CHAPTER I. 

 THE CELL IN GENERAL. 



IN all animal bodies are found certain tiny struc- 

 tural elements called cells. These are parts which 

 at one time or another are alive ; and all the varied 

 activities of the body are the result of the single or 

 combined activities of the cells which compose it. 

 It is very desirable, owing to their great significance, 

 that before commencing the systematic study of the 

 tissues we should acquire a definite conception of 

 the nature of these elementary organisms. We may 

 consider cells from a morphological and from a 

 physiological standpoint, asking first, what is their 

 structure ? and second, what do they do ? 



First, then, what is the structure of cells ? We 

 find in this a great diversity, some being extremely 

 simple, others quite complex. The most common, 

 and usually the most prominent structural feature 

 of the cell, that portion which gives to it form and 

 consistence, is called the cell-body. This usually con- 

 sists of an albuminoid material, sometimes transpar- 

 ent and apparently structureless, sometimes finely 

 or coarsely granular, and not infrequently present- 



23 



