UNITED STATES OF AMERICA
^ „  .  v
FOUNDED  1836
WASHINGTON,  D. C.
GPO  16—67244-1 
 
 
                /
Dunglisori's American Medical Library.
y £4l
THE
J, 4.
STUDENT'S COMPENDIUM

COMPARATIVE ANATOMY.
^"
             BY P. JSVERS,

LICENTIATE OF THE ROYAL COLLEGE OF SURGEONS IN IRELAND, &C»
" Sparsa coegi."—Ovid.
*X % t* H
                   PHILADELPHIA:
PRINTED AND PUBLISHED BY A. WALDIE, 46 CARPENTER ST.
1S39. 
 
                           TO





          PHILIP CRAMPTON, M. D.. F. R. S.





     SURGEON GENERAL TO THE FORCES  IN IRELAND,




                        &c. &c. &c.




AS AN INADEQUATE, BUT SINCERE TESTIMONY OF RESPECT,





                          TO





        DISTINGUISHED  SCIENTIFIC ATTAINMENTS,





                         AND





           DESERVED PROFESSIONAL EMINENCE,





                   THIS  VOLUME





                     IS INSCRIBED,





                          BY





          HIS GRATEFUL AND  OBLIGED FRIEND,





                                  THE  AUTHOR. 
 
PREFACE.
  In the compilation of these pages no originality is claimed, but
the labours of modern authors have been freely appealed to, and
it is trusted,  on every occasion, with due respect.   A list of the
several authors consulted has been added at the end of the book.
  I have to  acknowledge  several  obligations  to  my friend Dr.
Houston of this city, whose scientific acquirements and  connec-
tion with the Museum of the College, have well qualified  him for
the many auxiliary favours  he has conferred on  me.
                                                      P. E.
  Dublin, 33 Aungier Street,
      September, 1838. 
 
             COMPENDIUM

                      OF

COMPARATIVE   ANATOMY.
                        CHAPTER I.

                PRELIMINARY OBSERVATIONS.

  When we turn our attention to the busy theatre of animal life,
we  are  at once  attracted by scenes of wonder and delight.  The
works of nature appear unbounded  in extent, variety, and riches.
Wherever the eye is cast, from the icy regions of the  pole to the
scorching sands of the line, it beholds life displayed in forms as
endless as they are enchanting.
  Every region and every element is the abode of numerous animals,
and is admirably suited to their peculiar living habits and instincts ;
the  vastness of their number may be estimated from the declaration
of the celebrated Ehrenberg, that a single cubic  line which is less
than a drop of fluid contains 500,000,000 monads.
  But however varied and delightful the occupations of the zoolo-
gist may be, his  information is still defective,  and  he perceives that
the  interior machinery of life is hidden from his observation, and its
springs concealed by clouds which nothing but the light of dissec-
tions can dispel.
  When once engaged in this captivating department of his inves-
tigations, he begins to observe the beautifully progressive develop-
ment  of organisation, varied and modified in obedience to  certain
laws; he will often behold the7 same animal, according to the parti-
cular epoch of its existence, undergoing metamorphosis, appearing
under different characters, and playing very different parts  on the
stage of life.
  Having entered a little more fully into the details of comparative
anatomy, he will often observe an organ which has attained a high
degree of development, and whose functions are perfectly under-
stood in one animal; diminutive, rudimentary, and apparently use-
less in another.  Hence it must be obvious, that he who aspires to a
perfect knowledge of human structure and  function, must extend
his  researches to an examination of the animal kingdom in general;
and accordingly great advantage will be  found in a previous ac-
quaintance with some one  or more of the  most approved classifica-
tions in  natural history.
  Every classification hitherto proposed  has in some particular or
other its imperfections; but it matters little what scale we adopt. 
8
EVERS'S COMPARATIVE ANATOMY.
or whether we make use of several, provided that our object of con-
veying or acquiring a knowledge of the comparative structure of
animal bodies be attained.   This must be my excuse for appearing
in some places to have followed the arrangement of Cuvier, and in
others, that of Dr. Grant,  both having their excellences, and their
authors holding the highest place as authorities on  the subject.
  Cuvier's and Grant's  classifications are  therefore subjoined, ac-
companied by familiar illustrations of each, to lead the student at
one glance to the objects which each subdivision embraces.   The
examples appended to Grant's classification have been added by
myself, whilst those of Cuvier have been taken from Dr. Houston's
Descriptive Catalogue  of the Preparations  in  the  Museum of the
Royal College of Surgeons in Ireland, with a kw additional exam-
ples from Roget's Bridgewater Treatise.
  It might appear an  omission not to make some allusion to the
arrangement of the animal kingdom adopted by the immortal  Lin-
nseus, but. the researches of later zoologists have proved  it so defec-
tive, that it is not followed by any writer or  teacher of the  present
day, and needs therefore  but a cursory allusion.  Suffice it  to  state
that  he divided the whole  animal kingdom into six classes, Mam-
malia, Aves, Reptilia, Pisces, Insecta, Vermes, founding  his classi-
fication mainly on the  peculiarities afforded  by the respiratory and
sanguineous systems.
 OUTLINE OF CUVIER'S CLASSIFICATION OF ANIMALS.

                  FOUR GREAT DIVISIONS.
            1.  Vertebrata.             3. Articdlata.
            2.  Mollosca.               4. Radiata.


                      VERTEBRATA.

  Characters.—Internal skeleton—brain and spinal marrow in separate cavi-
ties—red blood and muscular heart—mouth  with horizontal jaws—five
organs of sense—never more than four limbs—separate sexes.


                         MOLLUSCA.

  Ch.—No skeleton—muscles all attached to external skin—nervous system
situated in  the visceral cavity and composed of separate masses joined by
nervous filaments—taste, sight, or as in one instance, hearing, the only senses
—organs of circulation, respiration, and digestion very perfect.


                        ARTICULATA.

  Ch.—No skeleton—two long nervous chords with ganglia at intervals-
have usually taste and sight—divided in jointed rings, soft or hard, to inside
of which muscles attached—sometimes lateral limbs, sometimes none—iaws
when present always lateral.                                   J 
CLASSIFICATION.
3
                             RADIATA.

  Ch.—Organs of movement and sense disposed circularly around a centre,
not symmetrically as in the preceding—no visible nerves—no organs of sense
or circulation—respiration by the outward integument—intestines often  a
simple bag—sometimes the animal is but a homogeneous  pulp without aper-
ture or cavity.
       I. VERTEBRATA.
Class 1.  MAMMALIA.
Order 1. 2.	BlMANA - -Q.UADRUMANA -	Examples,
3. 4.	Cheirotera -Insectivora -	——
5.	Plantigrada -	---
6.	Digitigrada -	---
7.	Amphibia - -	---
8.	Marsupialia -	---
9.	Edentata - -	——
]0.	Rodentia - -	---
11.	RtlMINANTIA -	---
12.	Pachydermata	---
13.	Cetacea	---
	Cl. 2. AVES.	
Ord. 1. 2. 3.	accipitres Passeres - -Scansores- -	Exam. ■
4. 5. 6.	Galhn.e - -Grallje - -Palmipedes -	---
	Cl. 3. REPTILIA	
Ord. 1.	Chelonia	Exam.
2. 3.	Sauria - - -Ophidia - -	___
4.	Batrachia	---
Man.
Monkey, ape, lemur.
Bat, colugo.
Hedge-hog, shrew, mole.
Bear,  badger, glutton.
Dog, lion, cat, marten, weasel, otter,
Seal,  walrus.
Opossum, kangaroo, wombat.
Sloth, armadillo, ant-eater.
Beaver, rat, squirrel, porcupine, hare,
Camel, deer, giraffe, sheep, ox.
Elephant, hog, rhinoceros, tapir, horse,
Dolphin, whale.
Vulture, eagle, owl, hawk.
Thrush, swallow, lark, crow, sparrow,
Woodpecker, cuckoo, toucan, parrot.
Peacock, pheasant, grouse, pigeon.
Plover, stork, snipe, ibis, flamingo.
Auk, grebe, gull, pelican, swan, duck,
Tortoise, turtle, emys.
Crocodile, lizard, gecko, chameleon.
Serpents, boa, viper.
Frog, salamander, newt, proteus, siren,
              Cl. 4.  PISCES.
Ord. 1. Chondropterygii Exam.
     2. Malacopterygii ---
     3. Lophobranchii  ---
     4. Pleclognathi   ---
     5. Acanthopterygii---
                                   Lamprey, shark, ray, sturgeon.
                                   Salmon, herring, cod, sole, eel.
                         ----      Pike-fish, pegasus.
                         ----      Sun-fish, trunk-fish.
                         ----      Perch, mackerel, sword-fish.

                         II. MOLLUSCA.


  cula which seive as feel. $
Progression  by  fins  placed }

                               3. Gasteropoda-----■  Slug, snail, lim-
                                                        pet.
                               4. Acephala    ------  Oyster,  muscle,
                                                        ascidia.
Head crowned  with tenta- ) Cl. I. Cephalopoda Exam.  Cuttle-fish, cala
                                                       mary, nautilus

                                                ----  Clio, hyalcea.
  near the head
Head  free  progression  on
  the belly.

Without distinct head.
2.  Pteropoda 
10
EVERS S COMPARATIVE ANATOMY.
Two long arms at the mouth
  for seizing objects.
Arms very numerous, arti-
  culated, horny.
5.  Brachiopoda Exam. Lingula, tereba-
                        tula.
6.  Cirrhopoda   ----- Barnacle, triton.
            III.  ARTICULATA.
Cl. 1. ANNELIDA.
Ord. 1. Tubicola  - -  -
     2. Dorsibranchia -
     3. Abranchia -  -
Exam.  Serpula, sabella, amphitrite.
-----  Nereis, aphrodite, lob-worm.
-----  Earth-worm, leech, nais, hair-worm.
         Cl. 2. CRUSTACEA.
Ord. 1. Malacostraca -  -  Exam.
     2. Decapoda   -  -  -  -----
     3. Stomopoda -  -  -  -----
     4. Amphipoda -  -  -  -----
     5. Ljemodipoda   -  -  -----
     6. Isopoda -  -  -  -  -----
     7. Entomostrata -  -  -----

         Cl. 3. ARACHNIDA.
Ord. 1. Pdlmonalia -  -  -  Exam.
     2. Trachealia -  -  -  -----
Ord.
     Cl. 4. INSECTA.
1. Aptera  -  -  -
2. Coleoptera -  ■
3. Orthoptera
4. Hemiptora -  -
5. Nedroptera
6. Hymenoptera -
7. Lepidoptera   -
8. Rhipiptera -   -
9. Diptera -  -   -
Exam.
Lobster, crab, prawn.
Squill, phyllosoma.
Grammarus, sand-hopper.
Cyamus.
Wood-louse.
Monoculus.
Spider, tarantula, scorpion.
Phalangium, mite.
Centipede, podura.
Beetle, glow-worm.
Grass-hopper, locust.
Fire-fly, aphis.
Dragon-fly, ephemera.
Bee, wasp, ant.
Butter-fly, moth.
Xenos, stylops.
Gnat, house-fly.
Class 1.  Echinodermata  -
     2.  Entozoa  -  -   -
     3.  AcALEPHiE -  -   -
     4.  Polypi  -  ■  -   -
     5.  Infusoria -  -   -
IV. RADIATA vel Zoophyta
         Exam.
Star-fish, sea-urchin.
Fluke, hydatid, tape-worm.
Actinia, medusa.
Hydra, coral, madrepore, pennatula.
Brachionus, vibrio, proteus, monas.
GRANT'S  DIVISION OF  THE ANIMAL KINGDOM.
Division.
i. cyclo-neuraJ
  vel RADIATA  1
I
 Class.
Polyastrica
Porifera  - -
Polypifera
acaleph.k -  -
Echinodermata
Exam. Monad, madrepore.
----- Sponges.
----- Polypes, corals.
-----■ Medusa, actinia.
----- Star-fish, sea-urchin. 
SKELETON IN THE INVERTEBRATA.
11
Division.
      Class.
f 6. Entozoa
II. DIPLO-NEURA
  vel ARTICULAR
  TA.
III. CYCLO-GAN-
  GLIATA  vel
  MOLLUSCA.
IV. SPINI-CERE-
 BRATA vel
 VERTEBRATA.
  9.
  10.
  11.
112.
U3.
fl4.
|  15.
«16.
|17.
LIS.
f 19.
|  20.
<(21.
|  22.
123.
Rotifera  -
Cirrhopoda
Annelida  -
Myriapoda
Insecta -  -
Arachnida
Crustacea
Tunicata  -
Conchifera
Gasteropoda
Pteropoda
Cephalopoda
Pisces  -  -
Amphibia  -
Reptilia  -
Aves   -  -
Mammalia
Exam. Intestinal worms, hyda-
         tids.
----- Patella.
----- Barnacle, triton.
----- Earth-worm, leech,
----- Scolopendra.
----- Bee, butter-fly.
—---- Spider, scorpion.
----- Lobster, crab.
----- Ascidia intestinalis,
----- Muscle, oyster.
----- Slug, snail.
----- Clio,  hyalcea.
----- Cuttle-fish.
----- Salmon, shark, eel.
----- Frog, toad, proteus.
-----Tortoise, lizard, serpent.
----- Eagle, heron, duck.
----- Man, kangaroo, whale.
  Many other arrangements of the animal kingdom have been pro-
posed by different zoologists; some, as Linnseus, founding their basis
of classification on the vascular and respiratory systems, and others on
the peculiarities afforded by the generative organs. Aristotle divided
all  animals into those with,  and  those without red  blood;  and
Lamark into the apathic, the sensitive, and the intelligent.
                         CHAPTER II.

               SKELETON IN THE INVERTEBRATA.

   General observations.—The skeleton gives figure, strength, and
solidity to  the  entire frame;  it serves  as  a basis of  support to the
soft  parts,  forms levers of locomotion, and encloses cavities to pro-
tect  and defend  the  most delicate and important organs.  Its use,
however, being chiefly of a mechanical nature, it will be found to
vary much, according to the respective wants, habits, and instincts
of animals.  In all the operations of nature we find  that there is a
rigid economy observed;  the means employed are  such  only as
are required, and always the  most simple by which the intended
purposes can be accomplished.  Hence we shall not be surprised to
meet with  infinitely  varied modifications  of skeleton throughout
the widely extended range of the animal world.  The chemical
composition of this solid frame-work .presents  some  variety.  For
instance, silica is found in the lowest forms of the radiata; carbo-
nate of lime in  the molluscous animals; carbonate and phosphate of
lime in the articulata; and phosphate of lime in the organised skele-
tons of the  vetebrata.  This frame-work is sometimes placed external
to the soft  parts, and in others  it is internal to them.  In no instance
do we meet with a bony skeleton except in animals possessed of 
12
EVERS'S COMPARATIVE ANATOMY.
a regularly formed brain ;  and here it is obvious to those who un-
derstand the difference  between the growth of shell and bone that
the former would  be  unfit  for the purpose, since there is no provi-
sion made for the enlargement of the original cavity.
  Radiata,  Cuvier ;  Cyclo-neura,  Grant.—In  this acrite  or
lowest division of the animal kingdom the skeleton generally holds
an  internal  situation, and is composed either of one large mass or
several smaller pieces symmetrically disposed, composed of silicious
or calcareous spicula.  In  many of the polygastrics the organ of
support consists in a condensation of the common integument en-
veloping the body—occasionally in the form of an elastic vagini-
form  sheath into which the  animal can retreat on the approach of
danger, <fec, as seen in the vaginicola innata.  Among the pori-
phera, skeletons are met with of a  horny, silicious, or calcareous
structure, variously modified.  In none  does nature seem to have
amused herself more in the construction of skeletons than among the
zoophytes.   Here they are met with internal or external, soft,  horny,
or calcareous ;  branched, globular, or filiform; free or fixed.  The
asterias and others of the echinodermata present us with skeletons
in the form of external crusts  or shells, disposed after the manner
of plates, and  composed of carbonate, with  a trace of phosphate
of lime.
  Articulata, Cuvier;  Diplo-nerose Animals, Grant.—The bo-
dies of these animals are  generally long, cylindrical, and divided
transversely into segments.  Their  skeletons are  generally thin,
light, and situate externally, chiefly composed of phosphate of lime,
though occasionally of  carbonate, as in the cirrhopoda and Crusta-
cea.  The  entozoa owe their peculiar stiffness and rigidity to the
tough, strong,  and transparent  covering  enveloping  their  entire
body.  In some of the inferior orders of them, as in the acanthoce-
phalous  species, their retractile  proboscis and part of their bodies
are set with dense, sharp spines, which enable them to move with
freedom  and precision  through the  fleshy media  in  contact with
them.   The rotifera  are closely allied to the entozoa in their ex-
terior  coverings.   In  the former, however, this texture possesses a
greater degree of firmness,  from the attachment of numerous mus-
cles to it.  There are no earthy deposits in any part of the body of
these  animals.  The cirrhopoda, like  the  mollusca,  are usually
enclosed in shells, dense, thin, laminated, and composed of  carbo-
nate of lime.  These testaceous coverings  are best developed in the
balani. and  least  in the anatiferae.  The reverse order of develop-
ment obtains with respect to their extremities.
  The annelida, or red-blooded worms,  lead  us a  step higher in
the development of skeleton;" for, although the halithea, the leech
the nais, &c, possess a flexible membraneous covering, many  others
as the serpulae, are shielded by adventitious, solid, calcareous tubes.'
The  common  earth-worm  is provided with  four  pairs of sharp
spines, or setae, for the purpose of progression.   The si eleton of
insects is for the greater part composed of a thin, epidermic layer, 
SKELETON IN THE INVERTEBRATA.
13
and a thick internal one resembling the woody fibres of plants, but
of an animal nature, termed chitine and coccine, blended with por-
tions  of  phosphate of lime,  magnesia and iron.  These animals
also present distinct legs and wings.
  In  the  arachnida we  meet  with a more consolidated form of
skeleton ;  generally more than three pairs of legs ;  and, at the sides
of their head, a pair of sharp-pointed piercing instruments, suited
to their retired, cunning, and  carnivorous  habits.   These animals
throw off periodically their exterior coverings, like the larvas of
insects; and, like the  Crustacea, they are  capable of reproducing
their  members  when  destroyed.  The Crustacea affords us by far
the most  solid form of skeleton met with in any of the articulata.
In the decapods it contains half its weight of carbonate of lime,
and  a considerable proportion of phosphate, with traces of iron,
soda,  and magnesia, all of which are secreted from the true skin.
These animals have generally five pairs of legs, two strong mandi-
bles,  two pairs of slender maxillae, and two pairs of antennae. The
solid  crust forming the skeleton of Crustacea is cast off periodically.
This  is accomplished  by the  animal first detaching the cutis and
muscles  from  the inner surface of the'old shell;  then secreting
from  the surface of the cutis a new layer of epidermis; next a layer
of colouring  matter;  and,  within this, the  calcareous materials of
the new  shell.
  Mollusca, Cuvier ;  Cyclo-gangliated animals, Grant.  The
shells of these animals are formed of carbonate of lime, without
the phosphate, and are remarkable for their want of symmetry on
the two sides of the body, and  their  inconstancy in animals of simi-
lar  structure.   In the  tunicata we meet with an exterior cartilagi-
nous  skeleton, in some instances thick and opaque, as in the ascidia
—in  others more delicate  and transparent, as in the cynthia papil-
lata.  The shells of the conchifera usually consist of two movable
pieces placed  on the  exterior of the  body, connected by ligament
and  muscle.   All these animals, however,  are not bivalved ; some,
as the pholades, have  additional pieces at the hinge of the valve,
constituting the  multivalves.   They have  a muscular foot, and a
pair of tentacula.  The gasterpoda possess hollow, unilocular, co-
nical shells.   Many  of  them  have no shell,  as the tritonia and
doris; some have a thin calcareous lamina within the skin  of the
back, as  the aplysia; whilst others have only a partial covering of
shell  as  the testacella.   In the cephalopodous mollusca we recog-
nise the  transition from  the external unorganised shells of the in-
vertebrated tribes to the internal organised  bones of the vertebrata.
  The shells are sometimes external, as in the nautilus, and some-
times internal, as in the sepia.   In  this complicated class of ani-
mals  we  find a near approach  to the cartilaginous fishes in the pre-
sence of cranium, spinal column, &c, in a rudimental form. 
14
EVERS'S COMPARATIVE ANATOMY.
                       RECAPITULATION.

  I. All animals are  included  under the heads vertebrata and in-
vertebrata.
  2. Great advantage to be derived from a knowledge of arrange-
ment and classification.
  3. The osseous system is neither the most important nor the
most uniformly existing.
  4. Skeleton exists in every class of animals, but modified accord-
ing to each class.
  5. Skeleton generally internal in the radiata, and external in the
articulata, subject to exceptions.
  6. Skeleton remarkable for inconstancy and want of symmetry
in the mollusca.
  7. Basis of skeleton—silica  in the lowest radiata, carbonate and
phosphate of lime in the articulata, and carbonate of lime chiefly in
the mollusca.
  8. No bony  skeleton  where  regularly formed brain   does not
exist.
                       CHAPTER III.

                        VERTEBRATA.

   General observations.—It will appear hereafter that the principal
part of the nervous system consists in a single central mass extended
along the back, and composed of a series of distinct portions, each
of which, like the cerebral ganglion of one of the sepias, is indicated
by its giving off one or more pairs of nerves.  To coincide with such
a disposition, the chief portion of  the skeleton is formed by a series
of osseous rings, which being mutually articulated and collectively
forming a closed cavity, compose a series of  spinal vertebrae consti-
tuting the spinal column—the distinctive character  of this division
of the animal sphere.  The  vertebral column,  which  is the  first
rudiment  of  skeleton observed in the human  embryo, is also the
primary and  most essential portion of it in the higher classes of ani-
mals generally, and in many cases alone composes nearly the whole
of the skeleton.
   Another characteristic of the skeleton in this department  of ani-
mals is, that it is placed internal to  the soft parts, and is not exu viable
in a mass, as  it  was in  most of the invertebrate classes.  Here
the phosphate of lime is the predominant  ingredient, and its propor-
tion increases as we ascend through the vertebrated classes.
   The appearance of the skeleton is greatly  varied by the situation
of the ribs; for instance, in fish and aquatic mammalia the thorax is
placed near the anterior part of the column, to allow of the mobility 
VERTEBRATA.
15
of the posterior portion for the purposes of swimming.  In birds,
tvhere the neck is used as a prehensile organ, the thoracic portion of
the column is situate near  its posterior extremity.   Whilst in quad-
rupeds and  reptiles balanced on two pairs of extremities, the solid
portion of their trunk is placed near the middle of their column.

                            PISCES.

  The bones of fishes closely resemble those of the higher grades
of organisation in their embryotic state, not only in their soft carti-
laginous character, but also in the isolated condition of their several
centres  of ossification, especially in the  complicated  bones  of the
head.  The bones of the cartilaginous tribes are composed of water,
gelatine, and  the sulphate, subcarbonate and  chloruret of soda;
whilst the more dense bones of the osseous fishes are indurated and
strengthened by the  more insoluble  phosphates.  As the  human
embryo  originally  consists almost exclusively  of  the vertebral
column, so also in fishes we find that the spine, and the head, which
is only an increased development of it, constitute the most impor-
tant parts of the skeleton.
   Spine.—The vertebrae in this class are very numerous, and  may
be divided into the abdominal and caudal.  The bodies of the verte-
bras are the elements first developed; they are the most important, and
form almost the entire of the skeleton in the lowest species of cartila-
ginous fishes.   They are  concave on both surfaces ;  consequently
enclose large spaces, filled with a thin gelatinous fluid ; and in many
of the cartilaginous species, the inter-vertebral substances communi-
cate and form a continuous elastic chord  passing through the entire
column as in the lamprey.  The spinous  processes of the abdominal
vertebrae  are very long superiorly, and  assist,  by their shanks, to
form the spinal canal; whilst the caudal  vertebras are distinguished
by having long spinal processes  both  above and below.  Between
the roots  of the inferior spinous processes there is enclosed a simi-
lar canal, but larger for the passage of the great systemic artery.
   The vertebral column in fishes is constructed in such a manner
as to give considerable perpendicular extent to the trunk, and  thus
favour their horizontal mode of progression.  The number of ver-
tebrce. varies greatly;  thus in the carp we find 41, in  the burbot 57,
in the eel 115, and in the shark as many as 207.  In the osseous
fishes, the ribs form an upper and a lower range;  the latter are
better developed and more  uniform in their existence than the former.
The number of ribs is generally determined  by that of the abdo-
minal vertebras. In some, however, as the chaetodon, scomber,  <fcc,
the caudal vertebras are furnished with ribs.  These bones articulate
with  one vertebra only, as a consequence of  which they ertjoy but
little  motion, and are  but slightly subservient  to respiration.  In the
shark they are cartilaginous : in  the  carp they are long and firm ;
in the eel short and slender ; and in many genera, as the  raia, fis-
tularia, &c, they are almost wholly absent.  The sternum, when 
16
EVERS'S COMPARATIVE ANATOMY.
present, consists, as described by Meckel, of a variable number of
V-shaped pieces, pointed  downwards and overlapping  each other.
This rudimentary bone is best seen in the herring and the dory.
  Head.—To the researches of Oken, Meckel, Cams, Blainville,
&c, we are indebted for the important fact that the cranium, is
nothing more than a highly developed  portion  of  the  vertebral
column.   The  composition  of the cranium in the  cartilaginous
fishes is very simple; in  many, as in the skate, consisting chiefly of
one large piece.   In  the  osseous tribes, on the contrary, the com-
ponent parts are very numerous—amounting to 80 in the head of
the perch.  The bodies of the vertebras continue forward in a straight
line with the spine along the base of the scull, forming the basilar
part of the occipital, the body of  the sphenoid, and the ethmoid
bones.  In the bony fishes the cranium is remarkable for being thin,
diaphanous, elastic  and  having  its elements united  by squamous
sutures, which favours the extension of the period of growth of each
part.  The cavity of the cranium is occupied chiefly by  the cellular
tissue of the arachnoid coat; the brain occupying but a small por-
tion of the base of the skull.
  The bones of the face present but few peculiarities.  The inter-
maxillary bone consists of three triangular pieces  inserted between
the vomer, the palate, the nasal, and  the superior maxillary bones.
The central  piece is generally cartilaginous.   In connection with
the upper jaw, we have to notice the os quadratum ; this is composed
of several pieces, which  closely resemble the ascending process of
the lower jaw in man.   The three portions of which it is  mainly
composed  are articulated, one to the inferior maxilla  and palate
bone, the second to the temporal bone, while the third consists of a
thin round plate, and is called os discoideum.  Behind the lower
jaw, and connected to the os  quadratum, is the operculum.  This
is a plate of bone usually composed of four pieces, which have been
considered analogous to the bones of the tympanum,  on account of
the absence of this  cavity from the ears  of fishes  ; others  have
regarded it as a portion of the lower jaw.  Be this as it may we find
the operculum covering the respiratory apparatus in the same man-
ner as the shells of bivalves cover the subjacent gills.
  The os  hyoides reaches a high degree of development here, as in
all water breathing vertebrata ; it consists of a body or lingual bone,
and five pieces on either  side  of  it: it  is suspended from the tem-
poral bones ;  and it is, by its free anteroposterior motions that  res-
piration is effected in fishes, and in  amphibia, as will be shown
hereafter.  It forms an arch, having the lower jaw above it, and the
scapular and coracoid bones belrw.   Its sides support the four pairs
of branchial arches, and  externally it has attached to it the opercular
membrane.
  Extremities.—In fishes fins supply the place of extremities ; the
anterior corresponding to the arms, and the posterior to the 'leo-s.
They are  named according  to the  parts they are attached to, lis
dorsal, pectoral, ventral,  caudal, and anal  fins.  The  anterior or 
VERTEBRATA.
17
pectoral fins are larger and more uniform in their  existence than
the posterior;  they also commence their development at an earlier
period; in all of which  they resemble the  embryo of the higher
classes.   The ventral fins are wanting in the apodes, as well as in
several species of other orders ; whilst the pectoral fins are generally
present.
   The anterior fins are generally joined to the back of the skull by
means of an osseous belt, formed behind by the scapula, and in front
by the coracoid bones.  A humerus, generally long  and angular, is
attached to these above, and to the radius and ulna below.  To these
succeed the carpal bones, and the member is  terminated  by long
and numerous phalanges.  The posterior  members, or  ventral fins,
have no connection to the spine, but are suspended from the rib-like
iliac bones, and placed on the lower part of the trunk, at a variable
distance between the head and anus.   The presence  of  a sacrum
in  this class  would  be  injurious to  the  free  motion  required  in
swimming.   In  the abdominal  fishes  the pelvic bones are uncon-
nected to the skeleton ;  and in the apodal families they are wholly
absent.   The long phalanges of the feet are attached directly to the
pelvic bones, there  being rarely a  trace  of  intermediate bones
developed.
   The  want of symmetry observed in the skeletons of  many fishes
forms a singular peculiarity in this class.  In the pleuronectes, for
instance,  one side  is turned  upwards, instead of the back; both
eyes  are placed on the same side; the cranial  vertebras  seem
twisted in their long: axis ;  and the lower part of the head is imper-
fectly developed.   The  bones,  especially the  intermaxillary, are
much larger on  the  side opposite to  that on which  the eyes are
placed.

                       RECAPITULATION.

   1.  The bones of fishes resemble the embryotic condition of the
osseous system in the higher classes of animals.
   2.  The spine is the most important part of their skeleton.
   3.  The spinal column enjoys very  free  motion, chiefly in the
lateral direction.
   4.  The construction of the head is as simple in the cartilaginous,
as it is complex in the osseous fishes.
   5.  The os  hyoides is greatly developed to support the branchial
apparatus.
   6.  The anterior fins are larger, earlier developed, and  more uni-
form in their existence than the posterior.
   7.  The pelvic bones and  posterior  fins are absent from the ske-
letons of  many cartilaginous fishes.
   8.  Want of symmetry is a striking peculiarity in the skeletons
of many  fishes.
       7__f                                      evers 2 
18
EVERS'S COMPARATIVE ANATOMY.
                          AMPHIBIA.

  In the Batrachia the ribs are almost wholly absent;  it is only
in the  rana  pipa and  the salamanders that small cartilaginous
appendages are found attached to the transverse processes of some
of the vertebras.   In these animals  the  spine  consists of dorsal,
sacral, and caudal portions—the distinction being marked by the
connection of one of the vertebras to  the ilium on each side.  The
salamander has  fourteen dorsal, one  sacral, and twenty-seven cau-
dal vertebras; in  the common  frog there are only nine vertebras;
and  in  the rana pipa but eight; whilst the siren has forty-three in
the trunk, and about forty-five in the tail; from the second to the
eighth  inclusive  have  rudimentary  ribs attached to  them.  The
bodies of the vertebras are concave on their surfaces;  so that, when
in apposition, they give rise to the  existence of an  intervertebral
oval cavity filled  by a gelatinous mass.
  When we consider the habits, food, and mode of progression, of
the frog—that  its movements,  which are chiefly on land, are both
active  and extensive, as well for the purpose of seizing its prey as
of escaping from  danger—it becomes obvious why its spine should
be short and  firmly anchylosed—how the presence of a tail would
be worse than useless, and why a  necessity exists for a full deve-
lopment of the  posterior extremities.   The absence of  ribs will
hereafter be accounted for by an interesting peculiarity in the func-
tion  of  respiration.
   Cranium.—The elements composing this cavity are remarkable
for remaining permanently ununited, a state of things  which  is
strikingly imitated during the progress of the development of these
parts in the higher orders of animals.  The maxillary, intermaxil-
lary,  tympanic,   and jugal bones are  greatly  expanded, in the
transverse direction, giving the face a flattened appearance.  The
lower jaw consists of three pieces on each side.
   Of all parts of the osseous system of this class, there is none so
interesting as the os hyoides, on account of the changes to which
it is  subjected during the transit of the amphibia from the pisciform
to the reptile state.  The branchiae are  external, supported by car-
tilaginous arches connected with  os  hyoides.   As  the age  of
the tadpole increases, the  branchias  disappear, the lungs  become
developed, and the  os   hyoides grows, from a small rhomboidal
point, to the large size  and peculiar from which it presents in the
full-grown frog.
   Anterior extremity.—The shoulder of a frog consists of scapula,
clavicle, and  coracoid bone, all of which unite to form the glenoid
cavity.   The humerus  is  short and thick,  having a round head
above, received by the glenoid cavity, and also a spherical  extremity
below, to articulate with the bones of the fore-arm, which consists
of radius and ulna so united that a faint line indicates their former
separation.  The carpal bones  are six ;  the metacarpal, four. The 
VERTEBRATA.
19
middle  and index  fingers have each two phalanges,  the  others
three.
  The posterior extremity, for reasons before assigned, reaches a
high degree of development. The cotyloid cavity is constituted by the
ilium, ischium, and  pubis. The femur is long and cylindrical. The
tibia and fibula are  consolidated into one bone, and joined inferiorly
to two bones representing astragalus and os calcis.  Between these
and  the long  metatarsal  bones are placed four small, irregular
bones.  Of the  five toes, the  internal  is best developed, and sus-
tains three long, slender  phalanges.
  The  structure and  form of the  salamander, proteus, and  siren,
are well contrasted with  those of the frog.   In the former animals,
the spinal  column  attains a high state of development:  the extre-
mities are reduced to a rudimental type.   The  bones of the fore-
arm and leg, instead of  being  anchylosed  as in the frog, maintain
a  permanent  state of separation.   The toes, which are four in
number, are but slightly developed.  The whole economy of the
frog is  admirably organised for rapid terrestrial progression, while
that of the other animals is designed to favour their movements
through a  watery element.
   Who can  fail to observe the extreme wisdom manifested in the
metamorphosis of these  animals?  In the early part of their exist-
ence, and  while  they enjoy an  aquatic mode of  life,  their organi-
sation is in due accordance; at first  their members are scarcely
perceptible, whilst  their  tail is of great length, and continues so in
those destined to continue their watery habitation ; but in the frog,
&c, which are to  breathe by lungs, the tail is gradually, removed
by absorption,  and the  extremities, particularly  the posterior, un-
dergo a rapid evolution.

