LYMPHATIC OR ABSORBENT VESSELS 89 



tically every body cell, being in the neighborhood of a 

 capillary, borders upon one of these cavities (Fig. 17). 

 Furthermore, the walls of the capillaries are very thin and 

 permit small quantities of liquid from the blood continu- 

 ally to diffuse into these spaces, and thus bathe the tissue 

 cells. This fluid, known as lymph, is of the highest im- 

 portance to the existence of the cells of higher animals. 

 Very much as a fish lives in water a cell lives in lymph. 

 It is the source from which it derives the food that has 

 been brought from the digestive tract, and the oxygen 

 that has come from the gills or lungs, and is the medium 

 into which it discharges its carbon dioxid, salts, and other 

 waste products. Lymph, therefore, acts in the nature of 



Fig. 17. — Diagram Illustrating Blood Capillaries (c) surrounded 

 by a lymph space (/) which is drained by an absorbent or lymphatic 

 capillary (a). 



a retail station intermediate between the wholesale supply 

 in the blood, and the consumer, or the cell. 



Lymphatic or Absorbent Vessels. — Lymph is con- 

 tinually diffusing through the capillary walls, as has 

 been described, and the excess usually escapes by way of 

 a special system known as the lymphatic or absorbent 

 vessels. This comprises a vast number of lymph capil- 

 laries, each of which ends in one of the circum-capillary 

 tissue spaces, and on the other hand unites with similar 



