosus and memhranosusj
and the strong muscles of the fibula, the gastrocnemii. The strong
tendo-Achillis is continued into the plantar aponeurosis, and the
patella-like bone already alluded to, as placed between the tibia
and tarsal ossicles, serves it as a pulley over which to play. The
muscles of the feet are greatly subdivided, and their short bellies pass
into delicate tendons.

The slightest or most rudimentary degree to which the muscles
of the trunk, including those of the back and ribs, are developed,
is met with in the Chelonia, by reason of the peculiar manner in
which their tegumentary is anchylosed to the true skeleton. The
muscles of the face are equally rudimentary, and upon removing the
hard closely overlying integument, we perceive only the temporal
and palpebral muscles. The muscles of the neck, and its nape,
are, on the contrary, well developed, particularly the m. spinalis
cerviciSf which divides into single detached bundles, and is inserted

NERVOUS SYSTEM. 149

into the carapace, beneath which it serves, together with the retra-
hentes capitis et colli, to retract the head of the animal. The
oblique and transverse muscles of the abdomen are of considerable
size, being important agents in the movements of respiration, and
there is found in this region of the body, as in Birds, a rudimen-
tary form of diaphragm, which arises as a broader thinner muscle
than in them, from the vertebral column and carapace, and is inter-
posed between the peritoneum and pleura, without, however, meet-
ing its fellow in the middle line from the opposite side. Beneath
the plastron lie the great pectoral muscles, which, like the large
glutaei, are strongly developed, this being the case also with the
muscles of the extremities, among which the flexor muscles of the
leg, the biceps femoris and semi-tendinosus, are remarkable for their
length.

In the Ophidia the cranial and maxillary muscles, especially those
of the lower jaw, are distinguished by their great development ; for
instance, the temporal, from which a layer is given off over the
poison-sac of the Venomous species, and acts upon it as a com-
pressor. The muscles of the trunk, however, by which locomotion
is effected, are the most remarkable in the Serpents. It is here
chiefly the intercostales, as well as the spinales, semi-spinales, in-
terspinales and inter-transversales muscles that act upon the very
moveably united vertebrae and the free extremities of the ribs. Of
the intercostals, some pass directly from one to the next adjoining
rib, while others pass over several of these bones. Even the pelvis
and rudimental feet of many Serpents (the osteological relations of
which have been described above) are provided with muscles that
bend the extremities as far as their ungual phalanx, and extend or
draw them in different directions.

NERVOUS SYSTEM.

The Brain of the Amphibia ranks greatly inferior to that of
Birds in the relative proportional size which it bears to the bulk
of the body, though it fills up tolerably the cranial cavity, and is
surrounded by the usual membranes. What is remarkable, it ex-
hibits no very important differences in the several orders, though
in this respect we are confessedly still in want of more accurate
investigations.

The Spinal Cord is prolonged into the caudal vertebrae, and is
generally furnished with two swellings corresponding with the

150 REPTILIA.

origin of the nerves to the extremities, but which are wanting in
the Ophidia ; the genus Bipes among the Sauria possesses only a
posterior swelling upon the cord, and Chirotes only an anterior,
in accordance with the position of the rudimentary extremities al-
ready described. The spinal cord is always traversed by a cen-
tral canal. The medulla oblongata is flattened like that of Fishes
in the naked Reptilia, and the rhomboidal sinus is broad and pa-
tulous ; in the Squamigerous Reptilia this part is more dilated,
especially in the proximity of the pyramidal tracts, and the pons is
absent. The cerebellum arises by two crura, and consists in the
naked Amphibia and Ophidia of a hollow medullary layer, which
passes as a small narrow band transversely over the fourth ven-
tricle, without covering it completely ; in the Chelonia it forms a
smooth spherical and hollow swelling, and in the Sauria, as in the
Crocodiles, it is provided with one or several lateral transverse
grooves. In front of the cerebellum are situated a pair of large
oval ganglia, hollow internally, and partly coalescing in the middle
line in the naked Amphibia, as the Ichthyic genera Proteus and
Amphiuma, but which are of largest proportional size, and distinct
from each other in the Frogs, and also in the Sauria ; they repre-
sent the corpora quadrigemina, probably incorporated with the
optic thalami. To these succeed the oval cerebral hemispheres of
considerable size, and which, smooth and devoid of convolutions,
give off* the olfactory nerves. Within their lateral ventricles is
placed, at least in the Crocodiles and Tortoises, an elongated gang-
lion, which corresponds perhaps to the corpus striatum ; and by
the side of this is a distinctly developed choroid plexus, while a
system of commissures for uniting the double parts of the brain
is always met with. The pineal gland is very large in the Che-
lonia, but smaller in the other orders, and lies uncovered by the
hemispheres in front of the corpora quadrigemina. Although this
gland is met with in all the Amphibia, it is difficult to determine
whether it is really present in the Frog. The pituitary appendage
is constantly present, and of noticeable size. The ventricles coalesce
together ; the aqueduct of Sylvius is a very wide canal, and the fourth
ventricle is quite open and uncovered from above, especially in the
Amphibia.

The Cerebral nerves admit of being very easily reduced to their
analogues in the human subject and the rest of the Vertebrata, and
have been traced with the most special care in the Frog, Tortoise,
and Serpent.

NEllVOUS SYSTEM. l^^l

In the brain of the Frog only eight separate nerves are found, the
facial, glosso-pharyngeal, accessory of Willis, and hypoglossal, ex-
hibiting no distinct roots j the facial is still supplied as a branch
from the acoustic ; the vagus, which arises behind the auditory
nerve from the most posterior limits of the medulla oblongata,
passes at a right angle through an opening lying to the outer side
of the articulating tubercle of the occipital bone ; some very deli-
cate nervous radicles, arising from the inferior %acts of the medulla
oblongata near to its anterior fissure, unite with it ahd appear to cor-
respond with the glosso-pharyngeal. Some of the roots of the ac-
cessory nerve appear to be absent, and the hypoglossal is given off
by the first pair of cervical nerves. In the Frogs, as in all the Rep-
tilia, even the Ichthyodea, which live habitually in water, the olfac-
tory nerves are of very considerable size, and proceed generally
from some medullary ganglia situated in front of the hemispheres.
The optic nerves are flat and form a chiasma, and at this seat of
miion there is found a partial decussation formed by the overlapping
of several distinct laminiform faciculi of nervous matter.

In the Tortoises, and probably all the Squamigerous Reptiles, all
the twelve pairs of cerebral nerves are to be found, and their roots
admit of being traced to the base of the encephalon.

As regards the Spinal nerves, their origin by two roots is always
very distinct, and those of the Amphibia, especially of the Frogs,
are particularly well adapted for the purposes of physiological experi-
ment. Their number varies very much, ten pairs being found in the
Frog, and several more in the Tortoise. In the Squamigerous Rep-
tilia the last cervical and first dorsal nerves usually form the brachial
plexus ; from the lumbar nerves is given off the crural, and from it
and the sacral nerves the ischiadic plexus.

The Sympathetic nerve, the existence of which was formerly over-
looked in the Serpents, has now been proved of general occurrence
throughout the present class. In the Frogs the ganglia admit of
being very readily demonstrated lying upon the sides of the Y^rte-
bral column ; they are here situated near to those small white ves;
icles which protrude by becoming swollen chiefly during the spring
of the year, and contain numerous microscopic calcareous crystals.
The plexuses of the sympathetic nerve unite with the vagus, and by
a ganglion with each of the spinal nerves. The sympathetic then
enters the skull through the condyloid foramen, and unites with the
ganglion of the fifth pair or trigeminus, and also with the other cer-
ebral nerves. The cranial portion of the sympathetic in the Ser-

152 REPTILIA.

pent establishes at the base of the cranium communications with
the n. trigeminus, vagus, glosso-pharyngeus, hypo-glossus, and
also with the facial nerve. External to the cranium we meet
with ganglia, which may be compared with the superior cervical
and spheno-palatine ganglion. Upon the heart and the greatest
portion of the trunk, and upon the internal processes of the ver-
tebral bodies, the sympathetic nerves may be traced as extreme-
ly delicate streaks. The ganglia ar-e also very small even in the
largest Serpents. In the Crocodiles, the cervical portion of the
sympathetic is situated deep within the canal formed by the
transverse processes of the cervical vertebrae. The vagus is dis-
tributed in the Serpents as far as over a third of the cavity of the
trunk.

The lateral branch, that arising chiefly from the nervus vagus,
runs along the sides of the trunk as far as the tail, and is of gen-
eral occurrence in the class of Fishes, is met with also in the
Perennibranchiate Amphibia, the Proteidea, and the larvae of Ba-
trachia ; but in the metamorphosis which the latter undergo, it
disappears by degrees, and becomes finally reduced to the auricular
branch of the nervus vagus, or some tegumentary offset correspond-
ing to the former. In the Serpents and Lizards, no lateral nerve
exists.

ORGANS OF THE SENSES.

Organs of Vision.

The Eyeball with its several component parts, approximates in
the naked Amphibia most in structure to that of Fishes, since
they live in the same element as the latter, and the globe of the
eye having to receive the rays of light through the water, is ac-
cordingly flatter in front, and the lens more spherical. In the
Squamigerous Reptiles, the structure of the globe of the eye agrees
more with that of Birds, yet even in them presents certain charac-
teristic diflferences, as may be readily perceived, upon examining
a longitudinal section of the eyeball. In Proteus the eye is very
small, but provided with a lens, and the usual tunics ; in the
genus Typhlops, the eye is still more rudimentary. The sclerotic
frequently contains a bony plate, or several bony scales united to
form a ring, as in Birds. This is the case with the Tortoises,
where ten bony pieces may be most usually counted, and in many

ORGANS OF THE SENSES. 153

Sauria, as Lacerta, Iguana, Monitor. The cornea is more convex
than in Fishes, and the anterior chambers of the eye of various
dimensions. The choroid coat is very thick, frequently covered ex-
ternally and internally with a dense layer of black pigment ; the
ciliary body usually gives off some projecting folds, or ciliary pro-
cesses. The iris in the Batrachia is invested in front, with a
gold-colored pigment. The pupil is capable of a slight degree of
expansion ; for the most part of a circular form, as in Pipa ; it fre-
quently, however, as in the Frog and Salamander, presents the
figure of a transversely directed nearly rhombic oval ; in the Croc-
odile, and many Ophidia, as the Viper, and Rattle-snake, but
without bearing any reference to the poisonous qualities of the
Serpent, the pupil forms a perpendicular slit. The optic nerve per-
forates the tunics of the eye in the direction externally and in-
feriorly, but usually enters the eye of a rounded shape. The
papillary layer of the retina is very greatly developed. The
vitreous humor is mostly small in proportion to the lens, which
last is in those Reptiles that live in water, very spherical, or else
compressed, and frequently, as in Emys, elliptical. In several
Sauria, as in Lacerta, Iguana, Chameleo, Monitor, a feebly-de-
veloped process from the choroid, slightly plicated, and invested
by a layer of pigment, is prolonged into the interior of the eye,
from the point of entrance of the optic nerve, and appears to be
analogous to the pecten in the eye of the Bird, though it never has
so many folds, there being occasionally only two. The globe of the
eye is usually moved by six muscles, four recti, and two oblique or
rotator muscles. To those is superadded in the Frog an infundi-
buniform muscle (suspensorius oculi) divided into several fasciculi,
which arises, in a manner perfectly similar to that described in the
Mammalia, from the bottom of the orbitar cavity, and is attached to
the posterior part of the eyeball.

The Protective and Glandular appendages of the eye exhibit
very diversified degrees of development in the Reptilia. In the
Ichthyodea, the external integument is partly continued over
the eye, as a transparent lamella. The Squamigerous Reptiles
have for the most part a superior, and larger inferior eyelid pro-
vided with a cartilaginous plate, and usually very moveable, and
in addition to these, a third internal eyelid, or nictitating mem-
brane. Numerous varieties however occur ; thus in Scincus, and
Gecko, both eyelids are small and immoveable ; the Salamanders
possess only two short eyelids, but the Frog the additional third

154 ' REPTILIA.

one, which is very moveable ; in the Chameleon the eyelids form a
thick cushion, furnished with a dense muscular layer, and having a
small central aperture opposite the pupil. The nictitating membrane
of the Frog slides underneath the upper eyelid, and is moved by a
mechanism, that reminds us of that already described in Birds.
There are found a detractor and an elevator of the nictitating
membrane ; the latter muscle arises superiorly and in front from
the nictitating membrane, and gives off a tendon, which passes
though a pulley to beneath the eyeball, perforates the infundi-
buliform muscle, and terminates by a small muscular belly attached
to the posterior angle of the eye. In the Ophidia the eye is covered
by a transparent lamella of epidermis, which is shed along with
what is called the exuvia or cast skin. Beneath it lies the conjunctiva
which is reflected over the sclerotic coat, invents the cornea, and so
forms a completely closed sac, which receives the excretory ducts of
the lacrymal gland, and conducts the secretion from the latter
through a duct between the maxillary and palatal bones into the
cavity of the mouth. The Lacrymal gland is situated behind the
eyeball, and is particularly large in the non-venomous Serpents, as
the genus Coluber, but also in the Vipers, e. g. V., berus, where it
was formerly falsely taken from the poison-gland. The Sauria and
Chelonia have for the most part two lacrymal glands, an external,
the largest, and an internal, smaller ; one of these is destined for
the nictitating membrane, and corresponds to the Harderian gland.
The naked Amphibia do not appear to be furnished with a lacrymal
apparatus.

Organs of Hearing,

The naked Reptiles completely approximate the Fishes in the
structure of their organ of hearing, while the Squamigerous sub-
class exhibit a higher grade of organization, by the appearance of a
true cochlea. The tympanic cavity is absent in the Ichthyodea,
and Tailed Batrachia, and both integument and muscles are con-
tinued over the external ear ; the oval fenestra is closed by a car-
tilaginous operculum, into which is inserted a horizontal, elongated,
style-shaped ossicle, like that in Birds, and called the columella ;
the Eustachian tube is wanting. The tympanic cavity is also ab-
sent in the Ophidia, but they have for the most part a columella
and operculum. The Anourous Batrachia have in general a mem-
branous tympanic cavity, which commences by an infundibuliform

ORGANS OF HEARING. % 155

cartilaginous ring, upon which the membrana tympani, uncovered
from without, is stretched. The fenestra ovalis is closed by a car-
tilaginous, slightly concave opexculum, upon which the broad end of
the columella rests, while to its outer extremity a small cartilage
is united, the swollen head of which is fixed upon the membrana
tympani ; the two Eustachian tubes open into the cavity of the
pharynx, and occasionally in the middle of the latter by a common
aperture. In the Chelonia and Sauria the tympanic cavity re-
ceives a partly bony, partly membranous Eustachian tube, which
is mostly very short and broad in the Sauria ; several of the latter
have also the membrana tympani covered by skin and muscle.
The fenestra ovalis is closed by an operculum, upon which rests the
columella, and is united to the membrana tympani by a small car-
tilaginous frequently divided body, that presents a discoidal form
in the Chelonia. If we compare this chain of auditory ossicles
with those of the Mammalia, the small cartilage united to the tym-
panic membrane will be found to agree with the malleus, the columella
with the incus, and the operculum with the stapes, if not in form, at
least in function. Two muscles are found in the internal ear of Rep-
tiles, namely, a tensor tympani, and a stapedius.

A variety of specialities belonging to the auditory apparatus oc-
cur in this diversely constructed class ; of these the following are
perhaps the most important to be mentioned. The operculum is
found in CoBcilia, Amphiuma, Siren, and Tortrix, and a small col-
umella, such as occurs also in the true Serpents, in Amphisboena.
Typhlops and Rhinophis have^io auditory ossicles. In the Sala-
mander there is situated a membrane upon the fenestra ovalis, be-
neath the operculum, and a short canal conducts to the vestibule.
The Bufo igneus, and Rana cultripes Cuv., perfectly resemble the
Salamanders, in the absence of a tympanic cavity, and they have
also, like Pipa, only a single opening within the pharynx for the two
Eustachian tubes. In the Tortoises, the incomplete canal of the
Eustachian tubes is seen at the base of the sphenoid bone, made
up inferiorly by membrane ; in several, as in the genus Chelonia,
the columella is lodged in a posterior excavation of the os quad-
ratum, which receives the membrana tympani, and in Emys expansa
is in the form of a foramen. The columella is moved by a single
muscle. In Chameleo, Anguis, Acontias (in which last the colu-
mella even is wanting), and partly in Pseudopus, the membrana
tympani is covered by muscles and integument, but is freely exc
posed on the contrary in Ophisaurus, while in Chirotes the whole

156 REP TIL lA.

tympanic cavity is absent. The malleal cartilage is tripartite in
the Crocodile, and round in the Chelonia. No external ear is pres-
ent in Reptiles, and it is only the highest form of them, the Croc-
odile, that possesses a rudiment of this structure, under the condition
of a double tegumentary fold or flap, the superior portion of which
contains in its interior a bony plate, and can be shut down by a muscle
like a valve.

All Reptiles have a bony labyrinth lined by a membrane, and
completely separated from the cranial cavity, with which it is merely
associated by the openings for the passage of nerves ; it is situated
within the temporal bone, and partly within the latero-inferior
pieces of the occipital bone. The vestibule is of varied form and size,
and receives the semicircular canals by four or five openings ; the
external canal is placed horizontally, and the anterior and posterior
stand perpendicularly, and have one of the crura common to them
both. Two grooves are usually found in the vestibule, and the sac
lying within it encloses a friable crystalline cretaceous mass, and
in rare instances harder lithic bodies ; the membranous canals ex-
pand into ampuUaB. The cochlea appears to be entirely absent in
the naked Amphibia, but on the contrary to be found in all the
Squamigera. It is found in its simplest condition, as a rounded
cavity with a sac in the interior containing a watery fluid, in
the Chelonia. Yet even in them, a round or cochlear fenestra,
separated from the fenestra ovalis by a thin septum, is found
placed in the direction backward, and closed by a second tympanic
membrane. In the Sauria and Ophidia the cochlea is a hollow
cone, blunt and somewhat dilated at the apex ; it includes a pair of
cartilages, which turned toward each other, are clothed by a plicated
membrane, upon which, as upon the spiral plate of the higher animals,
the auditory nerve expands into delicate filaments ; at the extremity
of the bony sphere is situated a peculiar retort-shaped sac (lagena)
which contains the fluid of the labyrinth, and receives, like the
vestibular sac, a twig from the acoustic nerve. The branches of the
portia dura pass only though the tympanic cavity, and there ap-
pears to be a true chorda tympani present. Hollow cells are fre-
quently found in the tympanic and mastoid bones, and stand in com-
munication with the internal ear.

ORGANS OF SMELL, TASTE, AND TOUCH. 157

Organs of Smell.

It is a very general character of the Reptilia, and is in rela-
tion to their peculiar mode of pulmonic respiration, that the pos-
terior nasal apertures perforate the palatal bones internally, this
being the case even in the Ichthyodea, though, however, some ge-
nera occur among these, in which, as in some Fishes, the nostrils
merely open as small slits behind the lips, as in Proteus and Siren,
while in Amphiuma, Menopoma, Acholotes, &;c., the openings of the
choanae or posterior nares are found in the palate. The nasal
cavities are frequently lined by a plicated pituitary membrane,
e. g. in Proteus, as in Fishes. It is rarely, as in Trionyx among
the Chelonia, that the nose is lengthened out into a small mem-
brano-cartilaginous snout. The nasal canals are in other respects
very simple in the Naked and in the Squamigerous Reptilia ; in
the Batrachia the nostrils are contractile externally. A cartila-
ginous partition separates the two nasal passages, and cartilaginous
plates, invested by mucous membrane, and which correspond to
the turbinated bones, clothe the rest of the nasal parietes, and
project slightly beyond the bones, as cartilaginous external nasal
organs. The nasal passages are of greatest length in the Sauria,
as the Crocodile, and are frequently expanded in front, in the form
of a pouch, and, as in the Cetacea, can be closed by valves ; feebly
developed cartilaginous, or bony turbinated organs are also present.
Besides the olfactory nerves which pass through small ethmoidal
plates, and divide and ramify is a simple manner, a twig also from
the fifth pair of nerves is distributed chiefly to the external part of
the nose. A special nasal gland is found in many Serpents, con-
stantly situated between the superior maxillary, lacrymal, and
nasal bones, and having a proper excretory duct, that opens into
the palate. The CcBcilia and many Serpents have also an orifice
between the nose and eye, which leads into a small blind sac, from
which arises a small tentacle ; the function of this organ is un-
known.

Organs of Taste and Touch.

Although it is doubtful whether the members of the present class
are endowed with a distinct sense of taste, this is certainly not the
case with the Land Tortoises. Reptiles swallow their food nearly

158 REPTILIA.

whole, and the Tongue, though frequently developed to a very great
degree, seldoni exhibits an organization adapted for the exercise of
the gustatory function. The tongue is very variously formed, be-
ing but slightly developed in many genera, and in some instances
scarcely projects from the bottom of the mouth ; it is for the most part
however freely moveable, frequently more or less deeply divided, and
surrounded at the root by a membranous sheath.

The tongue is developed in the most imperfect manner in the
lowest order, or that which comes next to the Fishes, and is ac-
tually wanting entirely in the Proteus and Siren, though this is the
case in some other Batrachia, as Pipa. In the Tailed Batrachia,
as the Salamanders, the tongue is attached to the floor of the
mouth. In the Frogs and Toads the tongue, which is soft, and
lubricated by a viscid secretion, is free and bifurcated posteriorly,
but on the contrary, is broad where it is attached in front behind the
symphysis of the lower jaw, and under this form is admirably adapted
for being flirted out of the mouth with rapidity, to seize the prey that
adheres when touched to its apex.

Among the Tortoises the tongue in the Marine species, at least in
Chelonia, is small and hard, slightly moveable in Emys, and provided
with depressions. In Testudo, on the contrary, it is more manifestly
constructed as an instrument of taste, being beset all over with small
soft papillae.

In the Serpents the tongue is soft and smooth, generally long,
highly moveable andprotrusile, slit at the apex, and surrounded at the
base by a sheath. The tongue is exactly similar in many Sauria,
as in the true Lizards, where it is very deeply slit, especially in the
genus Monitor ; it is entire, though at the same time retractile, in most
Apodal Sauria, as Anguis, Pseudopus. The smooth apapillary tongue
of the Crocodile is very flat, depressed, and united by its whole extent
to the floor of the mouth.

The Chameleon is remarkable for the peculiar stnicture of its
lingual organ. It is very large and protractile, can be stretched
out to a great length like a worm, is traversed by a central canal,
and terminates in front by a kind of fleshy disc, which is concave,
and covered by a viscous secretion. The creature is able to dart
out the tongue suddenly to seize the prey that adheres the instant
it is touched to the tip of the organ, which is so extended during
the act as to appear even longer than the entire body ; the exercise
of this function depends upon the peculiar structure and arrange-
ment of the lingual muscles. During rest the tongue lies retracted

ORGANS OF TASTE AND TOUCH. 159

within the mouth, lodged in a deep groove of the palate, and enclosed
within a long sheath.

The Lingual bone of the Reptilia, whith supports the tongue,
exhibits great diversities, and in the Ichthyodea it resembles most
that of Fishes. It consists in them of one or two middle azygos
pieces lying behind each other, and supporting in front a broad
cartilaginous plate. A pair of lateral pieces represent the anterior
cornua, and serve to attach the lingual bone, through the interven-
tion of ligaments, to the skull. Posteriorly, the single piece coa-
lesces with the superior pieces of the branchial arches, which rep-
resent in some respects the posterior cornua. In the Batrachia,
e. g., the Frog, a similar structure is met with in their tadpole or
larval state. At a later period of existence, after the disappear-
ance of their branchiae, the parts blend more together, and there
remain a middle piece or body, a pair of anterior flattened, and a
pair of lesser posterior, cornua. In the Chelonia, the lingual bone
is very different, and consists frequently of a great number of
pieces, amounting even to 20 in Trionyx. A single median body is
however invariably present, and two pairs of cornua, the posterior
of which usually consist of several pieces ; occasionally, a very
small third pair of cornua is appended to the body in front, as in
Emys. The lingual bone of the Ophidia is very simple, for here
the body is entirely wanting, and there are present only the ante-
rior cornua, as a pair of long cartilaginous filaments, connected in
front by ligaments. In the Lizards a very delicate cartilaginous
filament (^appendix styloidea Losana) unites the small body of the
lingual bone to the skull. The structure of the body of the bone
in the Crocodile is directly the reverse, being flat, very large and
broad, with only the posterior pair of cornua occurring as appen-
dages. In the rest of the Sauria the middle portion or body is pro-
longed into a fine cartilage which penetrates the substance of the
tongue ; two pairs of cornua are found, whereof the anterior are by
far the longest, and frequently present several curves ; the posterior
pair are more simple, regular in form, and always consist of bone.
Occasionally, as in the Lizards proper, the body is slit posteriorly
into two crura, or processes, which correspond to the single process
in Birds. In Ophisaurus and Anguis the anterior cornua are entirely
cartilaginous, and the body is very small in Amphisbcena, so that these
structures conduct at once to those already described as existing in
the Serpents.

As regards the Muscles, the tongue is furnished with a protrac-

160 REPTILIA.

tor and retractor, and four to five additional pairs of muscles, a de-
tailed description of which would lead us out of the plan of the pres-
ent work.

The study of the different structural conditions of the lingual
bone possesses a great amount of interest with the philosophical
or transcendental comparative anatomist, namely, in reference to
the development of the branchial apparatus, or of the visceral
arches, and the mode of division of the foetal vessels in the Verte-
brata.

The tongue may in the Reptilia be frequently used as an im-
plement of touch. Special organs of touch do not exist, but in the
naked Amphibia, as the Frogs, the whole skin is endowed with the
highest sensibility, being supplied by numerous nervous filaments,
and it is on this account that, on irritating the skin in these animals,
they exhibit such strong and varied reflex movements, and are there-
by best adapted for making experiments upon the dynamics of the
nervous system.

DIGESTIVE SYSTEM.

•

The form and armature of the jaws is exceedingly diversified in
the Reptilia. The Teeth, when present, never serve to masticate,
but only to seize the prey, or else they form, as in the Venomous
Serpents, what occurs in no other class of animals, peculiarly con-
structed weapons for inflicting a deadly wound.

The teeth are completely wanting in the order Chelonia ; the
maxillae, with the exception of those of the Chelydes, which are
merely covered by skin, are invested with horn, consisting of super-
imposed lamellae, like those of Birds. In Trionyx, however, the lips
are soft and fleshy.

Some edentulous genera are also found among the Batrachia,
e. g., Pipa. The Toads have palatal teeth, and besides these in
the Frogs, there are rows of short pointed teeth in the upper jaw,
and more rarely also in the lower jaw, as in the genus Hemifractus,
and the Tritons, and Salamanders. Similar diversities occur in
the Ichthyodea ; thus Proteus possesses teeth in both the upper and
lower jaws, and the Axolotl also upon the palate, while in Siren
a pair of large dental plates are found upon the palate, but no teeth
on the inter and supra maxillary bones.

The Sauria, however, exhibit the greatest variety in this respect.
In some cases, numerous very small and pointed teeth stand prin-

DIGESTIVE SYSTEM. 161

crpally upon the edges of the jaws, but occasionally on the palate.
In others, the teeth are either uncinate, chisel, awl, or lancet-shaped,
finely dentated upon the edges, or deeply serrated at the apices, and
occasionally they are conical and blunt. The teeth consist of osse-
ous substance, and a coating of enamel, are rarely implanted in dis-
tinct sockets, but are either anchylosed externally by their fang to
the maxillary bones {denies adnati), while internally the fang is free,
and only covered by the gum, or they are firmly (denies innali) an-
chylosed to the edges of the jaw. Thus the teeth in Monitor, Basi-
liscus, Anolis, Polychrus, Iguana, and others, belong to the first
kind, and to the latter those of Calotes, Draco, Stellio, Uromastrix,
Chameleon, and Ameira. The teeth are small and blunt in Lacerta,
Pseudopus, and Amphisboena, and denticulated upon the edges in
the Monitors. The Crocodiles have pointed, conical teeth, becom-
ing blunter posteriorly, and implanted in sockets ; the numerous
teeth that are destined to replace them are in^^edded, of a conical
form, in the interior of the first set. Upon the more minute
specific arrangements of the teeth, it is the province of Zoology to
dwell.

The Serpents, when unprovided with poisonous teeth, have
curved hook-shaped teeth in the lower jaw, and upon the palatal
and supra-maxillary bones, while the small inter-maxillary bone is
edentulous, or only rarely toothed, as in Tortrix. In different kinds
of Serpents suspected to be dangerous, we meet with a gradual
transition from the solid teeth of the non-venomous, to those of the
Venomous species. Even in our harmless Snake, the Coluber Natrixj
several of the posterior teeth of the upper-jaw appear to be larger
and longer than the others. In some other species, formerly in-
cluded under the genus Coluber, and in Dipsas, Homalopsis, &c.,
the last tooth of the upper jaw is not only longer, but provided with
a more or less deep groove, into which the poison escapes from the
posterior poison-gland. The superior maxillary bone is shorter in the
true Venomous Serpents, and supports upon either side a very long
pointed tooth, behind which, several smaller ones are situated with
their points curved backward, and which are destined to rise up
and replace each other in succession, as they may chance to be lost ;
they are all surrounded for the sake of protection with a common
wide membranous sheath, formed by an elongation of the substance
of the gum.. These teeth are either traversed by a demi-groove,
open externally, as in Elaps, Naja, Bungarus, or by a closed canal,
which stands in communication superiorly with the excretory duct

11

162 REP TIL I A.

of the poison-gland, and opens anteriorly at some little distance from
the apex of the tooth, as is the case in Vipera, Crotalus, Trigono-
cephalus, and others. During the commencement of development of
the teeth, this canal is an open channel, or groove in the tooth, which
becomes either a closed canal at a later period of existence, or re-
mains always open in particular genera, as already mentioned.

The Cavity of the Mouth is occasionally bounded from that of the
pharynx by membranous folds ; in the Crocodile these form a true
velum pelati, and opposite to this, inferiorly behind the tongue, a
second fold projects ; hard papillae frequently occur upon the
palate.

As regards the structure of the organs of digestion, and of the
alimentary canal, the differences that occur are by no means so
great as might be anticipated upon viewing the varieties of outward
form, and of the rest of the organization in the several orders of Rep-
tilia. The. peritoi^um, frequently colored, as in Fishes, by black
pigment, forms mesenteric folds, but never true omenta. It however
invests, more or less completely, all the viscera contained within the
abdominal cavity.

The CEsophagus is generally wiae, or at least very extensible, as
in the Ophidia, where it is thin and membranous ; it is much more
muscular in the Batrachia. In the Marine Tortoises, numerous
soft, cylindrical, and pointed papillas, arranged in an imbricated
manner, are developed upon the epithelium, and have received the
name of oesophageal teeth ; similar papillae occur also in the Fresh-
water Tortoises, but are much smaller in size, and more sparingly
distributed.

The Intestinal Canal always presents a gastric dilatation, although
that is frequently but slight, as in the Proteus, where the canal
passes as a tube, nearly as broad as it is straight from the mouth to
the anus. The stomach is generally very elongated, and has a
more or less perpendicular direction ; frequently, however, as in the
Chameleon, it is placed horizontally, and presents a somewhat
curved figure. It is here also most muscular, and provided inter-
nally with strong longitudinal folds, while, on the other hand, it is
most membranous in the Serpents. The Crocodiles are distinguished
by a very rounded form of stomach, divided into two cavities. The
first, which closely resembles the gizzard of a rapacious Bird, is of
very considerable size, lined with a hard epithelium, and exhibits ex-
ternally a feebly developed tendinous disc, while, by means of a narrow
opening, it leads upward and backward into the second lesser and

DIGESTIVE SYSTEM. 163

more thinly walled cavity that rests upon it. A similar double form of
stomach occurs also in other Reptiles, as in Trigonocephalus and Acro-
chordus javanicus among the Serpents, in whom both the sacs are
separated by a valve. A pyloric constriction is nearly always pres-
ent, but is absent in several genera out of all the orders. The
intestine often exceedingly short, as in Pipa, where there is no
trace of a division into particular portions, makes nevertheless in
most cases some convolutions, and is divided into small and large
intestine, the limits of the latter being defined by means of a coecum
coli. The intestinal canal is longest in the vegetable feeding Che-
Ionia, although it does not exceed the length of the body more than
twice, and next to them, in the Crocodiles.

The CoRcum Coli varies very much, being absent in the naked
Amphibia, and most Serpents, though it occurs among the latter in
Tortrix and Python ; among the Chelonia, Testudo is provided with
a short but wide coecum ; it is very small in Lacerta, somewhat
larger in Scincus. Other Sauria, as the Crocodiles, have no coecum
whatever.

The alimentary canal terminates by opening into the cloaca, and
is usually provided with longitudinal folds or cells, the forms of which
either vary greatly, or pass gradually into each other.

