196 



DEFECATION LACTEAL ABSORPTION. 



the surrounding parts ; and it is kept-in by a circular muscle 

 or sphincter, which surrounds the outlet of the alimentary 

 canal. But when the accumulation has taken place beyond 

 this amount, it excites a reflex action ( 195) in the muscles 

 that surround the abdomen; and these make pressure suf- 

 ficient to overcome the resistance of the sphincter, and to 

 force out the contents of the rectum. 



Absorption of Nutritive Material. 



217. We have only now to inquire into the mode, by which 

 the nutritive matter extracted from the food is taken-up from 

 the alimentary canal and applied to the nutrition of the body. 

 In all Vertebrated animals, there exists a special set of vessels 

 termed Absorbents; of which those forming one division, 



Thoracic Mesenteric 

 Aorta Duct Glands 



Origins of 

 Lacteal Vessels 



Intestine 



i .' / 



Lymphatic Mesentery 

 Vessels 



Fig. 114. CHYLE-VESSELS. 



known as Lacteals, from the milk-like character of their con^ 

 tents, originate in the numberless villi or minute projections 

 with which the mucous membrane that lines the small intes- 

 tine is covered ( 41). During the act of digestion, the 



