Comparative.] 
fowls have a pair. The difference in their wings, beaks, 
and claws, are obvious; and have been already in 1'ome 
meafure obferved. 
ANA TO MY of A MPHIBIOUS and AQUEOUS ANIMALS. 
Aqueous animals are generally divided into fuch as 
have lungs, and fuch as want them. The firft fpecies dif¬ 
fer fo inconfiderably from an ox or any other quadruped, 
that a few obfervations may be fufficient to give an idea 
ef their internal ftrudture ; for this purpofe, we fhall firft 
examine that fpecies which mod refenibles man in the in¬ 
ternal ftrudhire, the tortoife. The covering of this ani¬ 
mal is compofed of a (hell fo remarkably hard and firm in 
its texture, that a loaded waggon may go over it without 
hurting the (hell or the animal within it. In the young, 
this lit ell grows harder in proportion as its contents ex¬ 
pand ; and this creature never changes its (hell as fome others 
do : hence it was neceffary for it to be compofed ot diffe¬ 
rent pieces ; and thefe are more or lefs diftinft in different 
animals. Its feet are fmall and weak, and are exceedingly 
flow in motion. It has neither tongue nor teeth; to make 
up for which, its lips are fo hard as to be able to break 
almoft the hardeft bodies. The alimentary canal very 
much refembles that of the other clafs. The principal 
difference is in the circulation of the blood. The heart 
has two diftindl auricles, without any communication; 
and under thefe, there is the appearance of two ventricles 
fimilar in fhape to thofe of the former clafs: but they 
may be confidered as one cavity ; for the ventricle fends 
out not only the pulmonary artery, but likewife the aorta; 
for there is a palfage in the feptum by which the ventri¬ 
cles communicate freely, and the blood paifes from the 
left into the right one. From die aorta the blood returns 
into the right auricle, while that from the pulmonary ar¬ 
tery returns to the left auricle, from which it is fent to 
the left ventricle, &c. fo that only a part of the blood is 
fent to the lungs, the reft going immediately into the aor¬ 
ta ; hence the animal is not under the neceffity of breathing 
fo often as otherwife it would be. 
From the bafe of the right ventricle goes out the pul¬ 
monary artery and aorta. The pulmonary artery is fpent 
upon the lungs. The aortse may be faid to be three in 
number; for the aorta finiftra afcends through the peri¬ 
cardium in company with the pulmonary artery ; and af¬ 
terwards turns down, and fends off' a confiderable branch, 
which fplits into two; one of which joins the right aorta, 
while the other is diftributed upon the liver, ftomach, in- 
teftines, &c. What remains of this aorta runs to the kid¬ 
neys and pofterior extremities of that fide. An aorta de- 
fcendens, See. after piercing the pericardium, runs down 
and communicates with the branch already mentioned, is 
cHftributed upon the right kidney and inferior extremity, 
and alfo upon the bladder and parts of generation. An 
aorta afeendens, after getting out of the pericardium, fup- 
plies the fore-legs, neck, and head. The blood of the lu- 
perior part of the body returns to the right auricle by two 
jugular veins, which unite after perforating the pericar¬ 
dium. From the inferior part, it returns to the fame au¬ 
ricle by two large veins: one on the right fide receives the 
blood from the right lobe of the liver; the other on the 
left fide receives the blood from the left lobe, and alfo a 
trunk which correfponds with the inferior vena cava in 
other animals. The pulmonary veffels run in the left au¬ 
ricle in the common way. 
The abforbent fyftem in the turtle, like that in the for¬ 
mer clafs, conlifts of lacteals and lymphatics, with their 
common trunks the thoracic dufts; but differs from it in 
having no obvious lymphatic glands on any parts of its 
body, nor plexus formed at the termination in the red 
veins. The la&eals accompany the blood-velfels upon the 
mefentery, and form frequent net-works acrofs thefe vef¬ 
fels : near the root of the mefentery a plexus is formed, 
which communicates with the lymphatics coming from 
the kidneys and parts near the anus. At the root of the 
mefentery on the left fide of the i'pine, the lymphatics of 
66j 
the fpleen join the lacteals; and immediately above this a 
plexus is formed, which lies upon the right aorta. From 
this plexus a large branch arifes, which pafles behind tire 
right aorta to the left fide, and gets before the left aorta, 
where it a (lifts in forming a very large receptaculum, which 
lies upon that artery. 
