72 AGE, GROWTH, AND DEATH 



In all parts of the .body degenerative changes are 

 going on, and they represent collectively a third 

 phase in the cytomorphic cycle. But there is yet 

 one more phase, which is needed to complete the 

 story, namely the phase of the death and final re- 

 moval of the cells. The degenerative change, when 

 complete, always results in the death of the cell. In 

 many cases the dead material is removed merely by 

 being cast off, as is the case with the skin. All the 

 scales which peal off from the outer surface of our 

 body represent little scraps or clusters of cells which 

 are entirely dead ; and in the interior of the body, in 

 the intestinal canal, and in the glands of the stomach, 

 we find cells continually dying, dropping off from 

 their place upon the walls, and being cast away. Or 

 if we examine the saliva which comes from the mouth, 

 we detect that that also is full of cells which have 

 died and fallen off from their connection with the 

 body and are thus removed. 1 An even more impor- 

 tant method of the removal of cells is by a chemical 

 process in consequence of which the cells are dis- 

 solved and disappear before our eyes, very much as 

 marble may disappear from sight under the corrosive 

 action of an acid. Indeed, we know that all the 

 parts of the body, so far as they are alive, produce 

 within themselves a ferment which has a tendency to 



1 Two kinds of cells are commonly found in the saliva, the first are cornified 

 cells sloughed off the lining epithelium of the mouth, the second are salivary 

 corpuscles, which are really white blood corpuscles (leucocytes) that have 

 migrated into the saliva and died. Being dead they have enlarged themselves 

 by the imbibition of water. 



