68 ANIMAL LIFE 
sac-like part of the canal, called the abomasum. Tere 
the process of digestion goes on. The four sacs—rumen, 
reticulum, omasum, and abomasum—are called stomachs, 
or they may be considered to be four chambers forming 
one large stomach. In the abomasum, or digesting stom- 
ach, digestive fluids are poured from glands lining its 
walls, and the food becomes converted into a liquid called 
chyle. The chyle passes from the stomach into a long, 
narrow, tubular portion of the canal called the intestine. 
The intestine is very long, and lies coiled in a large mass 
in the body of the cow. The intestine is divided into 
distinct regions, which vary in size and in the character 
of the inner wall. These parts of the intestine have 
names, as duodenum, jejunum, ileum, cecum, colon, etc. 
Part of the intestine is lined inside with fine papilla, 
which take up the chyle (the digested food): and pass it 
through the walls of the intestine to other special organs, 
which pass it on to the blood, with which it becomes mixed 
and carried by an elaborate system of tubes to all parts of 
the body. Part of the grass taken into the alimentary 
canal by the cow can not be digested, and must be got rid 
of. This passes on into a final posterior part of the intes- 
tine called the rectum, and leaves the body through the 
anus or posterior opening of the alimentary canal. The 
whole canal is more than twenty times as long as the body 
of the cow; it is composed of parts of different shape ; its 
walls are supplied with muscles and blood-vessels ; the inner 
lining is covered with folds, papillw, and gland cells. It is 
altogether a highly specialized organ, a structurally com- 
plex and elaborately functioning organ. 
Let us now examine the alimentary canal, or organ of 
digestion, in some of the simpler animals. 
The Protozoa, or simplest animals, have no special organ 
at all. When the surface of the body of an Ameba comes 
into contact with an organic particle which will serve as 
food, the surface becomes bent in at the point of its con- 
