General Physiology of Animals. 339 



brane, it also assists the process of absorption by moistening 

 the wall of the intestine and by acting as an antiseptic. 



In the intestine also peristaltic movements (p. 277) per- 

 form the same function as the churning movements taking 

 place in the stomach, viz. that of mixing of the food-stuffs 

 and the digestive secretions. 



(c) Absorption. The third process in anabolism is ab- 

 sorption, or the reception into the circulation of the pre- 

 pared food-substances. Absorption takes place partly in 

 the stomach, partly in the intestine. The mucous mem- 

 brane of the stomach and intestine contains an abundant 

 supply of capillaries ; the walls of these vessels, as has 

 already been pointed out (p. 287), are only one cell thick, 

 consequently the soluble peptones and sugar will diffuse 

 readily into their interiors. In the intestine the area of 

 absorption is largely increased by means of the villi, which, 

 in addition to absorbing the food-stuffs just mentioned, also 

 take into their interiors the emulsified fat. The oil-globules 

 pass into the lacteals, which in turn communicate with the 

 chief vessel of that system, the thoracic duct, which opens 

 into the left vena cava near the shoulder. 



(d) Circulation. The food stuffs having been absorbed 

 are now circulated, and in their passage through the body 

 are altered in a variety of ways ; for instance, in the liver 

 the important starch-like body, glycogen, is abstracted from 

 the blood and stored temporarily in the hepatic cells ; the 

 elements of bile are likewise extracted and stored in the 

 gall-bladder or flow into the intestine directly, while prob- 

 ably urea and other products of metabolism are formed and 

 pass away in the blood-stream to the kidney to be got rid 

 of. In the lymph glands also the chyle, or alkaline nutritious 

 fluid absorbed by the lacteals, no doubt undergoes important 

 chemical changes. We have already (p. 288) referred in 

 sufficient detail to the course of the blood-flow, and general 

 physiology of the circulation. The action of the heart is 

 a purely muscular one under government of the nervous 



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