The Salivary glands are exhibited under very different degrees
of development, and are actually wanting in most genera, as en-
tirely in the aquatic Ichthyodea, Batrachia, and the marine Che-
Ionia. Even in the Crocodiles, and many other Sauria, they are
either absent entirely, or only very slightly developed. They occur,
on the contrary, very generally among the Ophidia. The Serpents
have in addition to a gland, that is occasionally developed to a great
extent at the base of the tongue and within the oral cavity, a pair
of considerably elongated glands, which cover the jaws. One of
these, called the supra-maxillary or labial gland, lies along the bor-
der of the upper jaw, and is very conspicuous in the Vipers, less
developed in the largo Serpents, and nearly obliterated altogether
in the true Venomous kinds, although it is still to be seen distinctly
in Homalopsis and Trigonocephalus. The other, the inferior max-
illary or labial gland, is situated upon the external side of the lower
jaw, and is tolerably distinct, even in the true Venomous Serpents.
The poison gland can not be included among the salivary glands, but
is to be viewed as a special organ of secretion.

The Liver of the Reptiles is of large size, either very elongated
and undivided, as in the Serpents and Ichthyodea, or broader, as in

164 REPTILIA.

the Sauna and Batrachia, while it is divided, and still more dis-
tinctly in the Chelonia, into two lobes. A Gall-bladder appears
to be always present, and the hepatic and cystic ducts usually pass
separately to the intestine ; they are very long and slender in the
Serpents ; occasionally, as in Python, several ducts proceed from
the gall-bladder, that subdivide themselves into ten tubes, opening
each singly into the intestine. Sometimes, as in the Frog, Viper
and Crocodile, the two principal ducts unite.

The Spleen is pretty generally present in the Chelonia, and is of
largest size in the Sauria, and, as in the Crocodiles and Tortoises,
situate more to the right than left side. The spleen is small and
rounded in the Batrachia, and more elongated in the Ichthyodea.
It is singularly situated in the Serpents, being, as in Coluber Natrix,
firmly attached to the pancreas, and smaller than it in size (though
in other Serpents it is larger), and readily distinguished from that
gland by its reddish color.

A Pancreatic gland, more or less developed, is always found ; it
is more rarely lobed than simple, and is frequently of a spherical
form. It is provided, as in the Chelonia, with a single, or, as in the
Crocodiles, with a double excretory duct, while in Python there are
several. They enter the small intestine behind the pylorus, accom-
panied by, or near to, the gall ducts. In the Serpents the biliary ducts
perforate the pancreas.

ORGANS OF CIRCULATION.

The diversities in the arrangement of the Circulatory system in
Reptiles are of a very remarkable character, and depend in the
Ichthyodea upon the peculiar combination of lungs and gills which
they possess, and in the Batrachia, upon the remarkable metamor-
phosis that they pass through from their larval, or tadpole mode of
respiration by gills, to that by lungs at a later period of existence.

Those genera of Ichthyodea, as the Axolotl, Proteus, and Siren,
which retain during their whole life three tufts of Branchiae, rank
nearest to the class of Fishes. The Heart, however, consists in
them of a single ventricle, and two auricles (the left the smallest),
separated by a delicate septum, and covering with their auricular
appendages part of the ventricle and bulb of the aorta. Within
the ventricle of the Siren, there is even found a rudimentary sep-
tum. The blood, returning from the body, is collected in the large
superior and inferior venae cavae, which dilate, as in Fishes, into a

ORGANS OF CIRCULATION. 165

great, contractile venous reservoir (sinus venosus), from which the
blood is driven into the right auricle, of considerable size also. The
blood of the two auricles becomes mixed in the ventricle, and its
regurgitation is prevented by means of valves. From the ventricle
arises the truncus arteriosus^ which soon dilates into a contractile
bulb, and is furnished with two pairs of superincumbent valves.
Three branchial arteries are always given off from this trunk, to
ramify upon the gills ; while from the latter three branchial veins
take their rise, and constantly unite into a common trunk, which,
anastomosing with that of the opposite side, forms the descending
aorta. The trunk of the pulmonary arteries is given off in a re-
markable manner from the most posterior of the branchial veins,
while the most anterior of these last furnishes the trunk of the
carotid. The pulmonary veins pour their blood into the left
auricle.

Those Ichthyodea, as the Menopoma, Amphiuma, and Meno-
branchus, which in their perfect condition have no gills, but only
branchial fissures, depart in some degree from the type of structure
just described. The trunks of the venae cavas, with the auricles
and ventricle, are similar in character to those of the Perenni-
branchiate Ichthyoidea, but the number of valves in the bulb of the
aorta is increased, and from it there arise upon either side two
main arches, which unite together behind the oesophagus to form
the abdominal aorta, after having given off branches for the supply
of the head.

In the larvae of Batrachia, the heart consists at first of a single
ventricle and auricle, with a sinus venosus, and bulbus arteriosus
which gives off branchial twigs, as in the Ichthyodea; the left au-
ricle is formed as the lungs become developed, and then the vas-
cular system resembles very much, e. g. in the larvae of the Sala-
manders, that of the fish-like Reptiles with persistent gills, e. g.
Proteus and Siren.

In the Batrachia, when perfectly developed, we always meet with
two auricles, not separated externally, but divided within from each
other by a membranous partition, and a single ventricle. From
the latter arises a single long arterial trunk, which is divided inter-
nally at its origin by an imperfect septum into two halves, and
then splits into two branches, each of which again subdivides into
an arch for the aorta, and an artery for the lungs; these two
trunks communicate throughout life by a pair of ductus arteriosi^
so that a mixture of two difierent kinds of blood takes place in

166

REPTILIA.

them, as well as in the single ventricle. In the Tailed Batrachiathe
aortic arches unite at an early period of existence and high up ; in
the Anourous kind very low down to form the abdominal aorta.

In the Squamigerous Reptiles, as in the Chelonia, the heart is
larger and stronger, the auricles separated externally and provided
with a stronger muscular partition, and the ventricle is divided into
two cavities, by a more or less perforate or complete septum, traces
of which occur, in Pipa, among the Batrachia. The ventricle is
properly the right one of the higher animals developed to a greater
degree, and the conus arteriosus is in like manner a special division
of the cavity from which the aorta and pulmonary artery arise.
Between the auricles and ventricles are interposed strong valves,
and the usual valv. semilunares at the commencement of the
arteries. Each of the two main branches of the pulmonary artery
gives off a large ductus arteriosus to join one of the two aortic arches,
which pass over the corresponding branch of the trachea to the
vertebral column, in order to unite and form the trunk of the abdom-
inal aorta.

Manifold diversities occur in the circulatory system of the several
orders of Squamigerous Reptiles ; thus the heart of the Ophidia, and
also of the Sauria, is more elongated, while on the contrary in the
Chelonia it is short and very broad. The true Ophidia on account
of their single lung have only the left branch of the pulmonary ar-
tery developed, which gives off its ductus arteriosus, and a twig to
the rudiment of the right lung. The two trunks of the pulmonary
veins usually enter the left auricle, united together, but rarely sep-
arate.

The Crocodiles exhibit the most complete form of heart, for in
them the arrangement of its several parts agrees essentially with
that of Birds and Mammalia. The walls of the heart are very thick
and muscular, and the two ventricles are completely separated by a
strong septum from each other. But just at the outlet of the ven-
tricles we find a communication established between the two, so
that the two kinds of blood, to wit, the vitiated and purified, become
mixed together, and thus a similarity is established with the rest of
the Reptilia, and the foetal condition of the heart in Birds and Mam-
malia. The ductus arteriosus of Botal is to a certain extent persis-
tent, and the aorta arises by an externally single, but internally double
trunk from the right as well as left ventricle of the heart, and thus
forms two corresponding aortae.

In all Reptiles the heart is surrounded by a pericardium, which

ORGANS OF CIRCULATTON. 107

in many, as in the Serpents, Tortoises and Lizards, and also in some
Batrachia, sends off one or more tendinous threads upon the apex of
the heart. The heart is generally situated far forward and in the
middle line.

As regards the course of the Arteries great differences naturally
occur in the several orders and genera, which can not be minutely
described in the present work. First of all, a single coronary ar-
tery usually arises from the truncus arteriosus. Two carotids are
generally present in the Squamigerous Reptiles, but only the left in
the Ophidia conveys the blood to the brain ; the right carotid situa-
ted more deeply gives twigs to the cervical muscles and ribs. A
common trunk usually proceeds from the aorta, for the supply of
the viscera, as the stomach, liver, spleen, intestines, and of the mes-
entery, or as in the Ophidia, the mesenteric artery arises separately,
or many small branches occupy the place of the two. In the Ba-
trachia there is found upon the carotid of either side a small dilata-
tion, which is formed by the artery here dividing into a number of
exceedingly fine vessels, -which constitute a spherical spongy kind
of vascular rete, through the meshes of which the main trunk of the
carotid is continued. In the Serpents several arteries anastomose
with the pulmonary arteries, for instance, the hepatic, gastric, and
oesophageal.

The Veins of the body in which, among the larger Sauria and
Chelonia, valves may be demonstrated, usually unite into a posterior
and two anterior vensB cavae, which pour the blood into the venus
sinus already described.

Reptiles possess a double Portal system, one for the liver, and one
for the kidneys, and both of these exhibit somewhat different rela-
tions in the several orders. In the Frog the veins of the intestinal
canal, of the spleen, <fcc., concur to form the vena porta of the liver ;
those of the abdominal coverings, the urinary bladder, and partly
of the posterior extremities, form the portal vessel of the kidneys,
while the efferent veins from the latter organs constitute the trunk
of the posterior vena cava, into which the blood returning from the
sexual organs and liver is poured ; some of the veins of the abdominal
parietes empty themselves into the umbilical vein. For a further
description of the renal veins the reader is referred to the description
of the urinary organs.

The Lymphatic vessels are highly developed as a system in
Reptiles, and form very numerous plexuses, but no glands. The
lacteal vessels, which are very abundant upon the mesentery, are

168 REPTILIA.

collected together into a receptaculum chyli ; one or several thoracic
ducts convey the lymph and chylfe into the anterior venae cavae.

The pulsating lymphatic hearts, v^^hich have been discovered
chiefly in the ischiadic region of the Frogs, Salamanders, Serpents,
Tortoises, and Crocodiles, constitute one of the most remarkable
peculiarities of the present system in Reptiles. They are provided
with muscular walls, the fibres composing which exhibit under the
microscope the peculiar transverse striae characteristic of the
voluntary muscular tissue. The posterior pair of these hearts may
be seen externally pulsating very distinctly immediately beneath
the integument covering the ischiadic region in the Frog ; they
discharge their contents into a branch of the ischiadic vein ; situated
more deeply above the third cervical vertebra, lie the anterior
lymphatic hearts in the same animal, and they appear to impel
their contained fluid into a branch that opens into the jugular
vein. These organs appear to be largest in the Chelonia, where,
placed invariably behind the superior extremity of the iliac bones
upon the origin of the semitendinosus muscle, they measure an inch
in diameter, and receive lymphatic vessels of the thickness of a
quill ; they pour their lymph into a vein that forms a twig of the
reno-portal vein.

If the results be correct (for some degree of uncertainty always
attends them) that have been obtained by injections of the vascular
system of Reptiles with mercury, it would appear that their blood-
vessels are surrounded, to wit, in the Serpents and Tortoises, in a
sheath-like manner by very large and broad lymphatic vessels, and
that plexuses of the latter cover all the viscera, and are moreover
attached by ligamentous filaments to the arteries. A very large
reservoir of lymph is usually situated in the lower part of the belly,
and from its bifurcation the thoracic ducts take their rise ; in the Frog
several such reservoirs are met with. A more direct passage into
the venous branches is never met with.

The relative size and form of the Blood-corpuscules in the present
class is most remarkable ; in all the naked Amphibia, as the Frogs,
Tritons, and Salamanders, they are large and oval in shape, but it
is in the Ichthyodea, as in Proteus, that they attain the greatest size
in the whole animal kingdom, being from eight to twelve times longer
than in man. The corpuscules are smaller, but invariably oval in
all the Squamigerous Reptiles, even in the Crocodiles, and resemble
in figure and diameter those of Birds. The rounded lymph-corpus-
cules are always smaller and more irregular.

ORGANS OP RESPIRATION AND VOICE. 169

ORGANS OF RESPIRATION AND VOICE.

One order is met with among the Amphibia, namely, that of the
Ichthyodea, in which several genera of the family Proteidea or
Perennibranchiata, including the Siren, Proteus, and Axolotl, breathe
thoughout the whole of life by means both of branchiae and lungs.
The remaining Ichthyodea, as the Menopome and Amphiume, respire
by gills like the raniform Amphibia and Salamanders, only during
their larval or tadpole state. The structure of the Branchi<B differs
in many respects i'rom that of the same organs in Fishes. They are
united in a similar manner to the lingual bone, but are not appended
to the skull as in Fishes. The branchial arches are constituted in
the Proteus of three, or, as in the Siren, of four strips of cartilage
upon either side, consisting of several pieces, and which are united
with the posterior shaft of the lingual bone, and frequently, like in
Fishes, are provided upon the surface turned toward the cavity of
the mouth with small teeth, while upon the external side they support
the fringed gills. The coverlids of the gills are merely membranous,
and the complicated opercular apparatus met with in the Osseous
Fishes is completely wanting. In the Derotremata, as the Amphi-
ume and Menopome, where the external gills are absent, an open
fissure exists throughout their whole period of existence. In the
larval condition of the Batrachia four cartilaginous branchial arches
are found, but these disappear at a later period, and then represent
the posterior appendages or cornua of the lingual bone. In this
respect the Tailed and Anourous Batrachia exhibit several differ-
ences.

Three external branchiae only are usually found in the Ichthyo-
dea and Tadpoles, the posterior branchial arch, when present,
supporting no gills. Each gill consists of a long shaft, supporting
upon its edges a double row of branchial fringes in the form of sim-
ple unbranched filaments, upon which the very fine arteries and
veins are so distributed as to form single currents of blood. In rare
cases the fringes are ramified, and project into small but broader
terminal leaflets. In the larvae of the Salamanders and Tritons the
external branchiae are very large, while in the Tailless Batrachia they
are more retracted internally, and a small hole conducts from without
into the branchial cavity.

The Trachea is completely absent in the Ichthyodea and some
Anourous Batrachia, as the Frog and Toad, in which the rudimen-

170 REPTILIA.

tary larynx is continued directly into the membranous bronchi.
In the Salamanders a short membranous trachea exists, and in some
genera of Batrachia, as in Pipa, more or less perfect cartilaginous
leaflets and rings appear upon it. In the Ophidia also, as in Colu-
ber and Vipera, the trachea is often membranous at its commence-
ment, but provided further down with cartilaginous rings, which are
frequently osseous, e. g., in Crotalus and Python, where their num-
ber is very considerable, amounting to 300 rings and upward. The
rings are continued also over the single, or, where two lungs are
present, double bronchi. In the Sauria, the trachea varies in length,
being short with only 20 — 30 rings in the Chameleon, while in the
Crocodile upward of 80 occur. In the Chelonia, as in Testudo
graeca, the trachea is divided deeply and higher up, and is furnished
with strongly developed rings, which are continued throughout the
bronchi into the lungs.

The Lungs exhibit remarkable diversities of form and structure.
Thus, in the Ichthyodea, as in the Proteus, the lungs form a pair
of very long narrow tubes which terminate inferiorly in a slightly-
expanded pyriform bladder. In the Triton they present the appear-
ance of elongated sacs, of tolerably uniform width throughout, and
terminating in a point, while in the Frogs they are much shorter
and broader. When the lungs have been fully expanded, they ex-
tend through the greater part of the abdominal cavity. In many
Sauria the lungs present similar characters, and are both of equal
size, e. g., Scincus. In the Apodal Sauria, as Anguis, Pseudopus, and
also in Chirotes, only one lung, and that usually the right, is pres-
ent, but in those Sauria with very short or only a single pair of feet,
as Zeps and Pipes, the left also exists, but is one third or more short-
er than that of the right side. In the Ophidia, as Boa and Python,
the length of the left lung is generally less by a third or half than
that of the opposite side, but in Coluber, Crotalus, and others, it is
much smaller, and quite rudimentary, appearing as an almost obliter-
ated appendage. The genera Coecilia and Amphisboena appear on
the contrary to have the left pulmonary organ developed, and the
right shortened, this arrangement probably varying according to
the species. In the Viper and other Serpents there is only a single
lung, which on that account is always very long. The lungs are
flat and short in the Crocodile, but largest and most perfectly form-
ed in the Chelonia, where they extend beneath the carapace as far
as the pelvis. Here and there, as in Polychrus and Gecko, and es-

ORGANS OP RESPIRATION AND VOICE. 171

pecially in the Chameleon, hollow ccscal diverticula are given off from
the lungs.

The internal structure of the lungs differs in the several
orders and genera of Reptiles, the respiratory surface being very
much increased in the Squamigera by the development internally
of cells, while in the lowest orders, the lungs are simply hollow bags.
In the Ichthyodea and Tailed Batrachia their condition is of the sim-
plest kind, as in Proteus and Triton, where they form, as already
stated, simple bladder-like sacs, directly continued from the mem-
branous larynx. In the Salamander the lungs begin to assume an
uneven appearance from the occurrence of small inversions. In the
Anourous Batrachia their respiratory surface is increased by mem-
branous cells which project into them internally, and form with the
lateral walls open rhomboidal, or more or less hexagonal or polyhe-
dric spaces, upon which lesser cells again rest, these last opening
in the inward direction into the common cavity of the lung. The
lungs are more perfectly formed in the Chelonia and Sauria, although
several genera of the latter frequently retain the simple character
of membranous sacs, with an areolar tissue developed upon the in-
ternal surface of their walls, but no internal dissepiments. In both
orders the cartilaginous rings of the bronchi becoming more imper-
fect are continued as strips, which, cartilaginous at first, are next
converted into tendon, and form rounded or angular meshes which
rest partly upon the walls of the lung, and enclose lesser meshes or
air-cells, or are united together internally so as to form numerous
dissepiments ; thus the whole lung is filled more or less by a coarser
or finer areolar tissue, and presents a number of cellular portions
which can be all inflated from any one point. The middle areolar
tisrsue is usually absent in the upper and lower (or only in the lat-
ter) parts of the lung, and the cells are then merely parietal, and
leave cavities of considerable size in the interior of the organ. The
lungs of the Crocodile and Monitor are the most completely made
up of cells. In the Serpents it is commonly only the commencement
of the one developed lung that is replete with cells and areolar tissue,
its posterior extremity being in the condition of a thin walled and very
extensible bladder. The size of the cells varies, but they are always
larger than in Birds.

In the Amphibia, which present the lowest forms of air-breathing
animals in the class Vertebrata, the study of the structure of the
Larynx as an instrument of voice is one indeed of particular interest.

Its simplest structure is exhibited by some Ichthyodea, e. g.^ Pro-

172 REP TIL lA.

teus, in which it forms a cylindrical cavity, which is narrow supe-
riorly toward the glottidean fissure, and beneath the latter is con-
tinued through the intervention of two sacs into the lungs. Within
this rudimentary larynx are situated several strips of cartilage, cor-
responding to the pars arytcBnoidea and laryngo-trachealis. In the
Tritons and Salamanders, where the sacs or rudimental indications
of the bronchi are absent, the laryngeal or vocal box, compressed
from before backward, is supported by a superior arytenoid, and
an inferior lateral or laryngo-tracheal cartilage. The structure is
similar in one family of Ichthyodea, comprising the Menopome, Am-
phiume and Axolotl, as also in Coecilia, where several tracheal rings
are already met with.

Resembling more nearly the larynx of the higher animals, but
with diverse modifications, we come now to consider the structure
of the laryngeal cavity in the Anourous Batrachia ; a subject of
special interest from the differences which it presents in the two
sexes of these Amphibia. This latter circumstance is very strikingly
exemplified by its conditions in the males of the genus Pipa. The
arytcBnoid cartilages are here of considerable size, triangular in form,
and articulate with the lateral or laryngo-tracheal cartilages situ-
ated beneath them, and here united into a single body ; this, which
corresponds to the thyroid cartilage, forms at the same time the up-
per part of the trachea, and diminishes greatly in size opposite to
the arytaenoid cartilages. The glottidean fissure is situated quite
close to the root of the tongue, and there are always found in this
situation, with but few exceptions, as in Pipa and Dactilethra, a pair
of vocal chords, that correspond to the ligamenta inferiora of the
Mammalia, and are attached before and behind to the arytaenoid
cartilages. Beneath the vocal chords are situated a pair of cavities
analogous to the ventricles of Morgagni. A pair also of inferior vocal
ligaments, narrower than the true ones, and formed by simple folds
of mucous membrane, frequently occur.

In the Squamigerous Reptiles, the separation of the larynx from
the trachea is more distinctly shown. The arytaenoid and thyroid
cartilages in the Serpents are frequently blended together. In the
Crocodiles and Tortoises, and in many of the Sauria, the thyroid
cartilage is very developed, isolated from the rest, and being pro-
vided with special processes, resembles that in the larynx of Man.
Frequently there is developed from it in the direction upward a
fold of mucous membrane or a processus epiglotticus, which as in
the Chameleon, may be viewed as a rudiment of the laryngeal valve.

* ORGANS OF RESPIRATION AND VOICE. 173

A true cartilaginous epiglottis is found to be present either as a nar-
row papilla, or broader lobule, in different Serpents and Sauria. The
vocal ligaments are not nearly so generally present among the Squami-
gera, as the Anourous Batrachia. They are wanting in all the
Serpents, the hissing sounds of these animals being produced like
the act of whistling in the human subject, by the edges of the narrow
laryngeal outlet performing friction against the air in expiration.
The Lizards possess a pair of narrow vocal chords. A thick fold of
mucous membrane with a subjacent pouch is all that is to be remarked
in the Crocodile.

A peculiar structure in the genus Chameleo, reminding us of the
laryngeal pouches in many Apes, is well deserving of notice. Be-
tween the larynx and first treacheal ring is found an opening which
leads into a membranous sac that can be distended with air.

As concerns the Laryngeal muscles, an expansor of the glottis {m.
dilatator aditus laryngis Henle) is found, very generally in the Ba-
trachia, and arises either from the vertebral column and the skull,
or from the lingual bone (this being the case in all the Anoura), and
is inserted into the edge of the vocal fissure, or into the cartilago
lateralis of its corresponding side. Besides this muscle, in examples
of a more perfect structure, we may distinguish three others, a di-
lator of the laryngeal inlet, with a contractor and a compressor of the
cavity of the larynx, all of which exhibit manifold diversities.
Among the Squamigera an elevator and a depressor of the larynx are
found in the Serpents, as a pair of long muscles, that are absent in the
higher orders of the sub-class, but a compressor and dilatator aditus
laryngis are universally present.

In some of the Anourous Batrachia, e. g., in the Tree and Meadow
Frogs (Hyla and Rana esculenta), but not in R., temporaria, accessory
organs are associated with the vocal apparatus. They consist of a
pair of thin-walled, very dilateable bladders, situated by the articu-
lating surface of the inferior maxilla, and which open always into
the cavity of the mouth below the Eustachian tubes ; they contrib-
ute to strengthen the voice, by serving as an apparatus of reso-
nance.

Between the carotid arteries and resting upon the trachea, a small
vascular gland, which may be viewed as the analogue of the Thyroid
gland, is found in several Squamigerous Reptiles, as in the Tortoises,
Crocodiles, and also in the Serpents.

174 REPTILIA.

URINARY ORGANS.

All Reptiles are provided with Kidneys^ which are commonly
situated far backward and deeply within the pelvis. In the
Anourous Batrachia, however, and especially in the Ophidia, they
are placed far forward, and in the latter order the right kidney lies
asymmetrically in relation to the left, being placed higher up and
in advance thereof. The size of these organs varies in the several
orders, but is generally very considerable ; they are very narrow,
elongated, and run to a point anteriorly in the Ichthyodea and
Tailed Batrachia ; of an elongato-oval form with slight incisures
in the Lizards and Anourous Batrachia ; in the Ophidia they are
for the most part very elongated and flat, and divided into round
lobules, while in others, e. g., Boa, they are portioned out into narrow
plates lying one upon the other; in the Crocodiles and Chelonia
they are broader, and frequently, especially upon the posterior part,
provided with indentations. Occasionally, as in the Rattle-Snakes,
each kidney is completely divided into an upper and under piece.
In rare cases both kidneys, as in Lacerta ocellata, appear to coalesce
inferiorly into one entire mass, a structure of which we are
reminded in several Fishes and Birds, and occasionally in its very
interesting occurrence as abnormal in Man, where it is due to an
arrest of development. As regards the more minute structure of
the kidneys, we may perceive in their early conditions in the Ba-
trachia and Ichthyodea, narrow coecal canals supported upon the
extremity of the ureter, and in the Ophidia these, which are much
longer and more contorted, unite together in a racemiform manner,
and give off at intervals small trunks into the ureter ; even in the
more compact substance of the kidneys in the Chelonia and Sauria,
the blindly terminating coecal canals are found to be continuous
from the peripheral to the middle part of the organ, with ramifica-
tions of the ureter. The kidneys, as has been already stated, have
a special portal system. The afferent veins form, e. g., in the Frog,
a couple of small trunks which enter the kidney inferiorly and
externally, and are distributed upon its posterior surface. The
efferent veins take their origin by radicles from the anterior surface,
and pass to the inferior vena cava. The ureters are mostly short
and delicate, situated usually upon the internal inferior edge of the
kidney, and in the Ophidia attain no inconsiderable length ; they
perforate the walls of the posterior region of the cloaca, discharging

PARTICULAR ORGANS OF SECRETION. 175

into that cavity in the Squamigeroiis, a constantly firm chalk-like
and crystalline urinary secretion, but which is on the contrary in the
Naked Reptiles in a fluid state. There arises usually from the
anterior walls of the cloaca (with however it would appear the ex-
ception of the Ophidia) a bladder which is usually small and round-
ed in the Sauria, elongated but simple in the Sirens, in the Chelo-
nia mostly slit into two round lobules, and frequently, as in the
Batrachia, fissured and developed to a very great degree ; this is fill-
ed usually with a large quanity of colorless fluid, and has been viewed
as an urinary bladder. Its walls are very thin and membranous,
traversed by vessels, and the fluid contained therein consists of real
urine and uric acid.

The Renal Capsules are found in all the Squamigera, and may
be distinctly demonstrated in all the larger Serpents, Lizards, and
Tortoises ; they are mostly of a yellowish color, elongated in form,
and are usually situated above the kidneys, either within the folds
of the peritoneum, or more freely near to the sexual organs ; inter-
nally they rest upon the vena cava, to which they are united by ves-
sels. Besides the Ichthyodea, they are wanting also in the Batrachia,
but in the Anoura, we meet with large, yellow-colored lobes of fat
divided in a digitate manner, and placed upon the anterior extremities
of the kidneys, while delicate streaks of granular fat course over the
anterior surface of those organs.

PARTICULAR ORGANS OF SECRETION.

In the order Amphibia the tegumentary follicles are occasionally,
as in the Toads and Salamanders, developed to a very considerable
degree, being in part distributed in small groups over a great extent
of the body, and forming, e. g, in Bufo and Salamandra, a protuber-
ant conglomerate mass upon either side the head behind the ears.
In the Salamanders and some Tritons they are situated chiefly in
rows along the back ; these follicles, as well as the crural glands of
the Lizards, have been described in treating of the tegumentary
system. Each aperture leads into a pouch, the commencement of
which is slit into small blind pockets or coeca. In some Sauria an
aperture is constantly found behind the anus, which conducts
into a small pouch secreting a substance of a peculiar odor. -
The analogous follicles in many of the Ophidia, as in the com-
mon Snake (Coluber natrix), male as wejl as female, are very
long and distinct. They are situated below the vertebral column
near to the penis and behind the anus, upon the verge of which they

176 REPTILIA.

open. They are lined internally by a mucous membrane, which is
covered with a net-work of flat cells and depressions, that secrete a
fetid kind of grease. An epithelium provided with the same cellular
surface rests quite freely upon the mucous membrane of these Anal
sacs. The Chelonia possess similar but more rounded anal sacs.
The Crocodiles have a thicker walled pouch situated beneath the
integument upon the middle of the lower jaw, and which is called
the musk gland, from its secreting a dark-colored grease smelling
like musk.

The most remarkable peculiarity in the secretory organs of the
present class is afforded by the Poison glands, which occur, however,
only in the order Ophidia.

The Poison-gland corresponds in some measure with the parotid
salivary gland, and agrees most strikingly in situation with the
latter in the Venomous Serpents, having posterior venom-teeth, e. g.
Dipsas, Homalopsis, where it lies more freely, not invested by any
fibrous tunic, and has a short excretory canal. In the typical
Venomous Serpents, as Vipera, Naja, Crotalus, Trigonocephalus, the
poison-gland is situated more behind and beneath the eye, consisting
of short tubes in Naja, or of hollowed ramified lobules (Trigono-
cephalus) and is surrounded by a dense, mostly double fibrous sheath,
this again being covered by a layer of muscular fibres, which
proceed partly from the temporal muscle, and serve to compress the
gland and forc^ its contained secretion into the excretory ducts ;
the latter courses along the external surface of the superior max-
illary bone, and enters an opening placed at the root of the poison-
tooth. The situation and structure of the poison-gland are similar
in the Aquatic Serpents (Hydrus and Hydrophis). This gland
occurs in an unusual situation in Causus rhombeatus, being ensi-
form, situated in a channel-like cavity, and extending to the 18th
or 19th vertebra, so that it reaches over more than a seventh part
of the whole length of the body ; its excretory duct extends from the
poison-tooth to behind the quadrate bone. The ejection of the
poison into a living animal is accompanied by peculiar and frequently
fatal effects.

ORGANS OF GENERATION.

Reptiles, like all the Vertebrata, have two distinct sexes, which
exist in tolerably equal numerical proportion to each other, though
with some preponderance upon the part of the female. The germ-
preparing sexual organs are always situated within the abdomen,

ORGANS OF GENERATION. 177

and usually in front of the kidneys. The ovaria and testes are
usually placed symmetrically upon the two sides, and are of equal
size ; it is rare for the testis or ovarium of the right side to be situated
higher up than the left, as in the Ophidia and Blindworms (Anguis),
where their asymmetrical arrangement reminds us of that of the lungs
and kidneys of the same side.

In all the naked Amphibia and among the Squamigera, as the
Ophidia and Sauria, the Ovaria are in the form of simple sacs or bags,
mostly of a rounded shape, e. g., Ichthyodea, Tritons, Salamanders,
and Ophidia, or of a more elongated form, e. g., Sauria, lined inter-
nally with a smooth mucous membrane, beneath which the ova are
developed, and externally invested by peritoneum. Occasionally,
as in the Anourous Batrachia, the ovaria are divided into lobes ; and
partitions projecting into their interior, form there cells within which
the ova are found. In the direction forward, each sacciform ova-
rium is provided with a round or sometimes tubular aperture for
the exit of the ova ; within the smallest and most primitive ova a
chorion, vitellus, and germinal vesicle may be clearly distinguished,
the latter being in the Naked Amphibia provided with numerous
small germinal spots. In the Squamigera the germinal spot is always
single. In the Chelonia each ovarium, as in Birds and Cartilaginous
Fishes, consists of a stroma, upon the free surface of which, namely,
that turned to the ventral side, the ova are developed.

The Oviducts are two long membranous, frequently multi-contort-
ed tubes, which are kept in their place by folds of mesentery, and
are provided in the direction forward in some Reptiles, as in the Che-
lonia, with an infundibuliform abdominal ostium, into which the ova,
after being detached from the ovarium, are received. In the Ba-
trachia the opening of the oviducts is placed at a great distance from
the ovarium, in the proximity of the heart. Strong and even mus-
cular fibres lie between the external peritoneal and internal mucous
membrane, and by means of these the oviducts are capable of exer-
cising considerable peristaltic movements like the intestines. Their
internal mucous membrane exhibits, chiefly in their lower or poste-
rior part, strong longitudinal folds or villi, upon which the albumen is
secreted, being the first investment which is here obtained by the ova.
The oviduct is usually more widely dilated in the posterior part.
Both oviducts open into the cloaca separately. A clitoris has been
found hitherto only in the Chelonia and Crocodiles.

The Testes are of an elongated form in the Ichthyodea and Ophi-
dia, or rounded, as in the Frogs, Sauria and Chelonia, and frequent-

12

178 4lEPTlLIA.

ly divided by constrictions into several portions. A single testicle
is most commonly found upon either side ; occasionally, however, we
meet with two and even several testes united one behind the other
merely by the seminal vessels, as is the case in the Salamanders,
where three to four such testes occur. The testes are invested ex-
ternally by a thick fibrous coat, and consist internally of long or
short and narrow coeca. The open extremities of these cceca pour
the seminal fluid into several ducts, which unite to form a straight
or contorted vas deferens, running down in front of the kidneys.
Both vasa deferentia open into the cloaca. Upon the testes, as also
upon the ovaria, there are appended occasionally in front, large
yellow-colored lobes of fat divided in a digitate form, e, g., in the
Tailed Batrachia, while on the Anoura the adipose lobes are elon-
gated, undivided, and attached by mesentery to the internal side of the
sexual organs, or that turned toward the vertebral column.

