Nos. 620-621] CANCER'S PLACE IN BIOLOGY 



399 



degree of regeneration of tissues, according to the obser- 

 vations of biologists, is in an inverse ratio to the degree 

 of their specialization and differentiation. One finds, 

 therefore, this regenerative factor a variable and un- 

 equal quantity among tissues of the human body. The 

 protective tissue cells (epitheliocytes) of the skin, for 

 example, are readily regenerated if not completely de- 

 stroyed over a large area; the cells of the retina, in all 

 probability, are never regenerated even after partial 

 destruction. Fibrocytic, erythrocytic, epitheliocytic and 

 leucocytic tissues, in all probability, represent types, the 

 special functions of which show the highest degrees of 

 regeneration. 



In many tissues of the body, coincidentally to normal 

 communistic activity, there is constant or periodic normal 

 destruction with constant or periodic regeneration, both 

 of which depend on communistic functional activity and 

 a constant or periodic destructive action of antagonistic 

 agents. The amount of regeneration depends on the 

 amount of destruction, which depends on the quality, 

 quantity and duration of action of the destructive agent 

 or agents. 



Tissue destruction and regeneration were made the 

 subject of investigation by the writer, in the protective 

 cells of the human skin (Fig. 3) and in the secretory 

 epithelium of the human mammary gland (Fig. 4). One 

 finds in these organs that some unknown irritant or irri- 

 tants of an apparent low degree of virulence, acting over 

 a prolonged period of time, produce certain reactive cel- 

 lular phenomena; there is first a destruction of the spe- 

 cialized and differentiated cells (textocytes). This de- 

 struction is associated with an hypertrophy of the so- 

 called basal cells (cells of the stratum germinativum, or 

 textoblasts) and a lymphocytic infiltration in the sup- 

 porting stroma. 



Space does not permit a consideration of the factor of 

 lymphocytic infiltration. The hypertrophy of the so- 

 called basal cells, however, is of great importance from 

 the standpoint of the subject under consideration. 



One sees clearly that nature, in building up the special- 



