188 MANUAL OF PHYSIOLOGY. 



tion is accomplished, it is necessary to have some idea of the 

 absorbent system generally ; it may be well, therefore, at this 

 place to give a brief account of the construction of the special 

 apparatus which carries on this function. Although the ab- 

 sorbent vessels form one continuous system, they may be con- 

 veniently divided into two provinces, namely, interstitial and sur- 

 face absorption. A certain modification of the latter called the 

 lacteal system occurs in the alimentary canal, and id 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 



FIG. 81. 



Tendon of mouse's tail treated with nitrate of silver, showing clefts or 

 cell-spaces around the bundles of fibrils as white patches. These interstices 

 may be called the smallest lymph-channels or spaces. (SchiifTer.) 



every texture is saturated with nutrient fluid. The surplus of 

 this irrigation stream is collected and carried back to the blood 

 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 ir- 

 regular anastomosing flattened channels, which convey the lymph 

 or any fluid forced between the tissues into vessels with more defi- 



