INTERSTITIAL ABSORPTION. 195 



apparatus which carries on this function. Although the absorb- 

 ent vessels form one continuous system, they may be conveniently 

 divided into two provinces, namely, interstitial and surface ab- 

 sorption. A certain modification of the latter, called the lacteal 

 system, occurs in the alimentary canal, and is described under 

 intestinal absorption. 



I. Interstitial Absorption. 



The blood flowing through the body in delicate capillary vessels 

 yields to the various tissues a kind of irrigation stream of plasma, 

 which, leaving the capillaries, permeates their substance so that 

 every texture is saturated with nutrient fluid. The surplus of 

 this irrigation stream is collected and carried back to the blood 



FIG. 81. 



Tendon of Mouse's Tail trrated with nitrate of silver, showing clefts or cell spaces 

 around the bundles of fibrils as white patches. Thee interstices may be called the 

 smallest lymph channels or spaces. (Sch&ffer.) 



current by a special set of fine vessels with slender walls, called 

 the lymph vascular system, which act as drains to the tissues, and 

 pour their contents into the veins. 



When the nutrient fluid escapes from the capillaries, it lies 

 in the interstices in the tissue elements, and here bathes the 

 tissue cells which commonly occupy these interstices. . (Figs. 

 81 and 86.) 



Communicating freely with the interstices of the tissues are 

 irregular, anastomosing, flattened channels, which convey the 

 lymph or any fluid forced between the tissues into vessels with 

 more definite walls. These vessels, which are lined with char- 

 acteristic endothelium, form a more or less dense network of 