The Spermatozoa contained in the semen of the Reptilia exhibit
very numerous diversities. Those of the Squamigera, however,
present the greatest degree of uniformity. They have, in general,
in the common Snake for example, like those of Mammalia, an elon-
gated body pointed anteriorly, and a very fine filamentary tail. In the
Naked Amphibia greater varieties occur, while in the Frogs their
body is elongated and narrow, but not very long ; the spermatozoa
of the Tritons and Salamanders are slender and circularly contorted,
attain a very remarkable length, and exhibit very peculiar movements ;
other anomalous and singular forms occur, e. g., in Bombinator.
The spermatozoa are probably of largest size in the Proteus, thus ex-
hibiting an interesting analogy with the blood corpuscules.

A proper external organ of copulation or sexual excitement, namely,
a Penis, is absent as a rule in all the Naked Amphibia, Batra-
chia as well as Ichthyodea. Still however in the Tritons, and in
some also, perhaps all the Ichthyodea, there is developed, at least
during the period of the coitus, an organ which may be viewed as
a rudiment of a penis. It consists of an acuminate papilla of con-
siderable size, situated within the cloaca, and continued poste-
riorly into two short thick crura, which form a groove with the
posterior wall of the cloaca, into which the semen is conveyed as it
issues from the adjacent mouths of the vasa deferentia. This pa-
pilla is imperforate, but, though very irritable, is incapable of erec-
tion. This structure resembles much the rudiment of the penis
that occurs in the male Ray-fish. Accessory glands occur in the
Ichthyodea and Tailed Batrachia. They consist of a very dense

ORGANS OF GENERATION. 179

glandular layer, which surrounds the cloaca, and forms a protuberance
around the anus, which consists of several layers of coeca, and pro-
jects very much at the time of the coitus.

The Lizards and Serpents possess a double penis capable of being
everted ; these two intromittent organs are in the Serpents often
very long, slender and pointed, and are here, frequently like other
organs, e. g.. Coluber natrix, asymmetrically developed, the left be-
ing the longest. They lie extended beneath the integument in a
cavity behind the anus at the commencement of the tail, and can
be everted from the cloaca, as in the Ducks and Geese, by a pair of
special muscles ; they are devoid, however, of elastic tissue and a
fibrous body. At the season of the coitus they form, when everted,
a double tube, which serves for the exit of the semen. Frequently,
as in the Vipers and Rattlesnakes, and also in Python, each of the
two penes is bifurcated at the extremity.

The penis is single in the Tortoises and Crocodiles, and resem-
bles more that of the Two-toed Ostrich among Birds ; it consists of
a fibrous body, and has a groove upon its upper and anterior sur-
face, which is imbedded in cavernous tissue, and into which the
seminal fluid is received from the seminal ducts. In front we find
a glans of varied form, infundibuliform in the Crocodiles, and very
largely developed in the Tortoises ; the whole of it consists, as in
Man and Mammalia, of cavernous tissue. A muscle serves to draw
the penis out of the cloaca. It is peculiar to all Reptiles, that the
urogenital orifice lies invariably, as in the higher Vertebrata, in front
of the anus.

In the males and females of the Tortoises and Crocodiles, there is
found what are called the Peritoneal canals, which conduct as mem-
branous tubes or slits from the peritoneal cavity into the cloaca,
and are continued upon the penis as far as the glans, and there ter-
minate blindly ; in the female they are to be traced to the root of the
clitoris ; in both sexes they remind us of the vaginal canals of the
Mammalia (see p. 54), and are probably the remnent of a foetal struc-
ture, viz., the excretory ducts of what are called the false kidneys or
Wollfian bodies.

The two sub-classes of Reptiles, differing, as we have already
seen, in so many important particulars from each other, are also
developed from the ovum in an entirely different manner. The
Naked Amphibia agree with Fishes in having neither amnion nor
allantois,both of which foetal structures occur, however, in the Squami-
gera, of whom many have proposed to form a distinct class, limit-

180 jBIBLIOGRAPHY.

ing to it the name of Reptilia. In the presence of these embryonic
structures, the Serpents, Lizards, and Tortoises, agree therefore with
Birds, Mammalia, and Man.

REFERENCES

TO THE PRINCIPAL WORKS UPON THE ANATOMY OF REPTILES.

In addition to the hst of General Works upon Comparative Anatomy
given at page 61, consult the Article Amphibia, by Thomas Bell, in Todd's
Cyclopsedia of Anatomy and Physiology, and the different treatises upon
Reptiles in the Penny Cyclopaedia.

Tegumentary System.

Mandl, Anatomic Microscopique. Paris, 1838 — 43.

Dumeril and Bidron's Erpetologie, vol. i. Paris, 1834.

Ascherson, iiber die Hautdiisen der Frosche in Miiller's Archiv, 1840.

Van der Hoeven, Icones ad illustrandas coloris mutationes in Chame-
leonte, 1831.

Meissner, de Amphibiorum quorundam papillis glandulisque femorali-
bus. Basil, 1832.

Osseous System.

Cuvier, Recherches sur les Ossemen fossicles. Tome derniere.

Cuvier, Regne animal, 2de Edition, tom. 3, on Osteology of the skull of
Serpents.

Wagler, Naturlich System der Amphibien. Munchen, 1830.

Duges, Recherches sur I'Osteologie et la Myologie des Batraciens a
leurs differens Ages. Par. 1835.

Job. Miiller, in Tiedemann's und Treviranus's Zeitschrift fiir Physiol.
Band. 4, upon the anomalous genera of Serpents.

Ed. D' Alton, de Pythonis ac Boarum ossibus commontatio. Saxonum,
1836.

Tiedemann, Anatomic und Naturgeschichte des Drachen. Nurnb. 1811.

Heusinger, in seiner, Zeitschrift fiir organische Physik. Band. 3, upon
Osteology of Apodal Sauria.

Joh. Miiller, iiber Chirotes und Pseudopus in Tiedem. und Trevir.
Zeitschrift f. Physiol. Band. 4.

Peters, in Miiller's Archiv. 1839, upon union of dermo and tegumentary
skeleton in Chelonia.

Bojanus, Anatome Testudinis. Vilnae, 1839. ,

Muscular System.
Consult in addition to the works of Duges and Bojanus, the Comparative
Anatomies of Cuvier and Meckel. D'Alton in Miiller's Archiv. 1834,
Carus, Erlanterungstafeln, and the Icones Zootomicae of Wagner.

BIBLIOGRAPHY. 181

Nervous Syste7n.

Valentin in Sommering's Hirn-und Nervenlehre.

Icones Physiol. Tab. 17 and 23. Brains of different Reptiles.

Cams, Darsteliung des Nerven systems. Leipzig, 1814.

Serres, Anatomie du Cerveau. Paris, 1827.

Treviranus, iiber Hirn und Nerven des Proteus, in Comment. Societ.
Gottingens, vol. 4., and Beobachtungen aus der Zootomie, Heft 1.

Mayer, Analekten zur vergleichenden Anat. figures and descriptions of
Brains of Ichthyodea.

Miiller, Vergleichende Neurologie der Myxinoiden.

Miiller, zur Vergl. Physiol, d. Gesichtsinn's. Leipzig, 1833, upon de-
cussation of optic nerves.

Volkmann, in Miiller's Archiv. 1838.

Voigt, Neurologie von Python, Miiller's Archiv. f. 1839.

Van Deens. Traites sur la physiol. de la moelle epiniere. Leiden, 1841.

Giltay, de Nervo. Sympathico. Lugd. Batav. 1834.
Organs of the Senses.

Cloquet, sur les voies lacrymales des Serpents, Mem. du Mus. d'hist.
nat. vol. 7.

Duvernoy, Ann. des sciences nat. torn. 30, and in Mem. de la see. d'hist.
nat. de Strassbourg, torn. 2, on tongue of Chameleon.

The wrorks of Scarpa, Windischmann, and Steifensand, see p. 128 of the
present work.

Rusconi, Monografia del Proteo anguino.

Miiller, in Meckel's Archiv. 1829, upon nasal glands of Serpents.

Rathke, Untersuch, iiber den Kiemenapparat und das Zungenbein der
Wirbelthiere. Riga, 1832.

Henle, vergleichend-anat. Beschreibung des Kehlkopfs. Leipz. 1839.

Losana, in meraorie della scienze di Torino, vol. 37, 1834, upon struc-
ture of lingual bone.

Digestive System.

Schlegel, in nona Act. Acad. Leopold, vol. 14, upon structure of
Poison-fangs.

Brotz and Wagemann, de amphibiorum hepate, liene ac pancreate.
Friburgi. 1838.

Organs of Circulation.

Owen, Anatomy of Lepidosiren. Trans. Lin. Soc. for 1840, and Trans.
Zool. Society, vol. 1.

Martin St. Ange, sur les organes transiloires et la metamorphose des
Batraciens, Ann. des sci. nat. tom. 24.

Hunter, Upon the Menopome in catalogue of Museum, R. C. Surgeons,
1834, vol. 2.

Rusconi, Descrizione anatomica degli organi della Circolazioile delle
Larve delle Salamandre acquatiche. Pavia, 1817.

Bischoff in Miiller's Archiv. f. 1836.

182 BIBLIOGRAPHY.

Voigt, InaugurabhandluDg zur Aoat. der Amphibien. Bern. 1839.

Huschke, iiber die Carotidendriise der Batrachier in Tiedemann's Zeit-
schrift f. Physiol. Band. 4.

Schlemm, iiber, das Gefass-system der Schlangenin Tiedem. Zeitscrift,
Band. 2.

Hyrtl, in den ostreichischen Jahrbiichern fiir Medicin. Band. 15, 1838.

Hyrtl, Strena anatomica de pulmonum vasis in Ophidiis nuperrime ob-
servatis. Pragae. 1837.

Calori, in den Commentar. BoDon. vol. 5.

Burow, de vasis sanguiferis ranarura. Regiom. 1834.

Gruby, Annales des so. nat. torn. 16, on venous system of Frog.

Bojanus and Jacobson in Meckel's Archiv. Band. 3, and

Nicolai in Oken's Iris for 1826, upon portal system of kidneys.

Joh. Miiller, iiber die Lympherzen der Schildkroten, Berlin, 1840.

Valentin's Repertorium, Band 1, 1836, upon lymphatic heart of Python.

Weber, in Miiller's Archives, for 1835.

Panizza, sopra il sistema linfatico del rettili richerche zootomiche. Pa-
via, ]833.

Organs of Respiration.

Meckel's Archives f. Physiol. Band 4, upon respiratory system of
Reptiles, and Henle and Rathke, opera citata.

Urinary Organs.
Fink, de Amphibiorum systemate uropoetico. Haloe, 1817.
Miiller and Magnus, in Miiller's Archiv. ] 835.
Nagel, in Miiller's Archiv. 1836, on structure of renal capsules.

Organs of Secretion.

Brandt and Ratzeburg medicinische zoologie, Band. 1.

Cantor, in Trans. Zoological Society, vol. 6, upon Hydrophis.

Reinwardt, in Miiller's Archiv. for 1841.

Rengger, in Meckel's Archiv. for 1829.

Organs of Generation.

Rathke, Beitriige zur Geschichte der Thierwelt, Baud. 1.

Wagner, Abhandlungen der math, physik Klasse der Akademie zu
Miinchen, Band 2, 1837, upon microscopic anatomy of seminal fluid.

Valentin's Repertorium, 1841, S. 357.

Finger, de Tritonum genitalibus. Marburg. 1841.

Isidor Geoffroy, and Martin St. Ange in Annales des sciences nat.
vol. 17.

TEGUMENTARY SYSTEM. 183

CLASS IV.— PISCES.*

TEGUMENTARY SYSTEM.

The skin and other tissues belonging to the tegumentary system
in the class of Fishes, exhibit very numerous diversities of structure ;
they have not, however, been so carefully investigated as hairs and
feathers.

An Epidermis is always present, lubricated frequently by a copious
viscid secretion, and occasionally entirely devoid of scales, as in the
Cyclostomi, Lophius piscatorius, Muraenophis, and others, while, on
the other hand, many Fishes that appear almost smooth and scale-
less, such as the Burbot (Gadus Lota), are in reality provided with
small scales. The scales are usually disposed in an imbricated
manner upon the body of the Fish, and adhere by one extremity be-
ing implanted in a sacciform depression of the corium.

The Scales generally exhibit great varieties of form, being either
round or angular in their contour, and frequently provided with
jagged edges. They usually consist of transparent, or highly re-
fractive laminae like mother-of-pearl ; upon their external surface
we observe a series of circular lines, which are disposed concen-
trically around a common nucleus or spot, which is not always

• Class PISCES.
Sub-Class I. Pisces Ossei s. Ostacanthi.
Order I. Acanthopterygii. — Ex. Perch, Bream, Mackerel.
II. MAXAcoPTERYon.— Ex. Carp, Pike, Salmon, Herring.

III. Plectoowathi.-Ex. \ ^j'^'i' Tetrodon, Ortkagoriscus, Ostracion, Balis-

I tes, ecc.

IV. LoPHOBRANCHii.— Ex.— SyngTurfAti*, Hippocamptu.

Sub-class 2. Pisces Cartilaginosi s. Chondropterygii.
V. Plagiostomi. — Ex. Rays and Sharks. .
VI. Eleutherobrawchi, — Ex. Sturgeon, Chinuera.
VII. Cyclostomi. — Ex. Petromyzon, Ammoccetes, Myxine, Bdellostoma.

Sub-class 3. (Provisional) . Pisces Anomali.
VIII. Amphibioidei. — Ex. Lepidosiren.
IX. Helmihthoidei— Ex. Amphioxus, s. Branchiostoma.

184 PISCES.

situated in the centre of the scale ; the circular are frequently in-
tersected by longitudinal lines, and of this arrangement there are
abundant examples. To determine the more minute structure of
the scales of Fishes is a subject attended with much difficulty. The
scales are always included within the cutis itself, and consequently,
unless the latter is injured, it is impossible for the scales to come
off. The layers, which cover the scales, are as follows: 1^^. An
epidermis, formed of tessellated cells ; these may be found detached
in small masses in the slime that covers a Fish, and constitute its
principal part. 2d. A layer of pigment-cells ; these are frequently
ramified, and are continued into spirally-contorted terminal canals,
which do not, however, anastomose with each other. Zd. The cutis,
consisting of a fibrous tissue, within the areolae of which is a deposite
of fat. 4:th. A very fine layer of membrane, distinct from the cutis,
and in which linear-shaped depressions and elevations may be re-
marked corresponding to the concentric grooves and ribs of the
scales. This layer consists of fibres, which, in a histological point
of view, are related to cellular tissue.

Each scale is lodged in a sac, formed by two lamellae of the cutis,
the superior of which is alone covered by pigment-cells and epider-
mis. Each scale has an inferior soft portion, consisting of fibro-
cartilage. It is not easy to determine whether or not the concentric
striae are merely the optical expression of the lamellae of the scale
lying upon each other. This part of the scale appears actually to
consist of bony tissue, although true osseous corpuscules are gener-
ally absent. The scales are, moreover, traversed by broader chan-
nel-like longitudinal lines ; these are, however, frequently absent, and
their nature and signification are unknown.

The manner in which the scales clothe the body of Fishes varies
very much in the several genera, as do the feathers upon Birds. As
a rule, the scales lie in an imbricated fashion upon each other, leav-
ing a part of their border free, so that they abut against each other in
a variety of ways. Occasionally the upper edge of a scale is provi-
ded with a hook-shaped process, which catches in a depression of
the inferior edge of the next scale that covers it. The lines of di-
rection.of the rows of scales upon the body vary also.

The form and contour of the scales present an almost endless
variety ; they are either round or oval, angular or provided with
undulated edges and projecting lobes ; these edges are fre'quently
dentated, and provided with several rows of spines. A row of pecu
liarly-formed scales is situated upon what is called the lateral line.

TEGUMENTARY SYSTEM. 185

and they are here perforated by a canal, or frequently by a short
tube, through either of which the mucous ducts, presently to be de-
scribed, open externally upon the integument.

The bony scales of many Fishes, e. g., Lepidosteus, Polypterus,
Trigla, differ from the ordinary scales of the Osseous Fishes, for in
them we find distinct osseous corpuscules. True tegumentary bones
occur in the Sturgeons, many Siluri, and in the genera Polypterus
and Lepidosteus, and form large bony plates, which are frequently
invested by enamel. In the Trunk-fish (Ostracion) these form
tolerably regular six-sided plates, which are so accurately fitted to
each other, as to form a very compact and hard coat of mail. In
the Spinous Globe-fishes (Diodon, Tetrodon), the scales project from
the surface of the body into long and pointed spines. Small acumi-
nate elevations are seated upon the integument in the Rays and
Sharks, and in the intervals between them, in the Rays, several lar-
ger ones, situated upon a broader basis, are prolonged externally into
a transparent spine, and exhibit internally, like the teeth, a medullary
pulp, to which vessels are distributed.

The integument is traversed by the peculiar narrow Mucous Ca-
nals, which give off short, transversely-directed branches, and termi-
nate externally by free open mouths, in different situations, but espe-
cially upon the lateral line, on the head and snout, e. g., in Fishes
of the Eel kind. In the Gadus merlucius, in which these mucous
canals have been most carefully examined, there is one which runs
like a vessel along the whole length of the body, bifurcates behind
the eye, and gives off a pair of branches to the snout, while at inter-
vals branches arise from it that open upon the integument ; a small
twig also passes over the praeoperculum to the lower jaw. In the
Rays and Sharks particularly strong and tortuous canals are found
imbedded in the integument of the head. In Torpedo two rows of
openings lie upon either' side of the back, and open into two cor-
responding longitudinal canals. Special layers of glands are situ-
ated beneath the lateral line, and are, in the Carp, Tunny, and
several other Fishes, much developed. They appear to secrete the
mucus, which passes out through the canals traversing the scales
of the lateral line. In rare cases these mucous canals are wanting,
as in some, but not all, the genera of the order Cyclostomi. The
raubous canals of the head are frequently covered by hard scales,
which se'rve.to protect them ; this is the case throughout the whole
course of the mucous canals in Polypterus Bichir. In other in-

186 PISCES.

Stances, these canals are even imbedded in the cranial and facial
bones.

The study of the structure of the scales of Fishes, in reference to
the deciphering of the fossil remains of the latter, has recently led
M. Agassiz to adopt them as an element of classification, and he finds
that the class may be divided in accordance therewith into four
great orders. 1st. The Placoidians ('rX«|, a broad plate). This or-
der contains Fish whose skin is covered irregularly with enamelled
scales, often of small size, in which case they give rise to an appear-
ance like the shagreen on the skin of the Shark ; or they are of
considerable dimensions, and provided with prickles. All the Car-
tilaginous Fish of Cuvier, including the various tribes of Sharks
and Rays, with the exception of the Sturgeon, are included in this
order. 2d. The Ganoidians (yf^vos^ splendor). The scales are here
angular, and form horny or bony plates, coated with a thick layer
of enamel. To this order belong the Sturgeon, the Bony-Pike
(Lepidosteus), and a large number of genera of fossil Fish, termed
Sauroid, from their approximation in several respects to Reptiles.
^d. Ctnenoidians {kteU, a comb). The Ctenoid Fish are covered by
hard scales, jagged on the outer edge like the teeth of a comb, and
devoid of enamel. The Perch and many other Osseous Fish will
serve as examples, ^th. Cycloidians {k^kIo^^ a circle). The Fish of
this last order have their scales soft and flexible, with simple
rounded margins and a variety of linear markings upon the upper
surface. The Carp, Herring, Salmon, and many other Fish, are
comprised under this order, which, with the former, includes almost
the whole number of existing species.

The above divisions, in their general application, are correct, but
are not always abruptly defined in nearly approximated genera. In
many cases, e. g., in Pelamys sarda, two kinds of scales occur upon
the same Fish ; most of them being round and with the margins en-
tire (cycloid), while around the pectoral fins the scales present a
jagged border (ctenoid). In other cases, in one and the same fam-
ily of genera, or even among the species of a single genus, some
have ctenoid, others, on the contrary, cycloid scales ; as is exempli-
fied in the family of Clupeae, Cyprinodontes, Gobiodae, and others.

The rays supporting the fins belong also to the tegumentary
structures. They consist either, as in the dorsal fin of many Fish
e. g., the Perch and Bream, of stifle, pointed, inarticulate horny
spines (rarfii spinosi)^ or they are soft, divided at the apex, and ar-

OSSEOUS SYSTEM. 187

ticulated throughout their whole extent by transverse joints (radii
articulati), as is exemplified by the majority of our freshwater Fish,
c. g., the Carp, Pike, and Flying-fish or Exocetus. The Osseous
Fishes have accordingly been divided into two great groups, the
Acanthopterygii or spiny-finned, and Malacopterygii of soft-finned ;
an arrangement, however, which does not admit of perfectly precise
definition. The pectoral, ventral, and caudal fins, are always provided
with soft articulated rays.

OSSEOUS SYSTEM.

In the external arrangement and structure of its several component
pieces, the Skeleton of Fishes exhibits by far the greatest diversities
of all the classes of Vertebrated animals.

As regards the Osseous Fishes, their skeleton indeed offers the
greatest analogy to that of the other Vertebrata, but even this, upon
a closer examination, is found to be less than it at first sight ap-
pears. For upon first commencing its study, we are too apt to
carry out the doctrine of analogy to the utmost extent, while, as we
advance, a higher and more philosophical method of comparing the
structure of the skeleton, namely, that which is based upon the
history of its development throughout the several classes of Verte-
brata, suggests itself, and causes many apparent analogies to dis-
appear.

The mirmte organization of the bones in Fish is still but little
known. The cartilage and osseous corpuscules are never so distinct
as in the other Vertebrata.

The Cranial bones of the Osseous Fishes, though exhibiting seve-
ral remarkable varieties, admit of being contrasted to a considerable
extent with those of the higher Vertebrata, and even the human
subject. Our best plan will be to select for the purposes of illus-
tration the skeleton of a Carp, as one which presents a tolerably
normal type of structure, and is generally found ready prepared and
mounted in nluseums, or else that of the common Perch and Pike.

The Occipital bone consists very generally of six pieces, two of
which are single, or not in pairs. The body, still very similar in
character to that of a vertebra, is not united to the first cervical by
means of a joint, but immoveably by means of firm ligaments, like
the other vertebrae. In the Carp the body of the occipital bone is
actually provided, inferiorly, with a strong pointed process project-
ing backward, and which supports a broad plate invested by car-

188 ' PISCES.

tilage, and opposed to the pharyngeal teeth. The two latero-inferior
occipital elements rest upon this basilar portion of the bone, and,
analogous in part to the articular or condyloid pieces of the higher
Vertebrata, concur in forming the lateral and superior parts of the
occipital bone, and leave between them the foramen magnum for the
exit of the spinal cord. Each of these pieces is perforated in the
Carp by a large oval opening, situated laterally above the foramen
magnum, and which remind us of similar apertures in many Wading
and Aquatic Birds. Superiorly to the above pieces are placed the
two latero-superior elements, which in many cases receive the mem-
branous semicircular canals of the auditory organ, and therefore
represent, in some respects, certain portions of the temporal; they
have been viewed, accordingly, by some anatomists as mastoid
bones. These two pieces are generally smaller than the inferior
pair, and correspond in part to the squamous element of the occi-
pital, which is here, however, principally formed of a single plate of
bone. This, the supra-occipital, is usually provided with a strong
crest or spine-shaped process for the attachment of the nuchal
muscles. This crest is more strongly developed in the Bream than
in the Carp, and to a still greater degree in Coryphaena, Chaetodon,
&c. It corresponds to the spinous processes of a vertebra.

The Sphenoid is divisible into seven pieces, three of which are in
pairs. The single body of the sphenoid is mostly of a very elon-
gated form, frequently also of great depth, laterally compressed
and keel-shaped, e. g. in Anarrhicas. It forms the largest and
chiefly the middle part of the base of the skull, abuts posteriorly
against the body of the occipital, and in front against the vomer.
It supports in the direction upward the two al(B majores, if we do
not regard these as partly united to the temporal bone. At the
point posteriorly where these pieces come in contact with the pe-
trous bone, they have a notch through which the second and third
branch of the trigeminal nerve issue from the skull. Still further
upward and forward are situated the al(£ minor es, which are fre-
quently two in number, but often replaced, as in the Carp, by a
single osseous leaflet, excavated superiorly by a keel-shaped groove ;
in other Fish they coalesce at an early period of existence into one
bone. All the above-named parts of the sphenoid are, like those of
the occipital, united together, and with the rest of the cranial bones,
by suture. This is not, however, the case with the two pairs of
inferior wings or pterygoid processes, which, of considerable size,
abut against the middle part of the inferior surface of the body of

♦ OSSEOUS SYSTEM. 189

the sphenoid, and are united in front with the palatal bones, and
posteriorly and inferiorly with the articular portion of the temporal.
Occasionally, as in Pleuronectes, they are divided into two pieces,
an internal and external alar lamina. As constituent elements of
the temporal bone, we regard with more or less justice a remarkable
number of ossicles, which may be resolved into two principal divis-
ions, belonging to the cranial and articular portion of that bone.
The cranial division consists always of three bones, which, inter-
calated between the already described pieces of the occipital and
sphenoid bones, are united with these, as well as the parietals and
frontals, by suture. The petrous bone is of larger size, disc-shaped,
and is situated most deeply, being interposed between the body and
inferior occipital bone, and also the great wings of the sphenoid ; it
rests upon the body of the latter bone, and is perforated by a large
opening for a branch, the opercular, of the fifth pair of nerves. In
the direction upward and backward is placed the mastoid bone,
which by some has been taken for the squamous element. We
may regard, however, as the squamous portion of the temporal, a
bone which rests in front of the mastoid, above and upon the pe-
trous ; but if this analogy will not hold good, it must be viewed as
a particular scale-like bone, comparable to that which occurs in the
Reptilia, and be called the posterior frontal. Between this portion
of the skull and the lower jaw a number of bones, amounting to
five at the utmost, or four, three, or only two in number, are intro-
duced ; the most anterior of these articulates with the lower jaw,
and constitutes the articular portion of the temporal, which, in Rep-
tiles and Birds, is reduced to the single quadratal bone. The first,
the uppermost and most posterior bone, is always the largest in
size ; it forms the superior articular bone, and unites itself by means
of a mostly moveable process with a corresponding depression in the
mastoid piece and squamous element of the temporal bone ; behind
and above we meet with a condyle upon it for articulation with the
operculum. In front of, and leading somewhat downward from,
the superior articular bone, lies the ^rea^ opercular, di. flat and very
thin bone, beneath which again is placed the narrow hamular ossicle
and against this the inferior articular, which articulates with the
lower jaw, abuts in the direction forward and downward. There
is found sometimes a fifth, smaller and flatter bone, situated between
the others. The above-mentioned bones are partly united together
by squamous suture, partly by fibro-cartilage, and concur to form a
bony wall, abutting posteriorly against the prcBoperculum, which

190 PISCES.

bone is reckoned not improbably by some as belonging also to the
articular division of the temporal. The whole of the quadratal bone
abuts in front and superiorly against the inferior wings of the sphe-
noid. In cases where several of the bones now described are want-
ing, or have coalesced together, four, three, or only two bony pieces,
may compose the articular portion of the temporal. Thus in Cy-
prinus and Esox we find five, but in most genera, as Perca, Pleuro-
nectes, and Cobitis, only four of these elements. The quadratal
bone, e. g. Zeus, Silurus, and Heterobranchus, is formed of three
pieces. Two pieces only, firmly united by suture, are found, e. g.
in Muraena and Mursenophis, where this bone more resembles in
form the os quadratum of the higher Vertebrata. A pair of mostly
small flat parietal bones, which are situated upon the upper surface
of the cranium, between the occipital, temporal, and frontal bones,
are very generally present. In front of these lie the double frontal
bones, mostly of considerable size, and to which the ethmoid is
affixed in front. This latter bone consists of a middle azygos piece
or lody, and two large lateral ethmoids, which have been viewed by
many as particular bones under the name of anterior frontals. Spaces
forming fontanelles occasionally intervene, e. g. Silurus, Cobitis, be-
tween the frontals and also the parietal bones. The distinct want
of symmetry in the bones of the two halves of the cranium in the
Plaice and Flounder is another osteological peculiarity deserving our
attention.

The greater proportion of the Facial hones in the Osseous Fishes
admit of being very readily referred to their analogues in the higher
Vertebrata. The upper jaw consists very generally of an anterior
pair of intermaxillary bones, mostly supporting teeth, and of a ^«-
perior maxillary, occasionally very rudimentary, situated behind
these, and scarcely ever furnished with teeth. In the Carp tribe
both bones are devoid of teeth ; the intermaxillary bone is usually
the smallest of the two, but is largest in Spams and the Fishes of
the Eel kind e. g. Mursenophis, in which the intermaxillary and
vomer appear to have coalesced, while the superior maxillary sup-
ports teeth. In some cases the latter bone coalesces with the vo-
merine, palatal, and nasal bones to form a single bone, which unites,
however, with that of the other side by suture, as in Orthagoriscus
and Diodon. The superior maxillary bone is very small and rudi-
mentary in Silurus, and is even absent in Balistes, where, however,
the intermaxillary is much developed. A second bony piece in rare
instances, e. g. in the Trout, Pike, and Herring, is situated above

OSSEOUS SYSTEM. 191

and upon the superior maxilla, and may be probably compared
with the labial cartilages of the Plagiostomi. Other bones, how-
ever, besides this occur in many of the Osseous Fish, which are still
more analogous to the system of labial cartilages in the Sharks.
Thus a cartilage is frequently found in the fold of the angle of the
mouth, which in Sciaena aquila is of very large size ; it is mostly
conical in form, attached by its basis to the lower jaw, and by the
other end, which is free, to a fold of the mucous membrane. It is
much more rare for a similar cartilage to exist in the upper jaw, as,
for example, the two fine strips of cartilage in Dactyloptera volitans,
where they correspond completely with similar structures in the
Sharks.

The vomer is attached posteriorly to the anterior extremity of
the sphenoid bone, and lies beneath the ethmoid. It very frequently
supports teeth, but in the Carp projects into a couple of rounded
nodules. The palatal bones are situated in front of and to the sides
of the ethmoid, and in the direction backward they abut against
the pterygoid bones. Each palatal bone is united to the vomer by
means of a joint, and by means of this the mobility of the bony
apparatus that rests upon the articulating or quadratal portion of
the temporal is effected. Occasionally, e. g. in Muraena, Muraeno-
phis, the palaial and pterygoid bones concur to form a single bone,
which is very large in Gymnotus. The nasal bones are usually
situated, as a pair of elongated flat bones, in front of and upon the
ethmoid, e. g. in the Pike. In the Carp, an elongated, stile-shaped
bone occupies their place ; it is somewhat dilated at each end, and
upon its sides there is always found a smaller discoidal bone. In
Fish of the Eel kind, the nasal bones, or their analogues, are com-
pletely absent. Externally, upon the lower edge of the orbitar
cavity in many Fishes, there is situated a series of flat bony scales,
frequently five in number, which are much developed in the Carp,
and the most anterior of which is the largest. They are called
infra-orbital bones, and, from their forming a kind of arch, may be
compared to the jugal bone. This chain of ossicles is subject to
much variety, being wanting in Muraena, Muraenophis, Balistes, and
other anomalous Fishes, while occasionally six bony scales occur, as
in Perca, where they are very small, or they are only four in num-
ber, as in Trigla, and of remarkably large size ; in some cases only
two or one exist. There is occasionally found upon the border of
the orbit, and situated upon the frontal bone, a peculiar bone of
small size, the superciliary ; examples of it are furnished by Cypri-

192 PISCES.

nus, Salmo, and Cobitis. The bones called nasal bones and infra-
orbital, are probably bones appertaining specially to the dermo-
skeleton, and are, therefore, improperly so termed. The inferior
maxilla invariably consists, upon either side, of at least two pieces,
of which the anterior is usually blended with that of the opposite
side to form a firm arch, and supports the teeth, whence it is called
the dental piece ; the posterior or articular piece articulates by gin-
glymus with the os quadratum. Usually, though not always, a
third bone, the angular piece, is found lying behind and beneath the
articular ; and more rarely a fourth, or complementary piece, is super-
added, which lies in the direction inward between the dental and
articular piece. Six pieces are rarely met with as in the genus
Lepidosteus, where the structure of the lower jaw reminds us of that
in the Reptilia, as the Crocodile. Occasionally a very considerable
gap remains between the dental and articular piece, e. g. in Zeus,
Pleuronectes maximus. The asymmetrical condition of the bones
of the cranium in the Plaice is extended also to those of the face,
but slightly to the lower jaw.

