THE DIGESTIVE SYSTEM 



73 



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 largo 

 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. The feces are here converted into the characteristic 

 balls by the contractions of the strong muscular bands of the walls. 



Fig. 20. — Diagrammatic longitudinal section of a villus to show essen- 

 tials in the structure of a villus. The columnar cells hning the intestine are 

 shown in section. L, Lacteal or lymphatic surrounded by a network of capil- 

 laries. The connective tissue, which actually exists inside the villus, has 

 been ignored for the sake of simphcity. (Stiles, Nutritional Physiology.) 



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 liver is the largest gland in the body (Fig. 21). It is situ- 

 ated in the abdominal cavity, just posterior to the diaphragm. 