                          REPTILIA.

   Chelonia.—These reptiles present a tolerably perfect form of ske-
leton.   Their spine consists of eight cervical, fourteen dorsal, three
sacral,  and from  twenty to  thirty caudal vertebras.  There are
eight pairs of immovable ribs, united to each other by sutures, and
attached between the bodies of the vertebras.  By the union of the
ribs with each other, and with  the spinous processes of  the dorsal
vertebras, they form the upper  shield or carapace.   The nine pieces
of the sternum which are movable in the turtle, form the lower
shield or  plastron.  This unyielding frame-work is well suited to
resist pressure, as well as to favour their muscular movements on
land, whilst the mobility of the several elements  of the sternum in
the aquatic species  is applicable to their extensive  respiration in that
dense element.
   The bones of the head are  firmly united by sutures.   The occi-
pital condyle presents  three facets, formed  by the  basilar and the
two condyloid portions.   The  inter-maxillary bones are narrow,
but  present a large palatine surface.   The bones of the ear are 
 20             EVERS'S COMPARATIVE ANATOMY.

 anchylosed, and the body and cornua of the  os  hyoides  are fully
 developed.
   In the anterior extremity, which is attached to the inner side of
 the  chest, we distinguish scapula and clavicle united  by suture;
 humerus twisted,  with a large articular condyle; radius and ulna
 short, strong, and expanded inferiorly, fixed in a state of pronation;
 carpal bones, sometimes as  many as  ten, arranged  in  three rows;
 five short metacarpal bones; and the phalanges, two for the thumb
 and last finger, and three for each of the others.
   The  ilia are long and cylindrical in the land tortoise; the pubis
 and ischium broad  and flat.   The  femur presents indications of
 trochanters, as  in  man; its head  is large, and joins the shaft at a
 right angle.  There is no round ligament in the  hip, though rudi-
 ments of semilunar cartilages connected to crucial ligaments in the
 knee.  The tibia  and  fibula are separate.  The  metacarpal bones
 are five, and the  number and arrangement  of the phalanges  the
 same as observed in the phalanges of the fingers, with the exception
 of the outer toe, which is generally rudimentary.  In the aquatic
 chelonia,  the bones of the extremities are longer,  straighter,  and
 more slender than  in the land  species.
   Ophidia.—The skeleton in  serpents consists of little more than a
 vertebral column, possessing such  a degree of mobility as enables
 them to  creep with speed along the surface, to swim through  the
 waters, to spring into the air, to climb trees, and to combat with and
 conquer  their prey.  Extremities  are  here wholly absent, and  the
 spinal column and ribs constitute the sole organs  of  progressive
 motion.   For this  reason the  spine  is  characterised by immense
 strength  and great mobility.  The vertebrae  are more numerous
 in this than in any other  class of animals, being 49 in the anguis
 fragilis, or blind worm ; 201 in  the crotalus horridus, or rattle-snake ;
 and 316  in  the coluber  natrix.  The  bodies of the  vertebrae have
 ball and socket articulations, so disposed as to admit of  free lateral,
 but limited antero-posterior motion. The ribs of serpents are tubu-
 lar, narrow and compressed  from before backwards.  Their head
 presents  a broad,  arched, concave surface, to articulate with  the
 rounded, prominent, transverse  processes of the  vertebrae,  whilst
 their ventral extremity tapers  to end  in a thin, flexible  cartilage.
 The ribs extend from the atlas to the anus, and are  32 pairs in  the
blind worm, 175 in the rattle-snake, and 204 in the  coluber natrix.
 They are all of the false kind,  there being  no rudiment of sternum,
 except in the ophisaurus and blind worm alone, in which also faint
 traces of shoulder and pelvis may be discerned.
  The head resembles the preceding order (or that of the chelonia)
in the small size of the cranium, whilst the multiplicity and detached
condition of its bones ally it to  the fishy tribes.   This loose state of
the component  elements of the head "is necessary in serpents, for
being deprived of organs of prehension, they are compelled to swallow
their prey entire.   As a  consequence of the looseness of the other
bones, the two parietals  are anchylosed along the median  line  to 
VERTEBRATA.
21
protect  the brain  during the exposure  of these  animals to the
trampling of quadrupeds, &c, whilst concealed in their natural
haunts. Their teeth are small, conical, and sharp ; they are placed
in the two maxillary, the intermaxillary, and the palate bones.
   Sauria.—In this order we meet with a more perfect development
of skeleton than in the last, as they possess a sternum, a scapular
and pelvic apparatus, together with atlantal and sacral extremities.
The lacerta  iguana presents 5  cervical, 11 dorsal,  9  lumbar,  2
sacral, and 72 caudal vertebrae ; the crocodile of the Nile 7 cervical,
12 dorsal, 5  lumbar, 2 sacral, and 34 caudal—articulated by ball
and  socket.   There are false ribs behind and before the true ones.
In the  chameleon  there are 17 pairs; in  the crocodile 12.  The
sternum is prolonged posteriorly as far as the pubis, and has attached
to it five pairs of cartilaginous arches, for the purpose of supporting
the abdomen.
   The head is extended forwards in a line with the spine, as in the
other inferior vertebrata; like these, also,  its component  elements
are loosely connected.   As in serpents, the basilar condyle is elon-
gated transversely, and the parietal bones anchylosed.  The lower
jaw consists  of six  pieces on each side; and here, as in serpents,
the prehensile teeth are attached  by broad base to the surface of the
jaw, and the new  teeth rise by the  side of  the old, and not in their
interior as in the crocodile.
   Anterior extremity.—The scapula  is broad, thin, and curved.
The acromion is a distinct bone,  and the clavicles  are  anchylosed
in form of a cross, on the front of the sternum.  The humerus is
expanded at its extremities, and the same form as in man; the ulna
is without an olecranon, stronger than the radius, and separated from
it below.   There  are  from four  to nine bones  in  the carpus, five
in the metacarpus; and  the phalanges are, two  for the thumb,
three  for the second and last fingers, and  four  for each  of the
others.
   Posterior extremity.—The three portions of the os innominatum
contribute to the formation of the cotyloid  cavity.   The ossa pubis
and ischii form a lengthened symphisis in  front; and the spine of
the iliac bones is extended backwards along each side of the sacrum.
From the front of the  pubic bone a process passes up towards the
sternum as in the marsupiales.   The head of  the femur is com-
pressed and directed forwards; the great trochanter is also flat and
turned towards the tibia.   The  patella is  small;  the  tibia  short,
thick, and curved;  the fibula slender in  the centre, expanded at its
extremities, and apart  from the tibia.  In  the crocodile there are five
bones  in the tarsus, four in the metatarsus, and  the toes  are  so
arranged that the most internal sustains  two phalanges, the second
three, and the third and fourth, four each.
   In the skeletons of the nilotic  crocodiles, alligators,  and other
reptiles destined to swim by the  lateral movements of a  muscular
tail  and long webbed  feet, their  long  bones are filled with a thin
oily marrow, and  the bones of the head firmly united. 
22
EVERs's COMPARATIVE ANATOMY.
                recapitulation.—Amphibia.

  I. In amphibia rudiments of ribs only are met with.
  2. Vertebras range from eight in the rana pipa to  eighty-nine in
the  siren.
  3. In the frog, the extremities, especially the posterior, are  fully
developed ; the tail is absorbed.
  4. Salamander, proteus, and siren, may be well contrasted  with
the frog ;  in the former the spinal column attains and maintains a
high degree of development, whilst their members are reduced to a
mere rndimental type.
  5. The bones of the cranium remain loosely united through life.
  6. The os hyoides undergoes  remarkable  changes  during the
metamorphosis  of the animal from the  pisciform to the reptile
state.

                 recapitulation.—Reptilia.

  1. The vertebrae and ribs are more numerous than in any other
class of animals.
  2. The chelonia differ from the sauria in having immovable ribs,
and from the ophidia in having arms and legs.
  3. The bones  of the head generally maintain a permanent state
of separation, except the parietals which are firmly anchylosed.

                             AVES.

  As in this department of my subject I avail myself of much of the
valuable  matter contained in the article, Aves, in the Cyclopasdia of
Anatomy  and  Physiology, by that clear, accurate, and scientific
writer, Mr. Owen,  it becomes necessary to state that he divides the
class into the following orders :—
  1. Raptores, birds of prey, or raveners ; 2. Insessores, perchers ;
3.  Scansores.  climbers; 4.  Rasores,  scratchers;  5.  Cursores,
coursers; 6. Grallatores, waders ; and 7.  Natatores, swimmers.
  Positive characters of the class.—Animal, vertebrated, oviparous,
biped; anterior  extremities  organised for flight;  integument plu-
mose ; blood red and warm;  respiration  and  circulation double ;
lungs fixed and perforated.
  Negative characters.—No  auricles, teeth,  lips,  epiglottis, dia-
phragm,  fornix, corpus callosum, or scrotum.
  The bones of birds are remarkable for being permeated by atmo-
spheric air, for their compact  and laminated  texture, their white
colour, and their fragility, owing to a preponderance of phosphate of
lime.
  The vertebra, are the first bones observed in the  development of
the osseous system of birds, and of all  parts of this system, they
present the fewest  variations.  The spine here consists of cervical
dorsal, sacral and caudal portions.  The first and last are the  most 
VERTEBRATA.
23
movable, and in  many species of the dorsal and caudal portions
admit of no motion at all.  This fixity facilitates the flight of the
bird, whilst the length and mobility of the cervical portion  of the
spine compensate, in some degree, for the  unfitness of the anterior
members to the purposes of prehension, &c.
  The cervical portion of the spine is generally composed of a greater
number of  vertebrae than any of the other divisions ; they are not
fewer than nine, as observed in the sparrow, nor more than  twenty-
three, as in the swan.
  The bodies lock into each other,  and are so disposed as to allow
the superior and inferior ones to move forwards, and the  middle
backwards.  The transverse processes  are long, and have rudi-
mentary ribs connected to them ;  these are particularly well deve-
loped in rapacious birds, and hence the great breadth of their necks.
The atlas  is a simple ring, generally articulated to the occipital
tubercle  by a single facet; but the penguin and ostrich  have two
other facets continuous with the central  one.   From the  dentata
down, a movable inter-articular cartilage is found, as in the joint of
the lower jaw of the mammalia.
  The dorsal vertebras range from six in the bull-finch to eleven  as
seen  in  the swan.  The bodies  of these  vertebras  are  short and
compressed laterally, except in the ostrich.  The  transverse  pro-
cesses are greatly developed.   The anterior cartilaginous surface is
convex in. the vertical direction, concave in the transverse, and
connected  by fibrous capsules and  synovial  membranes.  Most
birds have  the middle and lower vertebras anchylosed ; even the
transverse  and spinous processes of the superior are anchylosed  in
those birds requiring great fixation of the trunk ; while in those that
cannot fly, as the penguins, they  are all movable.
  The sacral vertebras are firmly anchylosed  with  one another,
and with the ilia laterally; consequently it is difficult to  determine
their real  number; it  is not, however, greater than  nineteen,  as
seen in the emeu and cassowary,  nor less than eight, as observed in
the hoopoe.  The bodies of these vertebras are broad, but shallow,
and the  canal  greatly enlarged,  to correspond  to  the size of the
chord, which here  supplies  nerves  to the  posterior extremities.
When it is considered that the head, posterior members, viscera, &c,
are suspended in flight from this  central portion of the  trunk, the
necessity for the mechanism consolidating these vertebrae will  be
readily appreciated.
  The coccygeal vertebras are generally movable, and  from five
to nine in  number.  With the exception of the last, they  are broad,
short, and  perforated for the spinal  marrow.  The last has  no pro-
cesses ; it is compressed laterally, and terminates above  and below
in a sharp  edge ; it supports the coccygeal oil-gland, and affords a
firm basis to the tail feathers, or retrices of Linnasus. These bones
possess ligamentous connections, except the sixth and seventh which
 re provided with a capsule and synovial fluid. 
24
EVERS'S COMPARATIVE ANATOMY.
TABLE OF THE VERTEBRA IN BIRDS.
ORDER RAPTORES	VBRTKI1R.K.				ORDER RASORES.	VERTEBRA			
Species.	3erv.	Dor.	Sac.	Cau.	Species.	Cerv.	Dor.	Sac.	Cau.
Vulture,	13	7	11	7	Crested Curas-				
Eagle,	13	8	11	8	sow,	15	8	10	7
Sparrow-hawk,	11	8	11	8	ORDER CCRSORES				
Kite,	12	8	11	8	Ostrich,	' 18	10	17	9
Hawk-owl,	11	8	11	8	Cassowary,	16	10	19	7
ORDER INSESSORES.					Emeu,	19	9	19	9
Fly-catcher,	10	8	10	S	ORDER GRALLATORES.				
Blackbird,	11	8	10	7	Heron,	18	7	10	7
Crow,	13	8	13	7	Crane,	19	9	12	7
Magpie,	13	8	13	8	Spoonbill,	17	7	14	8
Jay,	12	7	11	8	Avoset,	14	9	10	8
Starling,	10	8	10	9	Plover,	15	8	10	7
Bull-finch,	10	6	11	6	Woodcock,	18	7	13	8
Sparrow,	9	9	10	7	Curlew,	13	8	10	8
Goldfinch,	11	8	11	8	Oyster-catcher,	12	9	15	7
Lark,	11	9	10	7	Coot,	15	10	13	8
Redbreast,	10	8	10	8	Flamingo,	18	7	12	7
Swallow,	11	8	11	9	ORDER JfATATORBS.				
Humming-bird,	14	9	10	8	Pelican,	16	7	14	7
Kingfisher,	12	7	11	7	Cormorant,	16	9	14	8
ORDER SCANSORE3.					Gull,	12	8	11	8
Woodpecker,	12	8	10	9	Catarrhactes,	13	9	13	8
Parrot,	11	9	11	8	Swan,	23	11	14	8
ORDER RASORES.					Goose,	15	10	14	7
Pigeon,	13	7	13	7	Duck,	14	8	15	8
Peacock,	14	7	12	8	Sheldrake,	16	11	11	9
Pheasant,	13	7	15	5	Mergancer,	15	8	13	7
Turkey,	15	7	10	5	Grebe,	14	10	13	7
  Skull.—It has been already shown that the bones composing the
skull  of the crocodile, and other cold blooded vertebrata, were not
consolidated till a late period of life, giving rise to some difficulty
in tracing a correspondence between their bones and those of a
higher order. A still greater difficulty is experienced in determining
the component parts of the head in birds ;  for in them the bones of
the skull are anchylosed, and  every  trace  of suture  effaced at an
early  epoch ; therefore, in order to accomplish their perfect separa-
tion, it must be undertaken at an early period of their existence.
  In  the majority of birds, the head is articulated to the spine, by
means of a  single hemispherical tubercle on  the basilar process of
the occipital bone ;  but in  the penguin and ostrich, the condyloid
portions contribute to its formation, and the articulation  is such as
to admit of very great freedom of motion.
  The occipital bone is originally composed of  four pieces, basilar
spinous and two condyloid.  The temporal consists of the petrous'
squamous, and tympanic portions ; the last is movably articulated
to the inferior part of the squamous portion, and is sometimes called
os quadratum.  The alas majores of  the sphenoid bone  remain a
long time separate, and are called  interarticular, or  omoid  bones.
The remaining bones of the skull present no remarkable peculiarities 
VERTEBRATA.
25
save that they are all early and firmly anchylosed, with the excep-
tion of the tympanic bone.
  The bones of the face correspond in number and position to those
of the mammalia, especially the order rodentia.  They are movably
connected with the  bones of the cranium, and remain separate to a
much later period.  The upper mandible is chiefly characterised by
the presence of the intermaxillary bone.   This consists of three
processes, a central, and two lateral; the former passes  up between
the superior maxillary bones, and becomes joined to the nasal and
ethmoid ;  this union is ligamentous in the parrot, and  those birds
that apply the upper mandible to the purposes of climbing.  The
two lateral processes of the inter-maxillary bone, extend upwards
and backwards external to the  superior maxillary bones, to which
they are firmly united.
  There are few more ingenious or beautiful pieces of  mechanism
than that by which the mouth of  a bird is opened.  The tympanic
bone  as before observed, never anchyloses with the other elements
of the temporal;  on the contrary, it articulates with the zygomatic
portion of the latter bone, by two  transverse condyles above; below
it articulates by a broad surface with the upper and back part of the
lower  jaw, while  in front and near its lower extremity, it  has
applied to  it the long, slender malar bone  which reaches to the
superior  maxilla.  When the tympanic bone is drawn forwards,
either by the action of the pterygoid  muscles attached to it, or  by
the depression of the lower jaw, the malar bone is advanced  against
the superior mandible, which is elevated at  the same moment that
the lower one is  depressed.  The moment the pressure ceases to
exist below, the elasticity of the union of the intermaxillary bone
with the cranium restores the upper  mandible to its situation.
   The inferior maxilla originally consists  of six pieces on  each
side, named anterior dental, two condyloid, angular, supra-angular,
and opercular.  As this bone, together with the upper jaw, forms
the chief organ  of prehension in birds, it is but natural to expect
that it shall present numerous modifications, indicative  of the food
and habits of each species.
   There is more uniformity observed in the skulls of birds than in
any other class of the vertebras department.  It generally presents
the form of a five sided pyramid, the base represented by the occiput,
and the apex by the bill.  In the Raptores it is short, broad, and
deep; nearly  spherical in  the  Warblers; flattened,  and of great
breadth, in the Scansores ;  narrow, and slightly raised in theRaso-
rial birds ;  and remarkable for its great length in the Waders.
   Thorax.—The extent and energy of the respiratory function of
birds, are  clearly indicated by the peculiar and perfect condition of
this part of their osseous system.  The ribs, as in the mammalia,
are arranged into true and false, with this difference, that the false
ribs are  placed both above and below the true ones.  There is
some, though not very great variety in the number of  ribs presented
by this class: for instance, in the Insessores we meet  with seven or 
26
EVERS'S COMPARATIVE ANATOMY.
eight pairs;  and  in the  willock, of the order Natatores, twelve
pairs;  the  average number is  eight or nine pairs.  The true ribs
are joined to the  sternum by straight osseous portions, called ster-
nal ribs, instead of by elastic cartilages, and are movably connected
at each end.  It is highly interesting to observe the mode of articula-
tion of the vertebral extremity of  the  ribs.   In  such  as require
fixity of the  chest, for the purposes of flight, the rib is articulated
to the  side of the  vertebra, having no connection  to the inter-arti-
cular cartilage; but in  the ostrich, and others of the  cursores,
where  the dorsal vertebrae preserve their mobility, the heads of the
ribs are attached to the intervertebral spaces.
   There is another interesting fact connected with the ribs, in
birds of powerful flight;  it  consists in a number of small osseous
plates  being  detached from the posterior margin of each true rib,
and passing  backwards  and upwards to be connected  to the suc-
ceeding rib,  by means  of strong, oblique, fibrous ligaments.   In
the ostrich, rhea, emeu, and cassowary, these bony splints present a
mere rudimentary  type.
   Sternum.—The modifications  presented  by this  bone, strictly
conform to the functions which the anterior extremities are designed
to execute. Hence, in the cursorial birds which do not fly, it is met
with in the form of a simple square plate of bone like a shield, while in
those birds that possess  great  powers of flight, it extends over the
whole  of the lower aspect of the thorax  and abdomen, even to the
pubic  bones,  and  in order  to afford sufficient space for  the attach-
ment of the pectoral muscles, it is  armed with a huge crest, extend-
ing  the whole length of its lower surface.   This crest, or keel, is
uniformly developed in proportion to the size of the pectoral mus-
cles, and hence declares the power of the anterior extremities.  The
sternum is sloped obliquely on each side of its anterior extremity,
for the reception of the clavicle,  and in the  centre is  connected
with the fork-bone, either directly or by means of ligaments; the
true ribs are  attached to it on each side.  The sternum of the crane
has within it a large cavity, containing several convolutions  of the
trachea.   This condition is repeated in  the wild swan;  but in the
tame swan, and some of the grallas, as  the ciconia and gallinas, it
is but  very feebly developed..
   On  the internal surface of the sternum, chiefly along the mesial
line, several  apertures may be  observed, for the passage  of air into
the bone.
   Anterior extremity.—Here,  as  in the mammalia, the extremity
consists- of shoulder, arm,  fore-arm, and hand.   In the first,  we
recognise a scapula, a coracoid bone, and a clavicle.
   The scapula is generally  a long, narrow bone,  increasing  in
thickness  as  it approaches  the shoulder  joint, where it expands in
the  transverse direction, to form the posterior half of the glenoid
cavity; here also it articulates  with the coracoid bone and clavicle.
The direction of the scapula is longitudinal.   In birds with active 
VERTEBRATA.
27
powers of flight, it reaches to the last rib, while in the emeu it covers
only two.  This bone is broad and flat in the penguins.
   The  coracoid, or posterior clavicle, is a strong bone, broad  in-
teriorly, where it is received in a transverse groove in the sternum ;
it  extends  upwards, outwards, and forwards, to articulate with  the
scapula and clavicle.   The glenoid cavity thus resulting from  the
union of this  bone with the scapula, is  often unequal to'the recep-
tion of the head of the  humerus ;  hence, in  the raptores and inses-
sores, a small but distinct bone extends between the coracoid and
scapula, over the superior part of the cavity,Jwhich  it here completes.
It was discovered by Nitzsch, who called it the capsular bone.
   The clavicles are subject to considerable variety.   In the ground
parrots of Australia, for instance, they present only a rudimentary
type, while  in the psittacus mitratus, &c, they are wholly absent;
they are feebly developed in the emeu, rhea, and cassowary.  When
these bones are enchylosed together at their sternal extremities, as
they ordinarily are, they constitute a single bone,  named furculum.
In the ostrich they do not come in contact inferiorly, although they
reach the sternum; and in the toucans, they neither come in con-
tact below, nor reach the  sternum.   It is remarkable that in  the
ostrich they are anchylosed above with the coracoid and scapula,
whilst almost in  every other species they either continue separate,
or are movably jointed  superiorly.
   The  humerus attains its greatest length  in the albatross, and is
shortest in the struthious  birds and penguins, whilst in the swifts
and humming birds it  is  characterised  by its thickness, strength,
and the development of its muscular processes.   In the cursores it
is  short and  attenuated, resembling the  corresponding  part in  the
paddle of the  turtle.  Its head is oblong transversely, and enlarged
by two lateral crests, under one of which are to be found the air
passages leading into the  bone.   The lower extremity of the  hu-
merus  is formed  after the manner of a hinge, consisting of an in-
ternal spherical portion  to articulate with the ulna, and an external
oblong portion for the radius.
   The radius and ulna are straight and slender bones, enlarged at
their extremities, and placed one in front of the other, so as scarcely
to  admit of any pronation or supination.  In the penguins the bones
of the fore-arm are flattened, and articulated with the anterior edge,
and not the extremity of the humerus.
   The carpus is composed of two bones only, and so wedged in
between the metacarpus and fore-arm, as to limit the motions of  the
hand to adduction and abduction.
   The metacarpus is  chiefly formed of two bones,  a small ulnar
one, which supports a single phalanx, and a large  radial one, which
sustains two phalanges.  A small  rudiinental bone  is usually  an-
chylosed to the  outer side of the proximal extremity of the radial
metacarpal bone.
   Lower extremity.—The pelvic bones, like those of the shoulder,
are three in number: the  ilium represents the scapula, the ishium 
28
EVERS'S COMPARATIVE ANATOMY.
the clavicle, and the pubis the coracoid bone.  Unlike the shoulder,
however, these bones are always anchylosed  into one piece on
either side, and with one exception, never join in the mesial line;
this single  exception is afforded by the ostrich, in which the pubic
bones complete the pelvic circle  by anchylosing at their  inferior
extremities.  The vulture cinereus, and some acquatic birds, form
the nearest approach to this last condition.   In  them  the pubic
bones are often surmounted by a cartilaginous appendix at their
anterior extremity.
  The ilium is the only bone of the pelvis that comes  in  contact
with the spine ; it is elongated in form, narrow in the centre, and
expanded at its extremities.  This  bone is  anchylosed with the
sacrum, the ischium, and the spinous  and transverse processes of
one or two dorsal vertebras.
  The ischium lies  parallel with the  ilium; it is a small oblong
bone,  not presenting any peculiarity.
  The pubis  unites  with the ischium in a two fold manner in the
humming bird and some others, so as to form  two foramina obtura-
toria, while in  others, as the stork, it is only united to it at the coty-
loid foramen.  This cavity is always incomplete at its internal part,
where it is closed by  some fibrous bands.
  The femur is short, and slightly convex anteriorly;  its head is
hemispherical, and joined to the shaft at a  right angle, without
the intervention of a neck.  There is  but one trochanter; it  is of
a large size, continuous with the external part of the shaft, and gene-
rally rises  above the level of the head.   The  lower extremity of
this bone presents two  condyles, the inner one for the tibia, the
outer  one, which is longer and larger, rests on the tibia and fibula;
it is convex from  behind forwards, and  terminates in a groove in
both these directions.
  The tibia is the principal  bone of the leg, the fibula ending in a
point  inferiorly, and achylosed to the tibia for a considerable extent.
The lower extremity of the tibia forms a transverse trochlea, above
which there is a deep groove or foramen,  to transmit the tendon of
the extensor digitorum communis.  The upper and anterior part of
the tibia gives rise to a long pointed process, which ascends in the
shape of an olecranon  in front of the  joint, being also anterior to
the patella.
  The tarsus can only be recognised as a distinct segment of the
foot, when examined at an early period of the bird's  existence;
then only can  be found a distinct astragalus of a flattened  oval form'
convex  superiorly, and concave  below, where it meets the three
bones of the metatarsus partially separated. A rudiment of os calcis
may also be found in  the extensor tendons. - In the penguins the
three  metatarsal bones are  only anchylosed at their extremities1
but in other  birds,  faint grooves alone  indicate  their  existence!
The remote extremity of the metatarsus presents three convex facets
to articulate with  the toes.  These last are subject to great variety
as to number,  being reduced to two in  the ostrich, and increased to 
VERTEBRATA.
29
five in the gallinaceas.  The phalanges bear no proportion to the
size or number of the toes, being found to vary from one up to five.

                       RECAPITULATION.

  1. There is more uniformity observed  in  the skeleton of birds,
than in any other of the vertebrated classes.
  2. The bones are white, thin, and brittle;  in  early life, filled
with a thin serous oil, which is subsequently removed to be replaced
by atmospheric air,  especially in those of the  high-flying kind.
  3. The bones are early and rapidly ossified, particularly those of
the head, thorax, and pelvis.  This ossification also affects the ten-
dons of  the muscles of the leg, sclerotic tunic of the eye, inferior
larynx, and the rings of the trachea.
  4. Arms adapted  solely for flight;  legs for  support.
  5. Head and neck long, for the purposes of prehension.
  6. The dorsal and sacral portions of the spine the most fixed.
  7. Cervical vertebras  more numerous  than  in  the mammalia;
occasionally,  three times the number.

                          MAMMALIA.