Many Fishes exhibit greater varieties of cranium than those al-
ready mentioned, as is the case, for example, in Uranoscopus, Lepi-
doleprus, Lophius, Chironectes ; yet the description already given is
applicable in general to the Soft and Spiny-finned Fishes. The
genera Centriscus, Polyodon, Lepidosteus, Polypterus, &c., with the
Syngathi and Hippocampi, exhibit greater anomalies, not only in
the structure of their skull, but in the rest of the skeleton.

As concerns the Vertebral Column of the Osseous Fishes, it con-
sists properly only of thoracic and caudal vertebrae, the first verte-
brae supporting ribs as well as the others, so that the cervical series
is wanting. The number of vertebrae is very various : in the elon-
gated Fishes, as the Eel, and others of that kind, e. g. Sphagebran-
chus, it exceeds 100 ; in Trichiurus lepturus above 150 ; in Gymnotus
aud Ophisurus above 200 ; in others only 20 — 30, as in Balistes.

The bodies of the vertebrae in Fishes are well characterized by the
deep grooves upon their sides, and which penetrate so far as to per-
forate the latter, so that they present a series of apertures, as in the
Shad, Silurus glanis. Their anterior and posterior surfaces, where
the bodies unite to each other, exhibit a conical depression. In this
way a double infundibuliform cavity is formed, similar to that in the
Cartilaginous Fishes, between two vertebrae, and is filled up with a
gelatinous fluid which is found even in the centre of the vertebral
body. This fluid is enclosed in a membrane forming a kind of sac

OSSEOUS SYSTEM.

193

and being interposed in the above manner between two vertebrae,
constitutes an elastic apparatus, performing functions similar to
those of the intervertebral ligaments in Man ; it is formed partly-
cut of the remains of the chorda dorsalis and its sheath, as will be
pointed out more closely further on in speaking of the Cartilaginous
Fishes. The vertebrae frequently possess anterior oblique processes
(often absent) and posterior, which are rarely wanting ; both the
one and the other, however, can be but improperly compared with
the oblique processes of Man and the higher Vertebrata, seeing that
they are not united by articulating surfaces. The parts that form
the arch of the vertebrae are continued into very large superior
spinous processes^ which are well developed in Sparus, and still
more in Chaetodon, Pleuronectes, &;c. ; but they are, on the con-
trary, low and depressed in the Anguilliform Fishes and in Lophius.
In Syngnathus the superior spinous processes of the vertebrae sup-
port the dorsal fins, and are divided into several widely radiating pieces.
The thoracic vertebrae are frequently provided with transverse apo-
physes directed somewhat downward : although they may be called
transverse processes, yet, judging from what we know of the develop-
mental history of the vertebrae, they must be essentially different
from those of the higher Vertebrata. They are frequently absent ;
when present they support ribs, but invariably project backward
and downward, where, converging, they coalesce to form the infe-
rior arches, which together constitute a canal, opposite to that of the
superior arches enclosing the spinal cord, and through which the
aorta passes. Upon the caudal vertebrae they support very large
inferior spinous processes. Occasionally, as in the Carp, Shad,
Pike, in Clupea, Zeus, Trigla, one or more ribless vertebrae, pro-
vided with peculiar processes, are situated in front of the costiferous
set, and are regarded as cervical vertebrae. Situated above and upon
the superior spinous processes, to which they are usually connected
by membrane to a greater or less extent, are the accessory or inter-
spinous bones, frequently of considerable size, and supporting supe-
riorly the rays of the fins. It is rare for the interspinous bones to
advance, as in Plagusia, far forward upon the skull, and form there
a crest. The fin-rays are in some instances, as in the Acantho-
pterygii, simple, pointed, horny spines, but in others, as the Mala-
copterygii, they are softer, divided several times at their extremity,
and transversely articulated ; they a,re united by ginglymus with the
interspinous bones, and it is between them that the membrane of
the dorsal fins is expanded. Perfectly similar interspinous and ray-

13

194 PISCES.

bones are met with in the anal fins, where the foremost of these in-
ferior interspines are frequently of remarkable length and strength,
as in Pleiironectes. The last vertebrae, or those which abut against
the caudal fin, are usually formed in a peculiar manner, being very
strongly compressed laterally, and their superior and inferior spines
forming large flat bones. Frequently, as in the Anguilliform Fishes,
the last vertebrae become smaller in size, but exhibit no peculiar con-
formation from the absence of the caudal fin.

Most of the Osseous Fishes are furnished with Ribs, which vary
greatly in number, and are attached partly by their upper and
strongest extremity to the transverse processes, and partly to the
bodies of the vertebral series, inclining chiefly in the direction for-
ward. The ribs are never, as in Man and the higher Vertebrata,
laterally compressed, but from before backward, or they are rounded,
and frequently present the appearance of slender spicules. In many
fishes, e. g. Balistes, the ribs are small and few in number ; in others
they are rudimentary or entirely wanting, as in Lophius, in the Pec-
tognathi, and others.

In many Fishes we meet with a series of bones that have been
falsely termed accessory ribs ; they consist of lateral spines, which
are attached to the vertebrae above the true ribs, and are plunged
among the muscular fasciculi to which they properly belong. They
are greatly developed in the Herring, where they stand in two
rows.

It is only in a few Fishes that parts are found which admit of being
very remotely compared to a Sternum. To these belongs the chain of
little bones, parts of the dermo-skeleton, that in Zeus and Clupea
extend from the girdle of the thoracic fins to the anal fin. In other
Fishes, e. g. Balistes, a single long bone occupies their place. No
costal cartilages arc, however, found connecting the ribs with the parts
just described, so that the latter can only be viewed improperly as a
sternum.

The Thoracic Rxid Vetitral Jlns o( the Osseous Fishes correspond in
position to the anterior and posterior extremities, and attempts have
been made to reduce the osseous structures which serve for their
support to corresponding bones in the arm and foot of the higher
Vertebrata.

As regards the Anterior Extrfmilies, they appear to be completely
wanting in probably none of the Osseous Fishes. As in many
Serpents and Apodal Lizards, even where they are not indicated ex-
ternally by fins, they still exist, of which examples are met with in

OSSEOUS SYSTEM. 195

many Fishes of the Eel family ; and it is here that their structure
exhibits an interesting series of gradations. Their form appears to
be of the simplest kind in Muraenophis, where, upon either side,
there lies beneath the skin behind the gills a single bone, sloped
out anteriorly and surrounded by muscles, which supports no fin.
A similar pair of very delicate styliform bones, abutting together an-
teriorly, are situated behind the branchial apparatus in Sphage-
branchus ; these bones are more largely developed in Synbranchus
(Unibranchapertura, Lacep.), where they form a girdle that corre-
sponds somewhat to the clavicles. In Muraena each of these bones
is already divided into two, the uppermost of which may be viewed
as a rudimentary scapula, while the remaining divisions enter into
the composition of the fin — an arrangement approximating the usual
structure which is as follows : There is generally situated most
superiorly one bone, or occasionally several, that represent the
scapula. The uppermost is usually bifurcated, and unites by means
of its two processes with the occipital bone ; it is rarely, however,
firmly united to the skull by suture, but usually by ligament alone.
To this, or to a second small bone, succeeds inferiorly one that is
very much larger, presents a slight semilunar excavation in front,
and comes in contact with that of the opposite side, so as to form a
girdle for the anterior extremities, which gives off the main support
of the fin. The bone, which corresponds to the single one in Mu-
raenophis and Synbranchus, has been named, perhaps justly, the
anterior clavicular. 'It is more difficult to admit the title of posterior
or coraco'clavicitlar applied to the next bone, as the analogue of the
coracoid process of the Mammalia, and the posterior clavicle of
Birds. It is for the most part longer, more pointed, and rib-shaped,
and, in the direction backward and inward, rests against the convex
part of the anterior clavicle, and converges frequently to that of the
other side ; it consists usually of two pieces, of which the superior
is broad and flat.

To the above follows the second or middle division of the bones
of the thoracic fins, which is viewed as corresponding to the hu-
merus and antebrachial bones. This division consists of three, or
frequently only of two bones, perforated by openings, and often of
very considerable size. A row of smaller, flatter, and rarely more
elongated bones, follows the above division, and has, in conformity
with nature, been viewed as corresponding to carpal and metacarpal
bones. Four separate bones are mostly here present, but the num-
ber varies from two to five. A special division is in rare cases,

196 PISCES.

formed for the metacarpus. To these bones are appended the digital
articulations or fin-rays {radii pinnce pectoralis), which form the sup-
porting frame-work of the pectoral fins.

The varieties in the construction of the anterior extremities in the
several genera are very great. The arrangement in the Eel is of a
very simple kind, there being a single bone or scapula not bifurcated,
and below that the clavicular bone. In addition to these are two
bones for the second division, and several for the carpus and the
fin-rays. The bones are somewhat more developed in Gymnotus,
where the scapula is united to the skull. The genera Exocsetus,
Lophius, Silurus, Tetrodon, possess also but one bone for the scap-
ula ; most of the Osseous Fishes, e. g., Perca, Esox, Cyprinus, Cy-
clopterus, Trigla, Scomber, Chaetodon, Gadus, Brama, &c., are pro-
vided with two, an anterior and posterior, clavicular bones, two to
three brachial, three to four carpal bones, and next in succession
with fin-rays or phalanges ; many, as several species of Sciaena,
Sparus, Labrus, &c., have as many as three scapular bones ; the
posterior or coraco-clavicular bone is absent in Anarrhicas, Silurus,
Uranoscopus, Fistularia, Exocsetus, and consists invariably of only
a single bony piece in Cyprinus, Esox, Batrachus, Lophius, and
Chironectes ; in Chaetodon it abuts against the bones of the pelvis ;
in Zeus the two clavicles coalesce inferiorly ; the carpus in Lophius
and Chironectes is formed of two very long bones, that have been
falsely compared with the ulna and radius ; in Batrachus there are
five similar bones, aud in Polypterus two elongated bones, with one
or several discoidal ossicles interposed between them ; this Fish has
also, as an occasional peculiarity, a row (amounting even to 18) of
elongated bones, which correspond to the metacarpus. The carpal
bones are very seldom wanting, as in Exocaetus (where the fin-rays
are remarkably long) and in Uranoscopus. For the second or ante-
brachial division of the anterior extremity we find, in Silurus and
Heterobranchus, only one bone ; the first fin-ray is, on the contrary,
strong and linked to the anterior clavicular bone ; so that here, as in
Piraelodes, Piatycephalus, and others, it is very broad inferiorly, and
united with that of the opposite side by a zigzag suture.

The Pelvis and Posterior Extremities are but very rudimentary in
the Osseous Fishes, and not connected to the vertebral column, but
are imbedded simply in the flesh, as in the Amdominales, or abut
against the anterior clavicular bones, as in the Thoracici and Jugu-
lares ; occasionally they are completely wanting, or we find in their
place two usually long flat bones, which support on their posterior

OSSEOUS SYSTEM. 197

edge the digital portion or abdominal fin ; it is rare for a third set of
bones to be interposed between these.

More diversities appear in the posterior than in the anterior ex-
tremities ; thus they are often completely absent, as in Xiphias and
Fishes of the Eel kind, e.^., Muraena, Muraenophis, Sphagebranchus,
Gymnotus, &c., and are placed in some instances far forward, in
others far backward ; upon these varieties of position of the ventral
fins the old LinnsBan division of Fishes into Apodal, Abdominal, Pec-
toral, and Jugular, was based.

Both pelvic or iliac bones are usually more or less united to each
other ; in some Fishes they are completely anchylosed, in others
prolonged backward in the form of a spine, as in Cyprinus, Scomber,
Zeus, &c. ; they are occasionally separate, as in Lophius, Batrachus.
Polypterus possesses four elongated bones, that correspond as the
third division of the extremities to the tarsus and metatarsus.

The Skeleton in the Cartilaginous difl^ers altogether in structure
from that already described as belonging to the Osseous Fishes, and
it is only its fundamental types which are common to the two as
Vertebrate animals. It is scarcely possible to offer any general
remarks relative to the skeleton of the Cartilaginous Fishes, and we
must therefore characterize its peculiarities in the several orders and
families.

In the Cartilaginous Fishes the skeleton remains throughout life
in a cartilaginous condition, and true ossification occurs only in the
tegumentary bones, e. g., in the Sturgeon, or in particular parts of
the skeleton. In sOme Cartilaginous Fishes, such as those with free
branchiae (Acipenser, Chimaera), the permanent cartilage resembles
the cartilage that precedes the formation of bone in the Osseous
Fishes : the cyclostomi, however, are distinguished by possessing
a very peculiar kind of cartilaginous tissue with coarse cells, while
the Plagiostomi possess the cartilaginous tissue of the Sturgeon and
Chimaera ; and in addition thereto, other kinds of cartilaginous tissue,
namely, \st. The hyaline or transparent tissue, with more or less
membranous cartilaginous corpuscules ; this occurs in the Sturgeon,
and also in the Osseous Fishes, and forms mostly the internal part
of the cartilage, with the exception, however, of the vertebral bodies.
'Zd. The tessellated calciferous cartilaginous tissue, which occurs
only in the Sharks and Rays, and invests the hyaline cartilage like
a hard crust, with the exception of the vertebral bodies. This car-
tilage consists of prismatic pieces which resemble brick-work, and
are separable from each other. M. The cellular cartilaginous tissue

198. PISCES.

occurs in the Cyclostomi. The cartilaginous corpuscules disappear
by degrees, and the cartilage appears devoid of cells, like the hairs
of one of the Goat tribe. Ath. The completely-ossified cartilaginous
tissue, as exemplified in the solid vertebral bodies of the Rays and
Sharks.

The Sturgeon, although a true Cartilaginous Fish, effects the
transition from that type to the Osseous, of which we are reminded
by the disposition of the parts of its skeleton. Already do we find
in many of the Osseous Fishes, as the Pike and Trout, that the
cranium consists internally, where it encloses the brain, of cartilage,
upon the external surface of which the bones of the cranium, as
already described, are deposited. In the Sturgeon the cartilaginous
cranium becomes ossified at its base, this bony portion correspond
ing to the basilar element or body of the occipital and sphenoid.
But even here the ossific process has taken place only externally,
and that surface which forms the cavity of the cranium still contin-
ues cartilaginous ; the ossification is most apparent in the fibrous
tunic, which, continued from the fibrous sheath of the medulla spi-
nalis, lines the skull. In other parts the cranium is perfectly carti-
laginous, and covered in with firmly adherent bony scutes, which
belong properly to the dermo-skeleton, and admit only of an inaccu-
rate or very remote comparison with the cranial bones of the Osseous
Fishes. In front and on the sides the cartilage of the head presents
depressions for the eyes and nasal cavities, and then projects into a
long process. The palatal bones are separate from the skull, united
with the superior maxilla, and consists posteriorly of an azygos bony
plate, and two anterior osseous pieces in pairs. The quadratal bone
consists of a superior bony piece united to the cranium and two infe-
rior cartilaginous pieces ; the last of these is united to the lower
jaw, which, with the small and double superior maxillary bone,
closes the edentulous mouth.

In the Chimaera, the Sharks, and the Rays, the skull is a large
cartilaginous capsule, enclosing the brain and auditory apparatus ;
it is free of the vertebral column, and exhibits no traces of ossifica-
tion. In the Plagiostomi there usually remains upon its upper sur-
face an open space or fontanelle, closed only by a fibrous membrane.
This cartilaginous capsule is particularly flattened upon its upper
surface in the Rays, and has posteriorly an opening, the occipital or
foramen magnum, and lesser apertures also for the exit of nerves.
A portion of this capsule, convoluted upon itself laterally, forms the
orbitar cavities, and frequently presents superiorly, as in Scymnus

OSSEOUS SYSTEM. 199

an orbitar process. United -to the anterior extremity of the cranium
we meet with a deep hollow leaflet of cartilage, forming the nasal
fossa. The upper jaw is constituted by a narrow arch of cartilag(^,
occasionally, however, deep, as in the Sharks, and of a semilunar
form ; it is beset completely, both upon its edge and posterior wall,
with teeth. A quadratal cartilage, more simple and elongated, is
lodged in a posterior lateral depression in the skull, and articulates
with the lower jaw, an arch provided with teeth, and composed of
two lateral halves like the upper. There occur, moreover, in the
Rays small palatal cartilages, as also peculiar cartilages belonging
to the spiracles, and which correspond somewhat to the pterygoid
bones or processes in the Osseous Fishes. The intermaxillary bone
must be regarded as absent, if we do not consider it united with the
superior maxilla in the arch of cartilage just described. In the
Chimserae the skull is very peculiarly formed, being provided with
distinct convoluted nasal cartilages, while upon the fore part of the
head stands a style-shaped piece of cartilage.

Furthermore, there exists in many of the Sharks and Chimaeras
a peculiar system of labial cartilages, which is wanting in the Rays
and Sturgeons ; the question of its homology has given rise to
various incorrect speculations ; a portion of it was regarded formerly
by some anatomists as belonging to the maxillary apparatus. It
consists of several more or less elongated muzzles of cartilage vary-
ing in form and particularly remarkable in the Chimaera, which rest
externally and laterally against the upper and lower jaw. In Acan-
thias and other genera, for example, a lower labial cartilage is to be
distinguished lying upon the inferior, and a superior upon the upper
maxilla, and occasionally, as in Scymnus, Chimaera, a third carti-
lage situated above the latter one. Among the Rays, it is only in
Narcina that small labial cartilages are met with. In them and in
the true Electric Rays (Torpedo) there is situated in front of the body
a cartilaginous production of the muzzle which unites the pectoral fins
to the skull.

Still more abnormal is the structure of the cranium in the Cyclo-
stomi, and in them we are again met by numerous varieties in the
structure of the buccal cartilages. With this group, indeed, all at-
tempts to draw any analogy or comparison with the typical Fishes
must be laid aside.

The cranium of Petromyzon marinus and fluviatilis consists of a
hard, nearly osseous brain-capsule, having a detached flattened basi-
lar portion, that gives ofl" in the direction backward a pair of pro-

200 PISCES.

cesses. Upon its sides are found the hard, oval auditory capsules,
united continuously with the skull, and enclosing the membranous
labyrinth ; upon the upper part of the skull itself we remark, as
in the Rays, a fontanelle closed by fibrous membrane. In front also'
and inferiorly, the arch of the cranium is to a great extent mem-
branous. Superiorly, and in front of the skull, is the opening of the
nasal tube, which perforates the palate, and on its posterior wall the
olfactory nerve is distributed as it issues from the cranium. A num-
ber of cartilaginous plates lying behind each other belong to the parts
of the mouth : thus there is found an anterior and posterior operculum
of the oral aperture, to which are superadded inferiorly a pair of
lateral plates ; a ring-shaped piece of cartilage, the labial ring, cor-
responds to the maxilla, and to this is fastened laterally a styliform
cartilage, which is directed horizontally backward.

The skull is still more simple in Ammocaetes, where the parts of
the mouth just described are in a great measure wanting, while the
cranial capsule is essentially similar in structure to that of Pe-
tromyzon.

In the family Myxinoides very varied and peculiar forms of oral
cartilages are developed, while the cranium of the genera Myxine
and Bdellostoma admits of a comparison with that of Petromyzon.
All the essential parts described above, namely, in reference to the
capsule of the brain, are here repeated, and we meet with similar
hard auditory capsules ; but there is also a singular frame-work to the
pharynx formed of cartilaginous hoops, a long nasal tube consist-
ing, like a trachea, of cartilaginous rings, the nasal capsule, and the
palatal plate with its raised borders. In the Myxinoides the nasal
canal is open inferiorly toward the palate, while in Petromyzon and
Ammocaetes it there terminates in a coecal manner.

In the remarkable genus Amphioxus s. Branchiostoma, a case or
shell is completely wanting for the rudimentary brain, which is
merely included in a membranous capsule ; in the mouth, however,
is found a cartilaginous ring with cartilaginous filaments ; there is
also present a system of oral cartilages, as in the Sharks, Chimaerae,
and Petromyzon.

The structure of the head in the Amphibious Fishes, including
the genus Lepidosiren, of which it is doubtful whether it should be
arranged among the members of the present class or among Reptiles,
offers very great peculiarities. The skull, as in all Fishes, is im-
moveably united to the occiput, presents a cartilaginous substratum
upon which the peculiarly-formed bones of the head repose, and

OSSEOUS SYSTEM. 201

remain themselves partly cartilaginous. The number of the cranial
bones is small, and their homologies difficult to determine by com-
parison with those of other Osseous Fishes ; yet we find lateral
occipital elements, and a single bone forming the upper covering
of the skull ; to this last there corresponds a similar bone at the
base of the cranium, which may be viewed as the body of the sphe-
noid. The bones of the face also attract our attention from their
peculiarities ; the superior maxilla appears to be wanting, while the
intermaxillary is present ; and there exists moreover a system of
labial cartilages, which, with the tooth-bearing lower jaw, exhibits
a relationship of structure with that of Chimaera. A more simple
quadratal cartilage unites the inferior maxilla to the skull.

In the structure of the Vertebral Column of the Cartilaginous
Fishes we encounter peculiarities and differences in the several
orders and families, which are the more interesting when the de-
velopment of vertebrae comes to be studied, and the plan of their
formation followed out through the series of Vertebrate animals ;
an extensive subject belonging to the departments of philosophical
anatomy, and not to be entered upon here.

In the Sturgeon and Chimaera the vertebral column is constituted
by a fibro-cartilaginous tube, which is filled with a gelatinous sub-
stance, and surrounded by a fibrous tunic, that is closed above to
form a tube for the spinal marrow. Upon the inferior surface of
this fibro-cartilaginous tube are situated the rudimentary basilar
parts of the vertebrae j they are united beneath by a membrane,
along which the aorta passes. Between the upper triangular pieces
of the arch other triangular pieces of cartilage {cart, intercrurales)
are found, and the roof of the spinal canal is closed in by a series
of more elongated cartilages, above which there are placed in the
Sturgeon large spinous processes. The fibro-cartilaginous tube
of the Chimaera, very beautifully annulated by thin transverse
rings that were formerly falsely compared to vertebrae, remains in
a great measure exposed to view, and corresponds to that part in
the rest of the vertebrata, present only in their foetal condition,
but in Fishes morer or less persistent, namely the chorda dorsalis,
or central cylindrical axis, around which the formation of vertebrae
takes place. The persistent structure of the vertebral bodies in the
Sturgeon and Chimaera corresponds to that which exists only in
the foetal state of the Osseous Fishes. In these latter Fish, when
fully formed, the gelatinous tube is reduced to constricted masses of
gelatine, surrounded by the conical facets forming the bodies of the

202 PISCES.

vertebrae, and opposed to each other; but the gelatinous column
with its fibrous sheath that occurs in the Sturgeons and Chimserae,
and also in the Cyclostomi (as will be described further on), has a
cellular structure, like the chorda dorsalis, quite different from car-
tilage.

In the Plagiostomi the formation is of a more perfect kind, and
similar to that of the Osseous Fishes, for the upper and lower pieces
of the vertebrae having become more complete, the gelatinous column
is so enclosed that the conical facets of the vertebral bodies are
alone left. The points of ossification in its interior are very com-
plex. In some Rays and Sharks a hyaline cartilage rests upon the
surface of the vertebral body (e. g. Spinax, Scyllium) ; in others
the vertebral body, with cellular interstices, ossifies up to the sur-
face, but in its interior there remains a cross of hyaline cartilage, the
crura of which are directed toward the points of origin of the arches
and transverse processes (e. g. Carcharias, Zygaena) ; or other varieties
occur, as in many genera, e. g. Hexanchus, Heptanchus, where the
whole vertebral column remains cartilaginous throughout life. As
a rule, however, the vertebral bodies, the pieces forming the arches,
the intercrural cartilages, and the laminae forming the roof of the
spinal canal, are always to be distinguished. In the Rays a large
anterior portion of the vertebral column is not distinctly divided into
vertebral pieces, these being blended together.

In Petromyzon the fibro-cartilaginous tube is found to be annu-
lated, filled with gelatine, and surrounded by a fibrous tunic, which
forms above it a tube for the spinal marrow. In the upper mem-
branous tube cartilaginous crura are seen to arise, and may be
viewed as rudiments of vertebral arches.

In Myxine, Ammocaetes, and Bdellostoma, we meet with the
lowest persistent condition of the vertebral column, and one which
disappears at a very early period of existence in the higher Verte-
brata ; this consists of a chorda dorsalis, filled with gelatine, and
surrounded by a fibrous tunic that forms above a tube for the spinal
marrow ; but all special divisions or rudiments of ossification in this
tube are wanting. A similar chorda dorsalis, projecting as far as
the snout, together with a fibro-membranous capsule for the spinal
marrow, is found also in Amphioxus. Even in the Lepidosiren the
vertebral column consists of a mere chorda dorsalis, without any
indication of vertebral rudiments, and provided only with a liga-
mentous capsule and gelatinous substance.

Cartilaginous accessory spines occur in the dorsal and anal fins

OSSEOUS SYSTEM. 203

of the Sturgeon as in those of the Osseous Fishes ; in the Sharks
and Rays several divisions of triangular and quadrangular cartilaginous
laminae occur ; they correspond to the accessory spines and support
the fin-rays.

Many of the Cartilaginous Fish, as the Rays, Sharks, Sturgeon,
and the genus Lepidosiren, are provided with Ribs. The Cyclostomi,
at least the Lampreys, possess a peculiar sternal series, formed of a
number of ramified rib-shaped cartilages which are united together,
and to an elongated sternoid cartilage ; it encloses the gills, and may
be therefore most properly compared with the branchial skeleton of
other Fishes.

Among the Cartilaginous Fishes we meet with an entire absence
of Extremities in the Cyclostomi, while in the Sturgeons, Chimaerae,
Rays, and Sharks, they exist in the form of pectoral and ventral
fins. The anterior extremities of the Sturgeon resemble those of the
Osseous Fishes in being composed of several pieces, which correspond
to a scapula and clavicle ; the posterior extremities are a pair of small
ventral fins. The Chimaera approximates most in this respect to the
Plagiostomi.

Among the Plagiostomi the Rays present us with a surprising
development of their pectoral Jins, which correspond to anterior ex-
tremities, and are in some degree analogous to those of the Osseous
Fishes. Their first portion consists of a scapular and a clavicular
cartilage ; frequently, however, of three cartilages that form a pretty
broad arch, which in the Rays firmly unites with the anterior anchy-
losed section of the vertebral column, but does not reach the latter
in the Sharks. To this first portion succeeds a second, which con-
sist in the Rays of three or four very elongated cartilaginous
pieces ; next we meet usually with two rows of rays, the posterior
of which may be perhaps likened to the metacarpus, while the an-
terior or external represents as fin-rays the digital phalanges. In
the Rays the digital phalanges are somewhat dilated at the two
ends.

In the Plagiostomi and Chimaerae the arrangement of the posterior
extremities is rather more perfect than in most Osseous Fishes. An
iliac cartilage is here present as a rudiment of the pelvis, and to
this follows a series of more elongated cartilages, which may be re-
garded as tarsal, while arranged upon these are the rays or pedal
phalanges supporting the ventral fins. In the male Rays and
Sharks a pair of long, slender, cartilaginous appendages are united
to the iliac cartilage ; they are hollowed out by a groove above for

204 PISCES.

the passage and exit of semen, and thus perform the function of ex-
ternal generative organs.

The genus Amphioxus, like the whole order of Cyclostomi, is de-
void of all extremities. In Lepidosiren there are found externally,
in the situation of the pectoral and ventral fins, two pairs of inarti-
culate filaments. The first pair rest upon a bone or cartilaginous
girdle forming their support ; and for the posterior rudiments of fins
there exists likewise a pelvic piece.

MUSCULAR SYSTEM.

The Muscles of Fishes are characterized by their slight degree of
separation from each other, by the absence of long tendons (which
occur only in some anomalous muscles of the cranium, e. g. in the
Electric Ray), and by the softness of their fibres. The color of the
muscles is generally pale, being either white or having a tinge of
yellow ; occasionally, however, as in the Tunny (Scomber thynnus),
they are red like the flesh of Mammalia. Their microscopic struc-
ture does not differ from that of the other Vertebrata, nor are the
characteristic transverse striae wanting even in the whitest fibrillae.

Peculiar muscles of the integument do not appear to exist ; still
the small superficial muscles which move the several rays of the
dorsal and anal fins are obviously analogous to the muscles that act
upon the feathers in Birds, and upon the ventral scales in Serpents.
Each fin-ray is constantly provided with a single superficial muscle
upon either side (right and left) of its basis ; they arise from the
integument, and wave the fin to and fro so as to maintain the act
of swimming. Besides these, there are other muscles more deeply
seated, and of some length, which cover the interspinous bones.
Each fin itself is provided with a pair of protractor and a pair of
retractor muscles, those that correspond upon either side being
separated by the interspines, and covered by the great lateral mus-
cles of the body. By means of these muscles the dorsal and anal
fins can be elevated and depressed. Those Fishes which, like Gas-
terosteus, Silurus, Lophius, and Balistes, are furnished with certain
strong but loose spines or fin-rays as instruments of defence, present
greatly developed and isolated fin-muscles.

By far the largest portion of the fleshy mass of Fishes is made up
by the large lateral muscles of the body ; they consist of longitudinal
fibres, which are interrupted by numerous tendinous undulating
lines passing from the dorsal to the ventral aspect, and extend from

MUSCULAR SYSTEM. 205

the head and scapular arch to the base of the caudal fin. This mass
of muscle is not, however, so simple as it appears, but divided into
numerous parts. We may distinguish an upper layer where the
tendinous strips are directed obliquely backward, and then a second
and third, the last of which is situated beneath the lateral line.
The tendinous transverse strips here alter their direction, but cor-
respond to the number of vertebrae. These layers of muscle arise
from the skull itself, from the occipital and mastoid bones, in which
situation they correspond to the nuchal muscles ; also from the sca-
pula and clavicle, then from the lingual bone, the vertebrae and their
spinous processes, clothe the ribs, and are inserted by short tendons
into the base of the caudal fin. Below them lies another layer upon,
the belly, which corresponds to the abdominal muscles, while the
upper layers are analogous to the dorsal muscles of the higher
animals, especially the m. m. spinalis^ scmispinalis, muUifidus spin<B,
longissimus dorsij and sacro-lumbaris. The symmetry displayed by
the dorsal and ventral portions of the lateral muscles, upon a perpen-
dicular section, is most striking, and we are in this way best enabled
to see the peculiar infundibuliform arrangement of the several mus-
cular layers.

Each lateral muscle bends the body toward its own side, at the
same time producing powerful lateral inflexions of the rudder-like tail ;
movements so necessary in the act of swimming. The head can be
also moved to a slight degree, when its freedom of attachment to the
vertebral column admits of it. By the co-operation of the two lateral
muscles upon either side at their anterior part, the compression of the
swimming-bladder may be also afiected.

The several orders and genera of Fish naturally exhibit numerous
muscular varieties. Beneath the lateral muscles, between the ribs,
are found the intercostal muscles. In the interspaces between the two
great lateral muscles, both upon the dorsal and ventral side, but chiefly
upon the latter, two very slender muscular strips may be seen to pass,
as in the Perca fluviatilis, and to be interrupted only by the dorsal
and anal fins.

The caudal Jin is moved chiefly by small thin muscles, which form
two layers, a superficial and a deep, and are inserted, like those of
the dorsal fins, into the rays composing it ; occasionally there occurs,
as in Perca, a third layer. The several rays of the caudal fin can be
moved by means of these upward, downward, and laterally.

The muscles of the anterior extremities consist of two principal
layers, upon each of the two surfaces of the antebrachial and carpal

206 PISCES.

bones. The superficial layer of the external side arises from the
clavicle, and covers entirely that which lies beneath it ; that also of
the inner surface of the fin, or the one turned toward the trunk,
exhibits similar relations. The latter draws the fin toward the body,
while the external, as abductors of the fin, move and raise it out-
ward.

The arrangement of the muscles upon the posterior extremities^ or
ventral fins, when the latter are present, is of a similar kind. Here
we find proper elevators and depressors in a double series, which
arise from the pelvis and are inserted into the fin-rays. The rudi-
mentary pelvic bones obtain fasciculi from the lateral muscles, that
correspond to an oblique abdominal muscle and a rectus.

The muscles of the anterior extremities, or pectoral fins, are par-
ticularly developed in Lophius and in the Flying Fish, e. g. Trigla,
Exocaetus, among the Osseous Fishes.

The muscles of manducation are very strongly developed, and form
more or less a mass constituting what is called the cheek-flesh of
Fishes, and which in the Trout has a particularly delicate taste.
The whole depression occupying the external surface of the articular
portion of the temporal bone is covered by this muscular mass ; and
it arises not only thence, but also from the anterior edge of the
prsBoperculum, and is inserted partly into the upper, partly into the
lower jaw. The disposition of these manducatory muscles is very
diflferent from that of the masseter and temporal muscles of the higher
animals, to which, however, they correspond.

