850 ZOOLOGY. 
oue, has some resemblance to the horse’s hoof, in the mode 
of its connexion with the jaw. The cavity, containing the 
brain, is extremely small, in comparison with the size of the 
skull; the greatest part of which, in the turtle, is occupied 
by the large lateral fossae, holding the eye and the powerful 
muscles that move the lower jaw. This circumstance is still 
more remarkable in the crocodile. 
The trunk is consolidated with the two great shells of the 
animal; the dorsal vertebrae and ribs being attached to the 
upper, the sternum being fixed in the lower or abdominal 
shell. 
The same bones are found in the pelvis of these animals, 
as in the mammalia; but the proportion of their relative size 
is inverted. For instance, the ossa pubis are so deep and 
broad, that they form the largest flat bones in the whole ske¬ 
leton, while the ilia are the smallest. 
The form and position of the scapula and clavicle are the 
most extraordinary. The former has a most anomalous situ¬ 
ation towards the under part of the animal, just behind the 
abdominal shell; the latter consists of two pieces, joined at 
an acute angle, to which the humerus is articulated. 
Frogs and toads have no real teeth, though the margin of 
the jaws is denticulated. Their spine is short, and terminates 
behind in a straight and single bone, which is received into 
the middle of the somewhat fork-like os innominatum. 
They have no ribs; but the dorsal vertebrae are furnished 
with broad transverse processes. The scapula, which is thin 
and flat, and a pair of bones, corresponding to the clavicle, 
are joined to the sternum. 
Among the amphibia of the class of lizards, the crocodile 
may be taken as an example, on account of many remarkable 
peculiarities in its structure. In no other animal are the jaws 
of such immense size, in comparison with the extremely 
small cavity of the cranium. The anterior part of the upper 
jaw consists of a large intermaxillary bone, and the lateral 
portions of the lower maxilla are formed of several pieces 
joined together. The lower jaw is articulated in a peculiar 
manner in these animals, although the commencement of this 
kind of articulation is seen in the jaw of the testudines: it 
has an articular cavity, in which a condyle of the upper jaw 
is received. The condyle resembles in some measure, the 
pulley at the inferior extremity of the humerus, the trochlea, 
or rotula of Albinus. 
The old error of supposing that the upper jaw of the cro¬ 
codile is moveable, and the lower, on the contrary, incapa¬ 
ble of motion, which has been adopted even by such anato¬ 
mists as Vesalius and Columbus, has perhaps arisen from this 
peculiar mode of articulation ; which allows either of these 
bones to move when the other is fixed. 
The numerous teeth of crocodiles have this peculiarity of 
structure, that in order to facilitate their change, there are 
always two, of which one is contained within the other. 
But the most surprising singularity in the skeleton of the 
crocodile consists in an abdominal sternum, which is quite 
different from the thoracic sternum, and extends from the en- 
siform cartilage to the pubis, apparently for the purpose of 
supporting the abdominal viscera. 
The serpents have an upper jaw, unconnected with the rest 
of the skull, and more or less moveable of itself. 
We find in their teeth the important and clearly defined 
difference, which distinguishes the poisonous species of ser¬ 
pents from the much more numerous innoxious tribes. See 
the articles Anguis and Coluber. 
It appears, in general, that the number of vertebrae in red- 
blooded animals, is in an inverse proportion to the size and 
strength of their external organs of motion. Serpents, there¬ 
fore, which entirely want these organs, have the most nu¬ 
merous vertebra ; sometimes more than 300. 
Of all animals, serpents possess by far the greatest number 
of ribs; which amount, in some, to 250 pairs. It is neces¬ 
sary to mention here the costae scapulares of the cobra di 
eabelo, (coluber naiae) which enable it to inflate its neck. 
This is also the case with other species of the coluber; 
namely, the Egyptian coluber haje, which can dilate its neck 
very considerably when enraged. 
Serpents, with the exception of the anguis fragilis, (blind- 
worm) are the only red-blooded animals which have no 
sternum. 