  The number of vertebras contained in the spine, is very variable;
but the human type is by far the most generally predominant.  In
the cetaceas  there  is no distinction between lumbar, sacral,  and
caudal vertebras ; and  in the porpesse, there  are sixty-six posterior
to  the dorsal: these  mammalia, however, have no  pelvis.  The
cervical vertebras are  uniformly seven throughout this class,  not-
withstanding Cuvier imagined he had found a solitary exception in
the neck of the ai, bradypus tridactylus; but it has  been well as-
certained  since, that what  he conceived to be the two last cervical
vertebrae of this animal, have two rudimental  ribs attached to them.
When we are  reminded of the localities and  habits of the sloth,
hanging from the  branches of  trees, and passing from bough to
bough, aided  by the current winds, it becomes obvious why such a
provision  should exist, of modifying the two superior dorsal verte-
bras, and of consigning to  them the offices of cervical, rather than
infringe on a law which at present seems without an exception.
  The  dorsal vertebrae range from twenty-three, as seen  in  the
unau, bradypus didactylus, to twelve, as  presented  by man, mice,
bats, rabbits,  hares,  and several  apes.   In the  megatherium there
are sixteen, in the horse  eighteen, and  in  the elephant twenty.
The lumbar  vertebrae are generally  seven;  they vary, howe.ver,
there being two in the two-toed ant-eater, and nine in the lori. The
sacral vertebras are  seven in the mole; in the vampyre bat, opossum,
and some apes,  there  is but a single sacral  vertebra, the usual
number being three.  The caudal vertebras are  four in man and
the ourang-oiitang; forty  in the two-toed ant-eater; and  in  the
vampire bat they are altogether absent. 
30
EVERS's COMPARATIVE ANATOMY.
  In most animals, it has been said, that the head and neck together
equal in length the fore-feet,  except where the latter are used as
hands, as  in*the  apes and rodentia.  The neck attains its greatest
length in  the  genus camelus, and is shortest in the order cetacea,
ovvmg to  the  consolidation of  the vertebras.  According  to  the
statement of Gore, the number of cervical vertebras in certain of
the cetacea, as the balasna, manatee, and dugong, amounts only to
six.   In the rodentia, and most  long  necked  animals, the spinous
processes are  almost wanting.  The atlas, in  the carnivora, rumi-
nantia, solipida, pachydermata, &c., is  distinguished by its length,
and by its  large aliform transverse processes.  The free motion and
beautiful arch  observed in the necks of some horses, camels, &c, is
explained  by the  bodies of the cervical vertebras having  a  perfect
articular head on their upper surface, and a corresponding depres-
sion  on their  lower, similar to what we observe in the  necks of
serpents, with  this difference, that the surfaces are reversed.  The
ruminantia, rhinoceros, elephant, &c, are remarkable for the great
length of the spinous processes of the dorsal vertebras.  Bats have
scarcely any spinous processes;  and,  with the exception  of  the
second dorsal, they  are short in the rodentia.   In the  lumbar ver-
tebras, the  form of the transverse processes is very variable—almost
absent in  bats, very strong in  the ruminantia, rodentia, and carni-
vora.   The megatherium possesses long spinous processes.  In  the
sloth, the  length,  breadth, and consolidation of the sacral  vertebras
remind us of the sacrum of birds.   The few first only of the caudal
vertebras in mammalia contain a prolongation of the vertebral canal.
Animals with  long movable tails, as the two-toed ant-eater, have
oblong  triangular processes on  the under surface of the  caudal
vertebras, as in the crocodile.   The connection of the vertebrae is
almost always by means of interarticular cartilage, as in man, and
consists of concentric rings,  most evident in the whale.   In  the
pig and rabbit the  interarticular cavities are  filled with  an albu-
minous fluid, as in fishes.
   Ribs.—Man has  seven true  and  five  false ribs;  the balasna
whale,  one true and eleven  false;   in  the  unau,  or  two-toed
sloth, there are twenty-three pairs, of which  eleven  are  false; in
the horse  eighteen, and  eight of them  false;  in  wolves,  cats, and
some apes, there  are thirteen pairs, four of which are false; in  the
guinea  pig,  armadillo, and porpoise, there are thirteen, of which
seven are false; in  the manatee, of sixteen pairs, but two  are true;
in the dugong but three out of eighteen ; and in the ornithorhynchus
but six out of seventeen.  The breadth of the ribs is greater in  the
ruminantia, pachydemata,  in  the manatee, and  especially in  the
two-toed ant-eater, than  in other  mammalia.   The connection of
the ribs with the  sternum is in general effected by cartilage; but in
the cetacea, ant-eaters, dasypus, bradypus manis, ornithorhynchus
echidna, and frequently in bats, the union is completely bony
   Sternum.—This  bone, though essentially the same as in  the
human subject, is somewhat modified in form by the shape of the 
VERTEBRATA.
31
chest.  In  ungulated animals, where there are no  clavicles, the
sternum  is compressed  laterally, and projects  in  the ceutre like a
ship's keel.   The superior piece of the sternum is very considera-
ble in the mole, where it forms a distinct bone.  It is proportionably
small in the  bat,  seal,  horse,  rhinoceros.  In  the   cetacea it  is
short and large, being composed of five pieces in the dugong, and
three in  the  dolphin, the porposse, and the platanist.   In  the bat
and  ornithorhynchus, the upper part of the sternum is T-shaped,
the transverse process being for the articulation of the clavicle.
   The figure of the thorax in most apes, bats,  and the  greater
number of the rodentia, and, in fact, of the class mammalia, having
clavicles, agrees  with that of the human  subject.  In ungulated
animals,  on the contrary, where there are no  clavicles, the thorax
is laterally  compressed and elongated.
   The whole arrangement of  the thorax  proclaims man to .be
destined  to move in the  erect attitude: he is the only animal in
which its transverse exceeds the antero-posterior diameter; even in
the chimpanse, which approaches nearest to him, the latter exceeds
the  former measurement, reminding  us of the form of this cavity
in the very young  subject.   Its great lateral width and inconsider-
able depth from  sternum to spine, throw the  arms  apart, and in-
crease their sphere of motion.  The reverse  characters,  together
with the absence of clavicles in quadrupeds, allow the fore legs  to
approximate, to fall perpendicularly under  the front of the body,
and  support it with ease and security.
   Head.—We shall  cease  to wonder at the striking  differences
observed in the construction of this part of the skeleton, when we
consider that it forms the receptacle  for the brain, most of the ex-
ternal senses, the masticatory apparatus, &c.   Man  combines by
far the largest cranium with the smallest face ; and animals deviate
from these relations in proportion as they increase in stupidity and
ferocity.   In man, the area of the  section of the cranium is nearly
four  times  as large  as  that of the  face; three times as  large
in the ourang-outang; twice as large  in the  sapajous: and they
are  nearly  equal in  the baboons and carnivora.   In  the hare
and  marmot,  the face exceeds the cranium by  one third;  in the
porcupine  and ruminants, by one half.  The face  is three times
as large as  the  cranium in the  hippopotamus,  and  four times
as large  in the horse.
   The superior  maxillary bones of the human subject are united
to each  other, and contain all the  upper teeth ; in some other
mammalia, however, they are separated by a coniform bone, which
contains the incisor teeth, and hence named  os insicivum; but it
exists where  there  are no incisor  teeth, as in  the kerotophara, the
elephant, and the two-toed rhinoceros of Africa, and even  where
there are no  teeth at all, as  in the ant-eater and some of the ceta-
ceans, for which  reason Blumenbach calls it os intermaxillare.  In
some it  is  a single bone, in  others double; it is absent from the
chimpanse, though present in the ourang outang.  The former of 
32             EVERS'S COMPARATIVE ANATOMY.
these animals possesses supercilliary ridges, which are wanting in
the ourang.                                                  ,
   The head of the ourang, viewed in front, is pear-shaped, expand-
ing from the  chin  upwards, the cranium  being  much the larger
end.  The frontal sinuses are very large in the dog, wolf, porcu-
pine,  sloth, sheep, bull, pig, horse, and especially in  the elephant;
they are  small in bats, rats, squirrels, ant-eaters, the hippopotamus,
rhinoceros, &c.   In  cats,  martens, and  bears, the parietal bones
give off  from their inner and  posterior edge a process  of  bone
which projects into  the cavity of the skull, and forms  a perfect
bony tentorium cerebelli.   In the dog and  horse, similar processes
arise from the petrous portion of the temporal  bones.
   The lower  jaw is  subject to  many varieties in the mammalia.
In the whale  it  resembles  two enormous ribs, united at the point,
without  any trace of ascending  rami  or coronoid processes.  The
articular head here, as  well as  in the porpoise,  is directed back-
wards, and is attached  to the skull by  means of strong cellular
tissue, filled with oil.
  In  the hare, rabbit, and guinea-pig, of the order rodentia, the
coronoid process  is very small;  in others, as squirrels and rats, it
is pretty  large.   The condyloid,  or articular process, is compressed
latterally, directed from  behind forwards, and larger in front than
behind.
  In the  carnivora, the articular head is directed  transversely, and
so closely adapted to the glenoid cavity of the temporal bone that
the jaw retains its situation after the destruction  of  the ligaments.
This  is well seen in  the marten and sea-otter.   In the ruminants
the condyle is very flat, to admit of the  lateral  motion necessary
during the process of rumination.  In the carnivora, rodentia, and
ruminantia, the  two halves of  the  lower  jaw  are never firmly
united—in this particular  affording  us an instance  of the perma-
nence of a condition in other mammalia,  which in man is peculiar
to the earliest periods of life.
  Swine have two  small  bones  placed at  the aterior openings  of
the nares for the  support of the snout.  In fine, it is to be remarked
that  the  crania  of  all the  quadrumana, together with the other
mammalia, are distinguished by  the comparative  size, great length
and projection of the  jaws.
  Anterior extremity.—This extremity in  the lower animals cor-
responds  to the superior of the  human subject,  and contains all
the elements of it. modified  according to the habits of the animal.
Sometimes connected to the trunk by means of muscle only, as  in
the cetacea, pachydermata, ruminantia, and solipeda; in  other in-
stances by ligament and muscle,  as seen in the insectivora.
   Clavicle.—The importance of this bone, in the  motions of the
upper or  anterior extremity, may be well estimated  by the fact of
its being present in those animals only whose habits of life require
free and varied motions of the shoulder.  Thus in the quadrumana
it is strong and curved, as in the human subject.   The bat, hed^e- 
VERTEBRATA.
33
hog, and mole, among the insectivora, afford examples of clavicle
in  its  highest degree of development.  It is very  perfect in  the
rodentia, as the squirrel, beaver, rabbit, rat, &c.   Among the eden-
tata, those  animals only whose habits are fossorial possess clavicle,
as  the ant-eater, the  dasypus, and  the gigantic  megatherium;  in
the last named animal it presents the peculiarity of being articulated
with the first rib instead of the sternum.
  Where the anterior extremity is employed merely for the purpose
of progression, we  find no clavicle, as in the pachydermata, rumi-
nantia, cetacea, and solipeda.  In the carnivora, where  there is a
slight increase in the range of motion of the anterior extremities,
the clavicle exists  in a rudimental form, and its development is in
proportion  to  the motion enjoyed; hence it is small and short in
the cat, the bear, and the dog; in  these animals it has no attachment
to the sternum or scapula, but lies loose among the muscles.
  Scapula.—This bone forms an essential element of the thoracic
extremity,  and exists  wherever the latter is fully developed,  but
greatly modified, according  to the  uses to which the extremity is
applied.  The cetacea, in general,  have a  large scapula of a trian-
gular form; the  pachydermata, ruminantia, and solipeda, have a
long narrow scapula placed perpendicularly on  the anterior and
lateral part of the chest.  In the  carnivora and rodentia, where
strength  and freedom of motion are  required, the scapulas are placed
obliquely over the ribs; and it is  interesting to observe how the
obliquity of the  glenoid cavity varies with  the motions  required.
This fact has not escaped the observation of the horse-jockey, who
is well aware that the upright shoulder is  the mark of a stumbling
horse.
  Humerus.—When the fore-arm and hand are used for seizing
objects, as  in apes, many rodentia and  carnivora, or for flying, as
in  the bat, the humerus is  formed essentially in accordance with
the human type.   On  the contrary, when the anterior part of the
member  is but slightly  developed, as in the cetacea, the bone is
short and thick;  and in the whalebone whale, it is nearly as broad
as  it is  long.   In the mole it is short, thick, and  strong;  its tuber-
osities greatly developed, and its upper extremity  presents two arti-
culating surfaces, one for the scapula, and the other for the clavicle.
This large size of the bone  prevails in all the other fossorial ani-
mals, as the mighty megatherium, the pangolins, beavers, ant-eaters,
and monotremata.  The humerus of the lion is  remarkable for
being perforated by the brachial artery and nerve, in order to avoid
being crushed by the  huge and powerful mass of muscles exhibited
in this part of  the economy of the king of beasts.
  Fore-arm,.—The radius and ulna are very short in the cetaceans,
and in most of them  consolidated together at both extremities.   In
the cheiroptera they  are long, slender, and firmly united, to accord
with their  mode of progression by flight;  in some the olecranon is
wholly absent, and in others, as  the vampyre, it exists in the form
of a patella.  The ruminants and solipeds  have these bones con-
     7—g                                          cvers 3 
34
EVERS'S COMPARATIVE ANATOMY.
solidated into one.  The rodentia, many carnivora, pachydermata,
insectivora, and  edentata, the bones are distinct throughout, but
admit of no  motion.  The sloth, however,  among the edentata,
enjoys great freedom of pronation and supination;  here the bones
are long, arched, and widely separated in the  centre.
   Carpus.— The bones composing  this  part of the extremity are
usually disposed in two rows, as in man, though the number almost
invariably differs from  that  model.  The  following  is Cuvier's
statement of their number:—In man and the elephant. 8; in apes,
the hare, and the mole, 9:  in the solipeda, carnivora and several
rodentia, 7 ; in the ruminantia from 6 to 7 ; in the edentata, 6; and
in cetacea from-4 to 7.  In apes, carnivora, and several of the un-
gulata, the pisciform bone is very large, and by affording attachment
to the flexor  muscles of the hand, performs  the office of os calcis
in the foot.  The  simias, in general, have nine  bones in the carpus—
another  distinction between their hand  and  that of man.  In the
most anthropo-morphous of them, the chimpanse and the ourang-
outang, the ninth is a sesamoid bone in the tendon of the abductor
pollicis Iongus.
  The metacarpal bones in  the  whale  are five in number and
flattened  in the  form of phalanges.  These last are,  two in the
thumb, three in the little finger, four in the index and ring fingers,
and  five in the middle, collectively forming a short but strong
paddle.  The shovel-shaped hand of the mole consists of five fingers,
each  having  a  metacarpal bone and three phalanges.  In the
bat the thumb is short, and not included within the flying membrane,
The metacarpal bones are long, slender, and cylindrical:  the distal
phalanx is hooked, and sustains a nail by which the animal suspends
itself.  The simiae  have these parts constructed as  in man, except
the thumb, which is small, and extends only to  the metacarpo-pha-
langeal articulation.  In  bears and badgers the five fingers are of
equal length, and parallel to each other.   In  the endentata several
of the fingers disappear; for instance in the two-toed ant-eater, the
thumb,  index, and little  fingers,  are  merely rudimentary; the
middle finger, however, is proportionally developed.
  Among the ungulata the hand is  still  more diversified ; the ele-
phant, for example has five fingers all united into one mass within
the skin.  The pig almost wants the thumb ;  he, however, has four
perfect fingers, but walks only on two.  The ruminantia have but
two fingers, each metacarpal bone supporting three phalanges.  In
the solipeda there is but a single finger; for  instance, in the horse
the carpus corresponds to the  knee ;  the metacarpal bones are con-
solidated into one, cannon bone, behind which there are two small
splint bones, commencing  broad at the knee, and terminating in a
pointed  manner behind the lower third of the cannon bone    Here
we meet with three phalanges, the first  called  pastern, the second
coronet, and the third coffin bone.
  Pelvis.—It has  been  truly asserted that in the human skeleton
alone, a true pelvis is to be found.   This arises from the form and 
VERTEBRATA.
35
manner of connection of the  bones entering into the formation of
this  cavity.   The chimpanse and elephant afford us the nearest
approach  to the human  formation, even here the ilia are narrow
and elongated ;  and the sacrum and coccyx are flat, contracted, and
continued in a direct  line with  the spine.  Next in the order of
development may  be ranked  the  rhinoceros, the ox, the horse, the
carnivora and  the rodentia.  In ant-eaters, moles, and shrews, the
symphysis pubis  remains open ; and  in  the two latter genera the
pelvis is so small that the pelvic viscera are placed without it.  The
megatherium and  sloth, however, have pelvis of large dimensions.
Some-of the edentata, as the dasypus, have the  ilia joined to the
sacrum.  In others, as the sloth  and some of  the ant-eaters, the
ischium is connected with the sacrum, forming an ischiatic foramen,
instead  of a notch.   The cetacea  present but slight rudiments of a
pelvis in  the form of two  small bones united to each other and to
one of the vertebrae by cartilage.   Finally the  marsupial animals
present  a  small, elongated pelvis, especially remarkable  for the pre-
sence of two particular bones not found in any other niammiferous
animal  even in a rudimental state, and named ossa marcipialia.
These  bones are attached, but not articulated, to the anterior part
of the  pubis, near the symphysis; each  is about three inches long
in  the  kangaroo, flat, with  anterior thin, and  a posterior  thick
edge.   The bone  is triangular in form, the broad end being at the
pubis, while the narrow  has  attached.to  it the abdominal muscles.
The  use of these bones  is  to support  the marsupinm, or abdo-
minal pouch, in which the mammary apparatus is lodged, and the
young animal nurtured.
   The  posterior or abdominal extremity is altogether absent in
the cetacea.  In  the other mammalia inhabiting the sea, the seal,
for instance, the  several elements of  the posterior extremity, even
the  toe-nails,  are  distinctly  recognisable,  but  consolidated  by a
membranous web into a kind of caudal fin.
   The  femur  in  the  lower  mammalia  is short and straight; the
neck is either absent or  but little developed, the head being placed
vertically over the shaft.  The trochanters and linea aspera are
badly marked.  This bone is shorter than the tibia, the  converse to
what obtains in  man.   In the megatherium its thickness equals
half its length.  The trochlea is a deeper and the  transverse
diameter  of the condyles less than in  man.
   The  patella is usually present  in the mammalia; best developed
in the  pachyderms, solipeds,  and  monotrems; least so in the carni-
vora and quadrumana;  and wholly absent in the marsupiata and
cheiroptera.
   Tibia  and  Fibula.—Throughout the mammalia  these  bones
coincide pretty nearly with those of the fore-arm.  As in man, the
tibia forms  the chief bone of the  leg.  The fibula is analogous to
the  ulna, and is  found only  in a rudimentary state in the solipeds
and ruminants, as the latter bone was  in these animals.   In the
solipeds, the fibula is applied to nearly the upper half of the outer
surface of the  tibia, being  pretty  large above, and ending in a fine 
36
EVERS'S COMPARATIVE ANATOMY.
point below.   Ruminants, on the contrary have  the  fibula better
developed inferiorly where it forms the external nulleolus and ex-
tends but a short way up the leg.   Pachyderms, and all the ungui-
culata, possess a fibula well developed ;  and  in sloths  its lower
extremity ends in  a  conical point,  which enters  a corresponding
cavity in the astragalus.   In the rodentia, and insectivora, particu-
larly the mole, the "tibia and fibula are united through their inferior
half.  Carnivora have these  bones  fully developed and detached:
this  is well seen in the phocidas and felines.   In the dog they are
united posteriorly.
   Tarsus.—The  bones  composing this part of the foot  for the
greater  part  resemble  those of man.   The cheiroptera present a
remarkable peculiarity in the formation of a  long slender bone,
extending from  the  back of the os calcis half way to the tail, and
enclosed within the flying membrane.  Cuvier and Meckel supposed
it  to  be  a portion  of the os calcis,  whilst Daubeton conceived it to
be a distinct bone.  On the inner side of the tarsus of the  mole, a
sickle-like process of bone is found, similar to that observed on the
carpus.   The metatarsus and  toes in ruminants and solipeds are
disposed  pretty nearly as in the anterior extremities.  The rodentia
and  carnivora have  usually  five toes, the great  one  being often
shortened, or as in cats, dogs, and  hares, altogether absent.  The
quadrumana and marsupiales have the great toe separated from the
rest,  bearing the  same relation to the foot  as the thumb to  the hand.
   Although  the  disproportion in the  respective size and length of
the upper and lower extremities of the human subject, indicate the
different  functions they are designed  to  execute,  yet  they  present
many similarities  throughout their divisions, the construction of
their articulations, and the number and form of their bones.  The
arm, fore-arm, and hand, for 'instance, resemble the thigh, leg, and
foot;  the os innominatum may be  compared  to  the scapula; the
hip,  knee, and ankle, to the shoulder, elbow, and wrist: and the
carpus, metacarpus, and fingers, to  the tarsus, metatarsus, and toes.
Contrast.—A line  falling  perpendicularly from the shoulder in the
erect attitude, would pass behind the hip.  The upper extremities
diverge below, whilst the inferior converge. The deep acetabulum,
and  the  strong  tight, capsule of the  hip, may be well contrasted
with  the shallow glenoid cavity, and weak,  loose capsule of the
shoulder.  The  lower extremities  are  as long as the head and
trunk together, being only equaled  in this respect by the kangaroo
and  jerboa.
   The great length of  the shaft and neck of the femur, its  perpen-
dicularity with the spine, and the depth of its internal condyle, are
characters peculiar to  man :  in the fore-arm every thing conspires
to procure freedom of motion; in the leg, strength and security are
the objects aimed  at.  The hand  is articulated on a line with the
fore-arm, and enjoys free and  varied  motions; the  leg  joins the
foot  at a right angle, and moves chiefly in the angular direction •
the entire surface  of the tarsus, metatarsus, and  toes, rests on the
ground:  the  two latter circumstances are exclusively confined to 
VERTEBRATA.
37
the human subject.   The  parts composing the hand and foot are
disposed inversely as regards their development and importance.
The solid  part of the hand is  small, weak, and but slightly deve-
loped ; that of the foot  is  large, firm, and ossified at an  earlier
period of life.   The fingers are long, slender, and mobile ; the toes
are short, thick, and enjoy only a limited share of  motion.  But the
distinguishing characteristic  of the  human hand is due  to  the
strength, situation, and development of the  thumb, which is oppos-
able to the fingers, and  rendered  useful  in ihe thousand offices
which it has been designed to execute.
   Man is distinguished from all other animals by the great size of
the cranium over that  of the face.  One  method of expressing
these relative  proportions,  is  by the  course of the facial  line, and
the number of degrees in the facial angle.  A line drawn from the
greatest prominence of the forehead to that of  the upper maxillary
bone, in the erect attitude, describes the direction of the face, and
is called the facial line; a second line, perfectly horizontal, drawn
backwards from beneath the basis of the nostrils, forms with  the
other what is  termed the facial  angle, and gives the measure of
the relative prominence of the jaws and forehead.  In the adult
human subject the facial angle varies from  65° to 85°; in children
it reaches  90°; a sufficient proof of its inadequacy as a standard
for the measurement  of intellect.   The  situation of the foramen
magnum, and  occipital  condyles, being but little posterior  to the
centre of gravity, are also distinctive  characters of man.  A line
drawn forwards parallel to the plane of the foramen magnum, will
come out just under the orbits.  In the ourang-outang this line
would pass below the level of the lower jaw, and in most other
animals the foraman  magnum is placed on the  back of the head,
its plane being nearly vertical.  The great weight of the human
head, the absence of ligamentum nuchas, and  of the rete mirabile,
or some analogous provision for moderating the influx of blood to
the brain, coupled with  other  facts  hereafter to be mentioned, in-
contestably prove that man was intended for the erect attitude, and
that he is quite unfit to move on all-fours, as some modern authors
would have it.
   Nature has clad in defensive mail the armed rhinoceros, provided
the lion and the tiger with weapons of defence, clothed the sheep
in wool, and the bear in fur; every animal she  has bountifully
provided in all that was necessary for its subsistence, and adapted
to its destined mode of existence.  Man alone she has abandoned,
weak,  naked, and defenceless, unarmed  in the midst of dangers,
and uncovered to  the winds of heaven.  But she has bestowed on
him gifts far more than equivalent to all  that was denied: she has
given him an illimitable capacity for improvement; she has endowed
him with terrestrial ubiquity, or a capability of inhabiting every part
of the  known  world:  and  above  all, she has conferred on him in-
tellect  and inventive genius, which have raised him to a measure-
less superiority over the  rest of created beings.   By means of these
endowments he has made most animals subservient to his purposes, 
3S
EVERS'S COMPARATIVE ANATOMY.
and obedient to  his commands;  and such as their native ferocity
renders incapable of  utility, or  dangerous to his repose, he has
banished to the "howling wilderness."   In fine, the surface of the
earth  attests his industry  and  intelligence,  and nature herself  is
delighted to obey him.

       Recapitulation.—Characters Peculiar  to Man.
  Biped;  bimanous;  erect attitude; great proportion in the size
of the cranium over that of the face; development of brain ; direc-
tion of facial line; articulation of the head with the spine;  rational;
endowed with  speech  ; prominent chin, and  teeth  of peculiar cha-
racters; absence of ligamentum nuchas  and  intermaxillary bone;
great  transverse measurement  of the chest; curved spine, sacrum,
and coccyx; large pelvis; short arms;  long, powerful thumb, pos-
sessing separate  flexors;  length and  direction of  the neck  of the
femur; depth of internal condyle ; the whole flat of the foot resting
on the ground, and the leg joining it at  a right angle.  Man  is also
remarkable for the smoothness  of his skin, and the slowness of his
growth.
  The following are Camper's measurements  of an ourang-outang,
compared with those of man :
			MAN.			OURANG.	
Whole length of the		body					
from vertex	to heel	i	71 inches.		Less th	an 30 ir	id
Superior extremity,			32	cc	(<	24i	u
Inferior do,			39	u	cc	16	CC
Humerus.			13	cc	It	84	It
Ulna,			9i	cc	cc	9	((
Hand,			81	cc	cc	7	CI
Thumb,			4*	cc	'.(	u	((
Middle finger,			4|	cc	cc	3	cc
Femur,			20	cc	cc	7	Cf
Tibia,			16|	cc	u	7	((
Foot,			104	cc	cc	n 2\	Cf
Middle toe,			2*	cc	cc		cc
FOSSIL bones of animals.
  It is the undivided opinion of geologists, that  there has been a
regular succession of deposits in the earth, and that the remains of
different animals (many of them long since extinct) are to be found
in the several strata.  In the deeper strata, the remains of animals
low in the scale of organisation  are  to  be  met  with ; in hio-ner
strata, oviparous animals of large  size and complex structure'are
discovered; above these are found mammalia; and  still nearer to
the surface, the bones of the  megatherium,  mastodon, rhinoceros
elephant, &c.; and it is now thV prevalent opinion  that man was
created last of all. 
ligaments.
39
  Some bones are found with their animal ingredients remaining
others are fossilised.  The phosphate  of lime  loses its phosphoric
acid,  and the earth  remains incorruptible, while the soft animal
matter decomposes and  dissipates.  The  bone in this  condition
may become fossilised ;  silicious earth, or lime combined with iron,
may pass, by infiltration, into the interstices of the original earthy
matter, and in this state  it is permanent as the solid rock.
  There is preserved in  the Royal Museum of Madrid, a skeleton
of the enormous megatherium of  Cuvier.  It is supposed that  the
animal was seven feet in height; for its femur is three  times  the
diameter, and its pelvis twice the breadth of that of an elephant.
                        CHAPTER IV.

                          ligaments.

   In the lowest grades of animal beings, cartilages, synovial mem-
 branes, capsular or accessary ligaments,  scarcely exist at the joints.
 We here find the movable  points formed  of a  tough connecting
 material,  which,  by its elasticity,  admits of the limited  motions
 required.
   No ligamentary apparatus appears  in the  soft, gelatinous animal-
 cules ;  but the silicious and calcareous spicula of the poripherous
 radiata are supported by a tough, elastic  species  of cellular tissue.
 The plates composing the shells  of the echinida are  united  by
 sutures, and the enarthroidal joints of the  spine by capsules, and
 often by a ligamentum teres, as in the cidaris.  In the larger Crus-
 tacea and coleopterous insects  portions of the skeleton are locked
 into each other, where they move securely,  but to a limited extent,
 in the angular direction without ligaments.   The shells of the con-
 chifera  are  united by their locking teeth, and by a strong, tough
 ligament, which, by its elasticity, constantly tends to the separation
 of the bivalves.
   In the soft,  flexible skeletons of the cartilaginous fishes, the liga-
 ments are few, and confined to the organs for mastication and pro-
 gressive motion.  But in the osseous fishes the ligaments of the
 spine are white, fibrous, dense, and highly elastic ; and here, for the
 first time, we meet the contiguous ends of bones incrusted with car-
 tilage.  In the amphibia, and in the reptiles, the bodies of the vertebras
 are united byenarthroses, furnished with strong fibrous capsules and
 synovial secretion.  Here we have external fibrous  bands, inter-
 spinous ligaments, and occasionally loose cartilages  in the joints.
 The capsular ligaments of birds are thin and  strong: their cartilages
of incrustation are also  thin, but their  joints are  freely supplied
with synovia and their hip joint furnished with a strong ligamen-
tum teres. 
40
evers's comparative anatomy.
   In the mammalia, thick fibro-cartilages appear interposed between
 the bodies of the  vertebras, and  in  the carnassier and climbing
 mammalia, the articular processes are furnished with well developed
 synovial capsules.  The tails of many quadrupeds enjoy full motion
 from their  coccygeal vertebras  being  united by synovial capsules.
 The anterior  and posterior common ligaments  of the spine  are
 powerfully strong and highly elastic  along the pliant columns of
 the cetacea.  In the large  and heavy-headed herbivorous quadru-
 peds, the ligamentous nuchas is of great size and strength, extending
 from the occipital protuberance along the cervical and dorsal spines,
 and in  many  instances, to the coccygeal  and iliac spines.  The
 light-headed,  and active muscular carnassier have  this ligament
 short and small, and in the quadrumana and many of the rodentia
 scarcely a trace of it  is to be found.   The  inter-articular cartilage
 of the lower jaw is met with, in  this, but not in the preceding classes,
 the ligamentum teres is found in most of this class, but is said to be
 absent from the ourangs, the elephant, the rhinoceros, the hippopo-
 tamus, the  kangaroo, the sloths, and the monotremata.   The  two
 toes of those  ruminants, whose habits oblige them to make rapid
and bounding movements,  are secured by strong transverse liga-
ments passing between their phalanges.
                       CHAPTER  V.

      ON THE MUSCULAR SYSTEM IN THE INVERTEBRATA.

   General observations.—In the higher orders of animals, there is
a  close  relation, and  a perfect mutual  dependence  between  the
osseous  and the muscular systems; so much so, indeed, that  the
arrangement of one may be at once inferred by any one who pos-
sesses a  sufficient acquaintance with the other.  It is by means of
this system that animals are enabled to move from place to place, to
seize, masticate, and swallow their aliment, to circulate their fluids,
to  expel their excretions, to produce various sounds, and to accom-
plish an infinitude of other purposes. A system ordained to execute
so many offices cannot fail to present some interesting peculiarities
in  the animal kingdom.  In obedience to  a law, often alluded  to
we find  that the muscles of the  highest classes of red-blooded ani-
mals, during their  development, pass through the  soft, colourless
and gelatinous condition of those of the lowest species before thev
attain the characters  peculiar to them in their highest state of
development.                                    &
   Radiata.—No muscular fibres have been hitherto found  in  the
polygastnc animalcules.  Their rapid motions through the fluids
which they inhabit appear to be accomplished by means of the vibra
tions of minute cilia (which are analogous to the villi on the mucous
surface of a small intestine) growing from the outer  surface  of their 
          MUSCULAR SYSTEM OF THE INVERTEBRATA.        41

bodies ; the cilia which in these animalcules, serve the double pur-
pose of locomotive and respiratory organs, have been observed in
every class of animals, even the mammalia.
  In  the  zoophytes,  the soft,  fleshy mass, which we have  seen
secrete the solid matter of the skeleton, possesses distinct, but lan-
guid irritability: no part of these animals is, however, so irritable
and contractile as their prehensile sacs or  polypi.  It is not till we
arrive  at  the stellerida and asterias  that  distinct muscular fibres
have  been satisfactorily demonstrated ; and in the echinida strong
adductor and abductor muscles are seen attached to, and moving the
jaws of several species.
  Articulata.—Seeing that these animals possess an  extensive sur-
face for respiration, and a highly developed nervous system, we are
prepared to meet with considerable muscular energy.  Accordingly,
in the nematoid entozoa, strong muscular fibres are  seen  taking
different directions: the rotiferous or wheel-animals,  are  also re-
markable for the development of the muscular apparatus provided
for the movements of  their jaws, and long vibratile cilia.   The
common earth worm has distinct muscles appropriated to  the move-
ments of its conical pointed feet, and  its anus is well furnished with
levator  and sphincter  muscles.   The insects and the air-breathing
arachnida  possess a well marked muscular system ;  but of all the
branchiated invertebrata, the Crustacea possess the largest proportion
of muscle ; this they require for  the purpose of swimming, escaping
from  danger, &c.   Although  these animals are provided with ex-
ternal organs  of mastication, the interior  of their stomach  is set
with  numerous teeth, and  its  exterior  provided with  a suitable
arrangement of  muscle.
  Mollusca.—The muscular system presents much greater variety
of form in  this  than in the articulate class.  The tunicata possess
a distinct  muscular coat within their cartilaginous covering, by
which they act on  their entire body, and  empty  their thoracic
cavity;  the orifice of which, as well as the anus, is provided with
sphinctorial muscles.  The foot of the conchifera, by which  they
swim, creep, burrow, or attach themselves,  is hollow, and composed
almost entirely of muscular fibres, taking different directions.  This
foot occasionally admits the water into  its interior,  and is absent
from  the oyster  and others where the shell is permanently fixed.
In  the gasteropoda, the  foot is the largest  muscle in  the  body, and
in trachelipodous gasteropods or those residing in turbinated shells,
its fibres are traceable up to the neck, and backwards to be attached
to the shell. The predaceous gasteropods  possess a powerful mus-
cular proboscis  provided with a fleshy tongue, armed with sharp
conical teeth, as seen in the common whelk, (buccinutn undatum.)
In  the chephalopoda and pteropoda, muscular fins are attached to
the side of the trunk for progressive motion.   And in the naked
cephalopods, a  thin  panniculus carnosus with interlacing fibres, is
spread all over  the body, beneath the coloured skin of the  mantle.
The octopus is destitute of any lateral fins, but is provided with a 
42
EVERS's COMPARATIVE ANATOMY.
muscular  membrane extended  between the bases of its  feet,  by
which it is  enabled to swim ;  but what is curious about it is, that
it swims backwards by  impelling the water forwards.
                        CHAPTER VI.

        ON THE MUSCULAR SYSTEM IN THE VERTEBRATA.

                            PISCES.

   In all the vertebrata the soft parts are uniformly placed external
to the hard resisting textures : in them the muscles of animal life
are generally of a red colour, and connected to bone by at least one
extremity,  through  means of tendinous  or fibrous structure.  In
fishes, the  muscular fibres are soft, gelatinous, and colourless as in
the invertebrata, and the embryos of the higher vertebrated classes.
In  the salmon, however, they are of a higher red, especially about
the  head;   and in  the  lamprey they  are  blackish  gray.  The
arrangement of the muscles  in the osseous fishes is  such, that a
large mass extends from head to tail on each side, divided by fibrous
bands into  numerous strata.  The active movements of fishes are
not  subject to much variety; their  ascent or descent is  effected
by the  compression  or  expansion of the air-bladder,  and by their
pectoral fins, whilst they are impelled forwards by the lateral motion
of  the  tail  opposed  by  the  resistance of the  water.  When the
swimming bladder is absent, as in the sole genus, or very small, as
in the cobitis fossilis, the animal either  remains at the bottom, or
swims on one side by the vertical  motions of the tail.   The  remora,
lump-sucker, and others are  provided with a muscular disk in the
form of a  sucker, by which they adhere to other fish  or bodies
moving through the water:  so powerful is the muscular tail of the
salmon, that, aided by the great elasticity of its spine, it is able to
mount  over cataracts fifteen feet high.  The  shark  is especially
remarkable for speed, so  much so, that according to a calculation of
Sir  E. Home, it would,  if not compelled to rest, swim over the cir-
cumference of the globe  in thirty weeks.

                          AMPHIBIA.

   The proteus, siren, and the  tadpoles of the higher  anurous spe-
cies,  are moved through the water  by the same kind of lateral
motion of the spine and tail as in fishes.  The great lateral mus-
cles  that accomplish these  motions are still pale,  bloodless  and
feeble,  and their connecting cellular tissue is  soft, scanty' and
colourless;  the muscles are slightly connected to the skin, and pre-
sent but little appearance of tendinous structure.  So far'the mus-
cular system  closely resembles that of fishes, but in the adult state 
MUSCULAR SYSTEM IN THE VERTEBRATA.         43
of the anurous species, it presents characters very remote from them,
arising from their great extent of respiration, and their inhabiting a
rarer medium.  The oblique caudal muscles in the tadpole of "the
tailless tribe, become absorbed with the vertebras to which they are
attached, as the animal  assumes its permanent form; but its change
of  habits is still provided  for by the great  development  of the
muscles of the  posterior  extremity, in fact they closely  resemble
those of the human leg; and  hence the act of swimming in  man
is an  accurate imitation of that of the frog.   In this  animal, the
extensors are much stronger than the flexors of the leg, and those
of the arm are but feebly developed.

                           REPTILIA.

   The rarity of  the medium through which the air-breathing rep-
tiles move,  at once declares an increased development of muscular
energy in this class.  In the progressive motion of serpents, their
vertebral column forms several S-shaped lateral curves; is shortened,
and again stretched forwards, whilst the posterior part  of  the body
is fixed: this rapidly performed constitutes a leap or dart.  The ribs
being free at their distal extremities, admit of extensive  motion, and
are  furnished with large intercostal muscles  of various lengths,
some passing from rib to rib, and others over one or more to have
distant insertions.  These muscles have small shining tendinous
bands, by which  a  great  number  can be attached to a small space,
and thus admit  of great variety in the movements of  the  ribs,
which are  not only subservient  to respiration, but to progressive
motion in these animals.  The muscles of the head are strong, and
in the rattle-snake  and others, a  portion of the temporal extends
forwards like a buccinator, to  embrace the poison gland and force
its secretion into  the perforated fang.
  The saurian reptiles possess members sometimes organised for
progression  on the surface,  sometimes for  climbing, sometimes for
swimming,  and  occasionally for  flying; hence their muscles  are
more numerous and complicated than in serpents.  A  rudiment of
diaphragm may be perceived in the dragons and geckos ; and in the
prehensile tongue of the chameleon there resides a beautiful muscu-
lar apparatus ordained to govern its stealthy movements in obtaining
his food, and as Sir C. Bell aptly describes it, he lies more still than
the dead leaf, his skin is like the bark of the tree, and takes the hue
of surrounding  objects.  Whilst  other animals have  excitement
conforming  to their rapid motions, the shriveled face of  the  cha-
meleon hardly indicates life; the  eyelids are scarcely parted  ; he
protrudes his tongue with a motion so imperceptible towards  the
insect,  that  it is  touched  and caught more certainly than  by the
most lively action.  In the chelonia, the muscles of  the extremities
together with those of the shoulders and pelvis are well  marked,
whilst  those of the  jaws, lips, and chest are almost wholly absent. 
44
EVERS'S COMPARATIVE ANATOMY.
                            AVES.