The muscles of the Cartilaginous Fishes exhibit more noticeable
diversities. In the Plagiostomi, as the Rays, the dorsal and ventral
muscles are more separated by a horizontal tendinous layer, that
divides each lateral muscle into an upper and lower half. Several
muscles are also given off for the cranium, so that the head can be
slightly moved. Remarkably large horizontally expanded layers form,
in the Rays, the muscles for the great pectoral fins, without, however,
these admitting of a separation into superficial and deep layers, as in
the Osseous Fishes. In the Electric Ray a pair of peculiar muscles
with long tendons also occur ; their fleshy part or bellies arise behind
the skull from its lower surface, and are inserted into the anterior
margin of the head in front of the electric organs ; they have no analogue
in other Fishes.

In the Cyclostomi the same numerous tendinous strips are found
intersecting the lateral muscles, which are here much developed,
and surround the body. In the Myxinoides we find superadded a

NERVOUS SYSTEM. 207

system of lateral ventral muscles, which, as a rule, is absent in other
Fishes, and consists of an oblique and a straight ventral muscle ; by-
means of these the powerful movements and vermiform deflections of
these animals are effected.

NERVOUS SYSTEM.

The Nervous System also of Fishes, especially the Brain, exhib-
iting numerous diversities, it will be best to become first ac-
quainted with the regular arrangement of these structures as they are
found in the majority of Osseous Fishes, and then to describe their
varieties in the several genera and families of that sub-class ; lastly,
their mode of formation in the remaining orders.

The ordinary type of structure in the Brain of Osseous Fishes is
to be observed in many Acanthopterygians, e. g., Perca fluviatilis,
and Malacopterygians, as the Pike (Esox lucius), in both of which
it presents a very close conformity ; in the common Carp, however,
which, from its frequent occurrence, has been chiefly recommended
for the purposes of dissection, we already encounter peculiar cere-
bral anomalies ; and other species of that genus, as Cyprinus barbus,
are therefore better suited for examination.

The Brain in general does not nearly fill up the cranial cavity, so
that between the dura mater that lines the internal surface of the
cranium and the soft membrane which very closely invests the brain
itself, we find a free space filled up by a quantity of loose cellular
tissue, interrupted throughout by adipose cells. A fluid oil is fre-
quently found floating in large drops between the meshes of this tis-
sue. The membranes situated between the dura and pia mater may
be viewed as the arachnoid ; the analogy being still more obvious
where they cover the third ventricle. The dura mater is often of a
silvery lustre, or partially coated by black pigment.

We shall do best to commence the consideration of the several
parts of the brain with the medulla oblongata, which, though it
differs slightly, is to be distinguished from the rest of the spinal
marrow by being broader and flatter. Upon the medulla oblongata
may be distinguished four thickened tracts, two superior and two in-
ferior; the first are slightly enlarged, from the corpora restiformia,
and recede from each other in the middle line, so that the floor
of the fourth ventrical or rhomboidal sinus lies freely exposed to
view ; they give off processes that are prolonged, forming its crura,
into the cerebellum. Some transverse fibres upon the inferior sur-

208 PISCES.

face of the medulla oblongata probably replace, as in other higher
Vertebrata, the pons Varolii, that occurs only in the Mammalia.
The cerebellum is a large spherical ganglion, for the most part
slightly lobular in form, and curved upon itself posteriorly ; it is des-
titute of transverse grooves, but frequently furnished with obtusa
lateral projections. The fourth ventricle extends far into it. In
front of the cerebellum are situated two large obovate hemispheres
or ganglia, which in size, form, and situation, are similar to the
hemispheres of the higher animals, and, from their forming the most
considerable portion of the brain of the Osseous Fishes, have been
regarded as such by some anatomists ; others term them optic
lobes, and they obviously correspond to the mesocerebrum, the cor-
pora quadrigemina and optic thalami of the human subject taken
conjointly ; they may be called median lobes. Upon making a super-
ficial section of one of them, we find beneath a thin roof of medul-
lary matter, a large cavity extending through the whole ganglion.
Upon the flioor of this cavity or ventricle, in the posterior direction,
are usually situated four small round ganglia (e. g., in Perca, Esox,
some Salmonidae, Clupea, Trigla, Gadus Lota), more rarely two (as
in Gadus, Lophius, Blennius, Muraena, Cyclopterus, some species
of Pleuronectes), or six (e. g., Scomber thynnus, Salmo trutta) ;
these ganglia certainly appear to resemble the corpora quadrigemina
of Man, and are even united with the cerebellum by some fasciculi
of fibres, the crura cerebelli ad corpora quadrigemina. Further out-
wardly lies a larger ganglion, similar to the optic thalamus or corpus
strtiatum, and on its external side we perceive a radiated expan-
sion of fibres, called the staflf-wreath, or corona radiata. Several
transverse fibres or commissures are found, which partly correspond
to the corpus callosum, partly to the commissura mollis ; a rudiment
also of the fornix probably exists. The hollow space included be-
tween the above-named ganglia is prolonged deeply into the infun-
dibulum, and thence backward into the fourth ventricle, and cor-
responds itself to the third. Inferiorly and posteriorly, at the base
of the brain, and behind the chiasma or decussation of the optic
nerves, are situated a pair of mostly large ganglia, which agree
in their position with the eminentiae candicantes of the human sub-
ject, but can not certainly be compared with them. They are usually
styled the loli inferiores, are oval in form, and rest for the most
part upon the pituitary body. In front of the pair of mesocerebral
masses (lobi optici) are situated another pair of smaller yet tolerably
distinct ganglia, which are united also posteriorly by a narrow me-

NERVOUS SYSTEM. 209

dullary band, or anterior commissure ; the ganglia themselves cor-
respond principally to the hemispheres of the higher Vertebrata;
they are usually called the olfactory lobes, or lobes of the hemispheres.
These ganglia are solid, and almost always smaller than the meso-
cerebral ganglia ; for the most part they are composed of two kinds
of substances, an anterior and a posterior ; the first of these, the
largest, presents a delicately tuberculated surface, or, as it were,
traces of convolutions ; this is distinctly to be seen in the Pike, and
also in Gadus morrhua, the Salmonidae, and others. From, or in
front of, these ganglia of the hemispheres arise the nerves of smell ;
not, however, directly from them, but usually from small interposed
round or oval ganglia, which are occasionally themselves of some
considerable size, and have received the names of olfactory ganglia
or tubercles ; they are present in most, probably all, the Osseous
Fishes, and are very distinct in all our indigenous Fishes, e.g., Esox,
Salmo, Clupea, Perca, Pleuronectes, Gobius, Gadus, Labrus, Urano-
scopus, &c. They are, however, frequently so small and elongated
as to be easily overlooked, e. g.y in the Carps. A small, vascular,
and frequently all but membranous lobule, which is situated freely
exposed, and directly in the middle line between the mesocerebrum
and the ganglia of the hemispheres, may be regarded as the pineal
gland. The pituitary appendage is of considerable size, and depends
from its stem or the infundibulum ; it is particularly large in Pleu-
ronectes and Cyclopterus ; indeed, generally speaking. Fishes have
the largest pituitary body of all the Vertebrata.

The above-described is the usual arrangement of the structure of
the brain in the Osseous Fishes, but it is subject to many varieties in
the several families and genera, these consisting chiefly in the num-
ber of the several hemispheres or superficial ganglia being increased,
or in their being severally enlarged and subdivided to a striking
degree.

In Fishes of the Eel kind we find two pairs of olfactory lobes or
ganglia introduced between the small olfactory tubercles and optic
lobes. The posterior pair is largest, and manifestly identical in its
whole structure with the olfactory lobes of the remaining Osseous
Fishes ; for, as in them, they exhibit two divisions of structure, their
anterior portion being rendered uneven by rudimentary convolutions,
the posterior presenting a smoother surface. This structure is par-
ticularly distinct in the common Eel, but occurs also with modifi-
cations in the Conger and Murfenophis. In the Electrical Eel

14

210 PISCES.

(Gymnotus) the mesocerebrum is very strikingly developed. A lar-
ger lobe, divided by a median groove, arises from the optic lobes by
sloping semilunar-shaped roots, and forms a conical eminence that
extends far forward. The whole brain from this derives a peculiar
appearance ; it is in this ganglion that the roots of the nerves des-
tined to supply the electric organ arise, so that it may be termed
lobus electricus.

A median lobe is developed in a similar manner in Echeneis re-
mora, and probably contains the nervous elements for the supply of
those remarkable organs situated upon the skull, by means of which
this fish adheres to ships, stones, and other bodies.

Behind the cerebellum, and to the side of the fourth ventricle, are
situated frequently a pair of posterior lobes, which are occasionally
further subdivided into a special pair of lobes for the roots of the
nervi vagi. They are very small and rudimentary in many Fishes,
and are therefore easily overlooked ; but are most developed in the
Carps, being as large, or even larger than the optic lobes. Other
Cyprinidae likewise possess these lobes of the nervi vagi, and they
appear also to contain the special nervous elements for a very irri-
table and contractile organ situated at the base of the cranium above
the pharyngeal bones, and which will be described more minutely
in speaking of the organs of taste. The lobes of either side are
connected by transverse white fibres, forming a kind of commissure
upon the under surface of the medulla oblongata. There frequently
occurs, as in many also of the Carp tribe, a single median ganglion,
which rests upon the floor of the fourth ventricle. This ganglion is
of largest size in the common Carp, and appears to exist also in the
Sheat-fish (Silurus).

In many Fishes, e. g., in Trigla, from three to five ganglia are
constantly interposed behind the already-mentioned lobi posteriores,
near to the medulla oblongata, resting upon its upper tracts or cor-
pora restiformia ; they are also in connexion with peculiar struc-
tures, namely, with the large digitiform rays that are given off from
the pectoral fins in the Triglae, and which receive nerves of pro-
portionate size. Besides this, great diversities occur in the relative
proportions of the several parts of the brain ; thus the cerebellum is
in some cases greatly developed, in others very small. It is largest
indeed in the Tunny-fish (Scomber thynnus), and perhaps generally
in the Scomberidae, at least in S. scomber, where it forms a lobe
covering the mesocerebrum in the direction forward and upward.

NERVOUS SYSTEM. 211

In Silurus glanis it is very large ; very small, on the contrary, in
Gobius, but rarely provided, e. g. Echeneis remora, or Sucking-fish,
with transverse grooves, as in the higher Vertebrata.

A want of symmetry between the two sides of the brain occurs in
different Osseous Fishes ; it is present in the least degree in Gadus,
where the cerebellum is mostly placed more toward the right side.
In Pleuronectes this asymmetrical condition is carried to a greater
degree, being extended to the cerebral ganglia, the optic lobes (the
left of which is usually placed above the other), and still more to the
olfactory lobes and olfactory turbercles, which are much larger upon
the left or uppermost side than upon the right.

In the structure of the brain, as in many other points of its organi-
zation, the Sturgeon makes the transition from the Osseous to the
true Cartilaginous Fishes. The medulla oblongata is broader ; the
spinal canal opens into a very long and patulous rhomboidal sinus,
which is bounded upon either side by the ridges formed by the pos-
terior columns of the chord or corpora restiformia, that enter, as its
crura, the broad but small cerebellum. In front of the cerebellum
are placed the two moderately large optic lobes, which form the
mesocerebrum, together with the narrow mass that inferiorly and
laterally includes the freely exposed third ventricle. The olfactory
lobes are considerably larger in proportion than in the Osseous
Fishes, already presenting more the form of hemispheres, are further
subdivided and continued into small olfactory tubercles. The very
large pituitary body rests, without any stem or I'nfundibulum, upon the
base of the brain. Upon the sides of the medulla oblongata are a pair
of posterior lobes, which appear to b^ chiefly in connexion with the
root of the fifth pair of nerves.

The brain varies also in form in the Plagiostomi (Rays and
Sharks), but not nearly so much in proportion as that of the Osseous
Fishes ; and from its agreeing more, even when very different in
external appearance, with the brain of Amphibia, it is easier to de-
termine the signification of its component parts. The brain is chiefly
characterized by the more considerable development of its hemi-
spheres, from which arise either thick or slender nerves of smell ;
the lobes of the hemispheres are actually blended into a common
mass, divided only above in the longitudinal direction ; they are
either solid, as in most of the Rays when they have grown old, or
they are provided with a ventricle, which is continued then into the
olfactory nerves, as is seen chiefly in the Sharks, as Scymnus, Acan-
thias. This mass is prolonged by means of a narrow part of the

212 PISCES.

mesocerebrum that is open superiorly into the lesser optic thai ami
and quadrigeminal bodies. The open cavity corresponds to the
third ventricle. A pineal gland is not always distinct, but probably
occurs at least in the Rays. The middle cerebral ganglia or lobes
(lobi optici and corpora quadrigemina) are largest in the fcetal state
in proportion to the hemispheres, but are always much smaller than
in the Osseous Fishes ; they are hollow in their interior, but simpler
in structure, and covered in great part by the cerebellum. A pair of
large inferior ganglia are siuated in front of (not, as in the Osseous
Fishes, behind) the very large pituitary body (that is provided with
membranous appendages, and supplied by vessels of some size),
and partly beneath the narrow part of the brain enclosing the third
ventricle. The cerebellum is very large, of varied form, and for the
most part crucially divided by a longitudinal and transverse groove ;
more rarely, as in some of the Sharks and Rays, by several trans-
verse grooves, as in the higher animals. The medulla oblongata
forms a considerable ganglionic enlargement, and the corpora resti-
formia are usually much corrugated, and provided with ganglionic
dilatations, which may be viewed as posterior lobes or ganglia, such
as were described in the Osseous Fishes, and which correspond in
position to the clava of the human brain, as also to the funiculi
cuneati. The fourth ventricle is prolonged far backward into the com-
pletely open rhomboidal sinus. The roof of the fourth ventricle often
sends off several divisions into the cerebellum, e. g. in the large trans-
versely-furrowed braia of many Rays.

The cerebellum not utvfrequently exhibits an asymmetrical posi-
tion, as in many Osseous Fisl^es, e. g. Scyllium catulus and canicula,
and in other Rays and Sharks. The anterior or posterior lobe is in-
determinately placed in one instance more to the right, in another to
the left side.

In rare cases the posterior lobes are developed to such a degree as
completely to cover the fourth ventricle, as is ihe case in the Electric
Rays (Torpedo). The lobes of the fourth ventricle are here connect-
ed with the electric organ, and may be called electric lobes ; they are
characterized by their yellow color, and present under the microscope
a peculiar structure, consisting of numerous ganglionic corpuscules
surrounded by dense sheaths.

The structure of the brain in Chim<Era (at least C. monstrosa) is
very different from that of the Sturgeon, and approaches in a stri-
king manner to that of the Sharks ; only the hemispheres are far
removed from the mesocerebrum by the very long and narrow divi-

NERVOUS SYSTEM. 213

sion for the third ventricle. The brain exhibits a remarkable bend
from the mesocerebrum to the right.

Another form of brain occurs moreover in the Cyclostomi. In
Petromyzon we find a double (more or less fused) pair of ganglia,
from the anterior of which the nerves of smell arise ; the-y represent
the olfactory lobes and tubercles of the Osseous Fishes. Between
these and the pair of optic or quadrigeminal lobes, which are of
small size, is found the anterior part of the mesocerebrum, where a
single median lobe, that of the third ventricle (the pineal gland ?),
is developed. The cerebellum is in the whole genus uncommonly
small, consisting only of a transverse commissure connecting the
corpora restiformia. The inferior lobes aj*e absent or rudimentary,
and developed near to the azygos lobes of the third ventricle. The
posterior lobes appear to be absent, though the medulla oblongata is
very broad superiorly and somewhat corrugated.

The structure is still more abnormal and singular in Myxine and
Bdellostoma, where the brain is formed of several double divisions,
amounting to four pairs of ganglia, from the anterior of which arise
the olfactory nerves. A small median lobe belonging to the third
ventricle is also present. The cerebellum is absent, if the last bifold
division of the brain be not regarded as constituting it. The ventricles
are also absent.

The brain of the Lepidosiren has been described in speaking of
the Amphibious Fishes (see p. 150). It is considerably developed,
being very similar to that in the naked Amphibia, especially the
Proteidea ; it has two lobes of the hemispheres, single quadrigeminal
masses, a lobe for the third ventricle (glanduia pinealis ?), a narrow
medullary band representing the cerebellum, and a bilobed pituitary
appendage.

In the Vermiform Fishes, i. e. in Amphioxus s. Branchiostoma,
the rudiments of the higher senses are indeed present, as we shall
see further on, but the parts of the brain appropriated for the organs
of smell and sight are chiefly absent. The brain is not at all to be
distinguished from the spinal marrow ; the latter terminates obtusely,
and this part is to be viewed as the medulla oblongata, and as the only
appreciable part of the brain which is formed in this the lowest of ail
the Vertebrata.

The Spinal marroio of Fishes does not exhibit nearly so many va-
rieties as the brain. It is generally almost cylindrical ; in the genus
Petromyzon, however, and some other Fishes, e. g. in its posterior
part in Chima3ra, it is flattened out like a band and extensible ; it

214 PISCES.

possesses a central canal. Occasionally it is very short, as in those
Fishes, Orthagoriscus, Lophius piscatorius, that are provided with a
short truncate vertebral column. The spinal cord, however, is usually
very long, and exhibits generally a faint enlargement at the spot
whence the nerves arise that supply the extremities.

As regards the Cerebral nerves, from ten to eleven pairs are dis-
tinguishable in the Osseous and true Cartilaginous Fishes, and they
agree in the relations of their origin and course with those of the
higher Vertebrata and Man.

The olfactory nerves are for the most part slender in the Osseous
Fishes, and arise frequently by several roots (3 to 5), from the olfac-
tory tubercle of which they appear to be the immediate continuation.
In the true Cartilaginous Fishes they are often thick and short, as in
Scy Ilium, or, as in the Rays, frequently long and slender ; they arise
from the hemispheres, being in connexion with their ventricular cavity
when present, and form at their extremity very large ganglionic en-
largements, comparable to the clavate extremities of the olfactory
nerves in Man and Mammalia.

The optic nerve arises from the mesocerebrum (i. e. the lobi optici
and that narrow part of the brain that surrounds the third ventricle
in the Plagiostomi) : in the Osseous Fishes each optic nerves takes
its chief origin from the optic lobe of the opposite side ; both nerves
thus cross each other completely, so that the left passes to the right
eye, and vice versa; in the Herring, indeed (Clupea harengus), the
optic nerve of the right eye perforates that of the left, passing by
means of a slit through its fibres, without forming a chiasma. The
optic nerves form band-like strips, folded longitudinally. In the
Plagiostomi and the Sturgeon the optic nerves are united by a true
chiasma, some fasciculi only crossing each other.

The ocular nerves, namely, the third, fourth and sixth pair, ex-
hibit similar relations of origin and course to those of Man. The
oculo-motor nerve issues of large size from above and behind the in-
ferior lobes ; the nervus patheticus from between the optic lobes and
the cerebellum, and passes to the trochlear muscle. The delicate
abducens nerve arises distinctly by two roots at some distance be-
hind the inferior lobes from the basal surface of the medulla oblongata,
and passes to the rectus cxternus muscle. The ciliary branch of the
oculo-motor nerve appears to be absent.

The ffth pair (n. trigeminus) is in the Cartilaginous Fishes, at
least in the Rays, the most largely developed nerve, but frequently,
as in the Osseous Fishes, yields in respect of size and extent to the

NERVOUS SYSTEM. 215|

system of the vagus. It arises behind the optic lobes laterally from
the medulla oblongata by a series of roots, several of which admit
of being traced to behind the fourth ventricle upon the Rhomboidal
sinus. A large and small, or sensory and motor portion are found
to enter into the composition of the fifth pair ; several roots, e. g.y
in the Sturgeon, the nervous fascicula of its third and fourth root do
not pass into the ganglion, which is formed by other roots, and prin-
cipally its first. Three main branches are to be distinguished, as
in Man, namely, the orbitar, .supra, and infra-maxillary ; and besides
these, a large posterior branch {ramus opercularis), which proceeds
from the posterior root, and is principally distributed externally upon
the opercular apparatus of the gills ; it corresponds to the seventh
pair, which does not appear to be present as a separate n. facialis.

The auditory nerve is always separate from the rest, and is far
more strongly developed in the Osseous than the Cartilaginous
Fishes ; it takes its origin quite close behind the fifth pair, with
which it is united by a branch of communication {communicans
faciei?).

The ninth, tenth, and eleventh nerves, or the glasso-pharyngeal
vagus and accessory of Willis^ form a common system of nerves, with
many roots and united origins ; we must regard as its main branch
the branchial nerve {n. vagus), with which the glosso-pharyngeal
nerve is frequently united, while, however, the nervus accesso-
rius is usually free and distinct from it. This vagus arises fre-
quently by special ganglia that are occasionally much developed,
forms also upon its roots ganglionic enlargements, gives three main
branches to the last three gills and to the pharyngeal maxillae, and
passes then to the stomach and swimming-bladder. The twelfth
cerebral nerve, or hypoglossal of Man and the higher Vertebrata, is
absent in Fishes, owing to the want of mobility in their tongue ;
still, however, it has been recently described as occurring in the
Sturgeon.

From the vagus and accessory nerve proceed the large longitu-
dinal or lateral nerves of the Osseous Fishes, which run parallel
with the lateral lines, and straight within the muscles, to the tail,
and in their course enter into numerous communications with the
spinal nerves. Another longitudinal nerve is frequently present,
and is formed by two recurrent branches of the trigeminus and
vagus ; it passes through the supra-occipital bone, whence the nerve
of either side runs near the points of the spinous processes and be-

216 PISCES.

neath the fin-rays to the tail. Varieties occur in these lateral nerves
in the several genera of Fish.

The number of spinal nerves differs greatly in the several genera
of Fish. The two to four pairs of nerves that succeed the most ante-
rior pairs, usually give branches to the anterior extremities ; the suc-
ceeding pair of nerves passes, in the Pectorales, generally to the
posterior extremities or ventral fins ; in the Jugulares these same
nerves bend in the direction forward ; and in the Ventrales they usu-
ally arise further back from the seventh to the tenth pair. In the
Rays, which have such large pectoral fins, more than twenty pairs
coalesce together in one trunk for supplying the same ; about eight
or nine pairs pass to the also large ventral fins.

A Sympathetic nerve occurs in all the Osseous and Cartilaginous
Fishes, but is developed however in very different degrees. It runs
upon either side of the vertebral column, where it forms more or less
distinct ganglia, and enters into connexions with the spinal nerves.
It forms plexuses with the vagus, which accompany the arteries, and
are in several Fishes particularly distinct upon the stomach, swim-
ming-bladder, and sexual organs. It imites at the base of the skull
with the trigeminus and vagus, but unquestionably obtains twigs from
the other cerebral nerves.

In the very anomalous Cyclostomi the cerebral nerves, for exam-
ple, the ocular nerves, become simplified in their condition. In Pe-
tromyzon the abducens is absent, its elements being united with the
oculo-motor, but the trochlear nerve is present. The nervus tri-
geminus appears to contain motor fibres, since it ramifies upon the
muscles of the eye. A really distinct facial nerve also appears to
exist.

The Myxinoidse have only six pairs of cerebral nerves, the olfac-
tory, optic, trigeminal, facial, acoustic, and vagus ; the ocular nerves
are absent with their corresponding muscles, the eyes being merely
rudimentary.

Lastly, in Amphioxus all the cerebral nerves appear reduced to
the trigeminal. There arises, for example, from the cerebral end of
the spinal cord, a nerve somewhat thicker than the rest, that passes
to the snout of the animal ; it corresponds only to a part of the tri-
geminus, the greater portion of the head and sides of the mouth be-
ing supplied from the five succeeding spinal nerves. No branches
of spinal nerves appear to pass to the gills.

The Cyclostomi exhibit the peculiarity of being destitute of a

ELECTRIC ORGANS. 217

proper sympathetic nerve, this being replaced by the vagus. It has
been found in the Myxinoidae that the vagus nerve is not limited to
supplying branches to the stomach, but that upon the cardiac extrem-
ity of the latter viscus a single intestinal branch arises from both
vagi, and passes along the whole length of the intestinal canal to the
anus, and gives off those nerves of the organic system that are in
other Fishes furnished by the sympathetic. The lateral nerve is
present in Petromyzon, but is so short that it supplies with branches
only the anterior third of the body.

ELECTRIC ORGANS.

It is in the class of Fishes (and according to what has been hith-
erto observed, in this class of animals alone) that we meet with cer-
tain species which are provided with remarkable apparatus, capable
of producing, like an electrical machine or galvanic pile, electric
shocks, and so constituting weapons whereby these animals both
defend themselves and entrap their prey.

These Electrical Fishes^ as they have been called, are some in-
habitants of the sea, others of fresh water ; and all the species
known at present belong to the order Plagiostomi and to the soft-
finned Fishes. All the known electrical Fishes are characterized by
a smooth, naked, or scaleless integument provided with numerous
mucous canals. Two genera are known to belong to the family of
Rays. The European Electric Rays form the genus Torpedo, and
comprise two species, the T. narke s. ocellata and T. Galvanii s.
marmorata ; to these may be probably added a third, described by
L. Bonaparte under the title of T. nobiliana, and which is of very
rare occurrence. The first two species exist chiefly in the Mediter-
ranean and Adriatic seas, are in rare instances found in the Atlantic
ocean, and occasionally roam as far as the English coast and the
Northern sea. A peculiar species discovered by Ehrenberg.and
Hemprich, the T. Panthera, has been found also in the Red sea.
A second genus, Narcine, very similar to Torpedo, is found upon the
coasts of Brazil and India; three species of it are known.

From the family of Eels we are already acquainted with the
Gymnolus electricus, that has been brought alive to Europe, and is
met with in the inland seas and small tardily-flowing rivers of
southern tropical America, especially in Colombia, Surinam, and
Guiana.

The third electrical Fish, Silurus electricus, belongs to the family

218 PISCES.

of Sheat-fish, and occurs in the Nile, as also in other rivers in
Africa, as the Niger.

In the European Electric Rays, the Electric organs are situated
upon both sides of the head, occupying the space between the skull,
gills, and pectoral fins, and covered only by the fascia and skin,
through which they can be distinguished glistening both upon the
dorsal and ventral aspects. The electric organ of one side is com-
pletely separated from that of the other, is of a flattened form, i. c,
compressed from above downward, obovate in contour, being broader
in front where it extends nearly to the anterior edge of the body,
but narrower behind where it abuts against the gills. Upon both
the upper and under surface the electric organs present the appear-
ance of a tessellated pavement, divided into irregular obtusely-
angular, polygonal or hexagonal spaces. This depends upon each
organ itself being formed of a great number of triangular or hexan-
gular membranous prisms or columns passing into those of a globu-
lar form, and thus resembling basaltic crystallizations ; they may be
compared to so many galvanic columns ; each column is divided
into compartments by numerous transversely-disposed horizontal
lamellae, which can with difficulty be separated from each other.
Each column is moreover separated from the others by a tendinous
membrane or aponeurotic partition, which isolates the several col-
umns in a manner similar to that whereby artificial galvanic bat-
teries are carefully isolated by lateral glass rods. The number
of these columns differs in individuals of the same species, and
probably according to their age ; in young specimens only some hun-
dreds may be counted, while old animals, which attain a length of
four feet, number above a thousand. Upon the posterior edge of
the galvanic apparatus lesser rows of columns are to be observed ;
these are probably in a nascent condition. Each column may per-
haps contain 150 to 500 plates or septa, that may be compared with
the metallic plates of a galvanic pile ; the depth of the columns and
the number of their contained plates (?) varies according to age and
the position of the part itself, the middlemost columns being the
deepest (six to seven lines), while those upon the edges are more
depressed, and in small animals measure only about a line in depth.
The partitions between the columns are composed of fasciculi of
fibres, similar in character to elastic tissue. The transverse plates
or septa consist of a very thin and delicate prolongation inward of
the fibrous membrane composing the intercolumnar partitions, which
forms the basement membrane, invested upon both its free surfaces

ELECTRIC ORGANS. 219

with layers of epithelium. In the intervals between the septa is
found some fluid. Upon the septa themselves may be recognised
the terminal plexuses of vessels and nerves, those of the latter organs
resembling the terminal plexuses within the substance of voluntary
or transversely striated muscles. The electric organs, taken as a
whole, are very rich in vessels and nerves. Upon either side they
are supplied by four large nervous trunks, one of which, a branch of
the trigeminal nerve (n. electr. trigemini), is distributed specially
upon the most anterior part of the electric organ, while the three
other trunks are given oft' by the vagus ; the most anterior of these
is the largest, and much more developed than the branch of the
fifth ; the posterior is the smallest. The origin and mode of distri-
bution of these branches offer to our notice several remarkable pe-
culiarities. Thus the w. electricus trigemini arises, afong with the
inferior maxillary branch, deeper than the remaining roots of the
fifth pair from the medulla oblongata, and appears to correspond to
the lesser or motor root of that pair of nerves. The branches
proceeding from the tenth pair or n. vagus, pass to the electric
organs between the branchiae, and give ofif alternate twigs to them.
The branchial branches are furnished with ganglionic enlargements
containing ganglionic corpuscules, but these are absent upon the
far thicker fasciculi of the electric nerves. It appears that these
motor fibres, which here reach their maximum development, corre-
spond to the accessory nerve of the higher Vertebrata.

The structure of the electric organ is in Narcine very similar, but
here its shape is the reverse of that in Torpedo, being narrower an-
teriorly ; the nervous branch corresponding to the r. electricus nervi
trigemini is much more feebly developed.

In the Electrical Eel the organ in question is situated in the tail,
which, from the very anterior position of the anus, is so large in this
animal as to exceed more than a quarter the length of the whole
body, and is in great part filled up by the very largely developed
electric apparatus. This is divided into two detached parts and a
single one consisting of two that have coalesced : the first are situ-
ated laterally and more toward the upper surface, the last inferiorly,
and the extent of all three organs closely accord with that of the
caudal fin. Each of the two lateral organs is invested by a ten-
dinous membrane, and glimmers through the external integument ;
superiorly they abut against the muscles of the back, inferiorly
against the muscular system of the caudal fin ; posteriorly they run
to a point. The inferior electric organ is situated above and between

220 PISCES.

the muscles of the caudal fin, and is also invested by an aponeurotic
covering : it resembles in form a three-sided prism. The internal
structure of the electric organ is essentially similar to that of the
Torpedo, with this difference only, that the columns lie horizontally
upon each other, instead of standing perpendicularly. They resem-
ble a row of horizontal bands, are much shorter than in the Electric
Rays, and their septa are placed perpendicularly, owing to the po-
sition of the columns. The number of the septa admits of being
only proximately reckoned ; in an adult Electrical Eel there may be
perhaps several millions. The nerves that enter these organs in the
Eel are all spinal nerves ; neither the cerebral nerves nor the lateral
nerves giving branches to them. The number of nervous trunks
amount always to above two hundred, and from these sensitive
branches pasi ofT also to the integument. It would appear, too,
that the anterior or inferior motor roots of the spinal nerves, whose
branches are distributed to the electric organs, are more strongly
developed.

In the Electric Silurus, with the more minute anatomy of which
we are unacquainted, the electric organs extend immediately beneath
the integument from ihe fore part of the head and the branchiae to
the anal fin. An external and an internal organ may be distin-
guished, which receive their nerves partly from the n. vagus and
partly from the spinal nerves.

We know now, from the numerous experiments that have been per-
formed, principally in Europe, by eminent philosophers upon living
specimens of Gymnoti, that the electricity generated in the apparatus
of these animals can be discharged by the voluntary exercise of
their nervous influence, and that what is called animal electricity
is perfectly analogous to that which is produced by the Leyden jar
or voltaic pile. Some experimenters have gone so far as to succeed
in obtaining from the Gymnotus an electric spark ; aberrations also
of the magnetic needle have been observed, and it is probable that
heat also is developed, during the discharge. The Electric Eel is
capable of producing the most violent shocks, sufficient indeed to
stun and throw down men and horses.

ORGANS OF VISION. 221

ORGANS OF THE SENSES.

Organs of Vision.

The Eyes are generally developed in Fishes/ and provided with
all the parts that enter into their composition in the rest of the Ver-
tebrata. They are lodged in a cartilaginous or bony orbit, imper-
fectly closed. The external integument becoming thinner in texture
and transparent, forms usually around the eyes a shallow circular
fold, beneath which muscular fibres may be frequently seen to pass,
forming a kind of sphincter. In some instances the integument
forms a transparent lamina which is continued simply over the
surface of the eye, as in Fishes of the Eel kind, Ammocoetes and
others. Not unfrequently an anterior and posterior plica semilunaris
may be distinguished, as in Clupea, Scomber, Salmo, but particu-
larly in the Sharks, where a true nictitating membrane exists ; this,
however, being wanting in the genera Scyllium and Acanthias. The
Sharks possess also free eyelids, which in the Rays are soldered
together.

