282 DIGESTION 



(2) arrests gastric digestion, by neutralizing and pre- 

 cipitating the proteins which have not been entirely 

 digested; and by preparing the way for intestinal 

 digestion; (3) a slight antiseptic action. It is a known 

 fact, that if bile is not secreted in the human being, 

 putrefactive changes take place, with the resultant 

 formation of foul gases, and other, products noted in 

 the feces; (4) increases peristalsis, which aids in the 

 proper contractile movements of the w r alls of the intes- 

 tines, favoring intestinal digestion and defecation. 



The Functions of the Large Intestine. The large 

 intestine is that portion of the bowels which commences 

 at the ileum and terminates at the anus. Its sub- 

 divisions are termed: the cecum, ascending, trans- 

 verse, descending, and sigmoid colon, and the rectum. 

 It is a large musculomembranous tube covered exter- 

 nally by the peritoneum, and is from 4J to 5 feet in 

 length in a normal adult. 



The contents of the colon consist of the undigested 

 products of digestion, as a result of the food being 

 acted upon by the saliva, gastric, pancreatic, and 

 intestinal juices, and the bile; the nutritive parts, 

 peptones, fatty acids, glycerin, etc., being absorbed; 

 the resulting liquid and waste material contains 

 undigested particles of cereals, vegetables, seeds, 

 cellulose, etc., which are passed into the rectum by a 

 peristaltic wave of its walls similar to the phenomena 

 taking place in the small intestines, then expelled 

 from the rectum during the act of defecation. 



The mucus secreted by the glands of the large 

 bowel incorporates the liquid material and passes it 

 toward the sigmoid flexure of the colon, where it is 

 held prior to the emptying of the bowel. 



Defecation. This is the act whereby the waste 

 material resulting from digestion is expelled from 

 the intestine by the rectum and passes through the 

 anus. It occurs normally once a day. The walls 

 of the sigmoid colon contract and force the frees 