  A greater degree of uniformity pervades the muscular system of
this than any other of the vertebrated classes, yet it will be found to
present many peculiarities.  From  the rarity of the element they
inhabit, as well as from their rapid and long continued movements
through  it,  their muscles require  a considerable degree  of vital
energy, hence they are red,  vascular, dense, and irritable in the
high flying and rapacious tribes, although  pale, soft, and feeble in
those  of heavier and  slower  habits.  The  fleshy portions of the
muscles  are short  and thick, whilst the tendons are long, slender,
dense,  and  often  ossified; their trunk  being almost  fixed, the
muscles of the dorsal and lumbar regions are feeble and indistinct,
those of the neck, on the contrary, are well developed in accordance
with the perfect and varied motions of this part of the spine.  The
muscles of the abdomen are week and  feeble, and the diaphragm so
imperfect in  the centre as to allow the  heart to come in  contact
with the liver as  in reptiles.   Of all the  muscles, none reach so
great  a degree of development  as  those of  the anterior  extremity,
especially those attached to the humerus.   Birds possess three pec-
toral  muscles,  an anterior,  middle,  and  posterior: they  are  all
attached to the sternum and the proximal extremity of the humerus.
In birds of flight, the great pectoral often equals in weight all the
other  muscles of the body combined.  The latissimus dorsi and
deltoid are feebly developed,  whilst the psoas, obturator externus,
and quadratus lumborum, are wholly absent.  The  muscles of the
lower extremity are remarkable for their long, slender tendons, and
especially for the beauty and perfection of the mechanism by which
they support the bird when asleep on  roost, without any muscular
action.   This is accomplished by the gracilis, which, arising from
the pubis, descends along the inner side of the thigh, and ends in a
strong tendon, which passes in front  of the knee-joint,  and subse-
quently over the projection of the  heel to  terminate by attaching
itself to the outer origin of the flexor digitorum perforatus.  From
this disposition it  results, that the more the  joints are bent, the
firmer the twig on which the bird rests, is grasped, and the heavier
it  sleeps,  the  more secure it is.  Every one  is familiar with the
fact of birds  generally sleeping on  one leg, this is  for the  purpose
of throwing  the entire weight of their body on it, and so grasping
the firmer,  and in order to  increase   the effect by adding to the
weight of the body, some birds are in the habit of never going to
roost  without grasping a  stone, or some  ponderous body in  the
other foot.
   Flight, which is the  most chracteristic mode of progression in
birds, is effected by the animal springing into the air ; orf where the
legs are so short, and the wings so long that it cannot  jump high
enough to gain the requisite space for the expansion of the wino-,
it  throws itself from  some elevated  point.   The humerus is next 
           MUSCULAR SYSTEM OF THE VERTEBRATA.         45

raised, and  the  fore-arm extended, a considerable extent of sur-
face  thereby gained;  the  entire  member being  then  forcibly
depressed, the resistance which it  receives from the air, effects the
elevation of the  bird ; velocity of flight depends upon the rapidity
with which  these strokes succeed each other.   The eider-duck is
supposed to fly 90  miles an hour; the  hawk  150, and every one
has heard of the falcon belonging  to Henry IV.  king of France,
flying  in one day from Fontainbleau to Malta, a distance of 1350
miles.

                          MAMMALIA.

   Some of the  animals composing this  class are destined to move
like fishes  through a watery element, some to  fly through the air
like the feathered  tribes, some to  climb  treess, some  to  dig and
burrow in the earth, and others to walk upon its surface.  Habits
so diversified bespeak corresponding diversities of muscular arrange-
ment.  Many approximations to the  human type present themselves
on the one hand, and indisputable recurrences of simpler forms on
the other.   The fleshy portions of the muscles are generally large
and plump, proportioned to the  size of the body, or the massive
bones  of the skeleton.  The respiration being  here less extensive,
and the circulation more  slow, than in birds, the  temperature is
lower, the  muscular fibre less dense, and  the tendons less prone to
undergo ossific changes.
   The arrangement of the  muscles in the cetacea nearly coincides
with  that in fishes, the latter moving horizontally, the former chiefly
in a  verticle direction.  The muscles of  the ribs, spine, pharynx,
os hyoides, and exterior nares, are well developed, those of the pelvis
and posterior extremities disappear with those parts, and the muscles
of the anterior  extremities  are curtailed  and  simplified,  least so,
however, in the phytophagous cetacea.   The large herbivorous
quadrupeds  require  strong muscles to  move their massive and
heavy trunks, and the active and  predatory habits of the carnivora
demand a still greater development of this system.  In the ruminan-
tia, pachydermata, and those animals without clavicles, the anterior
extremities are placed under the trunk, which is suspended between
their long vertical scapulas by the great serrati muscles, in many
instances prodigiously developed.   The buffalo,  the bull, and others
of the ruminants, with many of the pachyderms, have  the muscles
of the neck  large  and powerful to move their heavy heads, which
are often armedwith large  teeth,  tusks, a  proboscis, or huge horns.
The  external muscles of the ear are greatly developed in many of
the herbivorous quadrupeds, and  the muscles  of  the nose in the
hog tribe.
   The panniculus carnosus, which is thin, and finely spread over
the trunks  of the  pachydermata, is strong and fleshy in the soft
skinned ruminantia, where  it is attached to"the  humerus and to the
femur.  In  the mammalia covered with spines, as the echidnia, the 
46
EVERS'S COMPARATIVE ANATOMY.
hedge-hog, and the porcupine, and those covered with scales, as the
manis and  the  armadillo, this  muscle is  important  in  erecting or
moving these epidemic organs,  and in coiling or uncoiling the booy
In the mole, and those animals that dig the earth, the flexors of the
arm, the pectoralis major, the lat.issimus dorsi, and the  teres major,
are of vast size.  In the rodentia, the muscles are pale, and those 01
the jaws of great magnitude. The marsnpiata have the panniculus
carnosus extended over the pouch in such a manner as to support
the vouncr  abortive-like foetus, and force the mammary  secretion
into'its mouth.  The arrangement of the muscles  approaches nearer
to the human type in the  quadrumana than  in  any others of the
mammalia.   In them the flexor muscles are strongly developed  on
all their extremities.   The thumbs, have  no  long separate flexors,
but receive tendons  from the flexors of other fingers.  The plan-
taris muscle, which is  very fleshy in monkeys, instead of termina-
ting, as  it does in  man, by insertion in the os  calcis, passes over that
bone to  be connected with  the planter fascia and flexor perforatus.
In other quadrupeds it passes over the os  calcis to  the  sole of the
foot, and supplies the  place of the flexor digitorum brevis.  The
glutasus maximus, which is the largest muscle of the human body,
is small and feeble in the simias  and other animals, its chief use being
to support the trunk upon  the lower  extremity, and thus assist in
maintaining  the  erect  attitude,  and not, as the pious  Spigelius
imagined,  to  form a soft cushion  for the body  to rest on during
divine cogitation.
   Finally, the extensors of the  knee, the flexors of the toes, and the
other muscles forming the calf of the leg.  are relatively larger in the
human  subject  than in any other animal.
RECAPITULATION.
  1. Muscular fibres have been satisfactorily shown to exist in the
higher species of the radiata.
  2. Muscle  is found all through the articulate and  molluscous
classes, but better and more uniformly developed in the  former.
  3. The soft parts are  uniformly placed external to the hard, in
the verfebrated classes.
  4. The muscles in fishes  are generally soft and pale,  as  in the
lower classes.
  5. In the amphibia, the muscles present different  characters in
the tadpole and adult state.
  6. Great variety in the reptiles, chiefly referable to their diversi-
fied habits.
  7. The  muscular system  in  birds  is characterised  by  great
uniformity throughout the class.
  8. The muscles  of the  aquatic  mammalia resemble  those  of
fishes.
  9. Serrati magni greatly developed in the quadrupeds not pos-
sessing clavicles. 
           NERVOUS SYSTEM IN THE INVERTEBRATA.        47

  10. Panniculus carnosus best marked in the echidna, the hedges-
hog, the  porcupine, the manis, the tatu, the marsupiata,  and the
thin-skinned ruminants;  less so in the pachydermata, and absent
from some, as  the  hog.   It is found in monkeys, but not in the
chimpanse.
  11. Lattismus dorsi, teres major, &c, are very powerful in the
mole and ant-eaters.
  12. The plantaris, which is rudimental  in man, is large in mon-
keys and some  quadrupeds.
  13. Man is characterised by the magnitude of his buttocks, thighs,
and calves.
                       CHAPTER VII.

       ON THE NERVOUS SYSTEM IN THE  INVERTEBRATA.

  This system, when perfectly developed, consists of an internal or
central, and an  external or circumferential portion ;  to the latter
belong the nerves and ganglions ;  to the former, the spinal cord, the
medulla oblongata, the cerebellum, and the cerebrum.  The  nervous
system presides over the movements of our muscles and the sensi-
bility of our bodies; by  it we are  connected with surrounding
objects, and  an injury inflicted on  any part of  the body, at once
declares the extent  of its distribution, as well  as the close relation
that subsists between its several parts.
  The nervous system has been detected in every division, although
not in every class, of the animal kingdom : it commences its develop-
ment at the circumference, and grows  towards the centre, and  its
forms corresponds pretty closely with that of the body of the animal.
  The nervous matter is extremely soft in the  inferior grades of
animals, as well as  in the embryo of the higher classes ; and  its
colour presents some variety, being bright red in the helix stagnalis ;
blackish red in the aplysias ; and bright yellow in the common fresh
water muscle. The nerves are composed of tubes filled with minute
globules.  The  brain is  also composed  of globules, eight  times
smaller than those of the blood, larger and more numerous in the
medullary, than in the cineritious  substance, and in the former dis-
posed in lines which gave it its fibrous character.
  Cyclo-neura, Grant.—In the two first classes of this division,
the  polygastrica and the porifera, no nervous  filaments have been
detected, yet, from their  active movements, their sensibility to the
impression of light, and their consciousness of each others approach,
it is but reasonable  to infer the existence of a nervous  system in
them, though from  its transparency or some other cause, it cannot
be demonstrated.  Both nerves and ganglions are found  to exist in
the  three remaining classes of the radiata.  Distinct  nervous fila-
ments  surround  the  muscular foot of the  actinia; and  in the 
48
EVERS'S COMPARATIVE ANATOMY.
acalephas and echinodermata, fine  nervous filaments  and  small
white ganglions surround the entrance of the alimentary canal.
  Diplo-neura, Grant.—In  this  great  division,  the  nervous
system, presents the same extended form as the body, placed on the
ventral surface of the alimentary canal, and except  in the higher
classes, not  enclosed in an  osseous  sheath.  Among the  higher
forms of the entozoa, as the ascaris, two fine nervous filaments
extend along the median line of the abdomen, separating to embrace
the oesophagus, and  the vulva of the female.   In the notommata
clavulata of the rotifera, we find nine pairs of ganglions disposed
along the course  of the lateral columns.  Scarcely a  trace of ner-
vous system can be perceived in the  simple forms of the annelida.
In the nereids, however, and many others of this class, the sympa-
thetics become quite distinct; and numerous nerves are seen to pass
off  in  the lateral direction.  The common  leech,  which presents
about eighty rings  in  the trunk  of its body, has five and twenty
ganglia placed along the abdomen, approximated  at the two  extre-
mities of the column.  In the most inferior of  the diversified class
of the crustaceans,  the nervous system presents itself in the form of
two slender abdominal filaments,  in imitation  of what we have seen
in the preceding classes, and by  a gradual development from the
peripheral to the central parts, it arrives at  that concentration  of
nervous ganglia around the oesophagus, which connects the highest
of the articulate with the molluscous classes.
  Cyclo-gangliata.—The greater number of  the  mollsuca being
aquatic,  their  nerves present the same pale and  soft  characters
observed in the other aquatic invertebrates ;  hence the difficulty of
indicating their particular distributions. Here as in the radiata, the
same  tendency to accumulate nerves  around the entrance to the
alimentary canal prevails, but in  this  case more generally accom-
panied with  ganglia.   In the lowest  classes of  the  division, as the
tunicata and conchifera, the nervous chords are placed beneath the
alimentary canal ; in the two next classes gasteropoda  and piero-
poda, they are more in the vicinity of the stomach; and in the ce-
phalopoda, which is the last and highest of the division, the nervous
ganglia attain a. more elevated  position, they  cease to  embrace the
oesophagus; and a distinct  brain, as in the vertebrata, with  nume-
rous symmetrical ganglia along the abdomen take their place.
                      CHAPTER VIII.

            NERVOUS SYSTEM IN THE VERTEBRATA.

                           PISCES.

  We no longer find the nervous system perforated by the alimen
tary  tract.   On,  the  contrary,  in all  the  succeeding classes, it 
            NERVOUS SYSTEM IN THE VERTEBRATA.          49

occupies a dorsal situation, and is protected by an  osseous sheath.
In the lowest orders of fishes, as the lamprey, and the gastrobranchus,
we perceive a  repetition  of  the  two nervous columns extending
along the back  as observed in the worm.  This simple condition
resembles the embryo state of this system in the  highest grades of
the vertebrata,  previous  to  the development of  their extremities.
With kw exceptions the spinal chord extends the whole length of
the vertebral column ; whence, from the great number of vertebrae,
it  attains a very remarkable length.  In  some, however,  as  the
lophius piscatorius, it is stated to be very short, forming a  kind of
cauda equina as in man.   It usually terminates in a single thread,
presenting several enlargements throughout its tract, which  corres-
pond very accurately with the number, magnitude,  and situation of
the extremities. For instance, when the anterior members are very
large,  as  in rays and flying-fishes,  the anterior  enlargements  are
proportionally developed ; and where  a large caudal  fin is to be
supplied,  the  chord  presents a  sensible  enlargement posteriorly
where  the nerves  join it.   The  spinal  marrow, here,  as  in  the
human foetus, usually contains a canal of considerable size, and is
distinguished  by an anterior, a posterior, and  two lateral grooves.
From the latter, the nerves arise  by  two roots, the posterior or sen-
sitive root having a ganglion on  it, receives  the anterior root  im-
mediately external  to the  canal.
   The brain  in fishes does  not  fill the  cavity of the cranium, a
considerable portion of it  being occupied by the  soft cellular tissue
of the arachnoid.  The medulla oblongata  is of great length, lobed,
and deeply grooved above by the calamus scriptorius.
   In  most fishes, the optic lobes  are  larger than the hemispheres,
they are hollow and communicate freely with  each  other and with
the fourth ventricle. The earlier they are examined the larger they
are found to be ; their development  is proportionate to that of the
optic nerves and eyes, and inversely to that of  the  cerebrum  and
cerebellum.  The cerebral hemispheres  are small  in  the osseous,
apodal, and cyclostome fishes, and in the plagiostorne species they are
larger than  the optic tubercles. In the osseous fishes they resemble
the embryo condition of the human  brain in being destitute  of ven-
tricles, and having no convolutions on the surface.   In sharks  and
rays the hemispheres attain  a large size, present irregularities on
the surface, and ventricles in their interior.  In  front of the hemi-
spheres are placed the olfactory tubercles, elongated transversely,  and
exceeding in magnitude the hemispheres themselves; subject, how-
ever, to considerable variations, regarding form, size, and situation.
   The cerebellum is  scarcely to be  recognised in  many of the
cyclostome  fishes.   When present it appears as a transverse band,
rising vertically in the osseous fishes, and forming a small vermiform
median lobe, slightly laminated in the plagiostorne fishes. In sharks
and rays not only does  this median lobe attain considerable  magni-
tude, but small hemispheres are developed laterally, corresponding
in size to that of the carpora restiformia.  The pineal gland is found
     8—e                                           evers 4 
50
EVERS'S COMPARATIVE ANATOMY.
in all  fishes, lodged between the hemispheres and optic tubercles,
but so  small in the osseous tribes that its existence has been  ques-
tioned.   These several lobes are covered with a layer of cineritious
substance,  and closely invested by a  delicate  layer of pia mater;
outside of which is the soft, gelatinous, cellular arachnoid tunic, and
all are surrounded by an envelope of dura mater.
  Nerves.—The olfactory nerves are  white  and fibrous ; they are
very larc-e  in the  rays and sharks, and  in many instances form a
ganglion before their termination ;  as may be  seen  in  the  carp.
The optic nerves are developed in proportion to the size of the optic
tubercles and eyes; hence they are large in the carp, and slender in
the eel.  In the osseous fishes they generally cross without any in-
termingling of fibres; in the  plagiostorne fishes  their  fibres  are
blended at the commissure as in the mammalia; and in the skate,
the right nerve goes through a fissure  in the left.  The third, fourth,
and sixth nerves are developed in  proportion  to  the size of  the
muscles they  supply.   The fifth nerve presents a greater size, and
gives off more branches in this class than in any other of the verte-
brata.  The  ophthalmic, superior,  and  inferior  maxillary are dis-
tributed to  the face, palate and lower jaw.   In the rays, and many
other fishes, it sends a branch to the ear, and in  the torpedo, to the
electrical organs.   These latter are composed of a series  of mem-
branous  cells  occupied by a gelatino-albuminous substance,  per-
forming the office of a Leyden  jar or electrical battery.   They lie
in the torpedo on the upper surface of the lateral fin.  In the elec-
tric eel, on  the posterior part of the  abdomen ; and in the silurus
electricus they are situate between the muscles  and skin over  the
entire body.  In the last named fish  the  nerves appear to be derived
from the  pneumo gastric.  Both portions  of the seventh  pair  are
small  and distributed without  any peculiarity.   The pneumo-gas-
tric arises from the side of the medulla oblongata,  behind  the  fifth
pair;  it  forms a  large  ganglion  below  its origin,  from which
branches proceed to the branchiae, the  oesophagus, the stomach, and
rudimentary  lungs.   This nerve gives off also a branch to  the
tongue analogous to the glossopharyngeal, and  one  to  the lateral
part of the body analogous  to  the spinal accessary, both of which
are rudimental in fish.  The  ninth pair is wholly absent and its
place supplied by a branch from the fifth.   The  distribution of the
spinal nerves is very  simple, and their development is always pro-
portioned to the size  of the fins ; the sympathetic is very slender,
and its ganglions small in fishes.  It is  most developed in the pla-
giostorne chondropterygii, and  least so in the cyclostome species ; it
receives filaments from the spinal nerves, and its meshes accompany
the arterial trunks in  their distribution on the digestive, respiratory
and generative organs.

                          AMPHIBIA.

  The condition of the brain, the medulla oblongata, and the spinal
chord  are nearly the  same in the perennibranchiate amphibia, and 
            NERVOUS SYSTEM IN THE VERTEBRATA.          51

in the larva state of those which undergo  metamorphosis,  as  are
observed in the osseous fishes.  The lobed form of the medulla
oblongata,  the small cerebellum, the optic thalami, with the ventri-
cles, and the diminutive extent of the hemispheres, all evince a
degree of perfection not much above that noticed in fishes.  The
spinal  chord is  prolonged, small  and tapering into numerous coc-
cygeal vertebrae, and  without sensible  enlargements  where  the
nerves are to come off to supply the future members.   The meta-
morphosis  of the caducibranchiate species, from the pisciform to
the reptile  state, develope an interesting series of phenomena. The
hemispheres  become enlarged, the cerebellum, which was scarcely
visible, increases in size across the median line;  as the limbs begin
to appear,  the spinal marow exhibits corresponding developments,
but dwindles  posteriorly as the coccygeal vertebras  disappear.  So
rapid are these  changes in the nervous system of the frog, that we
can  appreciate them from day to day.  The sympathetic system is
more distinct in  this class than in that of fishes.

                           REPT1LIA.
   In this  class  the cerebral  hemispheres  exceed in size the optic
lobes, and  contain a distinct ventricle.  The cerebellum is remark-
ably small; and. in the sauria and  chelonia, the  spinal marrow
presents  an obvious enlargement, opposite the attachment of each
nerve.  The  medulla oblongata  is  broad:  the nerves are large,
compared with  the cerebral centres,  but present no peculiarity of
distribution.   The plexuses  of  the sympathetic  are  here more
closely connected with  the  arterial trunks, than  in  the preceding
classes.
                             AVES.
   The brain and spinal chord are in this class developed with more
uniformity and  perfection than in  the cold-blooded reptilia; and
bear a remarkable correspondence with the perfection of muscular
energy which they  possess.  In  a pigeon weighing 3360 grains,
without the feathers, the brain weighed 37, and the spinal chord 11
grains=48.
   The spinal  chord extends from the  foramen magnum  to  the
coccygeal vertebrae, where it is greatly reduced in size, and expends
itself in distributing a few nerves through the lateral foramina. The
length of the  chord is considerable, compared with the  size  of  the
brain ; its  shape is cylindrical; its anterior  and posterior grooves
are very  distinct, as well as a  minute canal  extending through its
whole  length, arising from the  union of the two  halves of  the
chord: the" dilatation of this canal  in the  pelvic region, is  called
"rhomboidal sinus." Tiie  spinal  chord  is chiefly composed  of
white  matter, but contains  a  small quantity of gray,  internally.
Two enlargements occur on  the chord, bearing a relative size to
the development and powers  of  the extremities: in general the
posterior enlargement is the greater, especially when the business 
52
EVERS'S COMPARATIVE ANATOMY.
 of progression devolves on the posterior members, as in struthious
 birds.   The form of the chord  is not altered in the alar  enlarge-
 ment,  but simply increased  by an  accession  of gray and white
 substances;—the  lower one, on  the  contrary, not only  receives
 additional matter, but  the pillars separate, so that the fluid in the
 sinus is merely covered by pia mater.
   The brain  of the bird  differs  from that of the reptile in the
 greater size of the cerebrum, and the more complex  structure of
 the  cerebellum;  it  differs from  the  brain  of  a mammal in the
 smaller size  of the  cerebellum,  and the rudimentary state of the
 fornix; and it differs from the brain of every other vertebrate class
 in. the  inferior position of the  optic lobes.  The cerebral hemispheres
 are generally of a convex condiform shape, with the apex  directed
 forwards: they are  disunited through their whole extent, being
 only joined by a round anterior commissure; they are destitute of
 convolutions,  and have a  small  ventricle in their interior.  The
 olfactory  tubercles  are greatly  reduced in  size, and  retain  their
 tubular communication with the cerebral  ventricles.  The  optic
 lobes are  small ; gray on the  surface, white  internally, and contain
 each a  small ventricle ; they are  connected by transverse  medul-
 lary bands on  which the  pineal  gland  rests, with its  peduncles
 directed forwards over the optic  thalami.   These last bodies are
 covered  by the  cerebral hemispheres, united  by a  commissura
 mollis, and  destitute of transverse sulci.  The  medulla oblongata
 is large and wide; its components are  marked  on the surface,"bnt
 it is without tuber annulare.  The  cerebellum presents a median
 vermiform lobe,  and  rudimentary  hemispheres, sulcated trans-
 versely, with  a faintly-marked  arbor  vitas  in  the interior.   The
 membranes  investing the brain  differ  but little from those of the
 mammalia.
   Nerves.—The nerves in this class  present but few striking pecu-
 liarities, being distributed nearlv as they are in man.  The olfactory
 arise  from the  front of the hemispheres, pass forwards through
 distinct osseous canals  in the cribriform plate,  and are distributed
 in a radiated  manner on the superior spongy  bone.   The laro-e
 optic  nerves arise from the optic tubercles, and  form  a   perfect
 decussation in front of the infundibulum ; where, as in the  iUiana
 an incision displays a mutual  intermixture of the  fibres^  The
 remaining cerebral nerves are distributed pretty  nearly as in mam-
 malia ; the portio  dura is,  however,  small in accordance with the
 insensibility of the superficial parts of the face.  The spinal nerves
correspond in number to the vertebras ;  they arise by two roots the
posterior  having  a large ganglion on it.  The sympathetic, which
is well  developed communicates through  the  anterior lacerated
opening with the fifth and sixth nerves.6 From the third cervical
vertebra to the thorax, it is  contained in the canal in the transverse
processes, in  company with the vertebral  artery.  It form  a series
of ganglions, from the base of the skull to the end of  the corcvx ■
and communicates, in its course, with every neighbouring nerve  ' 
NERVOUS SYSTEM IN THE VERTEBRATA.          53
                          MAMMALIA.

  In this class the increased development of the nervous system is
marked by the size and length of the spinal chord;  the magnitude
of the cerebrum and  cerebellum, and  the number of their gray
deposits and commissures, as well as by the  number and arrange-
ment of the ganglions, together with the extent and systematic dis-
tribution of the great sympathetic.
  The spinal chord is larger in proportion to the size of the body,
but smaller when compared with  the brain,  in this than in any of
the preceding classes;  its internal  canal has almost  ceased to exist,
and its lateral portions are more  intimately  united.  It is shortest
in man, quadrumana, and the tailless cheiroptera,  and longest  in
the cetacea, where, as  in apodal fishes, tadpoles, serpents, and the
human embryo, it presents no posterior enlargements.  In the long-
tailed quadrupeds it extends to the sacrum; the posterior groove is
generally shallow,  though sometimes of considerable depth, as  in
cheiroptera and rodentia.  The medulla oblongata is  small: the
corpora pyramidalia decussate very distinctly:  the olivary bodies
are small, and generally contain a  corpus dentatum in their interior,
and the transverse fibres of the pons or great cerebellic commissure
are well seen.
   Brain.—In the  class mammalia, the  cineritious  matter bears a
small  proportion to the white substance.  The convolutions are
very superficial in the cetacea, edentata, ruminantia, and pachyder-
mata, and wholly absent in the rodentia, and monotremata, as  in
birds; whilst they are deep in man, monkeys, and carnivorous ani-
mals.  The  optic  lobes, without cavities, are  smallest  in man,
quadrumana, and carnivora, larger in the herbivora, and largest of
all in  rodentia and edentata.   A  contrary ratio obtains respecting
the development of the cerebral hemispheres, and the  olfactory
tubercles.  The  anterior and inferior cornua of the lateral ventri-
cles, as well as  the several commissures, are  always present in this
class.  The posterior lobe of the brain, and the posterior cornua of
the lateral ventricle, first appear  in the quadrumana; the former
has no convolutions.
   The vast superiority of man  over all  other animals in  mental
faculties, led physiologists at a very early period to  seek for corres-
ponding differences in  the  brains  of  man  and animals.  They
compared  the weight of the brain with that  of the  body, and their
researches led  them to  conclude that man had the  largest brain in
proportion to his body.   Since the time of  Aristotle  till within a
late period this opinion has been received : but more modem inves-
tigations have  proved that the proportion of the brain  to the body
in some birds exceeds that of man, and that several of the quadru-
mana and  some rodentia equal him in this respect.  The illustrious
Soemmerring proposed another mode of  comparison,  that of the
ratio which The mass of the brain bears to that of the nerves arising
from it, and in this point of view man is decidedly pre-eminent. 
54              EVERS'S COMPARATIVE ANATOMY.
   The brain of man far exceeds in size that of the simiae compared
 with  the nerves proceeding from  it, and in these latter and in the
 seal it is larger in proportion than in other animals,  while  it is
 smallest in  the glires, marsupialia, cheiroptera, and edentata.   The
 largest brain which  Soemmerring  has found in a horse weighed
 1 lb. 4oz., and in an adult man was 2 lb. 5ioz.: yet the nerves arising
 from  the former  were ten times  larger than those of  the latter.
 Coeteris paribus, small animals  have a larger brain in proportion
 to their size, than large ones, and  in  cold-blooded animals its di-
 mensions are very small, compared with those of a higher tempe-
 rature.  The following table shows the relative weight of the brain
 to that of the body in several of the vertebrate  classes of animals:—
   Fishes.—Silurus glanis, one-1887th ; dog-fish, one-1344th; shark,
 one-2496th ; carp, one-5G0th.
   Reptiles.—Turtle, one-56S8th;  colubar natrix, one-792d; frog,
 (amphibious,) one-172d.
   Birds.—Goose,  one-360th; duck, one-257th ; eagle one-260th ;
falcon, one-l()2d ;  sparrow, one-25th ;  canary-bird, one-14th.
   Cetacea.—Porpoise,  one-93d; dolphin, one-102d, one-60th, one-
36th,  one-25th.
   Solipeda.—Ass, one-254th ; horse, one-700th; one-400th.
   Ruminantia.—Ox, one-860th; stag, one-290th; sheep, one-192d;
calf, one-219th.
   Pachydermata.—Wild  boar, one-672d;  domestic,  one-512th ;
elephant, one-500th.
   Rodentia.—Beaver,  one-290th;  hare,  one-228th;  rabbit, one-
152d; rat, one-76th; mouse, one-43d; field-mouse, one-31st.
   Carnivora.—Doer, one-305th, one-47th;  fox, one-205th;  wolf,
one-230th;  cat, one-156th, one-82d; ferret, one-138th.
   Plantigrada.—Hedge-hog, one-168th; bear,  one-265th; mole,
one-36th.
   Cheiroptera.—Bat, one-96th.
   Lemurs.—Vari, one-84th;  mococo,  one-61st.
   Baboons.—Magot, one 105th; great baboon, one-104th ; macaque,
one-85th.                                                  l
   Apes.—Mangabey, one-48th; the monk ape. one-44th ; malbrouk
one-24th.
   Sapajous.—(American  apes) Coaita,  one-41st;  Sai, one-25th-
Saimiri, one-22d.                                              '
   Ourang-outancrs.—The gibbon, one-48th; chimpanse, 26 inches
in height, 11 oz. 7dr.
   Child of six years, one-22d; adult man, one-35th.
   The Cerebellum is smaller in proportion   to  the cerebrum in
man,  the saimiri, and the ox, than in any others of the mammalia
In the human subject  and in ourangs only,  is  it covered bv the
posterior  lobes of  the brain.   The  superior vermiform process and
the hemispheres of the cerebellum are  developed in every  class
in the inverse ratio of each other.  In the saimiri  ape, the cerebel
lum is to  the cerebrum as 1 to 14; in man and the ox  1 to 9 • in 
NERVOUS SYSTEM IN THE VERTEERATA.
55
the monk ape and  the  dog, 1 to 8; in the magot, papio, and wild
boar, 1  to 7 ;  in the sai and hare, 1  to 6; in the mole, 1 to 4; in
the rat and beaver,  1 to 3; and in the mouse, 1 to 2.
   Nerves.—The  olfactory nerves  are  largest in the ruminantia,
pachydermata, and carnivora, smaller in  the cheiroptera and qua-
drumana, and discoverable with  difficulty in many of the cetacea.
In the squirrel, rabbit, hare, and other large-eyed nocturnal quadru-
peds, the optic nerves are very large;  they are small in rats, mice,
bats, hedge-hogs, and subterranean moles, and in the sorex arraneus,
mus typblus, muscapensis, and others, they are said  to be altogether
wanting.   They unite  before the infundibuluin, and forma partial
decussation of their fibres.  The third, fourth, and sixth nerves are
distributed as in man, and are very small in subterranean animals.
Of all  the cerebral nerves, none reaches so great a degree of deve-
lopment as the fifth pair, in the inferior classes of animals and in
the fostal state of the human subject:  it is also of enormous size in
most aquatic  birds. Its branches are freely and extensively distri-
buted in those animals with proboscis, long muzzles, large lips, and
broad  bills, as the  cetacea, ruminantia, pachydermata, carnivora,
and ornithorhynchi, and also  in those  possessing  horns, spines,
bristles, and whiskers.   This nerve is supposed to preside over the
peculiar instinctive actions so remarkable  in those grades of ani-
mals which indicate an inferior degree of mental endowment, and
this opinion  receives strength from the fact of its great size in the
very early periods of human  existence, when we know the actions
are purely instinctive.   The remaining cerebral, the spinal, and the
sympathetic  nerves are distributed so much after the human type
as to merit no particular remarks.
   In  most mammalia the arteries of the brain form a complicated
net-work around the petuitary  body at the base of the cranium
named  rete  mirabile, obviously designed to  impede  the  flow  of
blood to the  brain, in  those animals with pendent heads.   The
veins occasionally run in osseous canals in order to avoid pressure;
this is  well seen' in the cribriform plate of the mole's skull, and  in
the bony falx cerebri of the  porpoise.  A bony falx cerebri is also
found  in the ornithorhynchus,  an animal  which  abounds in in-
stances of anomalous  structure.  Animals  which  possess a bony
tentorium  are of far more common occurrence: it is well developed
in most species of the  cat and bear kind; it is not so well marked
in the  dog, seal,  horse, and wombat, and it is merely rudimentary
in the pig, the rabbit, and the mouse.
   It has "been generally supposed that these structures exist in such
animals only  as jump  far, and that they served the  purpose of pro-
tecting the respective portions of the cerebrum and cerebellum from
undue  pressure during these active movements, but this opinion is
rendered quite untenable from the fact  of their  absence  in  many
animals notable for jumping, as the wild goat, &c, and their pre-
sence  in  those animals alike remarkable for their slow and easy
movements, as the bear.  It  is  more probable they exist for the 
56
EVERS'S COMPARATIVE ANATOMY.
 purpose of obviating  the concussion which would  arise from  the
 strong exertions  in biting;  for such exertions are made by all  the
 animals which possess them, even  by the horse in his wild state.

                       RECAPITULATION.

   1. A nervous system exists in every class of animals, though not
 in all the animals of each class.
   2. In the invertebrate classes it has a peculiar  tendency to accu-
 mulate around the oesophagus.
   3. In all the vertebrata its principal parts are protected by osseous
 sheaths.
   4. The spinal marrow is tubular in the human embryo, and most
 of the lower vertebrata.
   5. This system undergoes remarkable changes in the amphibia,
 during their metamorphosis.
   6. It is highly developed, and with great uniformity in birds.
   7. The chord presents enlargements corresponding in size to the
 members most used.
   8. The spinal chord bears a large ratio to the size of the body in
most mammalia.
   9. Man's superiority is due to his mental faculties.
   10. The brain is larger in proportion  to the size of the nerves
connected with it in man than  in any other animal.
   11. The fifth cerebral, or the nerve of instinct, is very large in
most mammalia, and in the foetal state of the human subject.
                       CHAPTER IX.

                      ORGANS OF SENSE.