From this receptaculum arife the thoracic dmfts. From 
its right fide goes one trunk, which is joined by that large 
branch that came from the plexus to the left fide of the 
right aorta, and then paffes over the fpine. This trunk is 
the thoracic dufk of the right fide; for, having got to 
the right fide of the fpine, it runs upwards on the infide 
of the right aorta, towards the right fubclavian vein; and, 
when it has advanced a little above the lungs, it divides 
into branches, which near the fame place are joined by a 
large branch, that comes up on the outfide of the aorta. 
From this part upwards, thofe veffels divide and fub-di¬ 
vide, and are afterwards joined by the lymphatics of the 
neck, which likewife form branches before they join thofe 
from below. So that between the thoracic duit and the 
lymphatics of the fame fide of the neck, a very intricate 
net-work is formed; from which a branch goes into the 
angle between the jugular vein and the lower part or trunk 
of the fubclavian. This branch lies therefore on the in¬ 
fide of the jugular vein, whilft another gets to the outfide 
of it, and feeins to terminate in it, a little above the angle 
bet ween that vein and the fubclavian. 
Into the above-mentioned receptaculum the lymphatics 
■of the ftomach and duodenum likewife enter. Thofe of 
the duodenum run by the fide of the pancreas, and pro¬ 
bably receive lymphatics from it, and a part of thofe of 
the liver. The lymphatics of the ftomach and duodenum 
have very numerous anaftomofes, and form a beautiful 
net-work on the artery, which they accompany. From 
this receptaculum likewife (befides the trunk already men¬ 
tioned, which goes to the right fide) two other trunks, 
nearly equal in fize, arife; one of which runs upon the 
left fide, and the other upon the right fide, of the left aorta, 
till they come within two or three inches of tire left fub¬ 
clavian vein; where they join behind the aorta, and form 
a number of branches which are afterwards joined by the 
lymphatics of the left fide of the neck; fo that a plexus 
is here formed as well as upon the right fide. From this 
plexus a branch ilfues, which opens into the angle between 
the jugular and fubclavian vein. 
The circulation in ferpents and crocodiles is fimilar to 
that of the turtle ; but we find only one ventricle. The 
blood goes from the right auricle to the ventricle which 
fends out the pulmonary artery and aorta; the blood from 
the pulmonary artery returns to the left auricle, that from 
the aorta going to the right auricle, and both the auricles 
opening into the ventricle. 
The frog and lizard differ from the former animals, in 
having only one auricle and ventricle: and befides, the 
ventricle fends out a fingle artery, which afterwards fplits 
into two parts; one to fupply the lungs, the other runs to 
all the reft of the body: from the lungs and from the other 
parts the blood returns into the auricle. 
ANATOMY of FISHES. 
With refpedt to Fifties we may firft obferve, that they 
have a very-ftrong thick cuticle, covered with a great num¬ 
ber of feales, laid one on another like tiles on houfes, 
This among other arguments is luppofed to prove the hu¬ 
man epidermis to be of a fquamous ftructure; but the 
feales referable the hairs, wool, feathers, &c. of the crea¬ 
tures tiiat live in air ; and below thefe we obferve the pro¬ 
per cuticula and cutis. The generality of fifties, particu¬ 
larly thofe ftiaped like the cod, haddock, &c. have a line 
running on each fide. Thefe lines open externally by a 
number of draffs, which throw out a mucous or ftimy 
fubftance, that keeps the Ikin foft and clammy, and feems 
to ferve the fame purpofe with the mucous glands or duff s 
which are placed within many of our internal organs. In 
the next place, thefe creatures have neither fuperlor nor 
inferior 
ANATOMY. 
