1 84 



PHYSIOLOGY. 



free ends, and then pass them slowly through their cyto- 

 plasm into the substance of the villus." HOWELL. 



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 bod generally 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 

 circulation. During most of the time the thoracic duct 

 and the lymphatics of the intestines would hardly be 

 noticed because they are filled with the- clear lymph. But 

 after absorption of fatty matter they are filled with a white 

 liquid, called chyle, and are easily seen. 



To show the Thoracic Duct and Lacteals. To show the thoracic 

 duct feed a kitten or puppy on rich milk, and after two or three hours 

 kill it as directed on page 27. As soon as you are sure it is dead, 



Lacteal with Valves Capillaries Muscles Epithelium 



Fig. 67. Elements entering into the Structure of a Villus. 



open the abdominal cavity and spread out the mesentery. The white 

 lacteals, filled with chyle, will be seen radiating through the mesentery. 

 Press on some of these, and it will be seen that they are thin tubes 

 filled with a white liquid. They converge toward the place of attach- 

 ment of the mesentery to the dorsal part of the abdomen. On the 

 dorsal wall of the abdomen, just posterior to the diaphragm, the recep- 