The Scleroticis usually dense and cartilaginous, or actually formed
of thin bony plates, which in many large Fishes, as in Xiphias,
coalesce to form an osseous shell, having an opening left posteriorly
for the passage of the optic nerve. In front of the sclerotic is
inserted the very flat Cornea, which is usually thickest at its margins.
The Choroid coat is usually separated from the sclerotic by a loose
mass of adipose cells, and consists frequently of two widely sepa-
rated layers ; the outer of these, or the pigmentary, is of a silvery
lustre in the Osseous Fishes, and consists of very delicate fibres,
which almost resemble under the microscope needle-shaped crystals ;
it is continued in front to form the iris, which encloses a pupil that
remains probably always round and immoveable. The inner layer
is very highly vascular, and covered upon the internal surface by
black or purple-colored pigment. Between the two layers of the
choroid is situated in many Osseous Fishes what is called the vas-
cular gland, which will be described more minutely further on.
In the choroid of the true Cartilaginous Fishes (Plagiostomi) a layer
of black pigment is placed externally, and internally a tapetum of
metallic splendor. The ciliary body is, for the most part, feebly
developed. In the* Sharks the ciliary processes are most distinctly
formed, but, though less so in many of the Osseous Fishes, they still

222 PISCES.

may be proved to exist. The Rays, e, g. Torpedo, exhibit a peculiar
disposition of the pupillary margin, for golden-colored processes,
shaped like palm branches, depend from the iris, and are capable of
closing the pupil like a curtain.

The Optic nerve in Fishes is generally formed of plicated laminae,
which can be unfurled from each other like the vanes of a fan. It
perforates the sclerotic obliquely, and at a distance from the cen-
tral axis of the eye. The point of exit for the retina is a round
opening, frequently, however, an elongated slit, from which the
nervous tunic of that membrane expands. The latter exhibits the
same component parts as in the remaining Vertebrata, such as a
strongly developed racemose or papillary layer arranged in a peculiar
manner. .

The Crystalline lens is of large size, perfectly spherical, and en-
closed within a thick capsule ; it usually protrudes through the
pupil, and approaches, like the iris, very close to the cornea, so that
the posterior chamber of the aqueous humor is completely wanting,
and the anterior very small, containing only a very slight quantity of
that fluid. The lens consists, as in other animals, of peculiar fibres,
which are united by toothed edges, like the sutures of the cranial
bones. The Vitreous body, fiat, and having the lens deeply imbedded
in it, contains a small quantity of thin fluid.

The eye of a Fish, when most perfectly constructed, presents
always a very flattened form of bulb and a short axis ; owing to the
watery medium in which they live being denser than that of air, the
vitreous and aqueous humors appear to be present in smaller
quantity, while the lens is more dense and spherical, so as to bring
the rays of light to converge at a shorter focus. But besides these
general, other special peculiarities occur in the structure of the eye-
ball in Fishes. Thus in Pleuronectes both eyes are placed asym-
metrically upon one side. In Anableps tetrophthalmos the cornea
of each eye is divided by a transverse band, and is thus rendered
double along with the pupil, while the other parts remain single.
The size to which the eyes are developed varies greatly ; thus they
are largest in many Osseous Fishes, and particularly so in the Pla-
giostomi, where, as in Friacanthus, they are of remarkable magni-
tude, and still more so in the rare Pomatomus telescopium, which
lives in the greatest depths of the Mediterranean sea. The eyes are
generally small in those Fish that bury themselves, as the Eels and
Cyclostomi, in mud and sand. There are Fishes also with very
small and rudimentary eyes, e. g. Silurus coecutiens and Apterichthus

ORGANS OF VISION. 223

coBcus. The eyes are in a still more rudimentary condition in the
remarkable, and in many respects anomalous, family of Myxines
among the Cyclostomi, which comprises some species that live as
parasites upon the internal viscera of Fish, although others are also
met with in a free state. The most imperfect state of development
is that presented by the Myx.ine, where the eye is not even visible
externally. It consists, in fact, of nothing else than a small bulb,
covered by muscles, but which contains a nerve, and internally a
transparent nucleus that may be compared to a vitreous body. The
rudimentary eye is larger in Bdellostoma, in which it projects some-
what above the surface, and is covered by a thin prolongation of
integument ; it is enclosed in a spherical cushion of fat, through
which passes the delicate optic nerve ; several ocular tunics are
distinguishable, v^^hich probably contain internally a transparent
nucleus. The lowest stage of structure appears, however, to exist
in the eye of Amphioxus ; for here we find, as in many of the Inver-
tebrate animals, only a couple of pigmentary spots, without, it seems,
any organs for intercepting the light in its passage through the eye ;
they receive, however, a delicate nervous twig from the cerebral end
of the spinal cord. The eyes are also but slightly developed in the
Amphibious Fishes, and are devoid of eyelids and muscles ; in the
small bulb, however, we may distinguish a cornea and a small lens,
while a delicate optic nerve may be also observed.

In many Fishes peculiar structures are superadded to the organs
of vision. To these belong the Choroidal glands of the Osseous
Fishes. Between the silver-colored and the internal plate of the
choroid there is situated, as already alluded to, in many genera a red
vascular mass, which, upon closer examination, is found to consist of
a plexus or rete mirabile of vessels, formed by tufted ramifications
of arteries as well as veins ; these belong to what is called the am-
phicentric system of retia mirabilia, or that with double arterial and
double venous vortices, and are connected with the vessels of the
accessory branchiae. Those genera which do not possess the latter
organs, as Silurus, Pimelodus, Cobitis, and Muraena, have no choroid
glands. The choroid, indeed, in all the Vertebrata is properly
formed of retia mirabilia, but these are made up by the radiating dis-
tribution of arteries and veins from a singlo centre. In the Carp this
vascular gland is much developed.

A still greater peculiarity occurs in many Osseous Fishes, as the
Pike, and in the Sturgeon among the Cartilaginous. In all these
Fishes, at the point where the optic nerve enters the longitudinal

224. PISCES.

slit, we find what is called the falciform process ; this is a fold of the
choroid invested by black pigment, that passes through the above-
mentioned slit and the substance of the vitreous body, and is in-
serted into the side of the capsule of the lens. A filament of the
ciliary nerve frequently accompanies it, and dilates into a pear-shaped
knot forming the pyriform body or campanula Halleri. Occasionally,
as in Muraena Conger, two falciform processes have been observed,
an anterior and a posterior one, which hold the lens between them
like two poles. These structures, such as the falciform process,
which reminds us of the pecten in the eye of Birds, are wanting in
the Plagiostomi and many Malacopterygii, e. g. the Carp.

The bulb of the eye is but slightly moveable in Fishes. In the
Osseous Fishes it is attached to the orbit by a short ligament near
to the insertion of the optic nerve ; in the Plagiostomi it stands upon
a moveable cartilaginous stalk, which articulates with a short pro-
cess of the sclerotic. Four straight and two oblique muscles move
the eye, and between them we find some adipose and cellular tissue.
In the Bdellostoma the rudimentary eyes are entirely destitute of
muscles, which in Petromyzon among the Cyclostomi are present in
their usual number and position.

Organs of Hearing.

In the structure of the organs of hearing in the class of Fishes we
meet with an interesting series of gradations, ranging from the low-
est and simplest stage, wherein their structure resembles that of the
Invertebrate animals, to that which exhibits a combination of parts
corresponding to some one or other of the more highly organized
Vertebrata.

The general arrangement of the auditory organs in the Osseous
Fishes is as follows : the whole membranous labyrinth lies for the
most part free within the cranial cavity, and adjacent to the brain,
or it is only imperfectly and partially enclosed in bones, which have
been already (p. 189) regarded as belonging to the system of tem-
poral and occipital bones. These cavities are, as it were, lateral
continuations of the cranial cavity, and are, like the latter, often filled
up by a lax cellular and adipose tissue containing freely floating
drops of oil. In cases where the auditory ossicles (which we shall
presently describe) of the membranous labyrinth are of very large
size, the cavities for containing them are dilated into a bladder-like
form, as in Gadus, Sciaena, and in a lesser degree in Perca and

ORGANS OF HEARING. 225

Others. The external coverings, namely, the skin and muscles, are
continued over the organs of hearing as well as over the whole skull,
so that the sonorous vibrations propagated in the water have no spe-
cial or direct access to the auditory apparatus. Still, however, we
may regard as external meatuses or conductors of sound certain
membranous intervals in the skull resembling fontanelles, and situa-
ted upon the crown of the head, e. g., Silurus, Cobitis, Clupea, &c.
It is very rare to find, as in Lepidoleprus, an infundibuliform canal,
comparable to the external auditory meatus, and invariably situated
above the external branchial fissure, where it opens upon the sides
of the occipital bone and is there closed by integument.

The Membranous Labyrinth consists, 1^^. Of the simple vestibule;
this is a transparent sac, provided with nervous expansions, and of
very varied form, which is loosely attached to the skull in the vicin-
ity of the cerebellum, and receives the ampullae of the semicircular
canals. 2d. Of the auditory sac [saccus vestihuli), which, lying
close upon the vestibule, is externally more or less detached, and
internally always separated from the vestibule by a partition. Oc-
casionally, however, it is united to the vestibule by a membranous
commissure, lies further posteriorly, and is usually divided into a
pair of chambers, which, like the vestibule, contain mostly auditory
ossicles or calcareous parts, surrounded by the fluid of the labyrinth.
3d. Of the arciform or semicircular canals ; of these an anterior and
posterior canal are constantly found, both standing perpendicularly,
and two of their crura usually opening together ; lastly, an external
horizontal canal. Toward the vestibule the canals are dilated into
ampullae, and their arched portions are not unfrequently received
partly into the adjacent bones, to which they are fastened by cellu-
lar ligaments. The structure is similar in the true Cartilaginous
Fishes (Plagiostomi) ; the labyrinth, however, is in them completely
separated from the cranial cavity, and completely imbedded in a
mass of cartilage, which is much harder where it is in contact with
the membranous labyrinth. The sac and vestibule do not appear to
be separate in these Fishes, though the labyrinth is elongated to form
a flask-shaped duct leading upward and outward upon the middle of
the occipital bone. In this situation are also placed either two or
four openings, closed by membrane, and approximated to each other,
which correspond to the two fenestrae, and have the external integ-
ument continued over them.

In the Rays, and some species of Sharks, we find four openings
upon the skull, two for each ear ; the posterior conduct only into the

15

226 PISCES.

cartilaginous vestibule, and correspond to the round fenestras ; the
anterior are comparable to the oval fenestrae ; between each of these
openings and the external skin a membranous sac is placed, which is
filled with a calcareous mass, and extends into the membranous ves-
tibule. At their commencement we find a muscle arising from the
integument, and serving to compress the two sacs.

The Plagiostomi have a pair of soft calcareous concretions (oto-
liths), composed of carbonate of chalk, appended to the walls of the
sacs ; the Osseous Fishes are generally furnished with three stones
(lapilli), hard and dense as porcelain, and of very varied form ; one
of these is situated in the vestibule, two in the two chambers of the
sac.

Manifold diversities occur in the form, number, and structure of
these otoliths. Thus the porcelainic otoliths are frequently, as in
Cyprinus, Gadus, Scomber, toothed at the edges, and are occasion-
ally, as in Sciaena, Lepidoleprus, and others, of remarkable size.

The form, size, width, and mode of union of the semicircular
canals, with their position also in the cranium, exhibit likewise re-
markable diversities ; while, e. g., in Cobitis, they are situated quite
free in the cranial cavity, the external and posterior canal, or only
one of the two, are partly enclosed in the bones, or, as in the Pike,
Orthagoriscus, the Sturgeons, and Chimaeras, they are more or less
surrounded by cartilaginous coverings ; this, as has already been
mentioned, is their condition generally in the Plagiostomi. The
ampullae are retained in their expanded condition by peculiar double-
coned septa, upon which the auditory nerve expands ; the expansions
and terminal looped plexuses of this nerve may be very easily and
distinctly observed under the microscope.

In many Osseous Fishes, but particularly the Yentrales, a most
remarkable communication subsists between the swimming-bladder
and the internal ear. The vestibule always gives off in the direction
backward a canal which coalesces with that of the opposite side
into a single reservoir (sinus impar) ; this latter is a pouch of more
membranous texture than the vestibule : it is situated in the basilar
portion of the occipital bone, bifurcates again in the direction back-
ward, and forms constantly a round saccule placed between the
first cervical vertebra and occipital bone, and filled with the fluid of
the labyrinth ; it is called the sinus sphcBrici s. atria sinus imparts.
Three ossicles are placed near to the three most anterior vertebrae,
and are connected to their transverse processes by joints and liga-
ments ; they are of varied form ; the most posterior, which is the

I

ORGANS OF HEARING. 227

largest, corresponds to the malleus, and is appended by an unciform
process to the swimming-bladder, the middle to the incus, the ante-
rior to the stapes. The last-named ossicle may close the prevesti-
bulum {atrium sinus imparis), and by pressure upon the swimming-
bladder may be drawn apart from or pressed against it. Each pre-
vestibulum is provided with a peculiar ossicle encircling it like a
staple (claustrum). The auditory ossicles are found distinct in all
the species of Cyprinus, in Cobitis, and Silurus, while in other Os-
seous Fishes they are wanting. The swimming-bladder is slit in
front to form two ducts, which enter the vestibule.

As Fishes, at least the Osseous, are destitute of external auditory
passages, sound in these animals must penetrate or be transmitted
through the bones of the head to the labyrinth. The different mem-
branous regions of the skull may indeed serve the function of tym-
panic membranes, and the swimming-bladder exert some similar
office by exercising compression upon the fluid contained in the laby-
rinth.

The organ of hearing becomes remarkably simplified in the lower
organized Fishes, and in this respect the Cyclostomi exhibit very in-
teresting stages of development, which partly correspond to the foetal
structure of the auditory organs in the higher Vertebrata.

The organ of hearing in Petromyzon and Ammocoetes consists of
a bony or cartilaginous part, and of a pair of hard, yellow, oval cap-
sules connected with the skull, and enclosing, like a bony labyrinth,
the membrane lining the same ; between the two is placed a fibro-
membranous layer. The membrane of the labyrinth consists of a
small sac, which is divided into two symmetrical cells by an external
groove that forms a fold projecting into its interior. Two wide, de-
pressed, simicircular canals arise with ampulliform enlargements, and
unite into a common opening which enters the vestibule. A single
smaller, more rounded appendage to the vestibule corresponds to the
auditory sac {sacculus) of other Fishes. Two branches of the audi-
tory nerve pass to the supply of the ampullae.

The structure of the auditory apparatus is still more simple in
Myxine and Bdellostoma. It is situated, as in Petromyzon and Am-
moccetes, in a hard ellipsoid capsule, the cavity of which resem-
bles a ring, filled up by a similarly formed membranous labyrinth,
within which the single semicircular canal is blended with the vesti-
bule.

Otoliths are completely absent in the hearing organs of the Cy-
clostomi. Not a trace even of calcareous crystals can be detected

228 PISCES.

by the microscope ; and this is the more remarkable, as these struc-
tures appear to occur generally in the auditory organs of the Inverte-
brate animals.

No vestige of an organ of hearing has hitherto been found in Am-
phioxus, so that we have an example among the Vertebrata of a
creature completely destitute of the auditory function.

The Amphibious Fishes have a more complete organ of hearing.
At least in Lepidosiren annectens a large labyrinth has been found
with three small semicircular canals, and two great sacs containing
otoliths, but without a trace of tympanic cavity.

Organs of Smell.

In all Fishes we find distinctly developed organs of smell. They
consist of cavities situated at the anterior extremity of the snout, in
front of the eyes, and beneath the nasal bones ; they are bounded by
the maxillary bones and vomer, present an elongated, oval, or round
form, and open by two nasal apertures lying one behind the other ;
the anterior opening is occasionally, as in Muraena, lengthened out
to form a short contractile tube ; the posterior is in some instances
removed to a distance from the first, and patulous. This is the gen-
eral arrangement of these parts in the Osseous Fishes ; the nasal
passages are scarcely ever perforate throughout, as in the air-breath-
ing animals, though in several species of Conger (as in the Am-
phibia that breathe by branchiae) they are found to open internally
beneath the upper lip. Minor peculiarities frequently occur in the
structure of these organs, as in Lophius piscatorius, where the nasal
cavities exhibit the form of two small bell-shaped sacs situated be-
neath the upper lip, and lined by folded mucous membrane. In the
Plagiostomi the nasal depressions are very large, and can be closed
by means of a membranous or cartilaginous operculum ; they are
placed inferiorly near to the angles of the mouth, and the operculum
can be raised by muscles. The mucous membrane lining them is
very vascular, provided with crypts that secrete a copious mucus,
and disposed in exceedingly delicate and frequently very vascular
folds. In some instances these folds radiate from a projecting mid-
dle elevation of the mucous membrane ; more frequently, however,
they arise like the teeth of a comb, in the form of ridges transversely
directed, from the sides of a middle longitudinal fold ; the transverse
plications in the Plagiostomi are further provided with stellated folds
upon their walls, in order to increase the extent of surface of the

ORGANS OF SMELL. 229

mucous membrane ; in other Fishes we even meet with tufted rami-
fications of the folds. The olfactory nerve usually dilates close
against the nasal cavity of its side into a considerable bulb, or it
forms, as in the Plagiostomi, an elongated knot corresponding to the
chief mucous fold, and from this its branches proceed along the
plaits of the mucous membrane and their subdivisions ; frequently
the olfactory nerve divides previously to this into several branches ; a
branch of the fifth pair passes also as an accessory nerve to the or-
gans of smell.

Peculiar arrangements of the organs of smell are exhibited by the
Cyclostomi, for in them the nasal cavity is single, but the two fami-
lies composing this order differ in some respects from each other.
In that family to which Petromyzon and Ammocoetes belong, we
find a single nasal aperture or spiracle upon the head, which leads
into a rather narrower nasal canal, that finally expands into the
single nasal cavity lined by plicated mucous membrane ; upon the
bottom of this cavity is found a more membranous, contractile
flask-shaped coecal pouch, an appendage that does not communicate
with the pharynx, but with the nasal cavity by a small opening.

In the second family, the Myxinoidae, the palate is perforated in
a remarkable manner, and in Myxine there is a broad naso-palatal
opening. In Bdellostoma the lesser naso-palatal opening lies above
a fold of the mucous membrane at the extremity of the palate, and
leads freely into the naso-palatal duct. The external nasal aperture
communicates by means of the nasal tube formerly described as com-
posed of cartilaginous rings, with the naso-palatal opening.

As regards the Amphibious Fishes, typified by the Lepidosiren,
the two species of this genus at present known appear to comport
themselves differently as regards the structure of the olfactory
organs. In L. annectens the nasal depressions are imperforate ; the
olfactory nerve passes through a cartilaginous ethmoidal plate to
the organ of smell, which always consists of a sac lined by trans-
versely-plicated mucous membrane ; an external opening is merely
found beneath the upper lip. L. paradoxa seems to agree complete-
ly with Siren and Proteus among the Amphibia, for in it we find a
posterior opening upon the internal side of the upper lip, and the mu-
cous membrane disposed in folds.

The organ of smell, recently discovered in Amphioxus, is of a still
more simple kind. It consists of a single depression, situated to the
left side, which terminates freely in a small cup, and rests directly
upon the central axis of the nervous system. It presents upon its

230 PISCES.

mucous membrane a glistening epithelium ; it does not perforate the
mouth, but terminates in a small blind pouch, having its mucous
surface increased by folds.

Organs of Taste.

The tongue is absent in Fishes, and the anterior part of the lingual
bone, which frequently supports teeth, exhibits neither in its exter-
nal condition, nor in the distribution of its nerves, any analogy with
the tongue of the other Vertebrata. In cases where the glosso-pha-
ryngeal nerve is developed, as in the Sturgeon, it only gives twigs
to the branchial arches and palate, which last is in Fishes probably
the seat of the sense of taste. No branch arises from the fifth pair
that can be compared to the lingual nerve.

That the gustatory function is probably seated in the palate, ap-
pears to be confirmed by the fact that in many Fishes, e. g. the
Cyprini and in C. carpio, peculiar organs, richly supplied by nerves,
are developed in that situation. In the Carp there is found at the
base of the skull, in front of the excavated plate, which is met with
on the body of the sphenoid, and supports what has been called the
Carp's stone, and also in front of the pharyngeal jaws, a single white
spongy mass, which receives numerous large branches from the
glosso-pharyngeal nerve, and is possessed of such a high degree of
irritability, that it becomes erect and turgescent upon mechanical
and chemical stimulants being applied. This organ forms a very
broad cushion immediately above the inner edges of the branchial
arches.

Organs of Touch.

As organs of touch in Fishes, we must unquestionably regard the
beard-like filaments that occur in many, as in sundry species of
Cobitis, upon the chin and at the commencement of the mouth ; they
receive large branches from the fifth pair of nerves,

DIGESTIVE SYSTEM.

If throughout the class of Fishes we have seen the hard parts of
the body assuming the greatest variety of structure as compared
with those of other Vertebrata, so also in the Teeth that form the
armature of the jaws, and other facial bones, shall we find the same

DIGESTIVE SYSTEM. 231

character to hold good in a pre-eminent degree. For not only do the
dental organs vary in their more minute structure, but in number,
form, situation, mode of attachment, and development, so that it is by
no means easy to give a general survey of these peculiarities without
describing them in the several families and genera.

All Fishes, vj^ith but few exceptions, are provided with teeth. In
some, however, they are completely wanting, as in the Sturgeon,
the genera Aodon, Syngnathus, Amphioxus, while others, as the
Salmons, exhibit them upon all, or nearly all, the bones that gen-
erally support teeth. These bones are chiefly the intermaxillary
and inferior maxillary, the palatal bones, the vomer, lingual bone,
and branchial arches ; also, though rarely, the superior maxilla,
instances of this bone supporting teeth occurring, at least in the
Osseous Fishes, only in Salmo, Clupea, and Muraenophis ; it is rare
too for the pterygoid bones or the sphenoid to be, as in Sudis, armed
with teeth. It is very uncommon for a broad dental plate to be
present upon the occipital bone, the base of which in the Carp ex-
hibits for this purpose a broad process with a concave surface.
Teeth are in some instances met with only upon the pharyngeal
bones, which are peculiar bones situated behind the branchial arches,
and found both above and ^elow the entrance to the pharynx, their
number varying from one to six. The jaws in the Cyprini are
edentulous, but there are teeth upon the pharyngeal maxillae, which
in the Carp exhibit broad molar-like crowns ; other forms occur in
other Cyprini, so that the several species may be partly distinguished
by the varieties of thfe pharyngeal teeth. In other genera, such as
Labrus and Scarus, the true as well as the pharyngeal jaws are
furnished with teeth. Occasionally, as in the Lampreys, and in the
genus Helostomus among the Osseous Fishes, the teeth are chiefly
fastened to the lips. As regards, however, the situation of the teeth,
the Rays and Sharks, and then the Chimaera, agree most with Man
and Mammalia, for in all three the teeth are limited to the two arch-
shaped maxillfe. A singular position for the teeth occurs in the
Saw-fish (Pristis), where, besides the jaws, the bill-shaped process
prolonged from the cranium is armed upon either edge with a row of
pointed teeth, giving it the appearance of a double saw.

Diversities occur, moreover, in reference to the mode of attach-
ment of the teeth in Fishes, such as are met with in no other class
of Vertebrata. In some instances the teeth are inserted in cavities
or distinct sockets, as in the weapon of the Saw-fish. Some teeth
have their basis hollow, and implanted like the claws of a cat upon

232 PISCES.

bony projections, which arise from the bottom of the dental socket ;
this is the case with the incisor teeth of Balistes, that thus present a
double gomphosis. There is frequently a slight anchylosis of the
bases of the teeth to the walls of the alveolar cavity, as in Sphy-
raena, Acanthurus, and others. In the majority of cases an actual
fusion of the bony substance of the jaws with the sockets of the
teeth exists. Before, however, this anchylosis is completed, the
tooth has been united to the jaw by ligament. Occasionally, as in
the posterior teeth of Lophius, the teeth are fastened by elastic liga-
ments to the maxillae, and so disposed that during deglutition they
yield downward and backward so as to offer no obstruction to the
passage of food, and again spring up into their usual erect position
when the pressure is removed. The teeth of the Sharks, for the
most part bifurcated inferiorly, are attached by ligaments to the partly
ossified edges of the maxillae. A very curious mode of attachment
is exemplified by the teeth of the Eagle-Ray (Myliobatis), in which
the flat hexagonal teeth are united by suture to a series of quadrangu-
lar pieces.

The form of the teeth, is likewise very varied, being either conical
as in most Fishes, flat, prismatic, or cylindrical. The conical kind
are frequently very numerous, and in such cases so small as to ap-
pear like papillae, and may possibly serve only as instruments of
touch ; in other instances they are longer, almost filamentary like
bristles, and divided at their apex into two or three prongs ; in many
Fish, e. g., in Trichiurus, they are provided at their points with
hooks ; they are frequently largely developed, for instance, the ca-
nine teeth of many Carnivorous Fishes, e. g., the Sea- wolf (Anai-
rhicas Lupus). The incisor teeth also may be perfectly flattened
like those of the human subject, as in Sparus sargus, L., and behind
these stand short cylindrical teeth with rounded flattened crowns.
Such flattened teeth differ both in form and size ; their plates are
cylindrical, elliptical, elongated, triangular or quadrangular, semilunar
or falciform ; the same flat, tessellated kind of teeth are found in the
jaws of the Saw-fish. It is not rare for the teeth upon the two
jaws to differ, as in the Sharks, where the teeth that are destined
to rise up and replace the others when they fall out, form numerous
rows lying like tiles one over the other upon the inner walls of the
maxillae.

The number of the teeth ranges from one to so many that they
can be scarcely counted. Thus the Myxinoidae (e. g., Bdellostoma,
Myxine) have only one single slightly-curved tooth on the palate.

DIGESTIVE SYSTEM. 233

The genera Ceratodus and Ctenodus have two teeth ab ve and
two below, while in Chimaera we find four superior and two inferior
teeth.

The substance of which the teeth in Fishes is composed presents
very different characters. The teeth of the Cyclostomi belong to
the category of epithelial structures, or horn-tissue. The dental
plate upon the occipital process of the Carp consists of a peculiar
brown, semitransparent tissue, harder than the substance of the
horny teeth of the Lampreys. In most Chaetodonts the teeth are
delicate, flexible, and elastic, and composed of a yellow transparent
tissue, this being the case also in the labial teeth of Helostomus. In
most Fishes, however, the teeth consist of Osseous substance,
slightly denser than that of the jaw^s to which they are attached. Oc-
casionally, as in Exoccetus and Echeneis, the substance of the teeth
is uniform throughout, and not invested by a layer of denser texture.
In others, e. g., the Sharks, the tooth is covered by a dense trans-
parent enamelloid substance ; it is not, however, true enamel, but
the proportion this substance bears to the rest of the tooth may be
determined from the larger quantity of earthy constituents which
it contains, the finer division and more parallel arrangement of its
calciferous tubules. In Sargus and Balistes the peculiar osseous
substance of the tooth is still harder, and covered by a thick layer
of a denser substance, which differs little from the enamel of the
higher Vertebrata. In Balistes also, and some other Fishes, we
find a third layer superadded, that may be compared to the cementum
of the Mammalia. In Scarus there is found even a fourth material,
forming a very dense ivory-like layer upon the periphery of the
tooth. In Fishes the small dental tubes (canaliculi chalcophori) are
extremely distinct, and the microscopic structure of the teeth in
general exhibits manifold modifications, which can not be further
discussed in a work like the present.

The Intestinal Canal offers for consideration a number of diversi-
ties, which, like those of the teeth, can not be well described without
entering into the anatomy of the several orders and genera.

The Cavity of the Mouth in ihe OsseoMS Fishes opens externally
upon either side through the branchial fissures. Peculiar tooth -like
processes stand out upon the internal edge of the branchial arches,
and protect the fissures between the latter from the intrusion of
food. The pharynx commences in the Osseous Fishes immediately
behind the pharyngeal teeth, and there is found surrounding it in
this situation a strong sphincter-like muscle ; an o3Sophagus may be

234 PISCES.

continued from it as a short infundibular tube, but frequently only
its commencement, or the pharynx, is developed, which then forms
an extremely short canal, which is surrounded throughout its entire
length by an annular layer of muscular fibres. There being no
larynx in Fishes, the oesophageal intestine is attached to the verte-
bral column and pericardium by cellular tissue. A dense mucous
membrane, frequently beset with tubercles and papillary projections,
lines the oesophagus, and is usually disposed in coarse longitudinal
folds, that are frequently continued into the stomach.

There are Fishes in which the intestinal tube is continued from
the pharynx without any indication of a gastric enlargement or of
convolutions, and with which no organ of secretion is connected,
except the liver. It is interesting to commence with such simple
structures and ascend to the more complex.

The greatest departure from the structure of the Vertebrata gen-
erally, and also from that of Fish, is furnished by the anomalous
genus Amphioxus. Its internal branchial cavity is prolonged into
a narrow canal, the oesophagus, which is continued into a much
wider intestine. The latter is always of a green color, as is also a
caecum that is developed from it. The green fluid or gall is secreted
by a glandular layer situated in the parietes of the intestine, and
which, as in many Annelides, has not yet freed itself from the intes-
tine in the form of a more highly organized parenchymatous liver.
The green-colored portion terminates by an abrupt line, and then
the walls of the intestine present, as do those of the caecum also,
their natural translucency and delicate texture. The intestinal sac
exhibits, upon the whole of its internal surface, a glistening epithe-
lium and an active vibratory or twinkling movement that hitherto
has not been observed in any other vertebrated animal. This re-
markable fish appears to be nourished simply by swallowing the
microscopic animalcules met with in the sea-water. Nevertheless,
excrements are extruded from the body of a dark color and stringy
form.

Devoid of convolutions, and without any special dilatation for the
stomach, if we except a slight increase in its width at one particular
part, the intestine runs straight from the mouth to the anus in the
Cyclostomi, e. g., Petromyzon, in Myxine, where, however, it is
wider, in Syngnathus, and in Chimaera, so that such is its condition
in the most different orders. In many other Fish, as the Cyprini and
Labri, in which the intestinal canal is long and spirally contorted, a
special gastric dilatation is also absent, while in others that are fur-

DIGESTIVE SYSTEM. 235

nished with smaller and insignificant convolutions, we meet with a
well-defined stomach, as in Gasterosteus, Gobius, and some species
of Blennius and Pleuronectes. In other instances the stomach is
not developed directly in the course of the intestine, but to the side
of the latter, and forms either an oval or spherical dilatation, as in
Cobitis and Blennius viviparus, or passes from this form into that of
a retort, examples of which may be seen in the majority of Bony
Fish, e. g. the Salmon. The cardiac portion of the stomach is fre-
quently extended into a more or less elongated caecum, e. g. in the
Eel, in Gadus, Scomber, Clupea, and many other Fish, but more
especially in Ammodytes tobianus. To the stomach, when present,
succeeds the intestine properly so called ; it makes either few or
many convolutions, and is not unfrequently continued backward to
form a thicker portion that may be regarded as the large intestine,
the limits of this being defined frequently by a caecal valve, as
those of the pylorus are by a constriction. Beyond this point,
however, the intestine frequently narrows toward the cloaca, as in
many Carps and Salmons, and it is not rare for the valve to be
wanting. Occasionally a valve is found upon the cardiac orifice of
the stomach. Anomalies also occur of a peculiar kind, e. g. in Le-
padogaster biciliatus ; for here to a short narrow pharynx succeeds a
dilatation from four to five times wider, which occupies the greatest
part of the ventral cavity, and represents at once both the stomach
and the small intestine, while after it comes another bag of a more
oval form, the large intestine. Applicable as they may so far
appear, we shall find that in other cases the names of divisions
borrowed from those of the intestinal canal in the human subject
are not applicable to Fishes any more than they are to some of the
naked Amphibia, and that it is better to adopt the terms oral,
meso, and anal intestine, as expressing the regions of the body to
which the portions of intestine may happen to belong. An equal
amount of variety is displayed also by the mucous membrane lining
the canal ; thus it is often simply disposed in longitudinal folds, as
in Pleuronectes, Silurus, Blennius, Cyclopterus, Petromyzon, or in
zigzag folds, e. g. in several Cyprini, while in other Carps, and in
Gasterosteus, transverse folds are observable, that are particularly
developed in the Salmon-tribe, in the terminal portion of the intes-
tine. Most Fishes, however, exhibit a very varied net- work formed
by confluent longitudinal and transverse folds of mucous membrane.
It is more rare for true papillae, or tongue-shaped prolongations of
the folds, to be met with, as in the Pike, and many species of

236 PISCES.

Salmon, Perch, and Flounder. Still, however, papillae similar to
those of the human subject have been found upon the smooth mucous
membrane, e. g. in Mugil cephalus. The mucous membrance lining
the stomach is usually soft as velvet, forms delicate reticulations, but
is rarely provided with papillae and projecting folds. Occasionally,
as in Uranoscopus scaber, we meet with clusters of secerning follicles
within the intestinal caeca.

