92 COMPARATIVE ZOOLOGY. 
no other office, so far as we know, than to moisten the 
food for swallowing. 
Taking Man as an example, let us note the main facts 
in the process. During mastication, by which the relative 
surface is increased, the food is mixed with saliva, which 
converts the starch into sugar.” Passed into the stomach, 
the now sweetish, pulpy mass is subjected to the action of 
the gastric juice, a peculiar acid, which has no effect on 
starch or oil, but readily dissolves the albumen, fibrine, 
gelatine, and like constituents of the food.“ While this 
solution is going on, the muscular walls of the stomach 
successively contract and relax, rolling the food about, 
and mixing it thoroughly with the gastric juice, and, at 
the same time, moving the whole mass toward the pyloric 
orifice.” Some of the chyme 
thus produced is at once ab- 
sorbed into the blood-vessels of 
the stomach; but the greater 
part is pressed forward through 
the pylorus into the duodenum. 
As soon as the chyme enters 
this cavity, it separates into a 
white, creamy substance, called 
Fig. 57.—Chyle Corpuscles, X 500. chyle, and a residuary mass, 
which is gradually converted into feces, and expelled 
from the system.” Exactly how this change from chyme 
to chyle is produced is not known; but it is the most im- 
portant part of the digestive process. 
Chyme differs from food in having starchy particles 
changed into sugar, and much of the albuminous por- 
tion chemically altered by the gastric juice; but the con- 
version of the starch is not complete, and certain albu- 
minous parts, and all of the oily particles, remain un- 
touched. In the duodenum, the whole mass is acted upon 
by secretions from the liver and pancreas. While the 