  General observations.—The organs of sense are those instru-
ments which are placed upon the distal extremities of certain cere-
brospinal sensitive nerves, whose office being to establish a relation
between the internal sentient principle and the external  objects of
surrounding nature, are necessarily placed in connection with  the
external surface of animals, and generally in the neighbourhood of
the entrance of the alimentary canal.  They are  more numerous
more varied, and more perfect in the higher than in the lower tribes
of animals, but they are  more developed in  the active insects and
others of the articulata, than in  the slow and torpid mollusca and
they attain their greatest degree of perfection in the vertebrata where
the most complicated and delicate  forms  of organisation are  con-
signed to their careful watch.
  Vision.—Organs of vision have been  figured and minutely de- 
ORGANS OF SENSE.
57
scribed in many of the polygastric animalcules; they vary in number
from one in the polygastrics, up to  eight in the acalepha.  In the
rotifera, optic nerves and ganglia are quite  visible, and in the aca-
lepha a lenticular body is superadded.   Visual organs are met with
in almost every class of the diplo-neurose  division ;  in some there
is but a  single eye, in others they are more numerous, and placed
apart on different aspects of the bead.  The medicinal  leech pos-
sesses ten prominent eyes disposed transversely, and the neiris nun-
tia has two large  pairs placed on the upper part of  the  head, and
nearly a hundred smaller ones grouped around the mouth.  Many
of the higher insects present in  their optical apparatus all the essen-
tial ingredients found in the highest forms of the organ.   The eyes
of the crustaceans, are generally compound like those of insects, and
in many instances are moved  by distinct muscles, and covered in
front by a transparent layer of  epidermis.  In the crustacea, as in
insects, the optic  nerves enlarge into a ganglion in the globe of the
compound eye, from which small filaments radiate to the several
lenses of the component eyes.
   Organs of vision are less required,  and  consequently less deve-
loped in  the torpid  mollusca than  in  the  active articulata ; they
never form groups of simple eyes like the myriapods, nor compound
organs like the insects and crustacea.  In the acephalous mollusca
they are simple, separate  and numerous as in worms, but in the
higher forms of  gasteropods, pteropods, and so  on, they are more
complicated, and  but two in number, disposed  on the sides of the
head as in the vertebrata ; and in these possessing opaque coverings,
as the inhabitants of bivalve shells, they are altogether wanting.  In
those, however, which enjoy rapid motion, as the pectem  maximus,
they are upwards of fifty in number, each being about a quarter of
a line in diameter.  The eyes  of these  animals  are  generally flat-
tened in front,  they possess a rudiment of membrana nicitans; the
iris and the  lids are usually motionless, yet in the general plan of
their formation they form a near approach to the condition of these
organs in the higher vertebrated classes.
  In all the  vertebrata the eyes  are two in number, and with  the
exception of a  few species, are symmetrically disposed on the sides
of the head  ; the differences they present being chiefly referable to
the density of the media in which the various animals reside.  From
the density of the watery element through  which fish move, their
eyes are generally of considerable size, except in the worm-shaped
fishes,  as the eel  and the  lamprey.  Sometimes they are directed
backwards or upwards as  in the  star-gazer: less frequently they are
placed on one side, as in the sole.  The eye is spherical posteriorly,
and flattened in front.  The conjunctiva is continued  across in front
of the  cornea, and admits of easy separation from it  in the eel and
many other  species.   The eyelids are merely rudimentary and the
lachrymal gland  is wholly absent.   The sclerotic tunic is  thick,
dense, laminated,  elastic, and occasionally ossified anteriorly.  The
choroid is divisible into three layers, the internal or  tunica Ruys- 
58
EVERS's COMPARATIVE ANATOMY.
chiana, the  middle or the membrana vasculosa Halleri, and  the
external with its shining pearly lustre passes  in  front of the iris
and produces the gold and silver colours  so  much admired.  The
cornea is remarkable for its flatness, the iris  for its immobility, and
the crystalline lens for its density, magnitude, and sphericity.  The
aqueous humour is scanty, the  ciliary processes are  rarely deve-
loped, and the yellow spot  of Soemmering is altogether wanting.
Between the layers of the choroid, and embracing the optic nerve, a
reddish mass of a  horse-shoe shape is found in most fishes named
choroid gland, which, according to some, secretes the  colouring
matter; according to others it is a sort  of rete  mirabile, and others
again look upon it as an enlargement of the optic nerve, whilst  the
prevailing opinion  at present seems  to  be,  that it  is  a  muscle
destined to modify in some  way the reflection of the rays of light.
From the inner layer of the  choroid another body, campanula
Halleri, passes  forwards  towards the  lens, somewhat analogous to
the marsupium of birds.  The  pupil in fishes is large and round,
and the eye is moved by four recti and two obliqui muscles.
   The  eyes of the amphibia are  very  large, and  like those of
fishes contain a small quantity of aqueous humour, and are flat in
front.   They enjoy great latitude of motion  and are provided with
palpebrae and a membrana nictitans;  the superior lid is small and
scarcely movable;  the  inferior large and  very  movable.  The
opaque  integument veils the  front of the eye in the proteus; in
most other characters the eyes resemble those of  fishes.
   The  reptilia present  us with characters  of eyes well suited to
the rare medium they inhabit, such as convexity of  cornea from
abundance of humours, and a compressed state of the lens.  Like
the amphibia, they are furnished with three lids, but unlike them
and  fish,  they are provided  with lachrymal  apparatus; they  ap-
proximate the succeeding classes in many respects, as having ciliary
processes,  a  movable  iris, generally a  vertical  pupil, a dark pecten
prolonged  from the choroid into the vitreous humour, and  osseous
plates around the anterior margin of the sclerotic.  In the  chame-
leon only a small portion of the eye  is  to be seen  through a  narrow
vertical slit between the margins of  the lids,  which conceal  a large
membrana nictitans.
   We  cannot fail to observe  how the  remarkable peculiarities pre-
sented by the organs of vision  in birds, coincide with the vigour of
their respiratory, circulatory, and locomotive systems.   In  all  the
other vertebrate classes we  meet with  instances,  where the eyes, if
not absent,  are at least rudimentary,  but in  this class they  are
remarkable not only for their uniform existence  but for their crreat
size and perfect development.  From the convexity of the anterior
segment of the  eyes and their lateral location, birds command an
extensive  sphere of vision, and in many of the high-flyino- rapa-
cious kind, the organ is prolonged in front into a tubular form but
in aquatic birds the anterior half is more flattened.  The sclerotic
is thin, flexible, and  elastic posteriorly; it  is divisible into  three 
ORGANS OF SENSE.
59
layers, between the middle and outer of which, from 15 to 17 osse-
ous quadrangular plates are placed anteriorly, a  repetition of what
we have seen in reptiles and fishes; these scales overlap each other,
they are connected by the sclerotic, and are capable of  a limited
degree of motion.   The cornea is dense, and possesses a consider-
able degree of convexity, as well  from the abundant  humours as
from  the  pressure of the  surrounding muscles; and, according to
the discovery of Crampton, it is  capable of varying its convexity
by the  action  of a  muscular sphincter attached  to the  posterior
layer at its circumference.  The  choroid  is the same as in mam-
malia :  the iris is remarkable for the freedom of  its motions which,
in some instances, seem voluntary: the pupil is  generally circular,
but elongated transversely in the  goose and dove, and  vertically
oval in the owl.  The chief peculiarity in  the eye  of birds consists
in the marsupium nigrum or pectcn plicatum ;  this wedge-shaped
body, which in  appearance simulates  choroid, is composed  princi-
pally of vessels, and  extends  from the entrance  of the optic nerve
through the vitreous humour towards the  lens which it sometimes
reaches, and gets  an attachment to.   Petit supposed that this sub-
stance rendered objects in front of the eye  more  distinct by absorb-
ing the lateral rays of  light: Home, that by  its muscularity it
retracted  the lens; but this is impossible when it does  not reach it.
   Owen  considers it an  erectile  organ, destined  to push forward
the lens either directly or through the medium of the vitreous hu-
mour;  others look upon it as a  gland for secreting  the vitreous
humour,  and  many are of opinion that it is  placed there for the
purpose of absorbing the super-abundant  rays of  light during the
exposure of the eye to the blazing sun when soaring aloft.
   The aqueous and vitreous humours present no peculiarities;
the lens is flat  in high-flying birds of prey, and  more convex in
the aquatic species ;  it is not  here as in the other classes an achro-
matic lens, in  consequence of the absence of central nucleus.  The
globe of the eye is  moved by four recti and two  oblique muscles.
The  lower lid is the  more movable in  birds and  is provided with a
distinct depressor muscle.  The third eyelid, or membrana nicti-
tans is a conjunctival fold connected with the inner angle of the
eye and  capable of being moved across the organ by a peculiar
 pair of muscles.  One of these, from its shape, is named quadralv.s ;
it arises from the upper  and back part sf the sclerotic;  its fibris
descend in a convergent manner  towards the optic nerve, a little
above which they terminate in a free semilunar aponeurotic margin,
containing a canal.   The second muscle called pyramidalis arises
from the inferior internal and posterior part of  the  sclerotic, its
fibres pass converging to the upper surface  of the optic nerve, where
it forms a slender tendon, which passes through the canal in the
quadratus;  it then passes  from the outer to the lower surface of the
sclerotic, conducted in a cellular sheath till it gains the free  margin
of the membrana nictitans, into which it is inserted.
   By the simultaneous action  of this pair of muscles the membrane 
60
EVERS'S COMPARATIVE ANATOMY.
 is rapidly and forcibly drawn downwards and  outwards over the
 front of the eye, and is restored  to its former situation by its own
 elasticity.  The  lachrymal  gland is situated at the external angle
 of the eye, and at the  internal angle there is another gland named
 Harderian, from its discoverer,  but is nothing  more  than  a con-
 geries of mucous follicles to compensate  for the absence of meibo-
 mian glands.   There  is a third gland in or near the orbit, called
 nasal, its secretion being wholly destined for the nose.
   In the mammalia the organs of vision  are constructed in perfect
 accordance with  the media the animals move in ; they are usually
 placed laterally, but in  the nocturnal quadrupeds they are directed
 forwards as much as  in  man, and in the quadrumana even more
 so.  The eyes are of a large size in ruminantia, rodentia and many
 pachydermata; and  they are small in moles, shrews, whales, and
 in most  cheiroptera.  In  the mus typhlus the  eye  is covered by
 hairy conjunctiva ; and in the mole of Ljbanus, it is so small as to
 be almost  invisible.   The form of the eye is generally spherical,
 but  in the cetacea flattened anteriorly as  in  fish, and in bats it
 approaches to that of birds.  In the cetacea the aqueous and vitre-
 ous  humours  are less abundant than in terrestrial quadrupeds, the
 cornea is flat, the lens is large, dense, and  round, and the sclerotic is
 an inch  thick  posteriorly in a whale, with an eye the size of an
 orange;  the lids are imperfectly developed, the lachrymal apparatus
 is absent, and the superior oblique muscle of the eye is destitute of
 a pully; but the smallness of the eye in this order of mammalia,
 compared with that of fish, bespeaks a higher development of internal
 perceptive organs.
  In  the carnivora the cornea is prominent, the pupil  vertically
 oval, the thick  choroid without pigmentum nigum posteriorly, and
 a blue or  green  tapetum glitters in the bottom of the eye.  The
 cornea covers half the eye in the rat and porcupine, and is elongated
 transversely in the marmot, and  generally in  ruminants.  The
 tapetum  also exists in the ruminantia, solipeda, pachydermata, and
 cetacea.  In the dog, wolf,  and badger it is white, bordered by blue.
 The iris is subject to numerous varieties  as regards its  colour
 structure, and  the shape of the  pupil: the latter is  of a circular
 form in  the rodentia, bats, and simiae; transversely oval in the ru-
 minantia, solipeda and cetacea;  in  these instances the oval  form
 does not seem to pervade the entire thickness of the iris but only
 its external layer.  The retina in carnivora, and  many rodentia as
in some  birds, is confined to the posterior  half of the eve • in the
former on  account of  the breadth  of the  corpus ciliare-'in the
latter on account of the width of the iris.
  In the mammalia the eyelids are formed generally as thev are in
man  the superior  being  the larger and more movable, and the
membrana  nictitans exist  in the entire class, with the exception of
man, apes, and  the cetacea   The ornithorhynchus histrix has but
a single circular lid.  In addition to the lachrymal gland, which is 
ORGANS OF SENSE.
61
found in all  mammalia, except the cetacea, the glandula Harderi
exists in the carnivora, ruminantia, pachydermata, and some roden-
tia.  Instead  of puncta lachrymalia, the hare and rabbit have a slit
opening into the nasal duct;  the eye is  moved by four recti and
two oblique muscles, and in many of the genus felis the superior
oblique  is perforated by the rectus superior:  the inferior oblique
has the same relation to the inferior rectus in the tiger, though not
in the lion.  All the muscles of the eye are said to be wanting in
those  animals in which the organ is in a rudimentary state.
   Hearing.—When we consider the many services arising from
this sense, such as indicating the approach of  danger, conducting
predaceous animals to their prey, the bringing together the two sexes,
&.c, we should expect to find, as we really do, an organ of hearing
in almost every division of  the animal  kingdom.  In the radiated
division of animals no distinct acoustic organs have been  detected;
it is probable, however, that the  undulations  produced by the per-
cussion of outward bodies in the media in which these low creatures
reside, produce some impression, though feeble it may be, upon the
general surface of their bodies.   It is not till we ascend in the scale
as high as the active air breathing insects  of the articulata that we
meet  with special organs appropriated to this sense ; and  here they
consist of auditory nerve, vestibule, and two rudimentary semicir-
cular canals.  In many of the inferior torpid mollusca there do not
seem to be any particular organs devoted to the  perception of sound,
but in the higher cephalopods which approach the nearest to fish
in their general characters,  the organs of  hearing present a similar
degree of complexity.
   Fishes,  like the cephalopodous mollusca,  receive their acoustic
impression by undulations through the dense medium surrounding
them, and  in the lowest  cartilaginous species, as the lamprey, the
organ consists of a simple vestibule,  and  three membranous semi-
circular canals, separated from the cavity of  the skull  merely by
dura mater.   In the  bony fishes the vestibule and semicircular
canals are highly developed, fenestra ovalis appears, and by and by
a rudimentary cochlea and tympanum without air are seen ; in the
cavity of the vestibule two or three small bodies are found, soft and
pulpy in the cartilaginous  fishes, but of  a  stony hardness in the
osseous kind, and composed of carbonate of lime.
   In the aquatic amphibia and in the tadpole state of the reptiliform
species, the organ of hearing possesses a near affinity to that  of
fishes ;  it consists of the vestibular cavity containing its cretaceous
bodies,  the  membranous  semicircular canals,  and fenestra ovalis
closed by stapes, all contained in a cavity of the temporal  bone, and
covered externally by the common integument.  But  in  the adult
state  of the frog and salamander the apparatus is more complicated,
the semicircular canals are lodged in  the temporal bone; the tym-
panum is  closed by membrana  tympani, contains three ossicula
united, and communicates with the fauces by a Eustachian tube.
   The reptiles present a higher development of acoustic organs; in 
62
EVERS'S COMPARATIVE ANATOMY.
serpents, however, they closely resemble the caduci-branchiate  am-
phibia, and* by their vestibular saculus, containing solid cretaceous
bodies, they resemble the osseous fishes.   The  cavity of the. tym-
panum is larger in the saurian than in the ophidian reptiles.   As
we ascend to the higher orders, we meet with a cochlea, which is
the last part of the internal ear that attains perfection, slightly curved
and divided into a scala tympani and scala vestibuli.
   In birds the organ of hearing resembles that of the crocodile ;
there is no cartilaginous external ear, and but a rudimentary concha,
which, however, is compensated  for, especially in rapacious birds,
by a peculiar arrangement of feathers around the external meatus,
which in general they can erect at will so as to catch distant sounds,
and by that means  either flee from danger, or pursue their prey
through dark and gloomy places.   The external ear of owls is fur-
nished with a crescentic fold of integument in the form of a valve.
The oval tympanum, surrounded by bone, communicates with the
air-cells of the cranium by three large openings, and  with  the
fauces by  two short  wide Eustachian  tubes which open by a single
orifice in the swan at the back  of the posterior nares.  There is but
one bone in the tympanum analogous to  the stapes, with processes
rudimentary of the malleus and incus, and moved by a single tensor
muscle, which comes from the occiput and increases the convexity
of the membrana tympani by drawing it outwards.  The cochlea,
though more developed than in reptiles, has not yet reached  perfec-
tion, and the other parts of the internal ear present no remarkable
peculiarities different from the inferior grades of the next  class.
   In the mammalia, generally, the organ of hearing is distinguished
by the development of a true cochlea ; by an increased number of
auditory  bones;  by the formation  of external  canal,  and  by  the
addition of an external movable ear.  We will meet, however," with
evident, though gradual, transitions from the simple state of organ
already seen in the inferior classes, up to man, where it has attained
its most complex and perfect condition.  The concha is very small
in otariae, beavers,  and otters, and wholly  absent  in the cetacea,
seals, walruses, the mole, the manis, and the ornithorhynchus.  The
aquatic shrew and  other mammalia which frequently  go into  the
water, form an approach to the  crocodlile in having the external
auditory opening furnished with a valve.   This  external  orifice in
the dolphin is merely large enough to admit a pin, and  from it a
long narrow winding passage leads to the tympanum through  the
fat which  lies under the skin.   As we ascend through the  mam-
malia, residing more exclusively on the land, the concha acquires
greater size, and by the development of cartilage  and  powerful
muscles it becomes  to enjoy very free and varied  motions   It is
large, movable, and directed  backwards in  the ruminantia  pachv
dermata, cheiroptera, and especially in the timid and feeble rodentia •
and in the carnivora it is small and inclined forwards.
   The cavity of the tympanum communicates with the mastoid cells
contains four movable ossicula and  three distinct muscles • it is 
ORGANS OF SENSE.
63
closed by a membrana tympani, which is concave externally, except
in the whale.  In the ornithorhynchus, which in so many points of
view constitutes the connecting link between reptiles and the higher
classes of  animals, the external passage is long and singularly tor-
tuous,  the  ossicula auditus anchylosed, the  cochlea  represents a
curved horn, as  in birds and  reptiles, and the semicircular canals
project into the cranium.  The Eustachian tube is wide in the ceta-
cea, it. opens at the blowing hole, where it is furnished with a valve;
the cochlea is short and convoluted in one plane in the cetacea, long,
narrow, and spiral in the rodentia, and in the guinea-pig, porcupine,
and aguti, it forms three turns and a  half; the other essential  parts
of the labyrinth agree on  the whole with  those of  the  human
subject.
   Smell.—No organs subservient  to this sense have been detected
in the cyclo-neurose  animals, but in the annelidesof thediplo-neura,
the sense is said to reside in the parietes of their mouths, or the pores
of their air-sacs, and in the palpi, and autennas  of insects.  The
entrance to the respiratory passages, the sensitive tentacula, and
even the whole surface of the body in the higher orders of the mol-
lusca,  are  capable of  receiving odorous  impressions.  The  lami-
nated organs of smell in fishes are placed in two small depressions on
the anterior part of the face; they are  protected by cartilage, lined
by a delicate mucous membrane disposed in radiated folds in the
pike: tufted in the cyprinus, and arranged like the barbs  of a quill
in the carp, ray, and  shark.  These cavities have no communication
with the mouth or pharynx; they are closed in front by a valve
formed of skin and cartilage, and a similar structure partly divides
each into two.
   In the perennibranchiate amphibia, as the proteus and  siren, the
organs of smell in  every respect resemble those of fishes, and in the
more  highly developed  genera, as  frogs and salamanders, they
approach in characters to those of reptiles.  The nostrils  are partly
cartilaginous, partly osseous, and open into the cavity of the mouth.
The olfactory nerves enter by two foramina  in the ethmoid  bone,
and are distributed to every part of the soft pituitary membrane.  In
serpents the nasal cavities  present  rudimentary turbinated bones,
and open posteriorly  by a single orifice.   The turbinated  bones are
larger and more curved in the sauria, and in the chelonia the olfac-
tory surface is greatly extended and concealed by a strong osseous
covering.
   In  birds the external nostrils vary much  as to size, shape, and
situation, they are  generally free and wide, but in some  instances
very small, as in the heron  and gannet.   The septum narium  is
partly bony, partly cartilaginous, and covered by a highly vascular
pituitary membrane in  the swan.   The nasal cavities in birds con-
tain three turbinated  bones and open separately into  the  pharynx,
except in the cormorant where they join previous to their opening.
The olfactory nerves are distributed  exclusively to the membrane
covering the septum narium and superior spongy bone. It is gene- 
64
EVERS's COMPARATIVE ANATOMY.
rally supposed that birds of prey are gifted with an acute sense of
smell, but the experiments of Mr Audubon go to prove the reverse
opinion ; and according to the researches of Scarpa, the following is
the order in which it is enjoyed, beginning with those  in which it
is most  acute; grallatores, natatores, raptores, scansores, inses-
sores, rasores.                                      .
   The organs of smell in the  mammalia are distinguished by the
more perfect  formation of external nose,  by the large size of the
nasal cavities, and  by the latter  receiving several new  openings,
such as the  frontal, nasal,  ethmoidal, sphenoidal, and  maxillary
sinuses.  The external openings are valvular in the  beavers, seals,
and camels, and variously modified  in other animals, according to
their different habits, as in the hog,  elephant, &c.  The turbinated
bones are long and simple in the  rodentia, ruminantia, and pachy-
dermata, and they form a complicated series of labyrinths in the
carnivorous tribes, where an acute sense is  so  necessary to enable
them to pursue their prey through  their dark retreats.  The large
olfactory nerves pass through the numerous openings of the cribri-
form plate, except in the cetacea, to be distributed on the surface of the
turbinated bones.  These nerves are large and hollow in the human
foetus, like  the olfactory tubercles of quadrupeds, and it is interest-
ing to observe how the sense of smell preponderates over all others
in the new  born child,  this can  be easily tested during the nuzzling
of the  infant at the mother's breast, when the loudest sounds  may
assail its ears without effect, and when its visual powers are limited
to the mere perception  of intense light.
   Taste.—A considerable degree of obscurity  prevails, respecting
the enjoyment of this sense  in the different classes of animals, and
although we cannot display  any organ especially appropriated to it
in the inferior tribes of animals, yet it is supposed  that all enjoy it,
from the polygastric animalcules up to man.  It is  generally seated
in, but by no means confined to the  tongue, this organ being absent
in some instances even in the human subject, where the  existence
of the sense has been proved; and in other cases, where the tongue
does exist,  its dense horny nature excludes it from  such an  enjoy-
ment.   The  form of the  tongue differs considerably  in  different
animals; in none, not even  in  the  simiae, is  it exactly like that of
man.   In the cephalopods distinct gustatory villi cover its surface;
in many fishes it has no papillae, and in others it is set with teeth;
in the chameleon it is an organ  of  very peculiar mechanism, and
admits of being protruded for several inches in pursuit of prey,  with
amazing celerity and precision.   This power, for  a  long period a
paradox with naturalists was discovered by Dr.  Houston\o be of an
erectile  nature. In birds it serves chiefly as an organ of prehension
in a few only does it possess papillae, being generally sheathed in
front  by horn.   With few  exceptions  among  the edentata, the
tongue in the mammalia serves as an organ of taste.  In the bisulca
it is covered with a thick epithelium; in the bat, the opossum,and 
ORGANS OF SENSE.
65
especially the lion, and others of the cat kind, it is beset with strong
sharp prickles, for prehensile purposes.
   Touch.—This is the most general as well as the most simple of
the senses, and the degree in which  it exists has reference to the
state of the tegnmentary membrane, and the condition of the nervous
system.  In the invertebrata no organs solely devoted to  the per-
ception of sensitive impressions have been detected, yet there is little
doubt, but that the cilia of most polygastrics, the tentacula of zoo-
phytes and mollusca, and the antennas of myriapods and insects are
subservient to  this sense.   Some fishes  have fleshy sensitive fila-
ments arranged around the  mouth after  the manner of tentacula,
and others have only the skin on the abdomen, or about the mouth,
uncovered with scales, and  capable  of  receiving external impres-
sions.   The tongue among serpents, and the tail among saurian
reptiles,  and some mammalia, constitute their chief tactile organs.
The organs of touch in birds are the bills, the cire in the falconidas
the wattles of the cock, and the caruncles of the turkey.  It must
be acknowledged, however,  that this sense is very limited  in birds,
which is in some degree compensated for by the  free distribution of
the fifth pair of nerves to their horny bills, especially those of the
aquatic species, which procure their aliment from mud.
   In many of  the mammalia the skin is shielded from external im-
pressions by the presence of  horny or spiny coverings, dense furs,
or thick hides;  and it is not till we arrive at the higher orders of
quadrupeds, carnivora and  quadrumana, that the organ of touch
makes any approach to  the perfect development of it observed in
 the human subject.

                        RECAPITULATION.

    1. Organs of  vision exist in every class of animals, and in  the
lowest orders the eyes vary  in number from one  to near 100.
   2. In  the vertebrata the eyes are two and vary much in  form and
 situation.
    3. No organs of hearing or smell have  been  detected  in  the
 radiata.
    4. Our knowledge concerning the organ  of taste is involved in
 much obscurity.
    5. No organ of touch has been detected in the invertebrata.
                        CHAPTER. X

        ORGANS OF DIGESTION IN THE INVERTEBRATA.

   General observations.—The organs engaged in the  function of
digestion  may be  arranged under two heads:  the primary,  or
       8__f                                     evers 5 
66
EVERS'S COMPARATIVE ANATOMY.
essential—including the alimentary  tract; and the secondary, or
tributary,  embracing  the liver, spleen,  pancreas, salivary,  and
mucous glands.                                        .
  There is no organ so universally present, nor so essential, as an
internal digestive cavity, and  hence so often  alluded to as consti-
tuting a line of distinction between  the  animal and the vegetable
kingdoms; indeed there is no class of animals without it, although
it is not found in every species of each  class.  The peculiarities
presented  by the digestive apparatus will  vary according to the
rank an animal holds in the scale of the creation, the kind of food
on which  it is destined to subsist, and the elaboration  that food
may require to undergo.  The alimentary surface of a plant is the
exterior of its  root spread out in the earth, and absorbing, by its
spongioles, the materials for its nutrition, but the alimentary surface
of an animal  is internal, and  continued from  the skin, like the in-
side of a lady's muff.
  Cyclo-neura, Grant—Radiata,  Cuvier.— In  the very  low
tribes of animals the digestive apparatus presents characters equally
diversified as the forms of the  creatures themselves.  The aliment-
ary cavity has often  but one orifice; there  are seldom teeth or
glandular organs, and the food is generally of the simplest sort.  In
the  polygastrica, as the term signifies, the cavities are numerous,
and their  various forms have been well  observed by  Ehrenberg,
who caused these transparent animalcules to swallow fluids coloured
with carmine,  indigo, or sap-green.  The monads and several other
genera have but one orifice which receives the openings of the several
cavities, and from the absence of intestine the entire group has been
named anentera.  In the higher  forms, however, the alimentary
canal is  furnished with an  oral and an anal orifice, the straight,
curved, or spinal intestine receives  the openings of numerous enseal
appendices through  its whole course.  In some  of the small monads
no internal cavity has been detected, and in other genera the num-
ber varies from one up to two hundred, as seen in a paramascium.
Many species  are provided with dental organs in  the form of stiff
spines disposed  around the mouth,  but in none of the class have
tributary or glandular organs been  observed.
  The porifera present a very simple form  of alimentary appa-
ratus, their absorbent canals closely resembling the ramified roots
of plants, and as we  ascend through the diversified series of  the
polypifera or  zoophytes we  perceive the system increasing in com-
plexity from  the  simple, genito digestive sac of the hydra up to the
complicated structure presented by the actiniform polypi, where the
stomach is provided with a  muscular and mucous  tunic lined with
vibratile cilia, and communicates inferiorly with the genital cavities.
The  greater  number of the acalepha possess a simple  broad and
radiated alimentary cavity, suited to their highly organised and
minutely divided food, but in the monostomatous species  which
live on coarser aliment, a cartilaginous masticatory apparatus and
biliary  secretion  are  superadded.  The torpid predaceous echino- 
         ORGANS OF DIGESTION IN THE INVERTEBRATA.       67

dermata afford in the structure of their digestive organs, connecting
links of transition from  the radiated to the articulated classes.   In
the  higher forms of the echinida strong masticating and salivary
organs are provided, the anal orifice, which  in the lower tribes is
placed on  the  inferior surface, gains a dorsal  aspect, which it con-
tinues to hold in the holothuriae and articulated classes.   Thus  we
perceive the digestive cavity, from  being a simple monostome sac,
gradually acquires  the form of a long  narrow canal, open at both
ends, and furnished with salivary and biliary organs.
   Diplo-neura, Grant—Articulata,  Cuvier.—The carnivorous
character of  this great division of the animal kingdom bespeaks  an
alimentary canal, limited in its capacity, straight in its form, and
simple  in  its  structure.  This  canal  usually takes a horizontal
direction, opens at  the two opposite extremities of the body, and is
provided at its commencement with prehensile, destructive, or mas-
ticating  organs.  In consequence of the simple nature  of the food
on which the entozoa subsist, many of them have but a single orifice
to their digestive sac.  In the higher and more perfect forms, how-
ever, of these as well as of the rotifera, the  canal  passes straight
or slightly winding through the body,  presenting an oral and anal
aperture, and surrounded by the genital and biliary organs.   The
cirrhopoda are  remarkable for the great size  of their salivary and
biliary apparatus, and the wide ducts of the latter, which open into
the stomach, as  in most of the invertebrated tribes.
   Among the  annelida the earth-worm is remarkable for its capa-
cious mouth, a small salivary gland, a sacculated stomach, consist-
ing  of three  continuous cavities, and  a narrow,  slightly bending
intestine.  The leech has three horny maxillas, furnished with sharp
teeth, with which it inflicts its tri-radiate wound, the straight, irre-
gularly sacculated  intestine is furnished with ten pairs of lateral
coeca, and  enlarges  into  a small sac near the  anus.   The carnivo-
rous myriapods are provided with three pairs of salivary and two
poison-glands, by their contracted oesophagus and elongated  mem-
branous  stomach, they resemble  the higher species of worms, and
by their  small, narrow intestine, ending in  a  wide colon, they are
allied to the ophidian reptiles.
   The  digestive organs of the insecta  present in an embryo state
nearly alTthe essential  elements of the chylo-poietic system in the
highest classes  of  animals, as  masticating organs, salivary and
mucous  glands,  liver, pancreas, &c.: they will be found to vary,
however, according to the peculiar living habits of the species, and
the quality of their  food.  The alimentary canal usually consists
of a  wide pharynx, a narrow oesophagus, a dilated crop, a muscular
gizzard, provided with sharp, conical, horny teeth, a capacious chy-
lific  stomach, a straight, narrow intestine,  a  short, dilated  colon,
and  a contracted cloaca.  In the herbivorous insects, the  alimentary
canal is  long,  capacious, and complicated.  The gall-bladder  is
usually single,  but  occasionally double.  The cunning carnivo-
rous arachnida resemble the  insects in the arrangement of their 
68
EVERs'ri COMPARATIVE ANATOMY.
masticating organs, whilst their straight narrow alimentary canal
and the compact state of their liver, ally them to the crustacea.
  Like  most  other  carnivorous articulata,  the cunning,  cruel,
aqautic  crustacea?is are provided with prehensile and masticating
organs well suited to destroy the prey in the rich element they in-
habit.   The maxillas vary from  one to five pairs, but are wanting
in the lower  orders.  The alimentary canal is  generally without
convolutions,  and opens by two  apertures.   The decapods present
a narrow oesophagus, leading to a capacious  muscular stomach,
furnished with numerous  solid calcarious teeth, and a straight in-
testine occupying the dorsal  portion of the trunk, and  receiving
near  its commencement the biliary and pancreatic  ducts.   The
salivary glands are absent except in the higher orders, where rudi-
ments of  them are perceived surrounding the oesophagus.   The
mucous  membrane forms rugae in the oesophagus and  stomach,
but not in the intestine, and the peritoneum forms no mesentery.
  Cyclo-gangliata, Grant—Mollusca, Cuvier.—This great divi-
sion  of  the animal  kingdom  being destined chiefly  to  subsist on
soft food, masticating organs are  little required by them, hence they
are often  but slightly developed, and in some cases wholly absent.
But  their food is greatly varied and often coarse, so as to require a
complicated form of alimentary canal, and  a high  development of
glandular apparatus.  The digestive organs of the tunicata closely
resemble those of the conchifera, being a little more complicated in
the latter.  Both are destitute of prehensile or masticating organs.
and  depend for  their supply of food  on the respiratory currents.
They possess a  short wide oesophagus, opening into a  capacious
muscular  stomach, without teeth, and receiving the biliary  ducts.
The intestine is generally short, wide, and  convoluted.   The con-
chifera  differ from the tunicata by their long and convoluted intes-
tine  passing between the  two aortas,  through the fleshy  substance
of the ventricle, and the mass of the liver.  The terrestrial pulmo-
nated gasteropods present a  more complicated digestive  apparatus
than the acephalous mollusca, especially those which  feed on  vege-
table substances.  They are  provided with a pair of horny jaws, a
muscular tongue and proboscis armed  with sharp recurved spines, a
large pharynx, a long oesophagus, and a capacious stomach, divided
in  the  phytophagous species,  into  several  compartments,  fur-
nished  internally with teeth, and receiving the biliary and pancre-
atic secretions.   One or two  pairs of salivary glands lie around the
oesophagus, and  the liver is of considerable size.  The intestine
is long and convoluted, and  opens in common with the genital or-
gans on the right side, near the anterior extremity of the  body.  In
the  pteropods and cephalopods, the oesophagus  passes through the
cranial cartilage  and ganglionic  ring, sometimes  dilating  into a
crop before entering the  muscular gizzard, which  is often  lined
with a thick  coriaceous epithelium.   The  intestine  is  short and
wide in the  carnivorous  species, destitute of ccecum-coli not  dis-
tinguished into  large and small as in the vertebrata, and no where 
VERTEBRATA.
69
imbedded in  the  substance of the liver, as in many of the inferior
mollusca.  The mollusca are without gall-bladder, and as yet no
portal circulation  has appeared.  The entrance of the hepatic duct
into  the  stomach is  guarded by a pair of prominent valves, pro-
longed so into the intestine as to allow of the passage of the pan-
creatic and biliary secretions into the gut during a state of vauiiiy
without entering the stomach or duodenum.
                       CHAPTER XI.