The structure of the intestinal canal in the Plagiostomi, or Rays
and Sharks, merits a separate consideration, though an extremely
near approach to it is made by the Sturgeon. They have a short
but wide oesophagus, continued into a large oval stomach that is
furnished with muscular layers ; to this wide gastric cavity succeeds
a narrow intestiniform canal, which may be viewed either as the
cardiac portion of the stomach or the duodenum ; in its place we
find, in the Sturgeon, a larger loop of intestine. In some instances,
and perhaps these are very rare, there would appear to occur, e. g.
Squalus maximus, a more compound kind of stomach than is usually
observed in the class of Fishes. In this Shark the stomach is par-
celled out by constrictions and inversions into several divisions, the
first of which is separated from the oesophagus by two large trian-
gular valves, and the fourth division by a strong internal pyloric
projection from the remainder of the intestine. This latter, in the
Sturgeon and Plagiostomi, is very wide, and (with some modifica-
tions peculiar to the different species that can not be considered in
this work) distinguished by a singular structure that is developed in
its interior. The mucous membrane here projects in the form of a
plate that winds spirally like a staircase as far as the very anus,
and in this way the extent of the absorbent surface of the intestine,
which throughout its course is very short, becomes much increased.
Posteriorly where it is continued into the cloaca the intestine narrows,
and presents to our notice, as in Squalus canicula, a small coecal ap-
pendage.

We have yet to consider, as occurring in many Osseous Fishes, a
peculiar set of caecal canals developed from the pylorus, and that
are known under the name of Pyloric appendages. These caeca were
formerly viewed as the analogues of the pancreatic gland, which is
actually absent as a true parenchymatous viscus in many Fishes.
The propriety, however, of thus interpreting the pyloric appendages
is rendered doubtful by the fact, that these organs have been found
in Fishes, e. g. the Trout, in which there exists also a compact
pancreatic gland. The pyloric appendages are invariably absent in

DIGESTIVE SYSTEM. 237

those Fishes that do not possess a perfectly-formed stomach, as in
the Cyprini, Gobii, and Syngnathi, but they are wanting also in
other Fishes with that organ properly developed, e. g. the Pike. As
a rule, however, they are present in the latter instances, and vary
exceedingly in number. It is very rare to meet with a single caecum,
as in Ammodytes tobianus ; there are sometimes two, as in several
Plaice (Pleuronectes), while other species of this genus have, like
the River Perch and Common Loach, three of them ; four occur, e. g.
in Mugil cephalus and Cottus gobio, five in Salmo spirinchus, six in
Perca lucioperca and in Sargus annularis, seven to eight in Trachi-
nus Draco, ten to thirty or more in many Salmons and Herrings, and
from eighty to ninety in the Salmon ; but these appendages are most
numerous in Gadus and Scomber, for in the Mackerel about two
hundred may be counted. These caecal appendages either encircle
the pylorus, or occupy longitudinally a greater or less extent of the
commencement of the intestine. In some of the Fishes already
named, as in the Herring and Mackerel, the caeca begin to divide,
and two of them open by a single aperture into the intestine. In
Gadus Lota two or three of the twenty caeca unite to form a common
trunk ; in the Tunny (Scomber thynnus) they divide so as to form
tufts ; in Cyclopterus, Gymnotus, and others, those of the second
row are further subdivided. In the Sword-fish (Xiphias gladius)
the finely-divided caeca are united by cellular tissue, and invested
externally by a common membranous covering, so that the whole
organ resembles a gland. In the Sturgeon, indeed, the pyloric ap-
pendages, by being still more subdivided and again united, acquire
the form of a true parenchymatous pancreas. The mucous mem-
brane lining the pyloric appendages exhibits a reticulated appear-
ance similar to that of the intestines. No nutritive matter is found
in these caeca, but only some slimy fluid ; chyme, however, has been
frequently observed in them. Their function is in other respect highly
problematical, though it is possible they may secrete a fluid analogous
to the pancreatic juice.

In the Osseous Fishes, e. g. the Eel, Pike, Trout, we constantly
find a true compact and glandular Pancreas of a yellowish-white
color, which sends from two to three excretory ducts into the intes-
tine ; these are frequently accompanied by the biliary ducts, but are
so closely attached to the latter as to be easily overlooked. In the
Sturgeon a second kind of pancreas has been described as also ex-
isting. The Rays and Sharks possess a lobulated and reddish-yel-

238 PISCES.

low pancreatic gland, more analogous to that of the higher Verte*
brata.

The Salivary glands appear to be very generally absent in Fishes,
or their place to be occupied by an increased development of the
mucous glands of the mouth. A small cylindrical and lobulated
gland has been found in Lophius piscatorius, lying immediately
beneath the integument posteriorly to the wide branchial opening ;
it would appear to be analogous to a salivary gland, from the fact
of the branchial cavity of this Fish serving as a receptacle for its
prey.

The Liver is in general of large size, and colored in different
shades of red, brown, or yellow. It is frequently very simple in
form, and alobular, or often tongue-shaped, e. g. in Petromyzon,
Syngnathus, Esox, Salmo, and, in a word, in the most different
families. It is bilobed in Silurus, Blennius, Perca, Cobitis, and the
Sharks, but trilobed in Gadus, Clupea, many species of Cyprinus,
and in the Rays. In other species of Cyprinus, e. g. C. barbus,
carassias, it is divided into a number of lobes united by narrow
bands, and placed between the convolutions of the intestine. The
biliary ducts do not usually unite into a single tube, but proceed
together into the gall-bladder, or into the vesical duct. The gall*
bladder is seldom wanting, as in Petromyzon, Cyclopterus Lumpus,
and in Scomber Leuciscus. Its form is either elongated and pyri-
form, cylindrical, or spherical. Occasionally it is completely im-
bedded in the liver, and in many cases, as in Uranoscopus scaber
and Orthagoriscus Mola, is of very large and disproportionate size
compared to that of other Vertebrata. The gall-dust {d. choledo^
chus), generally single, opens mostly in the vicinity of the pylorus,
but sometimes at a part of the intestine remote from the latter, as in
the Pike.

The Spleen appears to be either absent in several Fishes, or so
small as to be readily overlooked, e. g. in the Cyclostomi and Lepa-
dogaster. It is mostly of a reddish-brown color, small size, and
very varied form ; thus it is elongated in Blennius, triangular in the
Pike, large, irregular, and slightly lobular, in Cyprinus and the Stur*
geon, very large in many Sharks, and divided into lobes of unequal
size, but united together. The liver and spleen do not exhibit the
same symmetrical and regular position in respect to each other that
they do in the higher Vertebrata ; the greater portion of the liver
frequently lies to the right, but very often to the left side, while the

ORGANS OF CIRCULATION. 239

spleen is usually placed upon the right side, but often in the middle
line above or behind the stomach.

The Peritoneum in Fishes invests the whole intestine, and is
attached above to the pericardium, so as to form a kind of diaphragm
or partition, though not one of a muscular texture ; it also com-
pletely clothes the sexual organs, but not the kidneys. In some
Fishes, as in the Plagiostomi, the Sturgeon, and Salmonida^, a pair
of openings are situated upon either side of the anus which lead into
the cavity of the peritoneum, and allow the ingress of water to the
cavity and its contained viscera. The intestine is seldom secured
by a perfect mesentery, as is the case in the lower Fishes, e. g.
Myxine, but this is usually effected only by some thin filaments or
vasiferous bands. It is remarkable that during the embryonic ex-
istence of all Fishes a mesentery appears to be fully formed, but dis-
appears at a later period by absorption. When a swimming-bladder
is present, it usually opens into the oesophagus, but sometimes by a
second orifice into the stomach.

In the genus Lepidosiren several peculiarities occur in the organs
of digestion, and both spleen and pancreatic glands are absent.

ORGANS OF CIRCULATION.

To give a general description of the organs of circulation in the
class of Fishes is attended with much difficulty, from the many pe-
culiar varieties of structure which they present in the several genera
and families. Still, however, we may attempt a general survey of
the vascular system by first selecting a normal example of the
Osseous Fishes, such as the Common Perch, and a Shark or Ray, as
types of the Chondropterygians.

The principal or only heart in many Fishes is a branchial hearty
in other words, a heart that is placed between the trunks of the
branchial veins which it receives, and the trunks of the branchial
arteries, which it gives off; it corresponds therefore to the right
heart of Man and the higher Vertebrata, and is traversed by venous
blood alone. The heart consists of one auricle and one ventricle,
both of which are lodged within a pericardium, to the inner surface
of which the heart is frequently attached, as in many Amphibia, by
special filaments. In the Plagiostomi the pericardium communicates
by openings with the peritoneum, so that it is bathed by the water
brought through the apertures in that membrane, and already de-
scribed as being situated near the anus. The heart is placed be-

^0 piecES.

tween the pharyngeal jaws and the girdle supporting the anterior
extremities, and is small and angular in the Bony Fishes, but
broad and flat in the Plagiostomi ; it varies in size, and considerably
also in weight relatively to the entire body, in different genera and
species ; thus Meckel has calculated the weight of the heart in the
Ray at about gJoth, that of the Carp g^th or g^oth, and in other
Fishes yJp^ of the w^eight of the body. The auricle is generally
much wider and its parieies thinner than those of the ventricle,
above and somewhat behind which it is placed, while between the
two cavities we find mostly two, more rarely three, as in the Stur-
geon, muscular valves. The thick and very muscular ventricle ^s
characterized in most fishes by a peculiar structure, for it is com-
posed of two muscular layers so loosely connected to each other,
that the external consisting chiefly of longitudinal fibres, may be
separated, like a shell, from the internal, which is formed principally
of transverse fibres. The contractile trunk of the branchial arteries
arises from the anterior part of the ventricle by a strongly-developed
oval enlargement, called the bullus arteriosus, which is formed of
very powerful annular muscular fibres, and is likewise situated within
the pericardium. Between it and the ventricle we usually find two
valves, as in the Osseous Fishes and in Petromyzon ; in the Plagio-
stomi and in the Sturgeon, however, several, from two to five, rows
of semilunar valves are met with lying one above the other.

The ventricle discharges its blood through the aortic trunk into
the gills. This trunk of the branchial arteries usually divides upon
either side into four, as in most Osseous Fishes, or into five branches,
as in the Plagiostomi j these becoming gradually more slender, run
in a groove on the convex side of each branchial arch, and ramify
upon the branchial leaflets. Delicate ramuscules return the blood
into the trunks of the branchial veins, which are lodged in the same
groove behind the arteries, being usually single, but rarely double ;
they run upward to the base of the skull and the commencement of
the vertebral column, and here form a large circle of arterial vesfeels
{circulus cephalicus magnus) which receives the branchial veins and
gives off the arteries ; posteriorly the single aorta arises from it,
which sends first branches to the muscles of the branchial arches, to*
the mucous membrane of the mouth and pharynx, and to the upper
end of the kidneys ; very near to these branches and to each other
arise a coeliac and mesenteric artery, the two branchial arteries for the
pectoral fins, and some renal arteries. In fiont, or, as it were, from
the most anterior branchial veins, the two large posterior and two

ORGANS OF CIRCULATION. 241

smaller anterior carotids arise from the arterial circle ; slight varie-
ties and peculiar arrangements of these vessels occur, but can not be
investigated in this work. The posterior carotid supplies chiefly the
opercula of the gills, the pseudobranchiae or retia mirabilia, and mus-
cles of the lower jaw, with blood. The brain receives its arteries,
which are very small, from the anterior and posterior carotids.

After the aorta has supplied the liver, the intestine, the organs of
generation, and the swimming-bladder, it runs within the canal
formed by the inferior spinous processes of the vertebrae to the tail,
and there gives off branches to the kidneys, the muscles of the trunk,
and the pelvic extremities. The substance of the heart receives
its blood directly from the branchial vein. The blood returning
from the viscera enters partly into the inferior or posterior trunk of
the vena cava, which lies below the aorta, and is usually single in
the Osseous Fishes, but double in the cartilaginous ; partly also into
the hepatic veins, and from the two into a large sinus-like expansion
or contractile sac of the vena cava that opens into the auricle (being
frequently of larger size than the latter), but is situated external to
the pericardium. The blood also from the head enters the same
venous sinus by two anterior venae cava3, which are expanded into
sinuses upon the cranium ; they also receive the blood from the
branchiae and anterior extremities. Between this sac of the vena
cava and the auricle are found a pair of valves. The number of
hepatic veins is subject to variety.

A large proportion of the venous blood of the posterior half of the
body passes in Fishes from finer ramifications into trunks, that are
again subdivided to form a portal system. We find, as in many
Amphibia, a double portal system ; one for the liver, which obtains
its blood from the stomach, spleen, intestinal canal, and sometimes
from the generative organs ; the blood from these viscera usually
entering by several smaller branches into different parts of the liver,
but rarely uniting, before entering that gland, into a common portal
vein. The second portal system belongs to the kidneys, which or-
gans receive venous blood from the tail, partly also from the sexual
organs and swimming-bladder ; blood is also sent from this system
to the venae cavae. The arrangement, however, of the two portal
systems varies greatly, according to the species and genus.

Lymphatic vessels appear to be generally present in Fishes, and in
some number ; their parietes are thin and membranous ; they are
very wide, and form even large sacs and reservoirs, but are destitute
of valves, and have no conglobate glands or plexuses developed in

16

242 PISCES.

their course. They consist partly of lacteals that proceed from the
intestinal canal, and partly of ordinary lymphatic vessels. When
filled by injection with quicksilver, they cover the vascular trunks,
the veins for instance, completely. They unite in the anterior part
of the body, and pour their contents by two trunks into the anterior,
and partly also by several branches into the posterior, venae cavse.
The main trunks {ductus thoracici) proceed from lymphatic sinuses
near the cardiac orifice of the stomach, analogous to the cisterna chyli.
Several lesser lymphatic branches would appear to lose themselves
in venous ramuscules.

Peculiar Caudal and Cranial sinuses and a special system of Lat-
eral vessels were recently discovered in Fishes, and seem to belong to
the lymphatic system. Beneath what has been formerly described
(p. 185) as the lateral or mucous canal of the integument, we find
another sinus-like canal that is filled with a clear and limpid lymph.
and communicates with a number of adjacent branches, all pursuing
a subcutaneous course, and forming a ring of vessels around each
scale, so that the body of Fishes is completely intersected by this
net-work. This system of vessels communicates with a peculiar
caudal sinus, that is placed in many Fishes, as the Eel, in the same
situation as the caudal heart, which will presently be described.
This sinus is double, the divisions lying close upon either side of the
flat rays supporting the caudal fin ; but both of them communicate
by means of a transverse canal that passes through an opening in
one of the fin-rays. The sinus varies in size, and passes into the
caudal vein, being there provide^with a valve. It is invested by a
strong fibrous tunic, and contains a clear lymph ; whether it is en-
dowed with powers of expansion and contraction has not yet been
determined. A similar sinus has been observed upon either side the
cranial cavity external to the jugular veins ; it is pear-shaped, smaller
than the caudal sinus, and appears to be contractile. The octjurrence
and position of these reservoirs remind us very much of the lymphatic
hearts of the Amphibia.

The Blood of Fishes is, with one single exception, of a red color,
and contains almost always oval, flat, and slightly biconvex corpus-
cules ; those in the Plagiostdmi are distinguished by their great size, ,
and in this respect, as well as in their form, agree with those of
Frogs ; in the Osseous Fishes they are smaller. The Cyclostomi, at
least Petromyzon, have, however, circular biconcave corpuscules re-
sembling the human, but larger.

The greatest departure from the circulatory system of the rest of

ORGANS OF CIRCULATION. 243

Fishes is exhibited by the Amphioxus or Lancelet. The blood is
quite colorless, and has not as yet been found to contain any cor-
puscules. The hearts, however, are numerous. There is found,
1^^. An Arterial Heart, a tube of uniform thickness placed below the
branchial thorax in the middle line where the branchial artery in
other Fishes is situated, but without any trace of a pericardium ; it
is continued for a short extent backward as far as the end of the
oesophagus, where it makes a curve and joins the tubular hearts of
the venae cavae. 2d. The Bulhilli of the branchial arteries, which,
given off regularly from the arterial heart, are continued into the
angles between each pair of branchial arches, and represent the
commencement of the branchial arteries ; in young individuals we
find twenty-five, but in older specimens fifty, such branchial hearts
on either side. The branchial veins probably bring the blood into
the aorta that lies beneath the vertebral column, but in addition
to these, the blood enters the aorta through, 3c?. The Cardiform
aortic arches ; it is a double contractile ductus Botalli arising from
the median heart. Ath. A Portal heart, long and tubular in form
like a vessel, and contracted throughout its whole length, runs along
the ventral side of the intestine, and extends to the extremity of the
caecum, bth. A heart of the vena cava, which lies on the opposite or
dorsal side of the intestine, and is also tubular in form. Both venous
hearts contract alternately. This structure of the vascular system
obviously reminds us of that in the Annelida, where numerous pulsa-
ting heart-like vessels also occur.

The Cyclostomi are also characterized by many remarkable pecu-
liarities in their vascular system, but to describe them in the present
work would be entering into too great detail ; one distinguishing
feature, however, is the want of a muscular or contractile bulhus
arteriosus, the trunk of the branchial artery exhibiting a uniform
structure. In Lepidosiren annectens we find a bulhus arteriosus, and
a singte auricle and ventricle. In L. paradoxa we meet with a right
and left auricle imperfectly separated, the former receiving the pul-
monary vein, the latter the venae cavae.

Among the Osseous and Cartilaginous Fishes the number of hearts
is occasionally found to be also incr«ed. Thus in Chimsera an
elongated fusiform accessory heart is always developed upon the two
axillary arteries destined to supply the pectoral fins. • Similar axillary
hearts also occur in Torpedo, butiiot in Raia.

In the Eel there is found, upon both sides of the last caudal ver-

244 PISCES.

tebra, a pulsating organ which receives the blood from the delicate
veins of the end of the caudal fin and propels it into the caudal vein,
thus constituting a caudal heart, that occurs too in Muraenophis. It
is a true blood-propelling organ, but occupies the same position as
the already-described lymphatic reservoirs found in many Fishes, and
conjectured to be contractile.

In Myxine the sac of the vena porta contracts rythmically, and
so forms a heart ; thus in the class of Fishes have heart-like expan-
sions been found developed in different parts of the circulatory appa-
ratus, and would appear to be the more necessary from the numerous
plexuses of vessels through which the blood has to pass.

These plexuses, or Retia mirabilia, have been found of the most
complex form and arrangement in very different organs. Thus they
occur upon the hepatic, portal, intestinal veins, and cceliac artery in
the Tunny and several species of Shark ; in the choroid gland of
the Bony Fishes, in the swimming-bladder, and the so-called pseudo
or Accessory branchicB. These latter organs, which occur in most
Osseous Fish, were formerly, from their resemblance to the true
branchiae, regarded as such, although they differ completely from
them in structure. They are situated mostly upon the palatal por-
tion of the branchial cavity in front or external to the upper extrem-
ity of the branchiae, like which they are pectinated and provided
with cartilaginous strips for their support. The blood-vessels ramify
upon their leaflets in a regular manner, like the barbs of a feather,
and receive their blood, like the opercula of the gills and lingual
bone, through a branch which proceeds downward from the first
branchial vein. A second or glandular form of these accessory
branchiae also occurs, and consists of deep red vascular organs com-
posed of several lobes, not presenting the shape of gills, although
they are covered by the mucous membrane of the branchial cavity.
The lobules themselves, however, appear like small feathers with
cartilaginous shafts, the latter being provided with lateral leaflets.
Such glandular pseudobranchiae are found in the Carp, Pike, and
species of Gadus.

In the Sturgeon we find two accessory branchiae : a large one
situated against the operculum is a true respiratory pseudobranchia ;
the second, very small, and situated on the anterior wall of the
spiricle, consists of folds and transverse lesser folds, possesses the
plexiform structure of the pseudobranchiae, and obtains its arterial
blood from a branch of the vein upon the first branchial arch, while

ORGANS OF RESPIRATION. 245

the respiratory accessory gill receives dark-colored blood from the
branchial artery. A similar pseudobranchia is possessed by the Rays
and Sharks upon the valve of the anterior spiracle.

ORGANS OF RESPIRATION.

All Fishes respire by means of branchiae or gills, for the support
and protection of which organs we find a very complicated frame-
work of bone or cartilage developed, and exhibiting the greatest
diversities of structure in the several orders and genera. . The whole
of this apparatus may be reduced to three principal divisions : 1^^
The lingual bone and branchiostegous rays. 2c?. The branchial
arches. 3d. The opercula or gill-covers. A fourth division of this
part of the skeleton may be regarded as formed by the upper and lower
pharyngeal bones or maxillae, from the resemblance they bear to
branchial arches ; but as they do not support branchiae, but only teeth,
they more properly belong to the organs of digestion.

In the Osseous Fishes the Hyoid hone consists of a large arch,
situated behind the lower jaw in front of the first branchial arch,
and formed of several bony pieces symmetrically placed upon either
side of a single intermediate piece. The lateral branches of the
hyoid arch are of very large size in the Osseous Fishes, and corre-
spond to the great cornua ; they are composed almost invariably of
four pieces, the posterior of which, mostly style-shaped, is the me-
dium for attachment of the hyoid to the bone that is analogous to
the OS quadratum ; the several pieces sometimes coalesce into two
or one, but are generally united by fibro-cartilaginous bands. In
front the two lateral branches abut against and are united by a single
intermediate ossicle {copula) ; this represents the body of the hyoid
bone, and commonly supports in front an elongated ossicle, upon
which the rudimentary tongue rests ; this is called the lingual bone,
and is frequently provided with teeth. To the two branches exter-
nally a series of mostly narrow and slender, or frequently broad and
strong ossicles, are fastened by ligaments or moveable joints ; they
support the opercular membrane of the gills, and have been therefore
called the Branchiostegous rays ; their number varies according to thft
genera and species, or even sometimes the individual. In the true
Cartilaginous Fishes, parts occur which correspond to the hyoid arch,
but true branchiostegous rays are entirely absent.

In the above structures we meet with numerous diversities. The
hyoid arch is very narrow in Muraena, Syngnathus, and others, and

246 PISCES.

in the latter genus it always consists of a single piece, but in Diodon
and Tetrodon of two ; in all these genera, as in Uranoscopus and
Cyclopterus, the copula is wanting. The piece supporting the
tongue is absent in Tetrodon, Diodon, Balistes, Muraenophis, and
others. The branchiostegous rays are very rarely wanting, as in
Syngnathus. Polypterus has only one of these rays, while three are
found in Cyprinus, Cobitis, and others ; seven in Muraena anguilla,
twenty-five in M. colubrina, and upward of thirty in Elops. The
passage from the Osseous to the Cartilaginous Fishes is made by the
Sturgeon, in which the hyoid arch consists of three pieces instead of
four, and both copula and branchiostegous rays are entirely wanting.
In the Sharks a cartilaginous arch is found upon either side, sup-
porting some cartilaginous rays, divided simply in a digitate manner.
In the Rays similar arches are found, supporting a pair of pseudo-
branchiae.

Behind the hyoid bone is situated a system of bones or cartilages
called the Branchial arches, very generally four in number, and
which support the vascular fringes or leaflets of the gills. Each
arch consists of several pieces, varying in number according to the
species of fish and the several arches themselves. There are, how-
ever, never more than four pieces, mostly three, and rarely two ;
upon their convex side they are channeled out for the lodgement of
the branchial vessels, while on their concave side, or that turned
toward the cavity of the mouth, they are mostly beset with teeth,
and the upper segments of the posterior arches are usually so strong,
that they have been distinguished by the special name of ossa pha-
ryjtgea superior a ; the postero-inferior pharyngeal jaws are also in-
timately related, both by form and position, to the last and rudi-
mentary branchial arches. In the direction downward the branchial
arches are usually attached, like ribs to a sternum, to an interme-
diate chain of bones or cartilages, two to four in number, which are
articulated in front with the copula of the hyoid bone ; the posterior
arches are frequently united to this central chain by fibrous liga-
ments only, for it is seldom that all the arches are directly con-
tinued and connected to it by bone. Superiorly the branchial arches
are generally attached by muscles and cellular tissue, or by true
ligaments, to the basal surface of the skull, or sometimes further
backward to the first vertebrae. The teeth are usually disposed
in two rows upon the inner side of the branchial arches, and are
rarely absent, as in Cyprinus, Muraena, Muraenophis, Lophius, Fis-
tularia, and others. The median chain of ossicles uniting the

ORGANS OP RESPIRATION. 247

branchial arches below are seldom wanting, as in Muraenophis,
Syngnathus, and Lophius. The Cartilaginous Fishes possess simi-
lar branchial arches, only they are cartilaginous, and five instead of
four in number, of which, however, the most posterior corresponds
to a pharyngeal maxilla ; the arches abut, in the Sharks, against
some intermediate cartilaginous pieces, and consist themselves of
several segments ; the branchial arches in the Rays resemble in
general those of the Sharks, and are miited inferiorly by one or two
very broad sternoidal cartilaginous plates. In most Osseous Fishes
the branchial arches are situated beneath the skull, but in Fishes of
the Eel kind, e. g. Muraena, Muraenophis, they are situated further
back beneath the first vertebrae ; in the Rays and Sharks they are
united still further back to the commencement of the vertebral col-
umn. In the Cyclostomi we find a very peculiar branchial skeleton,
formed of narrow arch-shaped cartilaginous rays that isurround the
gills.

The gills, which in the earlier stages of development of Fishes
were freely exposed and unprotected, are always concealed at a later
period of existence beneath the skin, and protected also by special
covers or opercula ; these are most evolved in the Acanthoptery-
gians, and form for the most part a large bony apparatus, seldom in-
ferior in size to the branchial, but which is superseded in the Chon-
dropterygians by another contrivance. There are most frequently
four, or if we regard, with many anatomists, the praeoperculum as
the quadralal bone, three bony pieces, composing the opercula of the
gills. The Prdooperculum is of a semilunar form, and bounds pos-
teriorly the series of bones belonging to the articulating or quadratal
portion of the temporal bone. To this succeeds, in the direction up-
ward and backward, the true Operculum, a flat and more or less
quadrangular bone, the largest in size, and presenting upward and
forward a socket that articulates freely with a capsular head upon
the uppermost quadratal bone. Upon the posterior and inferior
edge of the operculum is situated the Postoperculum, and between
this and the praeoperculum, behind the lower jaw, is placed the
Interoperculum. This opercular apparatus serves as a valve, where-
by the fissure leading from without into the branchial cavity, and
placed between the posterior edge of the operculum and the ante-
rior girdle of the pectoral fins, may be opened or shut. The position,
but more especially the size of the opercular bones, varies ; one or
other of them is frequently ill-developed, as in the Eel family.
Among the true Cartilaginous Fishes we find, instead of this appa-

248 PISCES.

ratus, narrow, digitiform, cartilaginous plates, the analogues of the
branchial rays, and which are fastened to the quadratal cartilage.
The peculiar disposition of the branchiae themselves in the Sharks,
Rays, and Cyclostomi, renders a true operculum unnecessary.

In the majority of Fishes, but particularly in those of the Osseous
kind, a double row of pointed lanceolate leaflets project, like the
teeth of a comb, from the convex side of each of the four branchial
arches ; they are mostly separate as far as their base, where they
coalesce, but are sometimes united higher up ; each leaflet is pro-
vided in the middle with a thin fibro-cartilaginous plate, that keeps
it stifl* and straight. Upon these leaflets we find a number of
thin membranous transverse ridges, which contribute to increase
the respiratory surface, and the plexuses of blood-vessels further
expand upon peculiar siliquose elevations ; it is rare for only three
of the branchial arches to support such pectiniform leaflets, as in
Lophius, Batrachus, Diodon, Tetrodon ; and very rarely do three,
or only one row of branchial leaflets rest upon an arch. The
branchial leaflets in Syngnathus and allied genera forming the
group of Lophobranchii are of an unusual form, being lanceolate,
but very broad and short, so as to form tufts. All these branchial
combs are lodged in a common cavity situated behind the oper-
cular apparatus, and communicating with the mouth by the slits
between the branchial arches, and externally by a single large or
frequently very small slit between the edge of the operculum and
the girdle of the pectoral fins. The arrangement of these parts is
somewhat difl*erent in the true Cartilaginous Fishes ; upon the mid-
dle of each of their branchial arches we find a dense cellular plate,
which attaches them to the external integument ; in front and pos-
teriorly the mucous membrane of the mouth is prolonged over this
plate, and forms upon it elevated folds standing perpendicularly upon
the cartilaginous arches, like the branchial leaflets of the Acantho-
pterygians ; externally the mucous membrane is continuous with the
external integument ; each branchial arch is furnished with an an-
terior and posterior row of such branchial folds, but the anterior arch
has only the posterior set, so that only four and a half gills are to be
counted. From the branchiae being united externally to the integu-
ment, five (and in other genera, as Hexanchus, Heptanchus, six to
seven) branchial fissures are found both internally and externally,
between which the integument forms narrow bridge-like strips. The
Cyclostomi present a still more peculiar structure. There are here
from six to seven pairs of branchiae present ; each pair forms a flat

ORGANS OF RESPIRATION. 249

sac or pouch, upon the internal walls of which strongly-developed
folds project, as in the Plagiostomi ; each sac opens externally by a
round aperture, and in the inward direction by a canal into the oesoph-
agus, or even into a special membranous tube or bronchus, situated
beneath the oesophagus, and opening anteriorly into the pharynx,
where it is closed by a membranous valve, and terminates blindly
posteriorly.

The movement of the branchial arches, and also of the operculum
and branchiostegous membrane of the Osseous Fishes, is effected by
numerous muscles, which are absent in the Cartilaginous Fishes with
fixed gills. By their action the branchial arches are separated or
approximated, the branchiostegous membrane spread out, and the
operculum flapped to and fro so as to open or shut the external
branchial fissure. Smaller muscles move the double row of branchial
leaflets against each other. Similar muscular fasciculi are found in
the Cyclostomi, and serve to expand the branchial sacs. The water
taken in at and streaming through the mouth, is driven by the move-
ment of the branchial arches and hyoid bone between the gills,
where it bathes the leaflets with their superimposed plexuses of ves-
sels, and is again expelled through the external branchial fissures.

In many Osseous Fishes, Branchial follicles, as they are termed,
that secrete a copious mucus, are found at the posterior commence-
ment of the branchial cavity.

In addition to this mode of respiration by branchiae, we find that
in many Fishes this function is performed by pulmonary organs.
The Amphibioid Fishes, like Proteus among the true Amphibia,
possess a pair of truly-developed Lungs near to the gills. In Lepi-
dosiren annectens a partly single, partly double row of branchial
filiments project from the six branchial arches with the exception of
the second and third, and in the vicinity of the anterior extremity
we find the single branchial fissure. Besides these gills, however,
a double sacciform lung is present, each portion being divided into
several lobes ; it is situated behind the kidneys against the ribs, and
is internally cellular like the lung of a serpent ; anteriorly it opens
by a tolerably long, narrow, and membranous tube into the oesopha-
gus. Each lung receives a branch of the pulmonary artery which
arises from the branchial arteries.

Among even the true Bony Fishes we meet with Accessory or puU
monic organs of respiration, e. g., m Silurus fossilis of Bloch, and
among Fishes of the Eel kind in Amphipnous Cucia ; they consist
of vascular hollow sacs, which are either situated within the bran-

250 PISCES.

chial cavity, or extend thence to beneath the lateral muscles ; they
receive branches from the branchial arteries, and their veins enter
the aorta.

With the above organs we may also include the hollow arbores-
cent tufts of accessory branchiae which lie, in Heterobranchus anguil-
laris, behind the true gills, as also the labyrinthine accessory gills of
Anabas, Osphromenus, Ophiocephalus, and others ; a part of the
upper pharyngeal Maxilla is here divided into a greater or less num-
ber of leaflets, from between which cells arise, wherein water can be
retained for a long time. These fishes form a peculiar family, the
Pharyngii Labyrinthiformes, and are able by this structure to live a
long while on dry land; the arteries of these organs proceed from
those of the gills ; the veins enter, after the analogy of the branchial
veins, into the aorta.

THE SWIMMING-BLADDER.

Frequently as it has been compared with the lungs of the higher
Vertebrata, and certainly, from its mode of development, position, and
internal structure, reminding us exceedingly of these organs in the
Amphibia, still the disposition of its vessels forbids our regarding
the Swimming-bladder as an instrument of respiration, and thus we
are still in doubt as to its precise functions ; it occurs only in the
Bony Fishes, but not in all the genera, and among the Cartilaginous
in the Sturgeon alone, which forms the transition-link to the Osseous
Fishes. The swimming-bladder must, however, exist in connexion
with definite modes of life in several Fishes, since it is frequently
absent in different species of a genus, or in nearly allied genera, e. g.,
Scomber scorabrus, Polyneraus paradiseus, and the genera Pleuro-
nectes and Lophius.