The two chief divisions of the class amphibia, are dis¬ 
tinguished from each other by a remarkable difference in 
their muscular structure, which arises from a corresponding 
diversity in the skeleton. In the reptiles, for instance, and 
particularly in the turtles and frogs, where the trunk of the 
skeleton possesses but little mobility, the muscles are very few 
in number. Not only the diaphragm, but also the muscles of 
the abdomen and chest are wanting in the genus testudo. 
The other muscles are, however, of vast strength in this genus. 
In the serpents, on the contrary, they are more uniform and 
thin, and more numerous, beyond all comparison, in conse¬ 
quence of the vast number of vertebra and ribs, and the want 
of all external organs of motion. 
The muscular system of amphibia has been fully described 
under Serpentes and Reptilia. 
At fig. 47, we have the skeleton of a frog (rana tempo- 
raria); a, the parietal bone; b, the frontal bone; c, the eth¬ 
moid ; d, the superior maxillary bone; d, the zygoma; e, 
the intermaxillary bone -,f os quadratum; g-, inferior maxilla; 
h, appendage to the scapula; i, scapula; k, clavicle ■ /, furcula; 
m, xyphoid cartilage; n, sacral vertebra; o, ilium ; p, coccyx; 
q, symphysis pubis; r, s, elongated and closely approximated 
bones analogous to the astragalus and os calcis. 
Fig. 32. A view of the muscles on the anterior part of a 
male frog. Several muscles of the left side are removed; 
1, mylohyoideus; 2, hyoglossus; 3, geniohyoideus; 4, ster- 
nohyoideus; 5, deltoideus; 6, extensor digitorum; 7, supi¬ 
nator; 8, flexor digitorum sublimis; 9, flexor carpi radialis; 
10, anconeus; 11, pectoralis minor, or sterno-radialis, as it 
runs direct from the sternum over a pulley to the radius; 12, 
pectoralis major; 13, a cutaneous muscle; 14, abdominal 
portion of the great pectoral muscle; 15,rectus abdominis; 
16, obliquus descendens; 17, pronator; 18, flexor carpi ra¬ 
dialis; 19, flexor digitorum sublimis; 20, muscles of the 
thumb (flexor brevis, opponens, adductor pollicis); 21, in- 
terossei; 22, pectineus; 23, sartorius; 24, extensor cruris 
(vasti and rectus femoris); 25, adductor magnus; 26, gra¬ 
cilis ; 27, gastroconemii; 28, soleus; 29, flexor pedis (tibialis 
anticus); 30, abductor pollicis; 31, flexor digitorum pedis; 
32, interossei; 33, semitendinosus; 34, semimembranosus; 
35, extensor digitorum pedis. 
Fig. 33. Muscles on the posterior surface of the female 
frog, several being removed on the left side; 36, temporalis; 
37, levator scapulae; 38, depressores scapulae ; 39, scapularis; 
40, obliquus ascendens; 41, quadratus lumborum; 42, glu- 
taeus; 43, ischiococcygeus; 44, cutaneous muscle; 45, obli¬ 
quus descendens; 46, sacro-lumbalis; 47, latissimus dorsi; 
48, depressor maxillae inferioris, being inserted into the pro¬ 
cess behind the articulation of the lower jaw ; 49, abductor 
pollicis; 50, extensor carpi ulnaris; 51, biceps femoris; 52, 
iliacus internus (apparently supplying the place of the cru- 
ralis); 53, adductor longus; 54, pyriformis; *, the eyes; 
**, membrana tympani. The remaining references as in the 
preceding fig. It will be seen how materially the two sexes 
differ in general form, and in the condition of the muscular 
system, the thoracic region and the muscles of the anterior 
extremities being much stronger in the male than in the 
female. 
The skeleton of birds has considerable uniformity in the 
whole class; and it exhibits, when compared with the vari¬ 
ously formed skeletons of mammalia, a very great similarity 
to that of the human subject. 
The skull of birds is distinguished by this peculiarity, that 
the proper bones of the cranium, at least in the adult animal, 
are not joined by sutures, but are consolidated as it were into 
a single piece. 
Birds have, without exception, only a single condyle, 
placed at the anterior margin of the great occipital foramen. 
There is also, in the whole class, a bone of a somewhat 
square figure (called by the French os carre), by which the 
lower jaw is articulated with the cranium on both sides, in 
the neighbourhood of the ear. 
