Chap. IX] 



VASCULAR SYSTEM 



153 



LYMPH 



Lymph is a pale, straw-colored liquid that bathes all the tissue- 

 spaces of the body. It is slightly alkaline, has a salty taste, and 

 no odor. When examined with the microscope, it is seen to con- 

 sist of a clear liquid with white corpuscles floating in it. In com- 

 position it resembles the blood, the essential differences being : — 



Sources of lymph. — During the passage of the blood through 

 the thin-walled capillaries, the plasma is forced to transude into 

 such spaces as exist between the cells of the tissues. In addition 

 to this transudation it is necessary to assume an active secretory 

 process on the part of the endothelial cells composing the capillary 

 walls. This plasma plus the leucocytes that have left the vessels 

 by migration make up the lymph proper. Besides the lymph 

 proper, the lymph that fills the lacteals of the intestinal villi ab- 

 sorbs some of the products of digestion, especially the fats. 



This portion of the lymph that has absorbed the fats is milky in 

 appearance, and is called chyle. The lymph, broadly speak- 

 ing, is dilute blood minus its red corpuscles. The chyle is lymph 

 plus a very large quantity of minutely divided fat. 



Functions of the lymph. — The lymph bathes all portions of the 

 body not reached by the blood. Hence the lymph conveys the 

 nutrient ingredients of the blood to all cells not directly bathed by 

 the blood. It delivers to the cells the material each cell needs to 

 maintain its functional activity, and picks up and returns to the 

 blood the products of this activity, which products may be simple 

 waste, or matters capable of being made use of by some other 



