ABSORPTION 



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that absorption is by no means so certain as was at one time 

 supposed. Water, for instance, passes through the stomach 

 and undergoes no absorption ; salts are only absorbed with diffi- 

 culty ; sugars and peptones are taken up, but only if in sufficient 

 concentration ; ordinarily they are absorbed with difficulty. 



Intestinal Absorption. — The absence of stomach absorption 

 in the horse and ox points to intestinal absorption as being of 

 considerable importance in herbivora. That this absorption 

 is very rapid is proved by Colin's experiments. Hydrocyanic 

 acid injected into the small intestine of a horse caused death in 

 one to one and a half minutes, and potassium ferrocyanide 



Fig. 87. — Loop of Small Intestine of the Horse during Active'Absorption, 

 with Distended Lacteals. 



injected into the bowel, after tying the mesenteric lymphatics, 

 was detected in the blood six minutes afterwards. 



The Paths of Absorption. — The paths by which intestinal 

 absorption occurs are (1) through the villi into the lacteals, and 

 (2) through the bloodvessels into the venous system. This 

 points to the fact that some substances taken up from the bowel 

 may at once pass into the blood via the thoracic duct (Fig. 8j), 

 while others must first proceed to the liver by the portal vessels 

 for further elaboration before entering the blood. 



It will be remembered that the villi are found only in the 

 small intestines ; in the large intestines there are no villi. It 



