HOW ANIMALS DIGEST. 
93 
animals has no other office, so far as we know, than to 
moisten the food for swallowing. 
Taking Man as an example, let ns note the main facts 
in the process. During mastication, by which the relative 
surface is increased, the food is mixed with saliva, which 
moistens the food , 48 and turns part of the starch into 
grape-sugar. Passed into the stomach, the food meets the 
gastric juice. This is acid, and, first, stops the action of 
the saliva; secondly, by means of the pepsin which it con¬ 
tains, and the acid, it dissolves the albumen, fibrine, and 
such constituents of the food. This solution of albumi¬ 
noids is called a peptone , and is especially distinguished 
from other such solutions by its diff nsibility— i. e., the ease 
with which it passes through a membrane. These pep¬ 
tones, with the sugars of the food, whether original or the 
product of the action of the saliva, are absorbed from the 
stomach. The food, while in the stomach, is kept in con¬ 
tinual motion, and, after a time, is discharged in gushes 
into the intestine. The name chyme is given to the pulpy 
mass of food in the stomach. In the intestine the chyme 
meets three fluids—bile, pancreatic juice, and intestinal 
juice. All of these are alkaline, and at once give the acid 
chyme an alkaline reaction. This change permits the 
action of the saliva to recom¬ 
mence, which is aided by the 
pancreatic and intestinal juices. 
The pancreatic juice has much 
more important functions. It 
changes albuminoid food into 
peptones, and probably breaks 
up the fats into very small par¬ 
ticles, which are suspended in 
the fluid chyle. This forms an Fig. 59.—Chyle Corpuscles, x 500. 
emulsion , like milk, and causes the chyle to appear whit¬ 
ish. The bile has important functions, but little under* 
