THE CELLULAR CHANGES OF AGE 79 



% 

 Next the nucleus disappears, No. 7, probably by being 



completely expelledt from the cell, and by further con- 

 traction the enucleate cell assumes the cup-shape, 

 thus evolving the true mammalian non-nucleated red 

 corpuscle, No. 8. The cells have been differentiated 

 and are now degenerating. The last stage of all is 

 their death and removal. 1 Their usual end is break- 

 ing up into small fragments, which are then eaten by 

 phagocytes and so disposed of. Sometimes, however, 

 corpuscles are devoured whole by phagocytes. It is 

 possible that corpuscles are normally destroyed by 

 imbibing fluid until they burst, as is said to occur 

 under pathological conditions. To recapitulate: I, the 

 cells have little protoplasm ; 2, the protoplasm grows ; 

 3, differentiation occurs ; 4, degeneration ; 5, disinte- 

 gration of the cells ; 6, removal of their remains. 



Let us turn from the study of details and illustra- 

 tions, to the examination of general considerations. 

 Our first endeavour must be to answer the question : 

 How, from the standpoint of cytomorphosis, ought we 

 to look upon old age ? Cytomorphosis, the succes- 

 sion of cellular changes which goes on in the body, is 

 always progressive. It begins with the earliest de- 

 velopment, continues through youth, is still perpetu- 

 ally occurring at maturity and in old age. The r6le of 

 the last stage of cytomorphosis, that is, of death in life, 

 is very important, and its importance has only lately 

 become clear to us. I doubt very much if the con- 

 ception is at all familiar to the members of this audi- 



1 Compare Weidenreich, Anatom. Anzeiger, xxiv., pp. 186-192. 



