O- III. 



ABSORPTION, ULCERATION, AND THE STRUCTURES 

 ENGAGED IN THESE PROCESSES. 



Every organic cell, the most simple, as well as the most compli- 

 cated, when a separate organism, or when a part of a more 

 highly organized being, existing as a mere magazine of matter, 

 or performing some of the more striking of the vital functions, 

 invariably exhibits a phenomenon which is antecedent to all 

 others, absorption from without of materials for its own growth. 



The various kinds of cells in any organism differ from one 

 another in this respect, that they have the power, each after its 

 kind, of selecting and procuring from the circulating medium, or 

 from other sources, the sort of matter necessary for their own 

 growth : or they have the power of elaborating, or of conducing 

 to the chemical change of the matter which is absorbed by them. 

 In this respect, the component cells of animals and vegetables re- 

 semble the various species of beings of which they form parts : 

 they have not only the power of selecting food, but the various 

 species out of the same kind of food are formed of matter and of 

 parts which are specifically different. 



A most important circumstance in the history of cellular phe- 

 nomena is the duration of existence of a cell. Like the various 

 species of animals and vegetables, each species of cell has its own 

 average term of existence, each after its kind. This average term 

 is nevertheless contingent on the amount of action which each 



