THE BLOOD AND ITS CIRCULATION 



317 



LYflPH 



Function of Lymph. The tissues and organs of the body 

 are traversed by a network of tubes which carry the blood. Inside 

 these tubes is the blood proper, consisting of a fluid plasma, the 

 colorless corpuscles, and the red corpuscles. Outside the blood 

 tubes, in spaces between the cells which form tissues, is found 

 another fluid, which is in chemical composition very much like 

 plasma of the blood. This is the lymph. It is, in fact, fluid food 

 in which some colorless amoeboid corpuscles are foun^ Blood 

 gives up its food material to the lymph. This it does by passing it 

 through the walls of the 

 capillaries. The food is in 

 turn given up to the tissue 

 cells, which are bathed by 

 the lymph. 



Some of the amreboid 

 corpuscles from the blood 

 make their way between 

 the cells forming the walls 

 of the capillaries. Lymph, 

 then, is practically blood 

 plasma plus some colorless 

 corpuscles. It acts as the 

 medium of exchange between 

 the blood proper and the cells 

 in the tissues of the body. 

 By means of the food sup- 

 ply thus brought, the cells The exchange ^^ blood and ^^ rf 

 of the body are able to grow, the body, 



the fluid food being changed 



to the protoplasm of the cells. By means of the oxygen passed 

 over by the lymph, oxidation may take place within the cells. 

 Lymph not only gives food to the cells of the body, but also takes 

 away carbon dioxide and other waste materials, which are ultimately 

 passed out of the body by means of the lungs, skin, and kidneys. 



Internal Secretions. In addition to all the functions given 

 above, the blood has recently been shown to carry the secretions of 

 a number of glands through which it passes, although these glands 



