224 



STRUCTURE OF V1LLL 



insert the tip of the syringe nozzle, and inject. It will not be 

 necessary to ligature, for there are so many valves in the duct 

 that if a fair amount of the starch preparation be introduced 

 there will be little reflow. For this the yellow-colored mass 

 may be used. 



In each villus there are plain muscle fibers. When these 

 shorten they squeeze the chyle, that has already been ab- 

 sorbed, into the lymph tubes of the wall of the intestines, 

 and on into the main lymph duct. The chyle cannot return 



Epithelial Covering 



Lacteal 



Longitudinal Mus- 

 cular Fibers 



Capillary Network 



Fig. 68. Intestinal Villus. 



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. 



The whole digestive tube may be briefly and roughly 

 described as a muscular tube of varying diameter, lined by 

 mucous membrane. The muscular coat propels the contents 

 and mixes them with liquids ; the mucous coat is beset with 

 glands, making liquids, some of which merely soak the food, 

 others act on it chemically, while mucus serves to lubricate 

 the surface. It seerns that these myriads of Simple Glands 

 are not enough, so several large Compound Glands lie alongside 

 the food tube, and empty their secretions into it by Ducts ; 



