446 LECTURE XVIII. 



which this endogenous development plays any distinct 

 part, whilst in nearly all forms cell-division is met with 

 to a great extent. 



The essential points of difference between the several 

 modes of development of cells are therefore these : in 

 one class of formations the divisions proceed with a cer- 

 tain regularity, so that the ultimate products from their 

 very beginning exhibit a complete correspondence with 

 the parent structures, and the young structures at no 

 time deviate in any remarkable degree from the parent- 

 cells. Such processes are in ordinary life mostly desig- 

 nated as hypertrophies, but I have, in order to express 

 the nature of the change more accurately, proposed 

 the name of hyperplasice, inasmuch it is not an increase 

 in the nutrition of existing parts that takes place, but a 

 real formation of new elements (p. 94). 



In another class the development proceeds in such a 

 way, that divisions certainly also do take place, but make 

 very rapid progress and produce cells which gradually 

 decrease in size, and ultimately in some instances be- 

 come so small, that they can scarcely be distinguished to 

 be cells. The proliferation may cease at this point, and 

 then the cells severally begin to grow, and to become 

 larger ; and under certain circumstances a structure 

 may in this case again also be produced analogous to 

 that in which the development originated. This, how- 

 ever, is not usually the case ; generally, the young cells 

 pursue a somewhat different course of development, and 

 a heterologous structure begins to form. 



The mode of development, which I here describe to 

 you, may also run its course in such a way, that the 

 cells do not at once begin to divide, but the nuclei first 

 greatly multiply, becoming continually more numerous 

 and at the same time smaller. We find something simi- 

 lar to this in pus, in which a division of the nuclei very 



