SECRETION. 351 



in the absence of all certain knowledge as to 

 the mode in which it is excited and brought into 

 play in the living body, the chasm can for the 

 present be supplied only by remote conjecture. 



The process which constitutes the ultimate 

 stage of nutrition, or the actual incorporation of 

 the new material with the solid substance of the 

 body, of which it is to form a part, is involved 

 in equal obscurity with that of secretion. 



Chapter XIII. 



ABSORPTION. 



Absorption is another function, related to nutri- 

 tion, which deserves special notice. The prin- 

 cipal objects of this function are the removal of 

 such materials as have been already deposited, 

 and have become either useless or injurious, and 

 their conveyance into the general mass of circu- 

 lating fluids ; purposes which are accomplished 

 by a peculiar set of vessels, called the Lym- 

 phatics. These vessels contain a fluid, which, 

 being transparent and colourless like water, 

 has been denominated the lymph. The lym- 

 phatics are perfectly similar in their structure, 

 and probably also in their mode of action, to 

 the lacteals, which absorb the chyle from the 



