Absorption. 185 



Absorption by the Villuses. The digested food is in 

 liquid form and surrounds the villuses. The three main 

 substances to be absorbed are peptones, sugar, and fat. 

 The outer cells of each villus absorb these and pass them 

 inward. The peptones and sugars are taken into the blood 

 capillaries, while the fats enter the lacteals. 



Muscular Action of the Villuses. In each villus there 

 are plain muscle fibers. When these shorten they squeeze 

 the chyle, that has already been absorbed, into the lymph 

 tubes of the wall of the intestines, and on into the main 



Epithelial Covering 



..Lacteal 



Longitudinal Mus- 

 srl." cular Fibers 

 Capillary Network 



Fig. 80. A Complete Villus. 



lymph duct. The chyle cannot return to the lacteal when 

 the muscles relax, on account of the valves, similar to 

 those of the veins, in the lacteal at the base of the villus. 

 Then, when the muscles relax, the lacteal is empty, and 

 ready to absorb more of the emulsified fat that we call 

 chyle. This action also helps the flow in the blood 

 capillaries. 



The Lacteals and Lymphatics. While the main work 

 of the lymphatics, as we have seen, is the carrying of 

 lymph from the tissues of the body to empty into the 

 veins of the neck, the lymphatics of the intestines have 

 another important function. They absorb and carry the 

 fatty portions of the digested food into the general circu- 

 lation. During most of the time the thoracic duct and 