In ordinary cases the swimming-bladder is situated beneath the
spinal column, to which it is firmly attached by cellular tissue, and,
covered by the kidneys, overlaps the intestinal canal. It consists of
two coats ; of an external, which is very tough, fibrous, and glisten-
ing, and an internal or soft vascular mucous membrane. It is in-
vested upon its lower surface, or that facing the viscera, by perito-
neum. The swimming-bladder in some instances, as in Esox, Ga-
dus, itolocentrus, Cepola, is of very great length, extending through
the whole body ; in others, as in the Eels, it is very short. Its lon-
gitudinal dimensions usually predominate over the transverse, the re-
verse, as in Silurus and Orthagoriscus oblongus, being of rare occur-

THE SWIMMING-BLADDER. 251

rence. As a rule, the swimming-bladder contains only a single
cavity ; frequently, however, two, one placed behind the other, and
separated by a deep constriction, as in the Carps and many Salmons ;
in Blennius Phycis we find three, and in Polypterus two such divis-
ions ; in Trigla hirundo there are also three, but they are arranged
side by side. Pimelodus filamentosus is furnished with two com-
pletely-separated swimming-bladders lying one behind the other.
The swimming-bladder is sometimes provided with caecal pouches,
varying in size, form, and length, e. g., in some species of Gadus ; but
they are most distinct in the family of Sciaenidae, as in S. umbra, in
Johnius, Pogonius, Corvina, and Otolithus, where the appendages
are divided in a digitate manner. It is rare for cells to be developed
upon the internal surface of the swimming-bladder, in which case
that organ greatly resembles the lung of an Amphibian ; this is ex-
emplified in many Erythrini, and in several genera of Siluroidae, e. g.^
Bagrus and Arius, where the swimming-bladder is divided into several
intercommunicating chambers by imperfect partitions ; in Platys-
toma we meet, in addition, with a pair of cellular wings or appenda-
ges. The very long swimming-bladder of Lepisosteus, which ex-
tends from the pharynx to the anus, is provided superiorly with
two blind appendages, but is in other respects simple, except that a
part of its internal cavity is furnished with smaller cavities or
pouches upon the floor of which the mucous membrane forms a net-
work of parietal cells. In many Fishes the swimming-bladder is
peculiarly situated. Thus in Cobitis fossilis it is completely en-
closed in a bony capsule formed by the transverse processes of the
third cervical vertebra. In Heterobranchus it is situated trans-
versely within a conical bony capsule opening by a fissure inferiorly,
and formed by an expansion of the transverse processes.

The swimming-bladder is either entirely closed, or provided with
a tube, as in most of the Ventrales, while in the Pectorales and Jug-
ulares this is usually wanting. The tube consists of the same
coats as the bladder, and is either short or long, narrow and tortu-
ous ; it runs in the direction downward and forward, and perforates
the (Esophagus in different situations, and in some cases the com-
mencement, or what is more rare, the bottom of the stomach/ In
the genus Salmo the tube arises from the anterior extremity of the
bladder, or from its second division, as in Cyprinus, where it is very
narrow and tortuous ; in the Pike, however, it is short and wide,
and in Clupea it enters the base of the stomach. This opening of
communication of the swimming-bladder with the intestine has been

252 PISCES.

compared to a glottis, but this analogy will not hold good as re-
gards the laryngeal aperture of the higher Vertebrata, for the opening
of the swimming-bladder is usually found in the dorsal wall of the
gullet, and sometimes in its side, as in the Erythrini ; in Polypterus,
however, the two lateral swimming-bladders open by a common slit
of considerable size into the ventral walls of the gullet, so that here
indeed their resemblance to lungs becomes more striking. In many
Fishes, e. g.j Mursena and Gadus Callarias, the tubes are connected
with the oesophagus, but there terminate blindly ; a fact which is the
more remarkable, since the swimming-bladder is first manifested
during development as an eversion, like the lungs, from the oesoph-
agus.

A very remarkable union of the swimming-bladder with the or-
gans of hearing had been long ago detected in Heterobranchus, all
the species of Cyprinus, Silurus glanis, Cobitis, Clupea, and others,
and has been recently found to exist also in the Erythrini. This
union is in some cases, as in Cobitis, effected by means of the audi-
tory ossicles ; in others, as in Clupea and allied genera, large air-
canals are given ofT from the swimming-bladder and enter the laby-
rinth.

In many Fishes we find a red Vascular gland interposed between
the two coats of the swimming-bladder, usually in its inferior region.
This gland has been falsely compared to the thymus gland, and in
this way the supposed analogy of the swimming-bladder to the lung
has been further exaggerated. But the gland in question presents
much more the character of a rete mirabile, and agrees in this
respect with similar plexuses formed by the portal vein and choroid
gland. It consists of a double plexus of arteries and veins, and
these plexuses occur in many swimming-bladders, whether provided
or not with an air-tube. They extend over the whole swimming-
bladder in the Cyprini, so that in these Fishes we find no local con-
centration of vessels, and consequently no true vascular gland. The
arteries of this organ arise from the branchial veins, while its veins
enter those of the' body generally.

One or several pairs of muscles, arising usually from the trans-
verse processes of the adjacent vertebrae, are inserted into the swim-
ming-bladder of many Fishes, and appear destined to compress that
organ, and thus condense the air contained within its cavity. In
several Siluroidae, and probably also in other Fishes ( e. g., Ophidi-
um), a remarkable apparatus has been discovered npon the swimming-
bladder, which probably serves to rarefy or condense this air. Thus

URINARY ORGANS. 253

in the genera Malapterurus, Synondontis, and others, the first verte-
bra is invariably provided with a large process that arises from it,
narrow and slender, but finally expands into a large round plate,
which, when at rest, is deeply imbedded upon the anterior surface of
the swimming-bladder. A thick muscle arises from the internal sur-
face of the spine of the cranium, and is inserted into this plate. When
it contracts, it lifts the process from off the swimming-bladder, and
by thus removing its pressure upon the latter, renders the air within
it more rarefied. If this muscle be pulled in the dead fish, and then
the traction withdrawn, the bony process springs back by its own
elasticity, and condenses again the air in the bladder.

The swimming-bladder is almost always tightly distended with air;
this air consists usually of nitrogen and a very small quantity of car-
bonic acid gas; in some instances, however, it has been found to
contain nearly pure oxygen. Now, since the above-named gases
are difliised in the blood of the vertebrata, it is probable that they
have been disengaged in a free state by the vessels of the swimming-
bladder. Whatever be its other uses, this organ serves, for obvious
reasons, to facilitate the ascent and descent of Fishes in the water.

URINARY ORGANS.

The Kidneys are of very large size in proportion to the body in
Fishes, and distinctly developed without exception in all the genera ;
they are placed close to each other upon the sides of the vertebral
column, to which they are firmly attached, but they very seldom pro-
ject freely into the ventral cavity from behind the peritoneum, or
the swimming-bladder when that organ is present. In the Osseous
Fishes they extend more or less through the whole extent of the
ventral cavity, and as far forward as the commencement of the
skull ; in most of these Fishes, also, they coalesce in front and be-
hind into a single mass. From its anterior half each kidney sends
off" a large transverse lobe, so that the two together acquire the form
of a cross. In many instances the kidneys may be said to form only
a single mass, which is divided by the passage of the vena cava, that
vessels receiving much of its blood, and sometimes, as in the Cyclo-
stomi, appearing completely imbedded in its substance. The ureters
(frequently numerous) pass along the external or internal margin
of the renal organs, and emerge from their substance inferiorly.
They unite either into a common duct, or enter separately into a true

254 PISCES.

urinary bladder that is rarely absent, and is always situated posterior
to the intestinal canal ; a position by which, according to our pres-
ent knowledge, Fishes may be distinguished from all other Verte-
brata. The urinary bladder, or when this is wanting, as in Urano-
scopus scaber, the urogenital aperture, opens behind the anus. The
ureters open into different parts of the bladder, and the form of the
latter varies exceedingly, being either cylindrical or fusiform, and
frequently, as in many species of Gadus, prolonged into caeca or
cornua.

In the Rays and Sharks the kidneys are proportionately much
shorter than in other Fishes ; they are frequently more or less lobu-
lated, and resemble the kidneys of the Chelonia ; the urinary bladder
is either absent, or present, as in the Rays, where it is two-horned.
The Cyclostomi have no bladder, and in Petromyzon the external
rounded edge of the kidneys projects freely into the ventral cavity,
and the organs themselves are prolonged in front into a dense spongy
mass of adipose cells. In Lepidosiren annectens, the kidneys, long
and narrow, are completely separate, and the urinary bladder opens
into the posterior region of the cloaca. Some detached glandular
bodies have been found in the posterior part of the ventral cavity in
the vicinity of the abdominal pore in Amphioxus, and been stated to
be renal organs.

As regards the more minute structure of the urinary organs, their
substance is generally loose and spongy in the Osseous Fishes, but
firmer in the Plagiostomi. The urinary canals are for the most part
long and very tortuous, but not ramified ; in the Cyclostomi, at least
in Petromyzon, they form short, straight, caecal tubes. The Mal-
pighian bodies, or renal glomerules, are not absent, though they are
of small size in Fishes, and, as would appear from injections that have
been made of them, imperfectly formed.

Certain bodies have been recently discovered to occur pretty gene-
rally in Fishes, and been regarded as Renal Capsules. They are
particularly distinct in the Plagiostomi, as the Rays, but even in these
large Fishes they are very small, and, as in Raia oxyrhynchus, are
seen as small bean-shaped bodies, similar to the kidneys, but of a
paler color. The renal capsules of either side are connected by
vessels with the apex of the kidneys. In the Bony Fishes, which
were previously denied to possess these organs, a pair of small red-
dish-white corpuscules, mostly placed behind the kidneys against
the vertebral column, have been recently found, e. g. in Cyprinus,

SEXUAL ORGANS.

255

Cyclopterus, Pleuronectes, and been interpreted as such. In the
Sturgeon and Cyclostomi similar structures have not yet been met
with.

SEXUAL ORGANS.

The organs of generation in Fishes present in general a very sim-
ple type of structure, and those of both sexes, at least in the Bony
Fishes and Cyclostomi, are formed upon a very analogous plan. It
may be here observed, that the opinion which was formerly held, that
regular hermaphrodites occurred among Fishes, is equally incorrect
with the assertion of genera of these animals existing in which the
male sex was wanting, and only individuals with female organs could
be found ; it is true that the female sex occurs in disproportionately
greater number than the male, as is the case also in many Inverte-
brate animals.

The Ovaries of the Osseous Fishes are in general double, rarely
single, as in Perca fluviatilis, Cobitis, Blennius viviparus, tjiough
even in these instances the separation is usually indicated. In the
majority of Fishes the ovaries consist of simple sacs formed of an ex-
ternal fibrous and internal mucous coat, which last usually presents
transverse, more rarely longitudinal folds, and sometimes also inter-
rupted papillae that are frequently clavate in form. Thus we find
longitudinal folds in Cottus, Gobius, and others, transverse in Pleu-
ronectes, Belone, and Gadus Callarias ; in Gadus Lota we meet with
shaggy papillae, in Blennius viviparus with tubercles. Upon these
projections of the mucous membrane the ova are developed in great
number ; those which are nearly mature hang from a pedicle, and
the less ripe have a shorter attachment ; both kinds are invested by
a thin membrane, by the dehiscence of which, or the rupture of the
pedicle, the ova when ripe fall into the cavity of the ovarium. In
the ovum itself we may distinguish a chorion, yelk, and a very large
and distinct germinal vesicle, provided with scattered germinal spots.
Each sacciform ovarium contracts posteriorly to form a short oviduct,
which very soon coalesces with its fellow into a common duct, that
opens usually within a depression, more rarely upon a tubercle, be-
hind the anus, and in front of the urinary aperture. Such is the
usual arrangement of these parts in the Osseous Fishes ; but in some
genera of the latter, as Salmo, Cobitis, and Taenia, in the Sturgeon
also, and in the Cyclostomi, the ovarium, instead of being sacciform,
is a flattened plate, from the lower or ventral surface of which folds

256 PISCES.

or laminated projections, shaped like a frill, as in the Eel and Petro-
myzon, take their rise, and in these the ova are developed. In such
cases the oviducts are absent, and the eggs, having fallen into the
ventral cavity, are expelled the body through a single or double slit
lying between the anus and urinary opening, and more rarely through
an aperture communicating with the ureter; the latter arrange-
ment appears to occur generally in the Sturgeons, e. g. Acipenser
Huso, stellatus and Ruthenus, but not in A. sturio, where we find
the anal slits to be present ; these, however, being absent in the
other species, the ova, after having been freed from the ovaries, pass
into two membranous infundibuliform tubes, which are united with
and open into the two wide ureters about the middle of the kidneys ;
behind these apertures is a valve, to prevent the escape of the urine
into the ventral cavity j the ova thus pass out of the female through
the ureters.

The structure of the female sexual organs in the Plagiostomi and
Chimaerae is more perfect, and analogous to that in Reptiles and
Birds. The ovaria are here generally double, situated far forward,
and each presents the form of a more or less considerable plate,
rarely that of a sac, upon which the ova ripen in succession, the vi-
telline spheres gradually attaining a size equal to those of Birds. In
some Sharks only a single ovarium is present. A common and wide
abdominal opening conducts into the double oviduct, which is con-
structed like that of Birds, being wide, thick-walled, and lined with
folded mucous membrane. The oviduct at its commencement is
narrow, but dilates above the middle, and is generally surrounded in
the Rays, Sharks, and Chimaeras by a cordiform or reniform gland,
which is sometimes, as in those Sharks, e. g. Mustelus and Galeus,
that possess a nictitating membrane, and also a single ovarium, of a
spiral form ; it is in the majority of examples very compact, and
formed of filamentary follicles, like the caudal gland of Birds. Fur-
ther backward the oviduct expands considerably into a kind of
uterus, to make room for the large ova that are provided with horny
shells ; within this the embryos are attached and developed, as will
be described further on. The external sexual opening is situated be-
hind the anus, and we find there a papilla, or rudimentary clitoris. In
many Fishes the ovaries and oviducts are secured in their place by
mesentery, in others they are free.

Two ovaria with free oviducts, thus essentially repeating the type
of structure in the Plagiostomi, have been found in the Lepidosiren ;
the oviducts join the ureters and enter the cloaca ; the ovaries are in

SEXUAL ORGANS. 257

Other respects very elongated, the oviducts tortuous, and thus these
structures approximate those in the Ichihyic reptiles.

In Amphioxus we find, in the bladder-shaped ovaries that are
situated against the sides of the body, vitelline spheres with distinct
germinal vesicles and a single germinal spot.

The Male sexual organs of the Bony Fishes exhibit the same sim-
plicity and type of structure as the female. The testes are sacs,
mostly retained in place by mesentery, which, when in a turgid state,
like the ovaries, frequently occupy the whole length of the ventral
cavity. They are continued to form the seminal ducts, which soon
unite into a short and common excretory duct behind the anus, where
they frequently open upon a perforated conical projection or penis.
The two testes are not always symmetrical ; the right being often
the largest, in others the left. In most of those fishes where the
ovary is single, the testicle is also found under similar conditions ;
its division, however, into two halves is usually indicated. In Cobitis
barbatula, however, the testicle is double though ihe ovary is single.
The testicle is frequently plaited like a frill, as in the Eels and Pe-
tromyzon, and granular in texture ; while in the Osseous Fishes it
usually consists of slender caecal tubes, that are occasionally subdi-
vided. A glandular layer, that may be compared to the prostate, is
very often developed, e. g. in Gobius and Blennius, at the end of the
seminal duct. Conical and often elongated structures, resembling
intromittent organs, are found in Syngnathus, Gobius, Lepadogaster,
Blennius, and also Petromyzon. In the male species of Sturgeon
we find similar infun^ibula to those of the female opening into the
ureters.

Another type of structure for the male organs is furnished by the
Rays and Sharks, and jjie structure, for example, of their testicles is
of very great interest as regards the development of the spermatozoa.
The structure of these glands, and their connexion with the epi-
didymides, are best seen in the Thorny Rays (Acanthias). The testes
consist of white, mostly reniform lobules, which present their con-
vex edge externally. Within these lobules we may detect even with
the naked eye a granular structure ; the granules are round capsules
about one fifth of a line in size, and contain the seminal animalcules
in their interior. These spermatozoa are lodged, as in the other
Plagiostomi, e. g. Raia oxyrhynchus, in very neat and regular parcels
within the capsules. The spermatozoa are absent in the youngest
or smaller capsules, which merely contain granular matter, and are

17

258 PISCES.

always surrounded by a circle of vessels. The delicate seminal
canals proceed from the lobules of the testis, and from them arise
nine to ten short, transverse, and parallel vasa efferentia, that run
transversely toward the vas deferens ; the latter is very much con-
torted, and continued superiorly into a dense epididymis, which was
for a long time taken for a particular gland, its connexion with the
testicle having been overlooked owing to its being concealed by a
lobulated mass of white and granular fat, deposited upon the plexus
of seminal canals, as in the Rays and Squalus canicula. The testi-
cles and vasa deferentia frequently lie more close to each other, as in
Scymnus, where the large convolutions of the vasa deferentia distinct-
ly project above the much elongated cylindrical testes. Inferiorly
the efferent ducts expand to form bladders or long sacs that are
completely filled with semen. At the end of the cloaca we also find
some short tubercles tolerably well developed, and reminding us very
much of allied structures in the Tritons ; the semen issues from their
conical points, and a circular fold, surrounding them like a prepuce,
completes their analogy with the penis. We find also peculiar
auxiliary organs, belonging to the external generative apparatus, and
consisting of long cartilaginous styliform appendages hanging to the
anal fins or pelvic extremities, and channeled by a groove, along
which the semen actually escapes from the male, and is probably
brought by a kind of copulative act in contact with the female geni-
tals. These parts are often seen to be red, turgid, and besmeared
with a bloody slime. In their dilated or clavate extremities a num-
ber of interarticulated cartilages is recognised ; these, like the whole
organ, may be moved by adductor and retractor muscles.

The testes in Amphioxus consist of small bladders, similar to the
ovaries.

The Spermatozoa exhibit a variety of forms ; those of the Osseous
Fishes are rounded and conical, with very long and delicate tails
sometimes, as in Cobitis, they have a small appended nodule. In
the Plagiostomi they are very generally long and linear, with deli-
cate tails ; sometimes they are spirally twisted at the commence-
ment, as in the Passerine birds, but run to a finer point, or else
they are stiff and straight ; they are also spirally convoluted in the
Chimaerse.

In Fishes, as in Reptiles, we find many viviparous as well as ovi-
parous genera. Numerous diversities are visible in the form, size
and structure of the ova, but these belong to the developmental

BIBLIOGRAPHY. 259

history of Fishes. In the Rays and SharJis ihe large vitelline
spheres are frequently included in horny capsules, called " sea-
purses," which project into cornua or cylindrical threads.

Certain Sharks (e. g., Mustelus, Carcharias) attach themselves,
after the manner of the Mammalia, by an umbilical chord to a pla-
centa placed in the interior of the female genital organs, and thus
constitute a very remarkable exception among the class of Fishes.
In other Fishes, as in Syngnathus and allied genera, the young are
developed in a peculiar cavity, or incubating organ, opening by a slit,
and placed posterior to the anus beneath the tail. It is remarkable
that these pouches are found only in the male Syngnathi, while in
Scyphius it is the females who carry their eggs free in a mass
adherent to the belly.

REFERENCES

TO THE PRINCIPAL WORKS UPON THE ANATOMY OF FISHES.

For List of General Works upon Comparative Anatomy, see page 61.

Tegumentary System.

Kuntzmann, in Verhandlungen der Gesellschaft naturforschender
Freunde in Berlin, Band 1, 1824, describes and partly figures scales of 400
species of fish.

Agassiz, poissons Fossiles, tom. 1, and in Annales des Sciences Nat.
tom. 14 ; in tom. 11 of latter work, consult Mandl, and also his Anat. Mi-
croscopique, 2d part.

Monro, upon Structure of Fishes as compared with that of Man, dec.
Edinb. 1785.

Miiller, Beitragen zur Kenntniss der natiirlichen Fanoilien der Fische in
Wiegmann's Archiv f. 1843.

Osseous System.

Rosenthal, Ichthyotomischen Tafeln. Berlin, 1839.

Agassiz, op. supra cit., and Cuvier in Hist. Nat. des poissons, upon the
Common Perch.

Bakker, Osteographia Piscium. Greening, 1822.

Wellenbergh, de Orthagorisco Mola. Lugdun. Batav. 1840.

Miiller, Vergleichender Anat. der Myxinoiden, Erster Theil. Berlin,
1835.

Bojanus, Parergon ad Anatomen Testudinis. Vilnae, 1801 : good figures
of skull of Cyprinus brama.

Arendt Diss, de capitis ossei Esocis structure. Regiora. 1824.

260 BIBLIOGRAPHY.

Hallmann and Spix, in works cited p. 62.

Ritzen, iiber das Geriist der Bauchflosser in Nov. Act. Acad. Leopold,
vol. 14.

Otto, in der Zeitschrift f. Physiol, von Tiedemann und Treviranus,
Band 2.

Baer, in Meckel's Archiv f. 1826, and Brandt, in der Medicin. Zoologie,
Band 2, upon Skeleton of Sturgeon.

Henle, iiber Narcine, a new species of Electric Ray. Berlin, 1834.

Rathke, iiber den Bau des Querders in Beitragen zur Geschichte der
Thierwelt, Band 4, and Bemerk. iiber den Bau des Amphioxus lanceola-
tus. Koningsb. 1841.

Miiller, in Berichten der Berliner Akademie f. 1841.

BischofT, Monographic von Lepidosiren paradoxa. Leipzig, 1840, and

Owen, upon L. annectens in Proceed. Linn. Soc. for 1839.

Miiller and Agassiz, sur les Vertebres de Squales vivans et fossiles.
Neufchatel, 1843.

Rathke, iiber den ineren Bau der Pricke. Danzig, 1825, and Mayer,
op. cit. p. 181.

Muscular System.

Consult, in addition to the larger works of Meckel and Cuvier, Cuvier
et Valenciennes, Hist. Nat. des Poissons, torn. 1 ; Cams' Plates ; and
Miiller's work on the Myxinoidae, for the muscles of these and the Cyclos-
tomous Fishes.

Nervous System.

For the Brains of the different orders of Fish, Serres* Anat. du Cerveau,
and Desmoulin's Anat. des Systemes Nerveux, Paris, 1825, with Carus*
Darstellung des Nervensystems, may be referred to.

Gotsche, in Miiller's Archiv f. 1834 and 1835, upon Brains of Osseous
Fish.

Arsaky, de Piscium Cerebro et Medulla Spinali. Hal. 1 813.

Miiller, Vergleichende Neurol, der Myxinoiden. Berlin, 1840.

Biichner, in Mem. de la Soc. d'Hist. Nat. de Strasbourg, torn. 2, upon
Cyprinus barbus.

Valentin, Beitragen zur Anat. des Zitteraals in den Denkschriften der
allgemeioen Schweizerischen Gesellschaft fiir die gesaramt. Naturwissen-
schaften, Band 4, and in Miiller's Archiv f. 1842.

Tiedemann, upon the Brain of the Triglae in Meckel's Archiv f. 1816.

Stannius, in Miiller's Archiv f. 1843, upon Sturgeon's Brain, and Sym-
bolsB ad Anat. Piscium. Rostochii, 1839.

Weber, Anat. Corap. Nervi Sympathici. Lips. 1817.

' Electric Organs.

Consult the article Animal Electricity in Todd's Cyclop, of Anat.
and Physiol., and that by Valentin in R. Wagner's Handworterbuch der

BIBLIOGRAPHY. 261

Physiol. 1st Band; also Humboldt aud Bonpland, Recueil d'Observ. de

Zool. et d'Anat. Corap., Paris, 1811; John Hunter in Phil. Trans, for

1773 and 1775 ; and Valentin in op. cit. des Zitteraals.

Rudolphi, in Abhand. der Akad. der Wissensch. zu Berlin t 1824, and

Valenciennes, in Ann. des Sci. Nat. torn. 14, upon Electric Silurus.
Farady, in Phil. Trans, for 1839. Poggendorf's Annalen f. 1840, and
Schonbein, Beobacht, iiber die elektrischen Wirkungen des Zitteraals.

Basel, 1841.

Organs of the Senses.

Rosenthal, in Reil's Archiv, Band 10. Dissection of Fish's Eye.

Hannover, in Miiller's Archiv f. 1840, upon Retina.

Werneck, in Amnion's Zeitschrift f. Opthalmologie, Band 5, upon the
Lens.

Kolliker, in Miiller's Archiv f. 1843, on Eyes of Amphioxus.

Miiller, iiber Wundernetze in dessen Archiv f. 1840.

Erdl, Disquisit. de Piscium Glandula Choroideali. Monachii, 1839, and

Wharton Jones, in Medical Gazette, 1838.

Treviranus, Beitrage zur Anat. und Physiol, der Sinnesv^rerkzeuge.
Bremen, 1828.

"Weber, de Aure et Auditu Hominis et Animalium, pars 1. Lips. 1820.

Breschet, Recherch^s Anat. et Physiol, sur I'Organe de I'Ou'ie des Pois-
sons. Paris, 1838, with 17 plates.

Miiller, iiber Gehororgan bei den Cycloslomen. Berlin, 1838.

Krieger, Diss. Inaug. de Otolithis. Berlin, 1840, in Miiller's Archiv f.
1841.

Klein, Hist. Piscium. Lips. 1740.

Weber, in Meckel's Archiv f. 1827, upon the spongy palatal organ of
Carp.

Digestive System.

Consult Owen's Odontography, part 1, for the Teeth. Rathke, in his
Geschichte der Thierwelt, upon the Intestinal Canal of Fishes, and Miiller's
Archiv f. 1837.

Blainville, Mem. sur le Squale pelerin in Mem. du Mus. d'Hist. Nat.
torn. 18.

Alessandrini, in Meckel's Archiv, Band 6, upon second Pancreas of
Sturgeon.

Cuvier's Anat. Comp., tom. 1, part 2, Paris, 1836, is rich in details of the
digestive organs.

Organs of Circulation.

Cuvier, in his Hist. Nat. des Poissons, tom. 1, figures the vascular sys-
tem of the Perch.

Consult also Carus and Otto's Erlauterungs-tafeln, Heft 6.

262 BIBLIOGRAPHY.

Tiedmann, Anat. des Fischherzens. Landshut, 1809.

HyrtI, in Medizin. Jahrb. d. osterr Staats, Band 15, 1837, upon Vascu-
lar System.

Fohmann, Saugadersystem der Wirbelthiere, Heft 1. Heidelb. 1827.

Hyrtl, in Miiller's Archiv f. 1843, upon Vascular Sinuses.

Miiller, in Berliner Monatsberichten f. 1841, and J. Goodsir, Trans, of
Royal Soc. of Edinb., vol. 15, on Amphioxus.

Duvernoy, in Ann. des Sci. Nat., ]837, torn. 8, on Accessory Heart.

Marshall Hall on Caudal Heart, in his Essay on the Circulation.

Eschricht, iiber Wundernetze beim Thunfisch in Abh. der Berlin. Akad.
f. 1841.

Organs of Respiration.

Rathke, op. cit. p. 181, and Miiller on Myxinoidae.
Alessandrini, de Piscium Apparatu Respirationis. Bonon. 1838.

Simmming- Bladder.

De la Roche, in Ann. du Mus. d'Hist. Nat. vol. 16.

Miiller's Archiv f. 1842 ; Rathke, Cuvier and Valenciennes, op. cit. and

Jacobi, de Vesica Aerea Piscium. Berol. 1840.

Urinary Organs.

Steenstra-Toussaint, Comment, de systemate uropoetico Piscium. Lugd.
Bat. 18.35.

Retzius, Obs. in Anat. Chondropterygiorum. Lundse, 1819.
Stannius, in Miiller's Archiv f. 1839.

Sexual Organs.

Rathke, op. cit. Miiller's Archiv f. 1836. R. Wagner's Prodromus
Hist. Generationis.

Joh. Miiller, Abhand. iiber glatten Hai des Aristoteles. Berlin, 1842.

Hallmann, Bau des Hodens und Samenthierchen der Rochen. Miiller's
Archiv f. 1840.

Lallemand, Ann. des Sci. Nat., tom. 15. 1841.

Mayer, in Froriep's Notizen f. 1834, on claspers of Shark.

R. Wagner, in Miinnchner Denkschriften, Band 2, 1837.

APPENDIX.

A LIST is subjoined of the most useful works that treat upon the
Development of the Vertebrala, this being a subject of the highest
interest and importance when a general comparison is instituted
between the several classes.

Baer, Rathke, and others, in Burdach's Physiol. 2d ed. 1837, have
given a most complete and general survey of the development of the Ver-
tebrata. Upon that of the Mammalia, consult Von Baer's Entwickelungs-
geschichte der Thiere, Koningsb. 1837. Bischoft", Entwickelungsgeschichte
des Kanincheneies, Braunschweig, 1842, and Rudolph Wagner's Elements
of Physiology by Dr. Willis, part 1, on Generation, where copious biblio-
graphical references are also given. Birds, Von Baer, iiber Entwickelungs-
geschichte der Thiere, 1 ter Theil, 1828. Pander, Beitriige zur Entwick-
elungsg. des Hiinchens im Ei., Wurzburg, 1817. Reichert Entwickel-
ungsleben im Wirbelthierreich, Berlin, 1840. Reptiles, Baer, op. cit.
Band 2, on Batrachia. Rathke, Entwickelung der Natter, Koningsb.
1839. Reichert, op. cit. Vogt. Untersuch. iiber Entwickelungsg. der
Geburtshelferkrote, Solothurn, 1842. Fishes, Baer, Untersuch, iiber Ent-
wickelungsg. der Fische, Koningsb. 1835, and Vogt. Entwickelungsg. der
Forelle in Agassiz Hist. Nat. des Poissons d'eau douce de I'Europe, Neuf-
chatel, 1841.

The following Addenda comprise some new and valuable contribu-
tions to the literature and anatomy of the Vertebrata : —

Otto Kostlin, der Bau des Knochemen Kopfes in den vier Klassen der
Wirbelthiere, mit 4 Tafeln, Stuttg. 1844.

Reichert, Vergleichende Entwickelungsg. des Kopfes der nackten Am-
phibien, Koningsb. 1838. •

Rapp, Anat. Untersuch. iiber die Edentaten, Tubingen, 1843.

Natalie Guillot., Wrganiz. du Centre Nerveux d'Anim. Vertebres in
Mem. de TAcad. de Bruxelles, torn. 13. 1843.

Note to pages 49 and 61.

The thymus gland, according to Owen, trans. Zool. Soc, vol. 1, is ab-
sent even' in the foetus of the Marsupialia, but not in the Ornithorynchus.
The Cloaca appears only to occur in the female Marsupials.

Note to page 100.

Dr. Rudolph Wagner found that the bulk of the creamy fluid contained
in, and even the recticular membrane lining, the Ingluvial gland of an old
pigeon that had died two days after hatching her young, consisted of soft
whitish granules, about J-th to ji-Qth of a line in size, presenting in their
interior small highly refractive nuclei ; they consisted of protein combined
with fat, but contained neither milk-sugar nor fluid casein, although the
secretion of this gland has been constantly compared to the milk of a
Maramiferous animal.

264 APPENDIX.

Note to page 106.

Stannius, see Miiller's Archiv f. 1843, has found true Lymphatic hearts
in the Stork among the Grallatores, in the Ostrich and Cassowary among
Brevipennes, and, in the Natatores, in the Goose, Swan, Diver, and Auk.
He has as yet failed to detect them in the Fowl and Turkey. Panizza was
previously acquainted with their existence in the Goose ; these hearts lie
near the sacral bone, are connected with lymphatic vessels, and a vein
issues from them. As yet they have not been observed to pulsate, though
they exhibit distinct fasciculi of transversely-striated muscular fibre.

Note to page 117.

Tschudi, in Miiller's Archiv f. 1843, describes a remarkable structure
of the Trachea and Inferior larynx \n Cephalopterus ornatus, which seems
to agree closely with that in the Duck ; it consists of an expansion of the
trachea below the superior larynx into a large elongated drum-like cavity;
the inferior larynx is also similarly dilated ; this structure is the more re-
markable from its occurring in one of the order Passerinae and family of
Coracinidae. The bird utters a loud and unpleasant howling cry, and
occurs in the same latitudes, namely, S. America, as the Howling Apes.

Note to page 176.

Bachthold, iiber die Giftwerkzeuge der Schlangen, Tubingen, 1843, gives
beautiful figures of the Poison glands of Hydrophis pelamys and Naija
rhombeata. The length of the poison gland of the latter amountecj, in a
specimen eighteen inches long brought from the Cape, to three inches, or
a sixth part of the length of the body ; it is placed parallel to the verte-
bral column like a broad band, and surrounded by a strongly-attached
muscle, which draws the gland forward or toward the head ; the gland
consists of six perfectly parallel tubes, or long caeca, two of which unite to
form a common excretory duct. The poison tooth is not, however, of
large size.

Fischer's Amphibiorum, nudorum neurologioB specimen primum, Berol,
1843, contains beautiful illustrations of the cerebral nerves of Bufo, Hyla,
Bombinator, Pelobates, Pipa, Salamandra, Triton, Proteus, and Caecilia.

THE END.

■"6

3 1378 00494 8736

^/Lft^

;/^ / ^ ^"

w

/vv

• * 1 n * 1' 1