OF ANIMAL BODIES. 
99 
i er in which the aliment gets into the blood; which is a 
subject distinct from the preceding, and brings us to the 
consideration of another entire system of vessels. 
II. For this necessary part of the animal economy, an 
apparatus is provided, in a great measure capable of being 
what anatomists call demonstrated, that is, shown in the 
dead body;—and a line or course of conveyance, which we 
can pursue by our examinations. 
First, The food descends by a wide passage into the in¬ 
testines, undergoing two great preparations on its way; 
one, in the mouth by mastication and moisture—(can it be 
doubted with what design the teeth were placed in the 
road to the stomach, or that there was choice in fixing them 
in this situation?) The other, by digestion in the stomach 
itself. Of this last surprising dissolution I say nothing; 
because it is chemistry, and I am endeavouring to display 
mechanism. The figure and position of the stomach (I 
speak all along with a reference to the human organ) are 
calculated for detaining the food long enough for the action 
of its digestive juice. [PI. XVIII. fig. 1.] It has the shape 
of the pouch of a bagpipe; lies across the body; and the 
pylorus, or passage by which the food leaves it, is somewhat 
higher in the body than the cardia, or orifice by which it 
enters; so that it is by the contraction of the muscular 
coat of the stomach, that the contents, after having under¬ 
gone the application of the gastric menstruum, are gradually 
pressed out. In dogs and cats, this action of the coats of 
the stomach has been displayed to the eye. It is a slow 
and gentle undulation, propagated from one orifice of the 
stomach to the other. For the same reason that I omitted, 
for the present, offering any observation upon the digestive 
fluid, I shall say nothing concerning the bile or the pan¬ 
creatic juice, farther than to observe upon the mechanism, 
viz. that from the glands in which these secretions are 
elaborated, pipes are laid into the first of the intestines, 
through which pipes the product of each gland flows into 
that bowel, [PI. XVIII. fig. 2,] and is there mixed with 
the aliment, as soon almost as it passes the stomach; ad¬ 
ding also as a remark, how grievously this same bile of¬ 
fends the stomach itself, yet cherishes the vessel that lies 
next to it. 
Secondly, We have now the aliment in the intestines 
converted into pulp; and, though lately consisting of ten 
different viands, reduced to nearly a uniform substance, 
and to a state fitted for yielding its essence, which is called 
chyle, but which is milk, or more nearly resembling milk 
