400 



THE AMEBIC. 



ITU BALI ST 



[Vol. LII 



ized and differentiated protec- 

 tive cells of the skin and the se- 

 cretory cells of the mammary 

 gland, has also made provision 

 for an anticipated destruction, 

 an anticipation which is no more 

 remarkable in nature than that 

 of the butterfly which deposits 

 its eggs in a safe place and dies 

 with the inherent assuredness 

 that the eggs will some day de- 

 velop into caterpillars and event- 

 ually into butterflies to continue 

 the existence of the kind. In the 

 . : case of the cells of the skin and 



(SS^) the mammary gland, if the irri- 



fig. 3 Three diagram- tant ^ s removed, complete regen- 

 matic histologic stages of re- eration of differentiated or spe- 

 e^itheiium oi tVTkVunLr cialized cells takes place, pro- 

 a7 e m condi n «onr ita eo Normal vided ttie basal cells themselves 

 ii in si «,„. ,1 rei a have not been completely de- 

 ny the ^hadl?** rtion dlC Th^ Continuance of the action of 

 ••••s-'i,- t.'i ehronic 1 destruc 6 the destructive agent or agents 



Lmiila^a^T^StowLte P ro ^ lK ''^ livpt-rt ropliy. Iiyjii-r- 



rhis hyperplasia takes place plasia and migration of the basal 



a!.'n ii! I', n'xtocytes! depend- or regenerative cells (Figs 3 and 



Sitrof 1 The d XsTruSt n ion Ch, i°n ^' Coincidentally with such a 



this condition it la taapossihU 1 1 V j „ ■ rj > i ;i th.- ba>;il eelU ( 1 . • X t - 



ap^ra£°wh^ oblasts) do not always become 



difiViviitiat.-d i<. tin- I'mm of T 1 m 

 Represents the stage of migra- specialized squamous or secre- 

 fe°rent[ated tor - v cells according to their com- 



munistic normal f oreordination ; 

 they retain their oval or spheroidal form, become larger 

 and produce a massed overgrowth of undifferentiated 

 cells (Figs. 3 and 4). The degree of hyperplasia and 

 migration varies under different and perhaps the same 

 irritative circumstances, depending on inherited variable 



