182 SCIENCE AND PHILOSOPHY OF THE ORGANISM 



cannot exist in other fields of morphogenesis. But we are 

 searching for a new and independent proof; and that is 

 indeed not to be found here. 1 



At present it must be taken as one of the funda- 

 mental facts of the organogenetic harmony, that the cells 

 of functioning tissues do possess the faculty of reacting to 

 factors which have changed the state of functioning, in a 

 way which normalises this state histologically. And it is 

 a fact also that even cells, which are not yet functioning 

 but are in the so-called embryonic or indifferent condition 

 contributing to the physiological completion of the tissue, 

 react to factors embracing new functional conditions of the 

 whole in a manner which leads to an adaptation of that 

 whole to those conditions. 



This is a very important point in almost all morphologi- 

 cal adaptation, whether corresponding to functional changes 

 from without or resulting from the very nature of function- 

 ing. In fact, such cells as have already finished their 

 histogenesis are, as a rule, only capable of changing their 

 size adaptively, but are not able to divide into daughter- 

 cells or to change their histological qualities fundamentally ; 

 in technical terms, they can only assist " hypertrophy ' but 

 not " hyperplasia." Any adaptive change of a tissue there- 

 fore, that implies an increase in the number of cellular 

 elements or a real process of histogenesis, has to start from 

 " indifferent " cells, that is to say, cells that are not yet 

 functioning in the form that is typical of the tissue in 

 question ; and, strange to say, these " embryonic >: cells 



1 The ' ' secondary adaptations " observed by Vochting are too complicated 

 and too much mingled with restitutions to allow any definite analysis of the 

 fact of the "secondary adaptation" as such. 



