THE LIVER 465 



The large intestine is much smaller in cahber than that of the horse, has no 

 bands, and is not sacculated. Most of it is situated between the layers of the 

 common mesentery in the right dorsal part of the abdominal cavity. It is related 

 on the right to the lateral abdominal wall, from which, however, it is almost com- 

 pletely separated by the greater omentum. On the left it is chiefly related to the 

 rumen. The average length of the caeciom is about thirty inches (ca. 75 cm.), and 

 the diameter is about five inches (ca. 12 cm.). It is directly continuous in front 

 with the colon, the conventional demarcation being the junction of the ileum with 

 the large intestine. ^ From this junction, which is on the medial side and usually 

 near the ventral end of the last rib, the caecum extends backward and upward 

 along the right flank (from which it is separated by the greater omentum), and its 

 rounded blind end commonly lies at the right side of the pelvic inlet.! The caecum 

 is attached along its medial side to the mesentery, except the posterior third, which 

 is free and variable in position. The terminal part of the ileum runs forward along 

 the medial surface of the caecum and is attached to the latter. The dorsal surface 

 is attached by areolar tissue and peritoneum to the colon. The colon is about 

 thirty-five feet (ca. 10 m.) in average length. Its diameter is at first the same as 

 that of the caecum, but diminishes to about two inches (ca. 5 cm.). The greater 

 part of it is arranged in double elliptical coils between the layers of the mesentery; 

 the coils are attached to each other by areolar tissue. It begins as the direct 

 continuation of the caecum, runs forward a short distance, and turns dorsally and 

 backward opposite to the ventral part of the last two ribs. It continues backward, 

 in relation to the right flank laterally and the caecum ventrally, to the posterior 

 part of the sublumbar region. Here it turns forward and runs parallel with the 

 retrograde part as far forward as the second lumbar vertebra, turns backward, and 

 is continued by the spiral part (Ansa spiralis). The coils of this are alternately 

 centripetal and centrifugal (Gyri centripetales et centrifugales) ; they are best 

 seen from the left side. The bowel gradually diminishes in caliber, and the ter- 

 minal part (Ansa distalis) leaves the spiral mass, passes forward to the great mesen- 

 teric airtery, and runs backward dorsal to the terminal part of the duodenum. It 

 inclines to the right in relation to the ventral surface of the right kidney, forms an 

 S-shaped curve near the pelvic inlet, and joins the rectum; this part is attached to 

 the sublumbar region by a narrow mesentery, and is also attached to the recurrent 

 part of the duodenum. 



The rectum is somewhat shorter than that of the horse, and is usually covered 

 with peritoneum as far back as the first coccygeal vertebra. The retroperitoneal 

 part is surrounded by a quantity of fat. The anus is not prominent. 



The serous coat is of course absent on the adherent surfaces of the spiral part 

 of the colon. There is a large amount of fat in the mesentery. The longitudinal 

 fibers of the muscular coat are evenly distributed, consequently there is no saccula- 

 tion of the bowel. There is a valvular mucous fold at the ileo-csecal orifice. A 

 Peyer's patch occurs in the beginning of the caecum and one in the first part of the 

 colon. 



THE LIVER 



The liver lies almost entirely to the right of the median plane. Its long axis 

 is directed obliquely downward and forward, about parallel with the median plane, 

 and corresponds to the curvature of the right portion of the diaphragm. It is less 

 extensive, but thicker than that of the horse. Its average weight is about 10 to 

 12 pounds (ca. 4.5 to 5.5 kg.). 



1 In formalin-hardened material there is sometimes a constriction in front of the termination 

 of the ileimi. This might be regarded as the demarcation between the cfeoum and colon. The 

 opening of the ileum is directly forward, so that material from it enters the origm of the colon. 

 The posterior free part of the caecum is naturally variable in position; it may be bent ventrally, 

 so that the iDlind end faces forward. 

 30 



