THE DIGESTIVE SYSTEM 83 



The large colon is a massive viscus, from 10 to 12 feet long with 

 an average diameter of nearly 10 inches. Its capacity is more 

 than double that of the cecum. It commences at the crook of 

 the cecum and runs downward and forward, along the right 

 costal arch to the sternum, where it curves to the left, and is con- 

 tinued backward on the left part of the abdominal floor to the 

 entrance of the pelvic cavity. From here it doubles back on 

 itself to the place of commencement. 



The small colon is the sacculated tube which succeeds the large 

 colon and ends at the rectum. It is 10 to 12 feet long and 

 3 to 4 inches in diameter. It lies coiled in the left flank with the 

 small intestine. It is attached to the sublumbar region by the 

 colic mesentery. 



The rectum extends from the entrance of the pelvis to the 

 anus, the posterior opening of the digestive canal. It is 10 to 12 

 inches long and is dilated to form a pouch. 



The intestine of the ox is about twenty times the length of the 

 body. It is coiled in the right half of the abdominal cavity. 

 The small intestine measures about 130 feet in length and is 

 about 2 inches in diameter. The large intestine is of much smaller 

 caliber than that of the horse and is not sacculated. The cecum 

 is about 30 inches long and 5 inches in diameter. 



The liver is the largest and most important gland in the body 

 (Fig. 27). It is situated in the abdominal cavity just posterior 

 to the diaphragm. It is a dark red-brown color, and weighs 

 about 11 pounds in the average-sized horse and ox. The circum- 

 ference of the liver is marked by two fissures which divide the 

 gland into three lobes. Pressure from the soft organs and spe- 

 cial ligaments hold it in position. The bile-duct connects the 

 liver with the small intestine, which it enters about 6 inches 

 from the pylorus, along with the principal pancreatic duct. In 

 most animals a special reservoir for bile is present in the form 

 of the gall-bladder. The horse has no gall-bladder. Besides 

 having the function of manufacturing bile, the liver acts as a store- 

 house for glycogen, regulates the supply of glucose, forms urea 

 from ammonia, neutralizes toxic products, and eliminates waste 

 hemoglobin and broken down blood cells. These functions have 

 compelled us to look upon this gland as both a secretory and an 

 excretory organ. 



The pancreas so closely resembles a salivary gland in its struc- 



Digitized by Microsoft® 



