THE ALIMENTARY CANAL. 239 
The rectum is the terminal portion of the large intestine 
lying in the median line close to the dorsal body wall, from 
which it is suspended by the short mesorectum. Its structure 
is like that of the colon. It opens externally at the anus. 
The entire large intestine has a length about one-half that of 
the animal. At each side of the anus are two large secreting 
sacs, the anal sacs or glands, each about a centimeter in 
diameter. These open into the anus one or two millimeters 
from its caudal boundary. 
Muscles of the Rectum and Anus.—Owing to the close 
interrelation of the muscles of the rectum and anus with those 
of the urogenital organs, all these muscles will be described. 
together at the end of the description of the urogenital system. 
7, The Liver, Pancreas, and Spleen.._The Liver. Hepar. 
—The liver (Figs. 100 and 101) is a large red-brown organ 
occupying the cranial part of the abdominal cavity. It is 
closely applied to the caudal surface of the diaphragm and 
extends thence ventrad of the stomach so as to conceal all but 
its pyloric end. Owing to the position of the stomach the 
larger mass of the liver is on the right side and it extends 
somewhat further caudad on this side. 
The liver is divided by the dorsoventral suspensory liga- 
ment into the right and left lobes, and each halfis again divided 
into lobes. On the left is a small left median (4) and a larger 
left lateral lobe (a). The left lateral (2) extends caudad with 
a thin edge which covers the greater part of the ventral surface 
of the stomach. On the right there is a large right median 
(or cystic) lobe (¢, ¢’). Its cranial surface is dome-shaped 
and fitted against the right two-thirds of the caudal surface of 
the diaphragm. Its ventral edge is thin, its dorsal edge thick, 
and its caudal surface marked by a deep dorsoventral cleft in 
which lies the gall-bladder (Fig. 101, /). Dorsad and caudad 
of the cystic lobe is the right lateral lobe (d, @’), which is 
deeply cleft. Its elongated caudal division (d’) extends in a 
point to the caudal end of the right kidney and is adapted to 
the medial-half of its ventral surface. Its smaller and more 
compact cranial division (@) ends ventrally in a thin edge. It 
lies between the caudal division (¢’) and the cystic lobe (c), and 