                        VERTEBRATA.

  In this great department of the animal world the digestive appa-
ratus  presents a higher development and a greater degree of com-
plexity than  we  have  met with  before.   The alimentary  canal
always swells out into a distinct gastric enlargement, and is provided
with a large conglomerate liver, spleen and pancreas.   The duode-
num invariably receives the biliary and pancreatic secretions, and
 he salivary  glands are rarely  absent.   The teeth are generally
confined  to the alveoli, and there are none found in the stomach.
As  a  general  rule the canal is longer, larger and more sacculated,
and the  masticating and glandular apparatus  more developed in
the phytophagous than in the carnivorous tribes.

                            PISCES.

  Since  vegetable food cannot  be procured in the unfathomable
depths of the sea, we are prepared to meet with a short and simple
form of alimentary canal in fishes, suited to their predaceous habits.
Vegetable substances might even endanger their lives by an evolu-
tion of gas which would render them specifically lighter than the
water, and cause them to  float  upon its surface with the belly up-
wards.   The teeth of fishes are generally numerous,  destitute of
fangs, laminated, deciduous,  thinly  covered  with  enamel,  and
movable on  the  surface to which they  adhere, till maturity, when
they  become  permanently fixed.  The teeth  of  fishes are often
implanted in  the tongue as in many gasteropods and birds, in the
vomer as in  amphibia, in  the palate bones as in serpents, in the
pharyngeal bones, branchial arches and  os hyoides, as well as in the
maxillary and inter-maxillary bones to  which they are confined in
the saurian reptiles and mammalia;  the teeth are most numerous
in the pike and salmon, and are altogether wanting in some genera,
as  the sturgeon.  As  in serpents, crocodiles, dolphins, and other
predaceous non-masticating vertebrata, the teeth are not opposed to
each other but placed alternately, adapting them to their prehensile
office. 
70
EVERS's COMPARATIVE ANATOMY.
  The tongue is broad, short, and almost destitute of papillae.  The
salivary glands are only rudimentary, and even wanting where me
liver and  pancreas  are well developed, but the mouth is well sup-
plied with mucus.   The short, wide infundibnhform  oesophagus
has an external circular, and an internal longitudinal  layer o  mus-
cular fibres, and is lined with a pale, villous, longitudinally plica ed
mucous membrane provided with numerous mucciperous follicles.
The lar<re gastric cavity is sometimes long and tapering as in the
herrincr^nd sometimes  globular as in the lophius: its two orifices
are  cfosely approximated, so that the food  is retained in it for a long
period, hence,  if we feed a tame  perch till it is gorged, it will not
eat  again for ten or fourteen days; both orifices of the stomach are
sphinctorial, its mucous  membrane is plieated and forms a valve at
the  pylorus with  a  fringed margin, surrounded by a ring of carti-
lage.   The  intestine, in  many cases, does not measure  more than
half the length of the body, in others, however, as the sword fish, it
forms several convolutions, but rarely does it admit of any distinc-
tion into large and small.  In the sturgeon, ray, and shark the anal
is smaller than the cardiac portion, and  the reverse obtains in the
pleuronectes, gadi, murosnae, &c.  In  order to compensate  for the
shortness of the canal and the absence of valvulae conniventes, the
lining  membrane is peculiarly disposed,  being  reticulated  in the
sturgeon, forming spiral turns in the shark and ray, and  serpentine
folds" in the eel.  The rectum here as in  oviparous vertebrata, ter-
minates in the cloaca through which are discharged fasces, urine,
semen, and  ova.  On either side of the  anus there  is an oblique
valvular opening, admitting of free egress, but prohibiting any
thing from without, and  the  air-sac, or rudimentary lung commu-
nicates  by a membranous  tube with  the oesophagus, stomach, or
upper portion of the intestine.
  The  large elongated  liver is of a soft  texture, light colour, and
divided into many lobes, it is provided with arterial and portal cir-
culation, and generally with  a  large gall-bladder as in other pre-
daceous vertebrata.  Several long hepatic  ducts join  the cystic, and
many short  ones  run at once into the fundus of the gall-bladder,
and the short but wide choledochus either  opens separately or in
common with  one or more of the pancreatic  ducts into the upper
portion  of  the  intestine.  The spleen is  small, of  various forms,
attached to the side  of the stomach, generally simple, hut lobulated
in the  shark and sturgeon, as  in some of the cetacea. and in the
lamprey, which has  neither  pancreas nor gall-bladder,  it is wholly
absent, as in the  invertebrata.  The pancreas  which is wanting in
the centriscus, presents every stage of development, from one or
two simple follicles as in the  lophius, chostodon, &c, up to a large
compact, reniform mass, enveloped  in a  muscular tunic, as in the
sturgeon and xiphas.  The large pancreatic follicles are connected
by  loose cellular  tissue, and  admit  the digested food into their in-
terior,  like the biliary tubes of some  mollusca.  The  peritoneum
lines the walls of the abdomen, and surrounds the viscera in the same 
VERTEBRATA.                      71
manner as in snails, and the sepias: it form a small mesentery and
a rudimentary epiploon, and it presents  the remarkable peculiarity
of its cavity communicating with  the surrounding medium by the
two small openings, placed at the side of the anus.

                          AMPHIBIA.

   These  animals, like  the fishes, are  predaceous in  their habits,
and  swallow their food without mastication.   The whole of  them
have prehensile teeth in the palate; salamanders have  them in both
jaws, frogs in the upper only, and the toad and pipa in neither, but
in the toad two  small  transverse rows exist behind  the posterior
nares.   The teeth in the proteus nearly resemble those of the sala-
mander, but in the  siren they are  arranged in a quincunx order as
in many fishes, and  amount nearly to two hundred.  The salivary
glands are  absent in the aquatic, and  merely rudimentary in the
terrestrial amphibia.  In  the toad and  perennibranchiate amphibia
the  tongue  is  short,  thick,  and  fleshy,  but in  the  frog  it is
long* free, bifid, covered with papillae  and mucous follicles,  as in
reptiles   The short, dilatable, fleshy oesophagus, leads to a narrow,
transversely elongated stomach, muscular in  it parietes, and  over-
lapped by a large bilobate liver with a distinct gall-bladder.  In
the young tadpole of the frog the almentary canal is very long, the
intestine which is narrow and coiled, measures ten times the length
of the space from the mouth to the anus, but after the metamorphosis
has occurred, and that the mixed food of the tadpole is changed for
that of a more nutritious nature,  as snails,  worms, &c, the  canal
becomes gradualy shortened to one fourth of its former length.  The
duodenum  has  transverse folds like valvules conniventes, and the
short, wide  colon ends in the cloaca, together with the openings of
the  genital and urinary organs.   The mucous  membrane forms
longitudinal folds in the  proteus,  the triton, the pipa, and the sala-
mander;  transverse folds in the  frog, and  quadrangular cells in
the hyla.   A small pyloric valve  exists in the toad and pipa, and
the valve of the  colon  is distinct in the  frog, the triton, and the
hyla.  The liver, the spleen, and  the pancreas are found in all the
amphibia, varying in shape according  to the form of the animal.
Thus  we perceive in  the lower  orders of  amphibia, an evident
approach in their digestive organs to  those  in fishes, in the  great
number  of  teeth, shortness and  width of oesophagus, absence of
fundus to the stomach, want of distinction  between large and small
intestine, and the magnitude of the liver.  But  in many we discover
an approximation to the higher vertebrata,  in having fewer teeth,
an elongated tongue, fundus to the gastric cavity, distinction between
large and smalf intestine, absence of pyloric and colic valves, and
the"development of transverse folds in the  duodenum. 
72
EVERS'S COMPARATIVE ANATOMY.
                          REPTILIA.

  The ophidian and saurian reptiles chiefly subsist on animal food,
therefore their digestive apparatus will be found to differ from that
of the chelonia which live on vegetable substances.   The teeth of
serpents  are sharp, conical, inverted, unopposed, and set  in loose,
movable  bones, adapted for seizing and lacerating their prey, they
are attached to the maxillary, inter-maxillary, sphenoid, and palate
bones, and  the poison fangs of the venomous species  are perforated
and grooved in  front to transmit  the secretion of the poison gland
forced out  by muscular pressure.   The  tongue is  long, smooth,
sheathed, and  bifurcated.  The salivary glands vary in the differ-
ent species; the sublingual is always present, and the poison gland,
which is analogous to the parrotid, is confined  to the noxious spe-
cies, and  is placed below and behind each orbit.  The long, disten-
sible oesophagus, copiously supplied with mucus, leads to the long,
straight, capacious stomach, longitudinally plicated  and capable of
being distended to many times  the size of the body; it tapers to  the
pyloric orifice, which is provided with a distinct valve, and embraced
by sphinctorial  fibres.   The duodenum presents a villious surface,
and receives the pancreatic and biliary ducts;  the remainder of the
small  intestine is narrow and  convoluted to the commencement of
the short, dilated colon, where there is generally a  circular valve
and a small caecum.   The colon ends in the cloaca together with
the ureters, oviducts, or vasa  deferentia, and  the male organ of
generation,  single or divided, also passes through the cloaca, as in
other  oviparous  vertebrata.  The  liver, spleen,  pancreas, the  kid-
neys,  the testes, and the ovaria present an  elongated form conform-
able  to the shape of the body.  The small intestines are attached
to a mesentery,  and  the large are often sacculated for the purpose
of retarding the  passage of the food.
  As  most  of the sauria are carnivorous like the ophidia, they pre-
sent a form of alimentary apparatus equally simple.  Their prehen-
sile teeth are fewer and chiefly restricted to the  jaws; the stomach
is short and round in the form of a gizzard, with a pair of central
tendons; the small intestine is long in the phytophagous species
as the scincus and iguana, and in all other respects  they resemble
the ophidian reptiles.
  The phytophagous  chelonia  present a  higher development of
alimentary canal than the carnivorous species.   The place of teeth
is supplied  by the sharp horny margins of the jaws; the tongue is
covered with long papilla- ; and  the salivary glands are variously
developed in the different species.   The long, wide, muscular oeso-
phagus leads  to a large fleshy stomach, extended transversely and
without a pyloric valve. The intestine is about  six times the length
of the body,  and the colon presents a short, wide  coecum  and a
circular valve at its commencement in the terrestrial, but not in the
aquatic species.   The alimentary canal is wide and muscular and 
VERTEBRATA.
73
the mucous membrane folded longitudinally so as to form a surface
of considerable extent.   The  rectum dilates into a cloaca which
receives the openings of the urinary and genital organs.

                             AVES.

  Nothing can be more beautiful to observe than the rigid economy
which is  displayed  in  the accurate adaptation of the digestive
apparatus of  birds to the various  and  dissimilar kinds of food on
which, from their diversified living habits they are destined to subsist.
The  absence of teeth  in this class is  supplied  by strong horny
beaks and powerful muscular gizzards, the former performing the
part of cutting,  and the latter of grinding  teeth ; the  form of the
bill will vary according to the food of the different species of birds
and their mode of procuring it, thus in  the climbing frugivorous
maccaws, parrots, and cockatoos, it is broad and powerful to break
the hard  shelly coverings of seeds, and  most of the granivorous
order have a similar structure.  The broad bills of ducks, geese,
and other aquatic species are well adapted for obtaining worms and
other substances from watery or muddy situations, whilst the eagle,
the hawk, the  owl, and other rapacious birds  have short, strong,
arched, dense bills, with cutting edges,  equally suited to seize, cut,
or tear  their living  prey.  The tongue, which in birds serves the
purpose of a  prehensile- organ,  is  as variable in  form as the bills,
being long, broad, and covered with recurved spines in the swans;
short, round, and flexible in  the parrots and cockatoos, and short
and muscular in the struthious birds. The tongue of the flamingo
is very remarkable, it  is composed of an  elastic, cellulo-fatty sub-
stance, its form is nearly cylindrical, the  pointed apex  being sup-
ported by an osseous  plate inferiorly.  A deep groove  runs along
the centre of the upper surface with a row of recurved spines on
either side.   The os hyoides in this class very much resembles that
of reptiles, and the length of  its glosso-hyal element chiefly deter-
mines the length of the tongue.
  Since  the  food for birds remains but a short time in the mouth
and undergoes very little  change there, their salivary  glands are
small.  In the  crow they consist of a series of conical  follicles
situated  along the  sides of the mouth, and opening separately on
its  mucous surface; in most  other  birds, however, there are four
pairs, one  under the tongue, another at the junction of the angles
of the lower jaw, another close to the cornua of the os hyoides, and
the fourth is placed at the angles of  the mouth:  they are most
developed  in the frugivorous species.   The uvula and velum are
not present, and  the narrow laryngeal aperture is protected  by the
retroverted papillae at the base of the tongue, except in the coot, the
albatross, and a few others where  the  epiglottis exists merely in a
rudimentary  form quite insufficient to cover the opening.
  There is a remarkable pouch under the jaw of the pelican which
serves as  a net for seizing fish, and is capable of containing ten 
74
EVERS'S COMPARATIVE ANATOMY.
 quarts of water; a similar provision is found in the swift, the rook,
 the  male bustard at maturity, and other insectivorous birds.   The
 alimentary canal is much longer and more capacious, and the glan-
 dular apparatus  better developed in the  phytophagous birds  than
 in those which subsist more exclusively on animal food. The long,
 wide, fleshy oesophagus, with  a  cuticular  lining,  passes down
 behind  and  to  the right side  of  the  trachea, behind  the  heart
 and between the lungs.   In rapacious  birds it is capable of enor-
 mous dilatation, but in  the flamingo its diameter does not exceed
 half an  inch.  In the frugivorous, insectivorous, and omnivorous
 birds, the oesophagus presents nearly a uniform capacity all through,
 but in the raptorial eagles and vultures,  which gorge themselves at
 uncertain periods, it forms a lateral dilatation at the lower part of
 the neck termed the ingluvies or crop.   And in those birds which
 live exclusively on, and require to take a large quantity of vegetable
 food, the crop is large, globular or oval, single in the  common  fowl,
 and double in the pigeon ; it is altogetber wanting in the swan and
 goose.   The oesophagus  and crop  are supplied with an abundant
 mucous secretion, and are provided with an external circular and
 an internal  longitudinal  set of muscular fibres, the  reverse of the
 disposition  observed in the  human subject.  Mr. Hunter has re-
 corded in his animal economy,  some interesting  observations on
 the crop of the pigeon, from which it appears that this macerating
 paunch  takes on a secreting function during the breeding season,
 and supplies the young pigeons with an abundance of milk, a diet
 suitable to their tender age, and the analogy of the pigeon's milk to
 that, of the mammalia has not escaped popular notice.
  That part of the oesophagus which extends from the crop to the
gizzard, was  called  by Mr. Hunter the lower oesophagus; at its in-
ferior part, just above the gizzard, it  dilates into the glandular  divi-
sion of the stomach, variously termed the proveniriculus, ventri-
culus succenturiatus, bulbus glandulosus, echinus, infundibulum.
 In the omnivorous and  piscivorous tribes there  is no perceptible
dilatation here, but in all it presents  increased vascularity as  it is
provided with a number  of glands which secrete a fluid analogous
to the  gastric juice.  Beneath the infunbulum  is  the  powerful
muscular gizzard  directed transversely like  the  stomach  of the
vertebrata, overlapped by  the lobes of the liver, and lined internally
with a thick, dense epithelium.  At the upper part of the gizzard
are two  openings, one large, to  the left side, and communicatino-
with the proventriculus,  the other smaller,-and a little to the right',
leads into the duodenum.  In those birds which  feed on grain  and
other  hard substances, the muscular fibres of the gizzard are dis-
tinguished  by their density and red colour, they are arranged in
four masses, two lateral, called the digastric muscles, and connected
to anterior and posterior tendons, and  two smaller ones between
these, at the end of the  gizzard, termed musculi  intermedii    In
rapacious and carnivorous birds the  parietes of the gizzard are thin
and membranous, yet distinctly presenting the anterior and posterior 
VERTEBRATA.
75
tendons.  The gallinaceous  birds, in which  the  gizzard is most
powerful, swallow pebbles  and other hard bodies, which serve the
purpose of reducing their  food, like the gastric teeth of crustacea,
insects,  and gasteropods; but in the carnivorous birds, with a thin
membranous gizzard, no such substances are required, all the neces-
sary changes being effected by the activity of the gastric secretions.
The parietes of this organ are subservient in a remarkable manner
to a known law, to which the whole muscular system yields, that
of increasing its growth in proportion to the functions imposed on
it;  this was strikingly illustrated  in  the  case of a sea-gull, which
Mr. Hunter kept for a year, living, contrary to its nature, upon grain.
At  the  end of that period he contrasted its gizzard with that of
another sea gull, which had been living on fish, and found that the
digastric muscles of the former had acquired nearly three  times the
development of the latter.  He accomplished similar phenomena by
changing the food of an eagle and of a tame kite, the former throve
very well on bread,  but that it was dissatisfied with its fare, is to be
inferred from its  seizing  the  earliest opportunity of breaking its
chain, and effecting its escape. These facts show in a clear manner
the provision of nature for the preservation of life under a variety
of  circumstances.
   The intestine is  shorter in birds than in mammalia, its different
divisions are better marked than in the lower classes, and in the young
bird a remnant of the entrance of the vesicula umbilical is may be
seen on  the  interior  part of the  small intestine in the form of a
small coecal appendage, and in many gallinaceous and some aquatic
birds it remains through  life.  The course of the  small intestine
varies much in the different orders of birds;  the duodenum always
makes  a long fold, which embraces the long, bilobate pancreas in
its concavity.  The large intestine  is about  a tenth  part of the
 length  of the body, and usually has two coeca at its commencement,
except  in the bustard and  ostrich, it runs a straight course from
 the coeca to the cloaca ; it is generally a little larger than the small
 intestine, and its villi are shorter, coarser, and fewer.  The  coeca
 coli are  of great size in  the gallinaceous and other granivorous
 birds, where they arise by  two  narrow canals,  and enlarge into
 wide sacs, often several  times the  size of the intestine, as in the
 turkey.  In the ostrich they have the mucous membrane disposed
 in  the  form of a spiral fold.   They are least developed in the gral-
 latores and the nocturnal rapacious birds. In the herons and several
 other  birds there is but  one, as in the invertebrate and lower ver-
 tebrate animals, and as in the plantigrade carnivora, they are alto-
 gether  wanting in the zygodactylous birds.
 3  The rectum terminates by a round valvular orifice in a dilatable
 cavity, the upper part of  the  cloaca, which is the  remains of the
 allantois, and now forms  a  rudimental urinary bladder, and in the
 ostrich it serves for the retention of the urine as in the higher
 viviparous animals.  At the lower and back part of this urinal por- 
76
EVERS'S COMPARATIVE ANATOMY.
tion  of  the cloaca are the openings of the ureters, and external to
these, the openings of the oviducts, or vasa deferentia.
  To this" urethro-sexual canal, succeeds the preputial cavity, or
lower portion of the cloaca, which lodges the organs  of excitement,
clitoris or penis, as in reptiles, marsupial, and monotrematous mam-
malia.   In the median plain, and on the dorsal  aspect of the prepu-
tial cavity is the  opening of a conical sac, named Barsa tibricn,
which lodges the anal follicles, and is analogous to Cowper's glands.
  The  liver  is large in  birds, especially in  the  aquatic species, it
generally consists of two lobes, but occasionally  of three, as in the
pigeon,  goose, and swan ; the  right lobe  is usually larger than the
left, the latter, however, is larger in  the  bustard, where it extends
into  the pelvis.   The bile  is discharged by two ducts,  one goes
directly to the duodenum, the other to the gall-bladder, and when
the latter  is  absent, they both open separately into  the duodenum,
but in no case is there a ductus choledochus.  The  pancreas, long,
narrow, and  trihedral, is lodged in  the  fold of the  duodenum, its
ducts are two, sometimes three in number, as in  the pigeon, raven,
and common fowl, and they terminate separately in the duodenum.
The small, round, oval, flat, or elongated spleen is placed beneath
the liver, and to the right of the proventriculus; its texture is loose,
and  the blood would seem to be deposited in cells, from which the
veins take it up.
   When we contemplate the different lengths and forms of intestine
met  with in  this  class, we  cannot help attributing  it  to some wise
purpose, and a little reflection  on the greatly  diversified nature of
the food on which the various tribes of birds are destined to subsist,
irresistibly leads  us  to infer  that economy  seems  to  be the main
design ; for  instance, the colon and  coeca of  the African  ostrich,
which has to subsist on  the scanty and uncertain fare of the desert,
are fifty times the length of the same parts in the cassowary, which
inhabits Java, one of the most fertile countries on the  globe.
MAMMALIA.
  The digestive organs vary more in this than in any other of the
vertebrated classes, and the varieties will be found to refer chiefly
to the type of development and living habits of the sundry species.
The teeth present infinite varieties as to form and position ; however,
their density and fixedness are well calculated to disintegrate ali-
mentary substances, and blend them with the mucous and salivary
secretions.  The teeth are wanting in the ant-eaters, pangolins, and
the whalebone whale. The young ornithorhynchus paradoxus has
two molar teeth in each jaw on each side:  these are shed  in the
adult animal, and replaced by one large one on each side.  But in
the hystrix there are twenty small, blunt, horny teeth, near the base
of the tongue, and seven transverse rows in the corresponding sur-
face of the palate.  The incisor, canine, and molar  teeth exist  in
the quadrumana. carnivora, ruminantia, without horns, and in most 
VERTEBRATA.
77
of the  pachydermata;  but  it is only in the extinct anoplotherium
among  mammalia,  that  the three kinds of teeth  are arranged
in an uninterrupted series, as in  man.  The superior incisors are
wanting in  the ruminantia, and the inferior  in the walrus.   The
Ethiopian hog and certain  bats lose  their incisors at a particular
age.  The canine teeth are  absent in the rodentia, some ruminants,
and in  most of the  female  solipeda.  The rodentia have but two
incisors in each jaw, with the exception  of  the hare  and  rabbit,
which  have them double in the upper jaw; the kangaroo has two
below and eight above ; the daman two above  and four below.  The
molar  teeth are  the most essential, and are the  last to disappear:
hence the ornithorhynchus  paradoxus, the  tatu, and the two-horned
rhinoceros, are  restricted to them.  The  molar teeth are renewed
eight times in the  elephant, the  incisors  are shed twice in many
rodentia; and most of the teeth are renewed once in the  other
orders  of the mammalia. In most mammalia which feed on animal
substances, the crowns  of the teeth are entirely covered with enamel,
and only partially so in the phytophagous  quadrupeds.
   The  following is an outline of the process by which the teeth
are produced.  About  two months after conception, a gelatinous
substance lies along each alveolar  arch:  at  the third month this
substance is firmer,  and lodged in  a-shallow groove in the bone.  It
is next divided  into separate pulps by transverse filaments passing
from one side of the alveolous to the other.  These pulps are en-
closed  in, and connected by vessels to a  thin vascular membrane,
which,  between  the third and fourth month begins to secrete the
ossific  laminas from its outer surface.  This membrane, with  its
contained pulp, is supplied  from the dental vessels, and  nerves, and
is surrounded by a thick vascular  sac, separable into  two layers ;
'he latter membrane is attached to  the pulp only at its base, but is
firmly connected  by its outer layer to the gum, from which it derives
its vascular and  nervous supplies.  It is from the inner surface of
the internal layer of this sac that  the enamel is  secreted, and at
this  period  it becomes thick and vascular, whilst the  outer layer,
which  is only rudimentary in  man, secretes  the crusta petrosa in
the graminivorous quadrupeds. After the enamel has been secreted,
both layers of this  sac become wholly absorbed, hence they have
been termed the deciduous membranes, in contra-distinction to the
permanent, which  are described as three in number, one being the
periosteum  of the  alveolus, another the periosteum  of the root,
and  the third the  periosteum of  the  dental cavity, which secreted
the tooth.  But in fact these three permanent membranes are simply
a continuation of the  periosteum of the jaw  which first lines the
alveolus,  then descends, to form  the  periosteum of the root, and
lastly passes up in  the form of a hollow cone to enclose the pulp.
The period at which the teeth appear in the human subject is very
variable, some  children being born with two or more, whilst in
others  they may not appear for two or even three  years.  From five
to eight months,  however, is the most usual period;  they generally 
78
EVERS'S COMPARATIVE ANATOMY.
appear first in the lower jaw, and proceed in the following order :—
From  5 to 8 months, the four central incisors; from 7 to 10, the
lateral incisors;  from 12 to 16, the four anterior molars;  from 14
to 20,  the four cuspidati; and from 18 to 36 months, the four pos-
terior molars.
  The purposes  of prehension are accomplished by sensitive fleshy
lips, as in herbivorous quadrupeds, by a long, flexible tongue, as in
the giraffe and ant-eaters, and by other organs such as the proboscis
of the elephant.   The salivary glands are largest in herbivorous
quadrupeds, less  in the carnivora, and least in  the aquatic mamma-
lia.  The sublingual glands are wanting in cats. The velum palati
is large, but the  uvula is confined  to the quadrumana.   The os
hyoides, is most  developed in the herbivorous quadrupeds, and has
been shown  by Geoffroy to consist of twelve elements, a glosso and
basi-hyal  piece  for  the body, an apo a cerato, and a styl-hyal ele-
ment for each of the anterior cornua, and an ento and uro-hyal for
each of the smaller posterior cornua.   This condition is sometimes
found  as an abnormal state in man.   The oesophagus is wide and
dilatable  in  the carnivora, and narrow and fleshy in the herbivora.
The arrangement of its muscular fibres is the same as in man ; and
its mucous tunic, which  usually forms longitudinal and but rarely
transverse folds,  is lined with cuticle, which in the carnivora termi-
nates at the cardiac orifice in a fringed margin, but lines half the
stomach of the horse, the rat, the hog, and some others of the pecora,
and in the ruminantia it lines the three first cavities of the stomach.
The oesophagus  of the ornithorynchus hystrix is furnished with a
peculiar valve at its commencement, and numerous  papillas at its
termination, directed upwards, and its cuticular lining is continued
through the stomach.
  The animal nature  of the food of  the carnivora bespeaks a short
and simple form  of alimentary canal.  In some, as the lion and the
cat, the stomach  is elongated in form, and its orifices remote from
each other, this is particularly the case in the  lynx; in others, as
the  racoon, it is nearly globular, and  in all, with the exception of
the seal, its interior  is  smooth,  and almost  without  villi.  The
monotremata, cheiroptera, insectivora, and marsupialia, also present
a simple  stomach,  a  coscal  portion  being  but  little  developed.
When, however,  the food  is of a more mixed character, the stomach
becomes  more elongated  transversely, as  in the quadrumana and
others  of  the less carnivorous tribes.  In most of  the rodentia  the
thin cardiac portion forms a distinct  coecum, and is separated  by a
constriction  from the pyloric muscular  portion.   Several of the
pachydermata, marsupialia, edentata, and quadrumana,form a link
of transition to  the more complex  stomachs of the cetacea  and
ruminantia in the formation of folds  or cosca with cuticular linings.
Thy intestinal canal is very short in  these animals, the whole tract
not exceeding three times the length of the body in  the  lion and
wild cat.   In the badger there is scarcely any distinction  between
small and large intestine: but in the lion, seal, and others, it is well 
VERTEBRATA.
79
marked.  The caecum is small in cats, spiral in dogs, and generally
absent with the colic valve in the mustelidae.  Valvulae conniventes
are scarcely developed.
   In the cetacea the tongue is short, thick, fleshy, and but. little sus-
ceptible of motion, and in  the whale it often affords three barrels of
oil.  The  teeth are  prehensile, the salivary glands rudimental or
deficient, and the oesophagus short and wide. In the phytophagous
cetaceans the stomach is divided into  a  large cardiac, and a small
pyloric portion, by a contraction which gives origin to two tubiform
prolongations.  The coecum is simple in the dugong, and bifurcated
in the  manatee.   In the zoophagous cetacea  the stomach consists of
four or five compartments, none of which, except the first, have any
communication with the oesophagus, therefore no  rumination can
occur.   The first cavity is small and lined with cuticle, which ter-
n inates abruptly at the narrow opening leading into the second. A
small pyloric orifice leads to a dilated duodenum.  There is scarcely
any distinction between small and large intestine, and  the coecum
coli is but little developed.  Why so complicated a stomach should
exist in animals nourished by the most digestible and highly organ-
ised food, is an anomaly for which we can  offer no explanation, but
one which, from its interest, courts early investigation.
   The stomach of the kangaroo resembles the human colon and
coscum; the oesophagus  enters near its  left extremity,  which  is
small  and bifid ; the stomach first extends towards the right side,
and then upwards and to  the left, in such a manner as to completely
encircle the  entrance of  the oesophagus, and terminates  at the py-
lorus by a contracted orifice.  Its cavity gradually enlarges from the
left extremity till it nearly reaches the pylorus, it then dilates into a
round cavity with two lateral processes, and finally ends  by a
narrow orifice.  It presents a sacculated  appearance arising from
the presence  of anterior and posterior bands like those of the human
colon, and the  cuticle lines it to a certain  extent on  either side of
the entrance of the oesophagus.  This animal has been known to
ruminate when fed on hard food.  The kangaroo-rat and the vam-
pyre bat present similar modifications of stomach but have no part
of it  lined with cuticle, and in  the  former  there is a valve at the
cardiac  orifice.   The intestine of the kangaroo corresponds in its
great length  and convolutions with the coarse nature of its vegetable
food, and"the coecum is about fifteen inches  long.   At the cardiac
orifice of  the stomach  in the beaver and wombat there is a  large
gastric gland, like the glandular infundibulum in birds.
   The ruminating animals possess four stomachs ; the first magnus
venter, or paunch, receives the crude unmasticaied food,  while the
animal is grazing.   When this cavity is filled the animal retires  to
rest, and begins'to ruminate; the  unmasticated  food, softened in
the paunch,  now passes in small portions into the second cavity,
called reticulum, or honey comb; from this  it passes as a bolus up
through the  oesophagus to the mouth, where it  is thoroughly mas-
ticated and insalivated; it is next conducted  by the oesophagus to 
80             EVERS'S COMPARATIVE ANATOMY.
the third stomach, termed manyplies, or omasum, and from thence
into the fourth stomach called abomasum, or rennet bag.  Of these
cavities, the first is the largest, and the third the smallest.  1 he three
first are lined with cuticle, and the fourth, which is next incapacity
to the paunch is lined with a soft  mucous coat folded in the longitu-
dinal direction.  This is the proper digestive stomach, and is analo-
gous to the digestive sac  of carnivorous  and  higher quadrupeds.
The fourth stomach of the ruminantia is the first developed ; in the
earlier  periods of life it is the largest,  and the only one employed in
digestion.   The mechanism by which milk is transmitted directly
into the fourth stomach during the period  of suckling  is this, the
oesophagus enters just where the three  first cavities approach  each
other, here it can open directly into the  first or second stomach, but
instead of terminating there, it  is continued in the form of a groove
with prominent lips, which admit of being drawn together  so  as to
form a complete canal, which then constitutes a direct continuation
of the oesophagus into the third stomach, but this  cavity not having
been distended with solid food in the young animal, it merely forms
a tube  through which the milk passes into  the fourth stomach.   In
the adult animal the same mechanism continues,  but. here the third
cavity  having  been already distended, receives the bolus  after
rumination.
   In the  ruminants without horns,  as the dromedary, the camel,
and the lama, a somewhat different but not less beautiful mechanism
prevails, fitting  them  to live in  the  sandy deserts  and arid plains
they inhabit.  In these animals  the  paunch consists of two  com-
partments, the first of which receives the tin masticated food  from
which it  is returned  to the mouth, moistened  by the fluid of the
second or cellular compartment.   After the cud  has been chewed,
the food passes along  the upper part  of the second cavity into the
third, and from that to the fourth.  When the  camel drinks, the
water  passes directly into  the second cavity, and when this is full
it flows into the neighbouring cellular compartment of the paunch.
In the bullock,  the three first cavities are lined  with cuticle ; in the
camel  it lines only the two first,  and  terminates just within  the ori-
fice  of the  third, the surface of which has a  faint appearance of
honey-comb  structure.  From the  comparative view  which has
been taken of the stomach of the bullock and camel, it appears, that
in the bullock there are three cavities formed for the preparation of
of the food, and one  for its digestion.  In the camel, the two  com-
partments of the first cavity answer the purposes of the two first
stomachs of  the bullock ;  the second is employed as a reservoir for
water  only;  the third is so small and simple in its structure, that it
is not  easy to ascertain its particular  office, whilst the fourth is that
in which the process  of digestion is  accomplished.
   As  a general rule, it may be stated that the  intestinal canal is
long,  large,  and  sacculated in  the  herbivorous  tribes, and short
straight, and without sacculi, in the  carnivora.   Some'remarkable
exceptions,  however, present  themselves, for  inslance in  makies 
VERTEBRATA.
81
mice, and shrews which  are  purely  frugivorous, and  in  sloths,
which live  on vegetable food,  the intestine  measures only about
three times  the length of the body ; whilst in the porpoise and seal,
which live on animal food, it measures in the former 11 times, and
in the latter 28 times the length  of the body.  But  this apparent
anomaly is explained by recollecting that the  coecum plays  a com-
pensating part with respect to the other portions of the alimentary
canal, indeed the researches of the Heidelberg  professors authorise
us in believing that it acts  the part of a second stomach, and  that
where the latter is simple, the coscum  presents  a  complex  and
highly developed condition, and vice versa.  Hence by a reference
to the highly developed coecum and vermiform  appendix  of the
rodentia, we are enabled to reconcile their simple form of stomach
with their herbivorous food.   In the elephant,  the small intestine
measures 38 feet, the colon and rectum 20| feet, and the coscum l£.
In the camel,  the small intestine  is 71  feet, the colon and  rectum
56, and the caecum 3.   The intestine is 10 times  the length of the
body in  the horse, and  28 times in the sheep.  In  an ornitho-
rhynchus 17£ inches long, the small intestine  measured 4 feet  4
inches, and  the colon and rectum 1 foot 4 inches.   In this animal,
the rectum,  urinary,  and genital organs terminate in a cloaca, as in
birds and amphibia.
  The solidungulous pachydermata masticate their food before it is
swallowed, therefore they do not ruminate, and  require but a simple
digestive stomach ; but they have the same narrow lengthened form
of intestine, and a capacious sacculated coscum  and colon.  The
liver is largest in the cetacea and those animals that dive or burrow ;
smaller in the herbivora, and least in the carnivorous tribes.   There
seems to be  no general law  for the presence or absence of the gall-
bladder in mammalia more than in birds and fishes ;  it is  for the
most  part  wanting  in  the herbivorous species,  as the deer  and
the camel ; it  is also absent from most of the rodentia and pachy-
dermata;  and here the hepatic duct is generally much dilated, as in
the horse and elephant.   In the otter a similar  dilation exists in
conjunction with a  gall-bladder.  It  is remarkable  that  all the
mammalia which  want  this  reservoir, except the  porpoise, are
phytophagous.
  In the course of my dissections during my pupilage at the college,
I, together with my esteemed friend, Surgeon Bewley, of Moate, met
with a female subject about nine years of age, in which this recep-
tacle was absent.  I  invited the attention of  Dr. Houston to this, I
believe, unique  anomaly,  who has prepared  and deposited  the
biliary apparatus in the museum of the college.
  The spleen  is  long, flat, and attached  to tbe paunch in the rumi-
nantia, narrow and lengthened in the carnivora, and in the porpoise
it consists  of several portions.   The  pancreas is long, flat, and
attached to the right  end of the  first stomach in the cetacea, in other
mammalia it is longer, and  often  divided into several portions, its
     8— g                                       evers 6 
82
EVERS'S COMPARATIVE ANATOMY.
duct, which is double in the elephant, usually opens separately into
the duodenum.
RECAPITULATION.
   1. A digestive cavity is the most universal organ in animals, and
exists in all, with the exception of some of the monads.
   2. Masticating,  salivary,  and biliary organs are found in the
higher radiata.
   3. All these parts are more  highly developed  in  the  articulata,
and one or two gall-bladders are present.
   4. There has  been no gall-bladder found in  the mollusca.
   5. The stomach receives the biliary and  pancreatic fluids in all
the invertebrata.
   6. The invertebrated animals possess no portal circulation.
   7. In the vertebrata, the alimentary canal always swells out into
a gastric enlargement.   The tributary organs are large and conglo-
merate, and the salivary glands are rarely absent.
   8. The duodenum receives the biliary and pancreatic secretions,
and there are no teeth found in the stomach.
   9. As a general rule the alimentary canal is larger and longer in
the vegetable-eating animals, than in those that live on flesh.
   10. Fishes have a simple form of alimentary canal, their teeth are
often numerous, as  in  the pike, rarely absent as in the  sturgeon,
their salivary glands are rudimental, or entirely wanting, and their
whole canal often measures  but half the length of the body.
   11. The digestive apparatus undergoes interesting changes during
the metamorphosis of the frog, &c.
   12. The teeth are  absent in birds, and their place supplied by bill
and gizzard.
   13. The crop is double in  the pigeon, single  in  the  fowl, and
absent from the goose.   The gizzard "is thick and powerful in the
granivorous, but thin and  membranous in the  carnivorous  species,
and the great intestine  terminates in the dilatable rectal vestibule
which receives the openings of the ureters, of the oviducts, or vasa
deferentia, and of the Bursa Fabricii.
   14. The teeth are greatly  modified  in  the mammalia, being
rarely absent, as in the  manis or pangolin, the  myrmecophaga and
the echidna.                                             ^
   15. The digestive system is most complex in the herbivorous
ruminantia, and most  simple in the carnivora ; in the latter the
food requires  but little elaboration, hence the form of the teeth  and
the great strength of the jaws are admirably adapted for seizing and
tearing their living prey, here also we have a simple stomach  and
a short intestine, without any provision to retard  its contents'  In
the ruminantia, on the contrary, the jaws are elongated, and admit
of free lateral motion with flat grinding teeth, the stomach is  com-
plicated, and the intestine  long and  sacculated ; in  fact all things 
ABSORBENT SYSTEM.
83
conspire to ensure perfect comminution  of  the food, retardation of
its passage, and a due absorption of its nutritious particles.
                       CHAPTER XII.

                     ABSORBENT SYSTEM.

  Although Monro, Poli, Sheldon, and Carus, have described chy-
liferous vessels in many of the in vertebrated classes, their existence
in these animals has not yet been satisfactorily proved, and it is more
than probable that their function is performed by the veins, the white
blood of which  resembles the chyliferous fluid of the vertebrata.
The chyle  varies much  in its composition and properties  in the
various tribes of vertebrated animals, and even in the same animal
according to the sort of food it lives on, being of a pinkish tint, with
abundance of crassamentum in the different animals  which subsist
on nutritious animal food, while it is  limpid and pale, with a great
proportion of serum in the inferior animals.  The chyliferous, like
the other systems of the body, presents different grades of develop-
ment in  the different  vertebrated classes.  Thus,  in  fishes the
vessels seem to  consist  of a single tunic, destitute of valves, and
without conglobate glands ; they "form two strata of vessels between
the coats  of the intestine, and carry a limpid fluid to the recepta-
culum chyli, from which one or  two thoracic  ducts lead to the
jugular veins or other branches of the cavas.   The lymphatics and
lacteals communicate frequently  with one another,  and with the
neighbouring veins, and when injected  they present  a beaded ap-
pearance owing to the presence of rudimentary valves.
  The chyliferous system in the amphibia is the same as in fish,
but in the reptilia it presents a higher degree  of formation in the
existence  of valves, and  the  milkish appearance of  the chyle, the
place of glands is still supplied by the convoluted condition of the
vessels as in fishes ; here also, two or more thoracic  ducts, fre-
quently communicating, pass to the jugular or subclavian veins, or
the angle  between  them,  previously  receiving the lymphatics from
the head,  neck, and arms.  In the tortoise, the anastomoses  of the
thoracic ducts nearly conceal the trunk of the  aorta.   This system
presents a somewhat higher grade of development  in birds, both
sets  of vessels being more  numerous and distinct, the valves are
more abundant, but yet  admit  of the passage of  fluids from trunks
to branches.  Glands appear  now for the  first time,  in connection
with the lymphatics, but not with the lacteals.  Two thoracic ducts,
having but few  anastomoses, terminate by several openings at the
junction of the jugular and subclavian veins.
  In the mammalia the absorbent system  is better developed  and 
84
EVERS'S COMPARATIVE ANATOMY.
more distinct from the sanguiferous  than  in  any of the  preceding
classes, as manifested in the  sanguineous characters of the chyle,
the elaborate structure of the vessels, the perfect condition of their
valves, the increased number of conglobate glands, and the unity
and distinctness  of the  thoracic duct.  Sometimes this  duct is
double, as in the dog, and sometimes its branches open into the vena
azygos, as in  the  hog.  Occasionally its trunk divides, and having
enclosed  a narrow elongated  space, called insula Halleri,  the
branches again unite.   The  mesenteric glands are of great magni-
tude in the cetacea, more detached in the pachydermata, and grouped
into a mass, named pancreas Assellii, in the carnivora.

                      Recapitulation.

   I. Lymphatics have been described, but not satisfactorily demon-
strated, in the invertebrata.
   2. No conglobate glands have been found in fishes ; their absorb-
ents are thin, convoluted, and furnished with rudimentary valves,
and occasionally two thoracic ducts exist.
   3. This system is the same in amphibia as in fishes, but  in  the
reptilia the valves are more perfect.
   4. In  birds  the absorbents are  very  numerous, the valves still
more perfect, and glands for the  first time met with.
   5. In mammalia the entire system is marked by a  higher type of
formation: the thoracic duct is  sometimes double as  in the dog,
and occasionally opens into the vena azygos as in the hog.
                      CHAPTER XIII.

        SANGUIFEROUS SYSTEM IN THE INVERTEBRATA.

  The systemic, or  red-blood circulation was  discovered  in the
higher animals by Harvey, in 1619;  and  by the researches  of
modern comparative anatomists, it has been found to have a much
more extended existence ; there is a considerable number, however
of the cycloneurose classes of animals, in which no distinct vascular
system has as yet been detected.  The first appearance of it which
we observe m the lower animals, as in the earliest condition of the
human embryo, consists of  vessels alone,  through which the fluids
rnove in a circle, like the  colourless blood in the cells of a plant
In the astenas, echinus, and holothuria among the echinodermata,
a large vessel, in the  form of a ring, surrounds the commencemen
of the alimentary canal, from which  the  systemic arteries are
derived ;  the systemic veins send branches to the gills, from which
the blood is returned  by one large vessel to the heart. 
        SANGUIFEROUS SYSTEM IN THE INVERTEBRATA.     85

  Diplo-neura.—In the earth-worm two vessels, one above and the
other below, extend the entire length  of the body;  they communi-
cate by several cross branches, and join at their extremities, where
small dilatations are observable, supposed  to  aid in propelling the
blood, which moves in opposite directions.  The large vessels of the
annelida are endowed  with  a contractile  power, and in insects,
spiders, and the  lower species of crustacea, large dilatations occur,
capable of considerable contractility.
  In the leech, hirudo vulgaris, the two principal vessels are placed
on  the sides, and lesser ones above and  below, all  anastomosing
freely by transverse branches ; of these the superior longitudinal
and the inferior transverse  only pulsate.  It  is  the opinion of
Miiller  that the lateral  vessels alternately empty themselves  from
behind forwards ; and others state that the  blood is moved forwards
in the upper vessel and backwards in the lower.
   The arachnidans, which breathe by means of trachas, seem to have
a dorsal  vessel  only, without any ramifications.  Those, on the
contrary, which possess branchial lungs, have a well  developed cir-
culatory apparatus.   The blood leaving the heart by the arteries is
distributed to all parts of the body; having become venous it  is
returned to the  pulmonary branchiae by sinuses which  supply the
place of veins, and having undergone arterialisation, it is returned
to the heart by the branchio-cardiac vessels,  again  to be propelled
through the arteries.
   In the higher crustacea the heart consists of  two sinuses and a
ventricle ; from the latter, in the stomopoda, six vessels arise which
distribute the blood  to the eyes,  liver, antennas, (fee.   This  fluid
is next  returned to  venous sinuses  in the  neighbourhood of the
branchiae, through  passages  without any apparent  parietes; the
arterialised blood is brought from the branchiae to the sinuses of the
heart by vessels named branchio-cardiacs, from which it is received
by the ventricle and sent into the arteries issuing  from it, each  of
which is provided with a valve at its origin.
   Cyclo-gangliata.—The greater number of  the animals which
compose  this class are aquatic, and  enjoy a  branchial respiration.
In  the ascidiae the heart is very simple, consisting merely of a thin
membranous ventricle  destitute of valves.  The conchifera  have
two auricles and a ventricle; the gasteropoda andpteropodapossess
a strong auricle and ventricle provided with  valves.   In the cepha-
lopoda there is an aortic heart, and two branchial hearts, or dilata-
tions ; in these animals, the blood  having been carried to the system
by the arteries is returned by the veins to the branchial fringes;  in
some bivalves, however, a portion of it is sent direct to the  heart
without  passing through the respiratory organ.   In the gastero-
podous and other mollusca the rectum passes through the ventricle. 
86
EVERS'S COMPARATIVE ANATOMY.
                       CHAPTER XIV.

         SANGUIFEROUS SYSTEM IN THE VERTEBRATA.

  In the greater number of the invertebrate animals which we have
hitherto examined, the heart and principal artery were placed above
the alimentary canal and the chief part of the nervous system ; but
in  the vertebrate  classes the converse  order obtains, the  heart
being below the  alimentary tract; in the former division the blood
generally arrives at the heart after having  passed  through the re-
spiratory organ,  while in the latter the blood flows from the  heart
to the respiratory organ.   In the invertebrate classes, too, there  is
no vena  porta, the liver being supplied by  an  hepatic artery alone.

                           PISCES.

  The gills, which are the only respiratory organs of fishes, are
placed in the course of the arterial circulation.   The venous blood
from all  parts of the body is conducted to a  single auricle which
propels  it  into the ventricle,  from  which it is  brought by the
arterial bulb to the gills, where it is  arterialised, and from which  it
is distributed by the branches of the aorta to all  parts of the body.
The caudal vein of the eel presents a contractile dilatation, to which
Dr.  Hall, has applied  the name of caudal heart; this doubtless
assists in promoting the circulation  in the caudal branches of the
vena cava.   Many look upon  the heart  of fishes and the artery
issuing  from it  as analogous  to the right heart  and pulmonary
artery of higher animals ;  but it is much more just to consider the
heart as corresponding to the whole heart of  the warm-blooded
vertebrata,  seeing that in  some  of the reptiles possessing gills, the
blood is sent to these organs through the great systemic trunk.  In
fact, the heart, in these animals, acts at once the  part  of a  pulmo-
nary and a systemic heart in  propelling the blood not only to the
gills, but through all parts of the aortic system.
  Portal-circulation.—The porta in fishes carries  to  the liver the
venous blood from the stomach, intestines, spleen, pancreas  and
occasionally  from the genital organs, swimming bladder, and tail.
In the gadus, however, as in reptiles, the venous blood from the tail
and the central parts of the abdomen goes to the kidneys.  In the
silurus the  blood from the posterior  part of the body is distributed
to the liver and kidneys: and in the carp, pike and perch, to  these
organs and to the vena cava.  This vessel  also receives the blood
from the  testicle, ovary, kidneys, and frequently from the swimmino-
bladder.                                                      °
                          AMPHIBIA.

  The  metamorphosis which this class of animals undergoes  in
passing  from  the pisciform to the reptilian state,  is strikingly 
         SANGUIFEROUS SYSTEM IN THE VERTEBRATA.       87

illustrated  in  their circulatory  system: beginning  life  with the
single  heart of a fish, and ending  it with the double heart of a
reptile.  In the water salamanders the venous blood which has cir-
culated through the body, is  returned  to a systemic auricle, and
having passed  through the ventricle, it is received by the bulbus
arteriosus,  and  sent  by the  branchial arteries to the  branchial
leaflets.  The pure blood is now received by the pulmonary veins,
the confluence of which constitute, as in fishes, the descending
aorta.
  From this latter vessel a small branch passes off to the rudiment-
ary lung, which is afterwards to  become the pulmonary artery.  As
the animal changes from an aquatic to  an atmospheric respiration,
the branchiae  become absorbed, and the lungs proportionally  deve-
loped.   Their arteries experience corresponding changes, those of
the former organs diminishing, while those  of the latter increase
with the growth of the  lung.   The two veins which return the
blood from the rudimental lung also enlarge, and as they arrive at
the heart, they undergo a remarkable dilatation, which constitutes
the left auricle.  Till lately the bi-auricular form of heart was sup-
posed  to be confined to the  caducibranchiate amphibia, as frogs,
toads,  salamanders, and tritons,  but the researches of Owen  have
proved its existence in the perennibranchiate  amphibia also.
  At  the same time  that the systemic auricle receives the impure
blood  from the cavas, the pulmonic auricle receives  the aerated
blood from the lungs.  From both of these cavities the blood is sent
into, and mixed in, the single ventricle, from which it is sent by
the one impulse to the lungs and to the system generally.   From
this description it is obvious that the blood is  but partially purified,
mixed blood being sent through the pulmonary arteries, as well as
through the aorta and its ramifications.
                           REPT1LIA.
   In this class of animals we perceive a still higher grade of deve-
lopment than was met with  in the amphibia; the ventricle  is  par-
tially divided by a  septum into two compartments, corresponding
in most particulars to the two ventricles of warm-blooded animals.
In some the septum is so imperfect as to be incapable of preventing
the admixture of the blood derived from both auricles.  In others,
however, as the crocodile, the ventricles are separated completely,
or communicate by a small  orifice provided with a valve,  which
prevents the blood passing from one compartment to the other.   In
fact the heart in this singular animal  is  double, as in the higher
vertebrata,  so that the venous blood returned by the cavas  to the
right auricle, passes from the right ventricle through the pulmonary
artery to the lungs, while the pure blood returned from this organ
to the left auricle is directed from the left ventricular compartment
through the systemic arteries.  The auriculo-ventricular orifices are
provided with a muscular valve, and in the crocodile  there are two. 
88
EVERS'S COMPARATIVE ANATOMY.
 It is curious, however, that in the whole of this class the descending
 aorta is formed by  the  union of two branches, the  right branch
 arises  from the left  ventricular compartment, consequently carries
 pure, or nearly pure blood, which it  distributes to the head, neck,
 chest, and upper extremities.  The left branch, on  the contrary,
 arises  either from the right ventricular compartment,  or  what is
 tantamount to  it, from the pulmonary artery.   It is obvious, then,
 that the descending aorta carries a mixed quality of blood to the
 parts it supplies;  but  it is interesting to observe, that previous to
 the junction of the two aortic arches, the left gives off the coeliac
 axis which supplies the entire alimentary canal and digestive organs
 with venous blood.   In the turtle, lizard, and some serpents, where
 the septum ventriculorum  is imperfect, the  pulmonary artery and
 aorta at once  carry mixed  blood,  and in some of  the chelonia,
 as the  tortoise, the existence of ductus arteriosus  ensures  a  more
 complete mixture of venous and arterial blood.  The arteries arising
 from the ventricles are each provided wtth two valves.
  Portal  system.—In amphibia and reptiles,  as in  fishes,  there
are two  lesser venous  circulations; the  one belongs to the  liver,
and  the other, which does not exist in birds or mammals, belongs
 to the  kidneys.  In  some  reptiles all the venous blood from the
 posterior parts of the body is distributed to  the  liver  and kidneys,
while in others a portion  is  sent to  the inferior cava; this latter
vessel also receives the venous blood which has  circulated through
 the kidneys.
AVES.
  The heart, in this highly organised class of oviparous animals
consists of four separate and distinct compartments, and indeed pre-
sents a more perfect typical form than is met with in even the mam-
malia.   Its form is conical,  being sometimes  short and wide, as in
the crane,  and sometimes more elongated, as in the emeu.  Its
situation is mesial, its axis parallel to that of the trunk, and in con-
sequence of the partial development of the diaphragm its apex rests
between  the lobes  of the liver.   The right  auricle'seems consider-
ably larger  than   the left, and  the  auricular portion  is  distinctly
divided  from the  sinus by two semilunar  muscular  valves- one
attached  along  the anterior, and  the other  along the posterior side
of the  sinus.   The venous  blood is returned to  the  sinus of the
auricle by an inferior and two superior venas  cavas, and  it  is re
markable that the left superior cava  receives the coronary vein iust
before its termination.  The  orifice of this vessel is opposite to that
of the  inferior  cava, but separated  from it by  a  semilunar mem-
branous valve.  The auriculo-ventricular opening is a small oblique
slit, and reflux  from the ventricle is  prevented by a  thick strong
muscular valve so disposed  as  to give considerable impulse to the
flow of blood through the pulmonary  artery.  There  is  a  small
muscular column  at the upper part of the orifice, but it is only one 
         SANGUIFEROUS SYSTEM IN THE VERTEBRATA.       89

of the  carneas columnae, of which  few exist in the ventricle.  In
the left auricle a mere rudiment of valve is found between the sinus
and the appendix.   The parietes of the left ventricle are very thick,
and  the auriculo-ventricular  opening  is guarded  by  two mem-
branous folds corresponding to the mitral valve  in mammalia. The
pulmonary artery and aorta are provided at their origins with three
semilunar valves,  those of  the  former vessel  being thicker  and
stronger than those of the latter.  The extremities of these valves
will be found by careful  dissection to be attached to cartilaginous
or osseous points imbedded in the fibrous tunic  of the vessels.
   The pulmonary  artery having arisen from the right ventricle at
once divides into  two branches, one for each lung;  from these or-
gans the blood is  returned  by two veins, which  unite before they
reach  the left auricle.  From  the  left ventricle arises the aorta,
which  immediately sends  off two branches analogous to  arteriae
innominatas, for the supply of  the  head and  wings.   It may be
observed that birds possess no palmar arches, nor, strictly speaking,
a  radial artery.   The cerebral, orbital, temporal, and spermatic
arteries are remarkable for their free and plexiform anastomoses.
But of all the arterial plexuses, that of the organ of incubation
requires special notice.  It is formed by branches from the posterior
thoracic, abdominal, cutaneous, and ischiadic arteries, immediately
under  the integuments of the  abdomen.   This plexus  becomes
enormously enlarged during the period of incubation.
   The venous system in  birds is remarkable  for the frequency of
its communications, especially one which exists between the united
caudal, hemorrhoidal, and iliac veins and the vena porta, by means
of which the blood  from the viscera and posterior parts of the body
may flow either  into the cava or porta, a disposition obviously de-
signed to guard against congestions:  as yet it is a question con-
cerning which contradictory opinions prevail, as to whether  the
branches of the pulmonary artery extend to the air-cells distributed
over the body, or whether the blood in the systemic capillaries un-
undergoes  any change  tending to its purification in  the parietes of
these cells.

                          MAMMALIA.

   The form of the heart, and the distribution of the blood vessels in
the whole  of this  class so closely resemble the  human  type, that it
becomes necessary to notice only a few individual peculiarities; in
the dugong and rytina for instance, among the cetacea,  the heart is
cloven by the deep  separation of its two ventricles, and the orifice
of the inferior cava is guarded by a fleshy Eustachian valve, which
is  wholly absent in the lion, the bear, and the dog.   In  the  mono-
tremata, the marsupiata, the porcupine, and the  elephant, the right
auricle receives one inferior  and two superior cavas as in birds, and
the coronary vein  terminates in the left superior cava.   In the
ourang-outang and the mole, only, is the apex of the  heart inclined 
90
EVERS'S COMPARATIVE ANATOMY.
to the left side as in the human subject.  In the upper part of the
substance of the left ventricle of the pig, the stag, and other bisulca,
are two small flat bones, crucifbrmly disposed in the stag, they are
formed about the third year of the animal's life,  and are but slightly
developed in the female.   It  has been generally supposed that the
foramen ovale and ductus  arteriosus remain permanently open in
seals, otters, and cetaceans, and although the dissections of Cuvier,
Home, Blumenbach,  and  T.  Bell, go  to prove  that they have
remained unclosed in  a few instances, still we must look upon these
as exceptions, admitting,  however, that  these  passages  continue
longer pervious in these diving animals than in other mammalia.
  As regards the arterial system some remarkable  peculiarities  are
observed in the branches arising from the arch of the aorta, thus
in the horse, the camel, and many of the  long  necked mammalia,
this great  trunk just  after its origin divides into two branches, one
becomes the  descending aorta, the  other ascends vertically and
divides into a right innominata, a left subclavian and a left carotid,
which latter appears in direction the continuation of the trunk.   In
the elephant  there is  but one  coronary artery, and both carotids
arise by a  common trunk between the two subclavians.
  The dolphin  has an innominata on each side, this constitutes the
type of  the  cheiroptera.   In  the marmot and  the guinea-pig, the
right  innominata gives rise to the two carotids,  and the right sub-
clavian.  This also is the  type of the order quadrumana, and most
of the carnivora.  Among the peculiarities in  the distribution of
arteries  we may notice the rete mirabile formed by the internal
carotid at  its entrance into the cranium  in several carnivora and
ruminant  bisulca; the  plexiform arrangement  of arteries  which
exists under the pleuras and between  the  ribs in the cetacea ; and
the remarkable  anastomosing divisions of  the arteries of the extre-
mities and tail in the  slow moving and  climbing animals  as  the
bradypus,  myrmecophaga, pangolin, and stenops.  This  condition
of the arterial system doubtless has reference to the peculiar livin°-
habits of the animal it exists in, thus in the cetaceans these serpen-
tine  vessels  constitute so  many reservoirs for  containing arterial
blood during the obstructions to the circulation which are almost
inseparably connected with the aquatic habits of these mammalia,
whilst in those with depending heads, the rete mirabile is admirably
calculated  to  obviate the injurious  effects of  sudden  influxes
to the brain, and in  the  edentata the arterial divisions  alluded
to are no  less indicated, lest the large trunks of the extremities
should suffer  from pressure during "their long continued action
in climbing.
  The plexiform disposition, which characterises so  many parts of
the arterial  system, is no less  strikingly displayed in  the venous.
This is  well seen in the tortuous sinuses  which receive  the inter-
costal veins in the porpoise, the vena azygos being absent in this
animal.  A beautiful  distribution  of veins constituting  the rete
mirabile venosum, is  met  with on the foot of the horse, where these 
SANGUIFEROUS SYSTEM IN THE VERTEBRATA.       91
vessels run in innumerable parallel branches on the anterior surface
of the coffin bone.  Another peculiarity in this system is presented
by the inferior cava, in the porpoise, the seal, the common  and the
sea otter, consisting  in a considerable dilatation of this  vessel
between  the liver and  the diaphragm, similar to what is observed
in tortoises and diving birds.
  A general review of the vascular system indicates that the heart
in its simplest form resembles  a vessel endowed with contractility,
as exemplified  by the vessel-like multiple hearts which constitute
the vascular trunks of  the annelides, the contractile trunks  on the
alimentary canal of the holothuria, the dorsal vessel  of insects, &c.
In the embryo of the highest warm-blooded animals the heart is at
first tubular, and it is interesting to observe, that during the progress
of its development it passes through, and resembles the several forms
which constitute its permanent type in the adult state of fishes and
reptiles, even the clefts in the neck, with the arched divisions of the
aortic  trunk, which are persistent in reptiles, may be seen  in the
human embryo at a  very early stage of its development, and the
ductus arteriosus, which is single in mammalia, but double in birds,
is the last of those arches which remains unclosed in the foetus.
These arches may be well seen by inspecting  the embryo of a bird
on the third day of incubation.
   The frequency of the heart's action varies much in different ani-
mals, and even in the human subject, from  a variety  of causes.
           In a fish it beats in a minute from  20 to 24
           In the frog, about     -    -            60
           In birds, from        -    -      100—140
           In the bat,           -    -           200
           In rabbits,           -                120
           In the cat,            -    -           110
           In the dog,           -    -            95
           In the sheep,         -                 75
           And the horse,       -   -            40
           In the human embryo,     -           150
           At birth,             -    -    130 to 140
           During the  first year  -    -    115—130
           During the second year    -     100 — 115
           During the  third year,     -      90—100
           During the  seventh year,   -      85—  90
           About the fourteenth year  -      80—  85
           In the middle period of life, -      70—75
           In old age,           -    -      50—  65

                       RECAPITULATION.

   1.  The systemic circulation was discovered by Harvey in 1619.
   2.  In the higher radiata a large artery surrounds  the beginning
of the  alimentary canal, in  the form of a ring,  from which the
systemic branches arise. 
92              EVERS'S COMPARATIVE ANATOMY.

  3. A distinct heart is first seen in the crustacea.
  4. In the gasteropodous mollusca, as the snail, the rectum passes
through the heart.
  5. There is no portal circulation in the avertebrata.
  6. The heart of a fish consists of  a single auricle and ventricle,
and the blood of the porta is distributed to the liver and kidneys.
  7. All the amphibia have at first the single heart of  a fish, but
the caducibranchiate species terminate life with the double heart of
a reptile.
  8. The heart  of  birds consists of four distinct compartments, as
in mammalia, but rather more perfect, owing to the existence of its
fleshy valves.
  9. The heart  of the higher warm-blooded mammalia, even that
of man,  in the  course of its development,  represents the several
grades which constitute the permanent types  of  the lower animals.
                       CHAPTER XV.

        RESPIRATORY SYSTEM IN THE INVERTEBRATA.

  The respiratory organs are sometimes placed  in the interior of
the body in the form of lungs sometimes towards its exterior in the
form  of lamellated, ramified,  pectinated, tufted,  ciliated, or pin-
nated processes, termed gills,  or branchiae, and a third form of re-
spiratory apparatus is obtained by the development of a system of
tracheal tubes, ramified  to an exquisite degree  of minuteness, and
widely spread through all the organs  of the body.  Animals pro-
vided with lungs generally breathe atmospheric air, whilst in those
furnished with branchiae respiration is accomplished  by means of
water. An exception to the former, however, is met with in the holo-
thuria; and to the latter, in the terrestial crustacea.  It will appear
in the progress of this article that some of the  vertebrated animals
commence life by a branchial respiratory and terminate it by a pul-
monary, and that others enjoy a mixed  form  of respiratory organ all
through.  In fact, nature seems  almost to have exhausted her
ingenuity in the  construction and development of respiratory
apparatus.
   Cyclo-neura.—In the lowest classes  of  this division  the only
respiratory organs  detectible are small cilia pervading the entire
surface, but so minute as to require  high  magnifying powers to
render them visible.  The tentacula and the whole surface of the
body are subservient to the function of respiration in the polypifera.
In the asterias and sea-urchin among the echinodermata, the water
passes into and out of the cavity lined  by peritoneum, in'which the
viscera are lodged.  In the  holothuria the  water is alternately re- 
        RESPIRATORY SYSTEM IN THE INVERTEBRATA.       93

ceived and emitted from a tube which is ramified in an arborescent
manner, with terminal cellules.
   Diplo-neura.—The highly vascular skin of the entozoa performs
the function of respiration—in some, through the medium of water;
and in others the blood is oxygenated on the mucous surface of the
animals they infest.   In the cirrhopoda respiration is performed by
the arms and  by the  leaf-like  fringed membranes attached to the
anterior part of  the sides of the body.  The surface of the body is
in general  the seat of respiration among the annelida, but in the
lumbrici, nereides, and hirudines  respiration is in  part effected by a
series of minute membranous  sacs under the skin of the  abdomen,
each having a separate external opening.  Respiration is aerial  in
the greater number of insects, the air being received through a
number of stigmata, and carried by the tracheae in some cases into
vesicles, and in others into longitudinally ramifying trunks.
   Many insects  in their larval state breathe by means of branchiae
in the  water,  and some in their perfect condition breathe water,
although they have an internal tracheal apparatus ; from the water
in these branchiae the air  is separated, and  passed in the  gaseous
state through  the ramified tracheae.  There is a  very curious fact
connected  with the eristalis, this  disgusting insect has the  last ring
of its body elongated  into  a membranous tube,  within which there
is a second horny tube, which  the animal can extend to the surface
for the purpose of respiration,  whilst it lives at the bottom  where it
procures its food in the filth of sloughs, sewers, and stinking privies.
The tracheary arachnida resemble insects in their tracheal tubular
respiration, whilst the respiratory organs of the pulmonary arachnida
consist  of  small  sacs opening externally, and situated at the under
surface of the abdomen.   Both sets of organs are enjoyed by the
segestria and  dysdera.  In tracing the progress of development  of
the respiratory apparatus  in the  higher  crustacea, as the astacus
fluviatilis,  it will be found to present four principal periods ; lstly,
that which precedes the appearance of this apparatus  ; 2dly, that  in
which the  branchias are not distinguishable from  the organs dedi-
cated to locomotion or mastication ;  3dly, that characterised by the
transformation of these into organs wholly dedicated to respiration,
and distinct from the extremities; and 4thly, that  during which the
branchiae sink inwards, and become lodged in the branchial cavities.
   By reviewing  the respiratory apparatus in the different groups  of
crustaceans, it will be found that the several stages of development
of the higher orders constitute the permanent  types of the lower
series; thus, to the first stage of organisation  belong  the  greater
number of the entomostraca and copepoda; to the second, the bran-
chiopoda ;  to the third, the amphipoda; and to the fourth the entire
order of the decapoda.  The greater number of the crustacea live
under water;  some, however, as the gecarcini,  or  land-crabs, con-
stantly live out  of water,  but  it is necessary tl at their respiratory
membrane  shall  be kept humid, and for this purpose the membrane
is thrown into folds in the form of reservoirs for containing  water. 
94
EVERS'S COMPARATIVE ANATOMY.
   Cyclo-gangliata.—The greater number of this division breathe in
water, by means of gills, some however, breathe by lungs in the air.
The first mode of respiration is enjoyed by the tunicata, conchifera,
pteropoda, cephalopoda, and some of the gasteropoda, the remainder
of this class breathe atmospheric air, by meansof a lungin theform
of a large cavity, placed beneath the mantle.  A curious circumstance
connected with the conchifera is, that the eggs on escaping from the
ovary, are deposited between two layers of the branchial membrane,
where they increase in size and undergo incubation.
                       CHAPTER XVI.

         ORGANS OF RESPIRATION IN THE VERTEBRATA.

                           PISCES.

   This entire class is covered with branchiae, by means of which
they abstract the free oxygen contained in the water.  In the sharks
and rays, and in all the  osseous fishes there are four  gills on each
side, supported by as many branchial arches of cartilage or bone,
connected to the os hyoides.
   Each  gill  consists of  a double series of lance-shaped  lammellas
closed in by a movable cover, operculum.  Generally there is but
a  single opening  for the  passage  of the water,  but  in some
instances, especially among  the  cartilaginous  fishes,  there are
several.  In  consequence of the swimming bladder of fish beino-
supposed by Cams, Blumenbach, and many others, to besubservienl
to the purposes of respiration, it merits some notice in this place
   1 his organ, which is sometimes divided  by a  septum,  as  in the
genus cyprinus  and  sometimes absent,  as in  the  pleuronectes,
lophius  and mackerel, is placed  in the abdomen, close to  the spine
and below the kidney;  consists  of an internal vascular lining
membrane, a strong fibrous tunic, and a partial investment of peri-
toneum.  In fresh-water fishes, it has been found to contain nitrogen
and in  salt  water fishes,  chiefly carbonic acid gas.   From Si
onenTrinPfnnth ^^ if™*" Pneuma^us, passes forwards  and
opens  into   the oesophagus,  except  in  the  sturgeon  where  it
opens into the stomach.   This  duct is double in the cod  ?n the
carp it possesses valves so disposed as to admit  of  the egress bm
prevent the ingress of air; it is absent in the sciura,  cobitif  burbo
and others.   When we consider  that this organ is largest in such
fishes as swim with greatest velocity, and wanting in^hose where
large  fins or  a powerful tail  compensate for its abslnce we arldis

Eon0 ^ WUh th°Se Wh° Fegard * as an °« Fogr-st 
ORGANS OF RESPIRATION IN THE VERTEBRATA.      95
                          AMPHIBIA.

