MAMMALIA. 
5 
which it is lined in the interior. The fourth cavity, which is the 
true stomach, has received the name of caillette , or rennet-hag*, 
because it has the property (on account of the gastric juice with 
which its surface is saturated) of causing milk to coagulate. 
The first three stomachs, the paunch, the honey-comb bag, 
and the many-plies, communicate with the (esophagus, so as to 
allow the aliment to return easily into the mouth. 
From the rennet-bag, the food, going through an opening 
called the pylorus, passes into the intestines. There the alimentary 
mass yields all its nutritious elements, and is then evacuated. 
The length of the intestines varies in the Mammalia according 
to the kind of food they eat. Thus, in the Carnivora, their length 
is only three or four times as much as the length of the animal’s 
body ; while in the Herbivora the intestines are from twelve to 
twenty-eight times its length. In the domestic Cat the intestines 
are proportionately longer than in any of its wild congeners, 
having thus gradually become adapted (in a long series of genera- 
tions) to a less exclusively carnivorous regimen. 
The apparatus for the circulation of the blood has for its central 
organ the heart — a hollow muscle, composed of four cavities : two 
auricles and two ventricles. In all Mammalia there is a double 
circulation of the blood; there exists a great and a little circula- 
tion. The venous blood which comes from all parts of the body 
into the right auricle of the heart, conveyed by the hollow veins, 
passes first into the right ventricle, which sends it through the 
pulmonary artery to the lungs. There it is transformed into 
arterial blood — that is to say, it absorbs the oxygen of the air ; 
then it returns to the left auricle by the pulmonary veins. Thence 
it passes into the left ventricle of the heart, and discharges itself 
into the artery called the aorta, and thence into the other arteries, 
which distribute it throughout the whole body. The blood then 
comes back from all parts of the animal’s body into the right 
auricle of the heart by the veins — consequent upon the com- 
munication which is established between the veins and arteries, 
in the immediate vicinity of the tissues, by the general capillary 
net- work or system, 
The respiratory apparatus occupies, in Mammalia, the upper 
part of the bony framework formed by the ribs and the sternum , 
or breast bone. This apparatus is composed of lungs — double 
