186 A Manual of Veterinary Physiology. 



Intestinal Absorption. 



The remarkable fact that no absorption occurs from 

 the stomach of horses (see p. 134) points to intestinal 

 absorption as being of considerable importance. 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 1 to 1 1 minutes, and potassium ferro- 

 cyanide injected into the bowel, after tying the lymphatics, 

 may be detected in the blood 6 minutes later. 



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. 



The villi are found only in the small intestines ; they are 

 •04 to -07 inch long, and possess a diameter of from '02 to 

 •04 inch. They are comparatively small in herbivora, and 

 their number in the horse and ox, according to Colin, is 

 from 45,000,000 to 55,000,000, and these are distributed 

 over a surface of from 48 to 58 square feet. The lacteals 

 pass up the mesentery, and each of the 1,200 vessels 

 counted by Colin passes through a lymphatic gland before 

 gaining the receptaculum chyli ; here the chyle mixes with 

 the lymph coming from the posterior extremities, and the 

 whole is passed into the left jugular vein. 



The material absorbed by the bloodvessels passes into 

 the portal vein and reaches the liver before entering the 

 general circulation. This arrangement would point to the 

 fact that there are certain substances which need only pass 

 through a lymphatic gland before being suitable for the 

 blood, whilst others must pass through or undergo changes 

 in the liver previous to being rendered suitable for the 

 system. Physiologists have therefore devoted considerable 

 consideration to this subject, but it is far from being in a 

 satisfactory condition. In the large intestines there are 

 practically no villi. It must not, therefore, be supposed 

 that absorption is here exclusively carried on by the blood- 

 vessels ; for, remembering the large chain of glands along 

 the colon in particular, it, is probable that the material 

 absorbed passes through these glands to a greater or less 