  Frogs and salamanders  in their tadpole state, breathe by gills,
which  during the earliest periods of their existence are placed ex-
ternally; they also possess rudimentary lungs, which become deve-
loped as the animals change from the aquatic to the aerial respira-
tion.  The perennibranchiate amphibia, as the proteus, siren, and
axolotl also possess both sets of organs, and retain them through
life, but here the lungs always present the rudimentary type, and
it is even doubted whether they  subserve  at all to the function of
respiration.   In  these as well as in the larval  condition  of the
caducibranchiate  genera, the pulmonary organ is in the form of a
mere sac,  and it  is only during the metamorphosis that it assumes
the cellular character.  In  the adult state  of all the higher orders
of amphibia respiration is accomplished in a manner different from
all other air-breathing animals, viz., the mouth being fully distended
by the air  which enters through the nostrils, these passages together
with the pharyngo-oesophageal are closed, the mouth then suddenly
contracts  by the  action of the surrounding muscfes, and the air is
forced  by  an effort of deglutition  through  the glottis and trachea
into the lungs.  Hence, one of the most effectual ways of killing a
frog is to  keep its mouth open for a  short period; this mode of
inspiration  is accounted  for by recollecting that the  ribs are
absent in these animals.

                           REPTILIA.

  In most of the amphibia the trachea is very short and perfectly
membranous.  In this  class it is somewhat longer, and cartilaginous
plates begin to appear in it; these plates which are first seen in the
dactylethra, do not form perfect  rings, but  present the appearance
of perforated lamellae irregularly disposed.   In the bronchi of the
cascilias, however, the cartilaginous rings are much more complete.
In lizards  and serpents the "lung is  a mere cavity with cellular
parietes, having  perforations which communicate  with  the  neigh-
bouring cells. Turtles have a more complicated structure, approach-
ing that of warm-blooded animals.

                            AVES.

  The  lungs, in  this  class, are confined to the back parts of the
cavities of the thorax and  abdomen by the serous  membrane com-
mon to these cavities ;  they are of a flattened, elongated form, smooth
anteriorly, and grooved posteriorly by the ribs, between which they
are impacted ; they are of a bright red colour, and of a loose spongy
texture; on the  surface of the  lungs there are  openings through
which  air  passes from the  bronchial tubes into large neighbouring
cells.   In  birds not organised for flight these cells, are confined to 
96
EVERS'S COMPARATIVE ANATOMY.
 the abdomen, but in  others they extend along the neck, and even
 into the extremities:  they also penetrate the cavities and diploe of
 the bones, a discovery for which we are  indebted to Mr. Hunter.
 This great physiologist injected the medullary cavities of the bones
 from  the  trachea:  he also tied this tube, and  having broken the
 humerus  of a fowl, and the femur of a hawk,  he found that the
 birds respired for a short time through the artificial openings.  The
 proportion in  which the osseous system of birds  is  permeated by
 air has reference to  their respective modes of progression, thus
 almost every bone in the body admits air in the kite, the hawk, the
 eagle, and other  birds of high  flight; and in the hornbill even the
 phalanges of the  toes contain air.  Four uses have  been ascribed
 to this extension of the  respiratory system in birds—first, to sub-
 serve the  function of respiration;  secondly, to aid by mechanical
 pressure the  action of the  lungs;  thirdly,  to render  the body spe-
 cifically lighter for the purposes of flight;  and fourthly, by the dis-
 tension of the cells in the extremities to assist in  maintaining the
 wings in  a state  of extension,  during long-continued flight.   Mr.
 Hunter  supposed it contributed to sustain  the song of birds and to
 give it strength and tone.
  The air passages in birds consist of a superior larynx, a trachea,
 and inferior larynx, and two bronchi with their ramifications.  The
 superior  larynx is  situated behind the root of the tongue, resting
 on the uro-hyal element of the  os hyoides; it is composed of  from
 four to ten bony or cartilaginous pieces, and two pairs of muscles;
 thyro-arytenoidea and constrictores glottidis.   The trachea is  com-
posed of a series of bony or cartilaginous rings, which form com-
plete circles, with the  exception of the  two first;  they are closely
 approximated, and sometimes overlap.   Many birds, as the rasores,
 have no  inferior  larynx; in  others it presents different degrees of
 development, thus, in  the  genus  falco there is but one "pair of
 muscles; in the parrot tribe three, and in the insessores, where this
 organ attains  its greatest degree of perfection, five.   The rings of
 the bronchi do not form complete circles, but  gradually  become
 smaller, and finally disappear.

                          MAMMALIA.

  In the entire of this class there is great similarity in the respira-
tory organs, not only  to  each other  but to the human type of for-
mation.   An  epiglottis exists in all, and is divided at its superior
extremity  in the seal, the hare,  and the ant-eater.   The larynx in
 all the mammalia consists of the same parts generally as in man.
 but occasionally modified in obedience to particular circumstances.
 Thus, in  the  cetacea  this organ ascends  as  far as  the  posterior
 nares, and communicates with  the spouting hole,  which opens at
 the top of the head by a single  or double orifice, closed by a fleshy
 valve in the form of two semicircles.  The great size of the  larynx
 in the lion accounts  for the  powerful and terrific roar of that ani- 
       ORGANS OF GENERATION IN THE INVERTEBRATA.      97

mal.  The peculiar grunting voice of the pig is produced by large
lateral cavities communicating with the small ventricles of the
larynx, and the neighing of the horse results from the vibrations of
membranous folds connected with the chordas volcales.
  The trachea varies considerably in the length, breadth, and num-
ber of its rings; thus, in the seal, the porpoise, the cheiroptera, and
several rodentia, its rings form  complete  circles as in birds; their
number varies from 14, presented by the mouse, to 78, as seen in the
seal.  In the sloth  the trachea descends considerably in the chest,
and again  ascends to divide into the bronchi.  The lungs  present
very  few varietes in  the class mammalia.  In the cetacea they
are remarkable for their elongated, flattened form, and for  the free
communication of their cells with  each other.

                       RECAPITULATION.

  1.  The respiratory apparatus is very extensive and greatly varied
in the invertebrata, in the lowest orders of which it is usually con-
fined to the surface of the body.
  2.  Respiration  is performed  by gills in fishes, and in the caduci-
branchiate amphibia,  during  the  tadpole state; in  the  siren and
proteus it  is in all probability performed all through life  both by
gills and lungs.
   3.  In  birds this  system is  extended  into the bones and  into the
large cells  of the thorax  and abdomen.
  4.  The  organs of  respiration throughout the class mammalia.
are very similar to those of man.
                       CHAPTER XVII.

        ORGANS OF GENERATION IN THE INVERTEBRATA.

   Notwithstanding the varied modifications observed in the organs
of  generation  throughout, the animal  kingdom, the reproductive
function will be  found to conform to a few leading types, as the
fissioarous, gemmiparous, oviparous, viviparous, and ovo-vivipa-
rous.  Fissiparous generation consists in the division of an animal
into two or more, similar in every respect to the original being. In
this form of generation, which is met with in some of the infusoria,
cestoidea, and annelida, the line of separation takes different direc-
tions, being transverse in the paramoecuim, and vertical in the vor-
ticellae.  In gemmiparous generation the young appear as sprouts
from the body of the parent:  it  is more extended  than  the  last,
being  met with in  the  polypine and  coralline animals, in sponges,
cyst norm  entozoa,  and in some  acalephae.  These two  forms  of
     q__H                                        evers 7 
98
EVERS'S COMPARATIVE ANATOMY.
reproduction appertain  to animals  unprovided with special organs
of generation.
   In  oviparous generation, which  belongs  to birds, many reptiles
and fishes, the egg, after  fecundation, passes  through the oviduct
from  the body of "the parent,  to be  hatched by  the  influence of
external agents. Most mammalia afford examples of the viviparous
form  of generation, here  the ovum remains within the  uterus of
of the female until  it  is  capable of independent life. Many animals,
however, besides mammalia, bear their young  alive,  examples of
which are  to  be met with  among the reptiles, fishes, mulluscous
and articulate animals.  The last form of generation above alluded
to is  the ovo-viviparous,  which  implies the production  of  living
foetus, the  ovum being hatched within the body of the parent;
but never contracting a vascular connection with the uterus,  this is
the case with the monotremata, as the echidna, and ornithorhynchus,
and also with the monotrematous marsupiata, as the opossum, and
kangaroo.
   All the higher classes of animals  possess generative  organs of
two kinds, the co-operation of which,  for the purposes of reproduc-
tion, constitutes the distinction of sex, into male and female.
   The following table  exhibits a view  of the reproductive process
in the different classes  of animals,  as given by Dr. Thomson, of
Edinburgh, in  his  matchless article on generation, in the "Cyclo-
paedia of Anatomy  and Physiology."
                                f Parent splits, each part a new ani-
                                       mal.
                                I   1.  Transverse.
               fFissiparous  .  .   \   2.  Longitudinal.
                                   3.  Irregular.
                                 Parent splits  and discharges the
                                       young.
               1 Gemmiparous .   \ Budding upon the parent stock.
                L                I feeparated buds, gemma;, or sporules.
                                   1.  On all parts of the body.
                                   2.  On one part or oigan only.
               f Hermaphrodite    Both sexual organs on one individual.
                                   1.  Self-impregnation.
                                   2.  Mutual impregnation.
                                f Oviparous laying eggs which are
                                       hatched.
                                I    1.  External fecundation.
                IDioecious   .  .   {   2.  Internal fecundation.
                                 Ovo-viviparous, eggs hatched within
                                       the maternal body.
                                ^Mammiferous, suckling  the young.
                                    1.  Monotrematous.
                                   2.  Marsupial.
                                   3.  Placental or strictly viviparous.
   From the above table, it appears  that there are a vast number of
animals wholly destitute of generative apparatus, and where organs
first appear, the animals seem to have the power of propagating by
means of ova,  without  copulation; in many of the lowe?animals,
Non-sexual  ■{
^Sexual 
       ORGANS OF GENERATION IN THE INVERTEBRATA.      99

however, as the annelida, the acephalous, and gasteropodous mol-
lusca, both sets of organs are placed on the same individual, con-
stituting  it an hermaphrodite.  Some of animals of this class, as
the holothurias, possess the power of  self-impregnation,  whilst
others, though possessing double organs, require mutual impregna-
tion ;  this is the case with the leech, and the common earth-worm.
In all the insect tribes the sexes are separate, the male organs being
the testicles,  the vesiculae  seminales, the excretory tubes,  and in
many, the prehensores or organs for seizing the female  during
coitus.  The female organs consist of the ovaria, the oviducts, the
spermotheea, or  receptacle  for the male semen, and the ovipositor,
an instrument for directing the ova to their proper location at the
period of extrusion.
  The generative system of the arachnida and  crustacea is very
simple, consisting in the male, of testes and vasa deferentia, and in
the female, of membranous ovaries with their  excretory ducts.
These organs are -double in each sex,  and quite distinct from each
other.
  In the mollusca, the generative organs present some peculiarities;
there  is but one testicle in the male, and one  ovary in the female,
each placed on  the right side of the neck.  The penis is of huge
dimensions in the gasteropoda, while in the cephalopoda it is quite
rudimentary;  but, by  way of compensation,  the vas deferens is
large, convoluted, and muscular.
  When two snails amorously disposed, meet, as Professor Jones,
of London, lucidly observes, they begin their blandishments  by
rubbing  the  surfaces of their bodies together;  after some  hours
the generative  orifice on the side of the neck is seen to dilate, and
to display within its cavity  three apertures, one  from the  penis,
another from the female organs, and the third from the sac which
contains  a calcareous quadrangular spike, called the dart; the use
of which seems to be to excite to love its sluggish, sleepy, apathetic
associate,  by pricking the surface of its body;  at  length his dart is
broken, and he becomes in turn the object of a similar attack ;  both
the reptile cupids having thus exhausted their quivers, and received,
each,  the  love inspiring wound, the other two orifices now dilate,
from one the long whip-like penis protrudes, aud is received by the
vaginal orifice of the other; these phenomena being reciprocal, they
mutually embrace and impregnate each other. 
100            EVERS'S COMPARATIVE ANATOMY.
                      CHAPTER XVIII.

         ORGANS OF GENERATION IN THE VERTEBRATA.

                           PISCES.

  In this extensive class, the generative apparatus is comparatively
simple, consisting in the female osseous family of two large mem-
branous ovaries, with short oviducts, opening in the vicinity of the
anus.  The ova are generally very numerous, and are deposited in
shallow water where they receive the fecundating influence of the
male, and the genial heat of the solar rays.   In the males the tes-
ticles are of great size and composed of a congeries of convoluted
tubes; the semen is discharged by the vasa deferentia,  and diffused
through the water in the neighbourhood of the ova, which are thus
impregnated.  The presence of a penis in this class is not necessary,.
seeing that copulation does not occur; to this, however, there are
a few exceptions, in  which the ova are fecundated prior to  their
discharge;  and in the blennius viviparus, the young are  produced
alive, being hatched within the oviduct.   In these  rare instances,
the vas deferens protrudes  externally in the form of a little penis.
In the eel, the lamprey, and many  cartilaginous fishes, the ova are
suspended in the interior of the abdomen where they receive the
influence of the semen, and are discharged by a simple orifice near
the anus.

                          AMPHIBIA.

  The ovaria of these animals are smaller,  but in  other respects
similar to those of the lamprey ; the oviducts  are long and  tortuous;
they commence by a fimbriated extremity, and previous to  their
termination in  the cloaca they enlarge to retain the ova for some
time before expulson.  In  the frog, the testicles, which are two in
number, are placed on the kidneys, and  their excretory tubes dis-
charge themselves into the ureters.  In the  majority of instances,
the ova are fecundated in exitu  by the sprinkling of the semen  from
the male which is  placed on the back of  his mate.  In the triton,
and a few others, the semen diffused through the water passes into
the genital  organs and  produces internal impregnation.  The sala-
mander alone possesses a rudimentary penis, and  in this case, too,
the eggs are hatched within the oviduct.
  The reptilia, for  the greater part, possess a generative system,
the same as  the amphibia; the higher orders accomplish internal
impregnation.  The males of serpents are generally provided with
two  penises which, instead of being perforate, are grooved for the
passage of the semen into the cloaca of the female.  In the sauria
the penis is bifid, and its extremities covered  with recurved spines. 
ORGANS OF GENERATION IN THE VERTEERATA.     101
                            AVES.

  In the males of this class, the testes, two in number, are placed
high in the abdomen, beneath the kidneys;  they are subject to re-
markable variation of size, according to the period of the year their
office is required; thus,  in  January the testicle of the sparrow is
about this size, o, and  by April  it attains the size of a large  pea.
The vasa deferentia, seldom  much curved, pass down and terminate
separately on a rudimentary penis  in  the  urethro-sexual pouch.
The epididymis is quite rudimentary, and varies much in colour,
being black, yellow, or green.  Coitus is usually effected simply by
an eversion of the cloacae, therefore the intromittent organ is only
rudimentary: in those birds, however, which copulate in water, as
the drake,  swan, &c, it  necessarily  attains a  larger  size.   It  is
sometimes  double  as in  serpents, and is always grooved along its
upper surface, for  the  passage of the semen.   The ovarium  and
oviduct are confined to the left side, they primarily, however, exist
on both sides, but rarely continue their development  on the right.
A clitoris is  present in the females of those species whose males are
provided with a penis.

                          MAMMALIA.

  The male organs of generation in this class consist of the  testicles,
vasa  deferentia, penis, urethra,  vesiculas seminales, the prostatic
and  Cowper's glands, and with one interesting exception, supplied
by the monotremata, the genito-urinary systems are quite distinct
from the digestive.  In by far the greater number of mammalia the
testicles descend into the scrotum as in man  ; in  some, however, as
the amphibious  mammalia, the cetacea, the elephant, and the orni-
thorhynchus, they never leave the abdomen, and in others,  as the
bat, the mole, and  the hedge-hog, among  the insectivora; the rat,
the guinea-pig, the porcupine, and the squirrel, among the rodentia,
they descend during the rutting season, and return into the abdomen
after it is over.  The communication between the tunica vaginalis
and the peritoneum  remains  unclosed in those animals in which the
testicles descend, except  man, and where these glands occasion-
ally pass into and  out of the cavity, the communication is very
free.  The  vasa deferentia are very serpentine  in those  ani-
mals where the testicles remain in the abdomen,  and in ruminants,
the elephant, and especially  the horse, they are greatly dilated near
their termination in the urethra.
   Vesiculce. Seminales.—There seems to be  no general law for the
presence or absence of these accessory bodies.  They are met with
in the camel, elephant, bull, ram, horse, boar,  guinea-pig, rabbit,
hedge-hog,  <fcc.  In these  animals they have either no communica-
tion, or  a very imperfect  one, with the vas deferens.  In man and
the simiae only is the communication free and direct.  The prostate 
102
EVERS'S COMPARATIVE ANATOMY.
is more constant in its existence than the vesiculac, being found in
all  orders of the mammalia, excepting perhaps the greater number
of the rodentia and  insectivora.  It is double in the elephant,  the
camel, the  horse, and some others.  Cowpefs glands, which  are
small, and  situate  behind the  bulb of the  urethra in  the human
subject, are large, and  often increased in number in other animals,
thus  in the opossum and kangaroo-rat there  are four, and in  the
wombat, kangaroo, and others, as many as six.   They are  absent
from  the greater number of carnivora, ruminantia, and cetacea.  In
the marsupiata they are covered by a strong muscular stratum, and
in  the icheneumon,  their ducts run forward,  and  open near the
extremity of the penis.
  Penis.—This organ is  modified considerably throughout  the
class.  Thus, in the digitigrade carnivora, as the dog and the lion, its
two crura are separated by a distinct fibrous septum, which is absent
in the cetacea, pachydermata, and plantigrade carnivora.  In  the
cheiroptera, quadrumana, cetacea, rodentia, and carnivora, with the
exception of the hyena, and a few others, the penis is occupied  by
a cylindrical bone occasionally grooved.  Remarkable peculiarities
exist  in the  intromittent organ of the marsupiata; in the opossum
the glans  is bifid, and  has three  openings, one  for the  urine, and
two for the semen.  In the ornithorhynchus paradoxus the penis is
double anteriorly, and  in the  hystrix, it divides  into four glands,
each  furnished with  sharp papillas  perforated  for the discharge of
the semen,  but in neither of these strangely organised animals does
the urine pass  through it, this organ being concealed within the
cloaca.  The urethra shall be deferred till the  consideration of the
urinary organs.
  The female organs of generation in the mammalia consist of the
vulva, clitoris, nymphas, vagina, uterus, Fallopian tubes, and ovaries.
These latter organs are  invariably  double;  in the marsupiata
their structure is racemose as in  birds, but in  all the other genera
they are more solid,  and approach  more or less the human type.
The Fallopian tubes present  but few peculiarities, except  in'the
echidna and ornithorhynchi, where they experience a dilatation  in-
ferior] y to supply the place of a uterus, and afterwards open sepa-
rately into the short vagina, on each side of the orifice of the urin-
ary bladder.  In the lower orders of mammalia  the urethral and
sexual passages are blended together, the uterus is  elongated in form,
and thin in its  walls; in the carnivora, ruminantia, pachydermata,
and cetacea, a mesial cleft appears, and the cornua are greatly deve-
loped  ; and  in the  marsupiata and most  rodentia, the oro-an is
divided  into two lateral halves, each opening separately into the
vagina, which, in  the  virgin  state of the sloth, the ass, the  mare,
the pig, and the cow, is divided by a narrow vertical septum.   The
external organs of generation afford no striking peculiarities'except
in the deficiency of nymphas and hymen.
  From a  review of the above details of the generative organs in
the marsupial and monotrematous orders, one must expecf to find 
         ORGANS OF GENERATION IN THE VERTEBRATA.      103

some peculiarity in  their mode of generation.  In  all the other
mammalia the  ovum is fecundated in the ovary, from which it de-
scends through the  Fallopian  tube to the  uterus, in the higher
orders about the twelfth day.  An intimate  vascular connection is
now established between the ovum and the uterus, by means of the
placenta, and continues till  the embryo is fully formed, and as we
say,  capable of enjoying an  independent existence.   This consti-
tutes the  period of utero-gestation, which, in the human subject is
ten lunar months, but varies in almost every species of the class.
A very different process, however, takes place in  the animals above
alluded to, thus in the kangaroo, the  foetus, small and imperfect,
leaves the uterus about the thirty-ninth day after conception, and
is lodged  by the mother in the marsupium or pouch formed for its
reception  on the lower part of the abdomen, by a  fold of integument
in which the mammary gland is  placed.  Shortly after it reaches
the pouch, it is found attached by its mouth to one of the nipples,
from which it receives a constant supply of  milk;  this is rendered
more secure by the gland being covered over by  a stratum of  mus-
cular fibres, which enables the mother to feed the foetus at pleasure.
   The mode of breeding of the monotremata is  as yet involved in
some obscurity.  The word monotremata means  animals with  a
single  outlet from the genito-urinary and digestive organs, called a
cloaca; and  is applicable to all  the  marsupiata, but is at present
confined to the edentate species of them, as the echidna and  orni-
thorhynchi. Previous to the late valuable researches of Mr. Owen,
the existence of mammary glands in these animals was denied,
which, combined with the  structure of their ovaries, and their pe-
culiar  development of uterus, led to  the supposition of their being
oviparous in their generation.
   Although the structure of their generative  organs, the presence
of mammary glands, their bearing their young alive, and suckling
them, confer on them the ovo-viviparous type of generation, it  must
be acknowledged  they  possess  many characters in common  with
reptiles.

                       RECAPITULATION.

   1. All forms of generation conform to the fissiparous, gemmipa-
rous, oviparous, viviparous, and ovo-viviparous.
   2. These organs  are separate and  distinct in the insecta, the
annelida, and the  crustacea.  In  the mollusca they are single, and
confined to one side.
   3. This system is simple in  fishes, and a rudimentary penis oc-
casionally present.
   4. Internal impregnation  rarely occurs among the amphibia or
reptiles.
   5. In birds the size of the testicles varies according to the season,
and the penis is often absent. 
104            EVERS'S COMPARATIVE ANATOMY.
  6. In some orders of mammalia  the  testicles never leave the
abdomen, and in others they descend at certain periods.
  7. There is no general law for the presence or absence of vesi-
culas seminales or prostate, the latter is more generally present.
  8. The  penis  in  many instances is furnished with a bone; in
some  it is  bifid, and  in  the ornithorhynchus  no  urine passes
through it.
  9. The. generative organs  and mode of generation are  peculiar
in the monotremata.
                       CHAPTER XIX.

           URINARY ORGANS IN THE INVERTEBRATA.

   The urinary, like the biliary and lachrymal apparatus, consists
of four principal  parts, each having its peculiar office consigned to
it, and all jointly contributing to the same end—namely, the sepa-
ration from the blood, and the discharge from the system, of certain
decomposed and  effete  animal and saline matters.   The urinary
organs, when complete,  as they are in the higher orders of animals
consist of the kidneys, the ureters, the bladder, and the urethra.
  Although the mollusca secrete urine, and  uric acid has been de-
tected in the long convoluted cosca of insects, and even through
the bodies of cantharides; yet no perfect urinary system has been
discovered in the great invertebrate division of animals.  It is more
than probable that the  function of the  kidneys in the majority  of
instances devolves on the respiratory, the cutaneous, and  the biliary
systems, together with certain glands, many of which serve not only
for the elimination of noxious materials from the system, but as or-
gans of defence on the approach of danger; in this latter light may
be regarded the acrid secretions of bees,~"beetles, wasps, and spiders •
as also the ink of the cuttle-fish which has the effect of blackening
a considerable extent of the surrounding water, and thus baffling
the attacks of its enemies: and among the  vertebrata,  a striking
example is presented by  the yagouare of Azara, one of the mephiti?
weasels o( Chili, whose  urine is rendered so intensely offensive bv
the secretion of some adjoining glands, that  dogs or other animals
which have been sprinkled with it during their pursuit of this crea
ture, are  said to have torn portions of their own skins off from dis
gust, notwithstanding careful and repeated ablutions 
URINARY ORGANS IN THE VERTEBRATA.         105
                       CHAPTER XX.

            URINARY ORGANS IN THE VERTEBRATA.

                            PISCES.

  The kidneys in this class are long and narrow, sometimes extend-
ing the whole length of the abdomen,  as  in  the burbot.*  They
generally  present the appearance  of forming  but a single mass,
their separation being only indicated by the presence  of the ureters
and the cava.  The ureters, which arise by numerous fine radicles,
soon unite in all the osseous fishes, into a single tube, which forms
a heart shaped  dilatation previous to its termination behind the
anus, in common with the sexual organs.
  Bladder.—This  reservoir is  absent from all  the osseous,  and
several of the cartilaginous fishes, as the ray and shark, in which
the ureters open as in birds, into a cloaca:  when  it is present as in
the lump-fish, it receives the ureters anteriorly, and opens behind
the anus in common with the vasa deferentia.

                          AMPHIBIA.

  The  kidneys are more distinct in this class than in fish.  They
are greatly lengthened in the aquatic genera, but are much shorter in
the froo-.  The  ureters  convey the urine to the bladder, which is
situated in front of the rectum : in the frog it is of considerable  size,
its walls are thin, and its fundus presents two cornua.  In the rep-
tilia the kidneys afford  but few peculiarities, being elongated in the
lizard, as  in fish, and somewhat oval in  the tortoise.  The ureters
are longer in this class than in the amphibia, and discharge them-
selves either into the cloaca or bladder.  This organ  is absent from
the ophidia, and several of  the sauria, as the lizard,  and  the croco-
dile.  It is very large in the chelonia, as the tortoise, and it is sin-
gular, that the ureters instead of going to it, empty themselves into
the urethra in front  of it, so that theurine has to re-ascend to the
urinary reservoir.

                             AVES.

  In  this  extensive oviparous class the kidneys are of great length,
extending along the  spine,  from the lungs to the lower end of the
rectum.   These organs are  relatively larger in birds than in the
terrestrial mammalia—a circumstance which is explained by recol-
lecting  the nature of their integuments,  and the little transposition
they admit of.   They are of small  size in  the bustard and heron,
and  their lower extremities are somewhat blended together in the
coot.   Their structure  is remarkable for the  absence of cortical
portion ; the  tubuli uriniferi run to the  surface,  and by  their con- 
106
EVERS'S COMPARATIVE ANATOMY.
fluence form the commencement of the ureter, which descends
along the surface of the kidney, and posterior wall of the  rectum,
and terminates in  that, part of the cloaca called the urethro-sexual
cavity.   The space between their termination and that of  the rec-
tum is large in the owl and many aquatic birds, and is looked upon
by some  as a rudiment of urinary bladder.
  The supra-renal capsules are small, of a bright yellow colour,
and  placed on the  inner and upper part of each kidney, in contact
with the testicle or the ovary.   They are erroneously supposed by
some to have some functional relation to the generative  system.

                         MAMMALIA.

  The kidneys are lobulated in the cetacea, seals, otters, bears, the
elephant, the ox, &c, as in the human  foetus.   In the otter each
kidney consists of about ten lobules; in the bear of about fifty, and
in the seal as many as a hundred and thirty.  They present a lobu-
lated appearance in many other mammalia during the early periods
of existence. The ureters enter the bladder  in an oblique direction,
a little behind its neck, in all the animals of this class, with the ex-
ception of the  echidna and ornithorhynchus, in which  they open
into  the urethra near its commencement, so that the urine must re-
ascend to the bladder, as in the chelonian reptiles.  In the mamma-
lia generally the bladder lies  more  loose in  the abdomen  than in
the  human subject, owing to its more perfect peritoneal investment.
For  the  greater  part it is more muscular and less capacious in the
carnivora than in the herbivorous tribes. In the rodentia, however,
it is small  and fleshy.  The shape of the bladder will be found to
vary in obedience to age, sex, and species, the younger  the  animal,
however, the more elongated will it be found, and  in  the human
embryo it is cylindrical, tapering towards the urachus  above, and
the  urethra below.
  The renal capsules, like the kidneys, are lobulated in the  cetacea,
and  other aquatic  mammalia,  and are  found relatively very large
in the young of  animals possessing them.   The urethra, as in the
human subject, consists of a membranous  or muscular, and  of a
spongy portion, the former receiving the accessory secretions.  In
the  boar  and many ruminants these two portions join at an angle.
The corpus spongiosum arises by two roots in most of  the marsu-
piata, and in the kangaroo, the urethra runs through the centre of
the  penis to its extremity.


                      RECAPITULATION.

  1. In the great invertebrate division of  animals, the functions of
the  kidneys seem to be performed by other  parts, as the surface of
the  body generally, and certain glands.
  2. Kidneys exist in all fishes, but a urinary bladder  is confined
to the cartilaginous tribes. 
NAMES OF AUTHORS CONSULTED.
107
  3. Birds have kidneys and supra-renal bodies, but no bladder.
  4. The kidneys are lobulated in the adult state of many, and in
the foetal state of most mammalia.
  5. The ureters open  into  the bladder in  all  the  mammalia,
excepting the monotremata.
                          LIST

   OF  THE PRINCIPAL AUTHORS  CONSULTED.

Baron Cuvier.—Lecons  D'Anatomie  Comparee—Regne  Animal—By
          Griffith, &c.
      Linn.eus.—Systema Naturae.
      Grant.—Outlines of Comparative Anatomy, &c.
      Lamark.—Histoire Naturelle des Animaux sans Vertebres.
      Owen.—Clycopaedia of Anatomy and Physiology, &c.
      Coldstream.
      Edwards.
      Lawrence.—Zoological Lectures.
      Bell.—Cyclopaedia of Anatomy and Physiology.
      Auduin.
      Todd.
 Sir C. Bell.—Mechanism of the Human Hand—Bridgewater Treatise.
      Blumenbach.—Comparative Anatomy, by Lawrence.
      Deshayes.—Cyclopaedia of Anatomy and Physiology.
      Harrison.
      Sharpey.
      Carus by  Gore.—Introduction to the  Comparative Anatomy of
          Animals.
    F. Cuvier.—Histoire Naturelle des Mammiferes.
      Houston.—Descriptive Catalogue  of  the  preparations  in  the
          Museum.
      Pyfe.—Outlines of Comparative Anatomy.
      Thomson.—Cyclopaedia of Anatomy and Physiology.
      Jacob.
      Jones.
 Sir E. Home.—Lectures on Comparative Anatomy.
      Mueller.—Elements of Physiology.
      Hunter.—Animal  (Economy.
      Roget.—Bridgewater Treatise.
      Rees.—Cyclopaedia.                                 .   .
      Blainville.—De  l'Organisation  Des   Animaux,  ou  Pnncipes
          d'Anatomie Comparee. 
 
CONTENTS.
CHAP. I. Preliminary Observations,
          Cuvier's Classification of Animals,
          Grant's Classification of Animals,
       II. Skeleton in the Invertebrata—General Remarks,
       III. ----------— Vertebrata—General Observations,
          -------------Pisces,
          -------------Amphibia,
           -------------Reptilia,
           -------------Aves,
           -------------Mammalia,
          Recapitulation,     -
          Fossil Bones of Animals,
       IV. Ligamentary System,
        V. Muscular System in the Invertebrata,
       VI.----------------------Vertebrata,
           ----------------------Pisces,
           ----------------------Amphibia,
           ----------------------Reptilia,
           ---------------------Aves,
          ----------------------Mammalia,
           Recapitulation,
      VII. Nervous Syslem in the Invertebrata
     VIII.--------------------Vertebrata,
           --------------------Pisces,
— Amphibia,
— Reptilia,
— Aves,
— Mammalia,
    Recapitulation,    -
IX. Organs of Sense—Vision,
    .---------------  Hearing,
    ---------------Smell,
    ---------------Taste,  -
    ---------------Touch,
    Recapitulation,    -
 X. Organs of Digestion  in the Invertebrata,
XI.________________________Vertebrata—Pisces
     Development of Teeth,
     Recapitulation,
XII. Absorbent System,
Amphibia,
Reptilia,
Aves,
Mammalia, 
112
CONTENTS.
XIII. Sanguiferous System in the Invertebrata,
 XIV. ---------------------—- Vertebra la—Pisces,
      -------:-----------------Amphibia,   -     *
      ------------------------Reptilia,
      ------------------------Aves,
      ------------------------Mammalia
      Recapitulation,   ....
  XV. Respiratory Organs in the Invertebrata,
 XVI.-----------------------Vertebrata—Pisces,
      --------■--------------Amphibia,
                               Reptilia,
— Aves,
— Mammalia,
        Recapitulation,
 XVII. Organs of Generation in the Invertebrata,
XVIII. —------------------------Vertebra I a—Pisces,
        .-------------------------Amphibia,
        _------------------------Reptilia,
        -------------------------Aves,
        .-------------------------Mammalia,
        Recapitulation,    ....
  XIX. Urinary Organs in the Invertebrata,
   XX.--------------------Vertebrata—Pisces,
        --------------------Amphibia,
        --------------------Reptilia,   -
        --------------------Aves,
        --------------------Mammalia,
        Recapitulation,       ....
        Names of Authors who have been consulted, , 
 
 
 
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