MAMMALIA— PHYSIOLOGY 



459 



S -Thoracic c/uct 



of the optimum composition of the blood, even at the expense of the 

 constancy of lymph. 



Lymph consists of nutritive material absorbed from the walls of 

 the alimentary canal and colorless food materials in the blood not 

 yet utilized. After meals the color of lymph becomes whitish from 

 the admixture of chyle^ and 

 many fat droplets are pre- ^' 



sent. Lymph coagulates 

 when drawn, since the fibrin 

 factors are present; but the 

 process is less prompt and 

 the clot is less firm than in 

 the case of blood. Lymph 

 contains three proteins, 

 fibrin, serum-globulin, and 

 serum-albumen. It con- 

 tains, in common with 

 plasma, cholesterin, sugar 

 and inorganic salts. The 

 proteins are less abundant 

 than in plasma. The 

 amount of urea is greater 

 than in plasma. 



Lymphatics. — From the 

 alimentary canal, materials 

 pass in part directly into 

 the blood vessels surround- 

 ing the canal, and in part 



into vessels called lacteah 



1 • 1 r J • ^u '^^ Fig. 247. Diagram of paths of absorbed 



which are found m the mtes- ^ , 1 ^' , ° ■ ^ ,t^ n 



, .... _ , food from the digestive tract, (trom Lonn 



tmal villi. Lacteals trans- ^^^ Budington. Courtesy of Silver, Burdett 

 port chyle to the receptac- and Co., New York.) 

 ulum chyli of the thoracic 



duct. The lymphatics and the lacteals form a simple, branched 

 vascular tree which opens into the jugular veins at their bases by two 

 trunks, the left-thoracic duct and right-lymphatic duct. Through- 

 out the course of the lymphatic vessels are many lymphatic glands 

 which are the foci of multiplication of white blood corpuscles and 

 act as strainers for poisons. (Figure 246.) 



Flow of Lymph. — No organ corresponding to the heart keeps the 



