This system consists of the organs directly concerned in the reception
and digestion of the food, its passage through the body, and the
expulsion of the unabsorbed portion. These organs are conveniently
grouped under two heads, viz.: (1) the =alimentary canal=; (2) the
=accessory organs=.
The =alimentary canal= (Tractus alimentarius) is a tube, about 100 feet
(ca. 30 m.) in length in the horse, and extends from the lips to the
anus. It has a complete lining of mucous membrane, external to which is
an almost continuous muscular coat. The abdominal portion of the tube is
largely covered with a serous membrane—the visceral peritoneum. The
canal consists of the following consecutive segments: