FUNCTION AND FUNCTIONAL STIMULUS. 139 



show the following characteristics: first, enlargement (functional 

 hypertrophy) with increased stimulus; second, atrophy from 

 inactivity upon cessation of the stimulus; third, regeneration 

 of organs of functional structure to the condition of the original 

 structure would only be possible in the presence of function and 

 functional stimuli (functional regeneration); and fourth, the 

 successful transplantation of functional structures would only 

 be conceivable if after transplantation the organs involved were 

 supplied with an appropriate amount of functional stimulus. 

 The principles, therefore, necessary for an acceptance of the 

 theory of functional adaptation are: functional hypertrophy, 

 atrophy from inactivity, functional regeneration, and functional 

 transplantation. (Various other factors which are similarly 

 instrumental in this connection will be dwelt upon more exten- 

 sively in a subsequent paper.) Should it now appear that these 

 essential principles in so-called functional structures are non- 

 existent, the theory of adaptation would then fail to adequately 

 account for so-called functional structures. 



Before giving the results of my experiments I wish to say a 

 few words about the general value of Roux's theory of functional 

 adaptation. 



This theory at a cursory glance has many merits, and at the 

 time when first introduced by Roux it marked a substantial 

 advance, inasmuch as it showed that it was possible to produce 

 highly purposeful structures through the influence of purely 

 mechanical principles. On this basis the theory has become 

 a material factor in connection with the investigations and studies 

 of many workers in the realms of pathology and physiology. 



Roux's theory, however, has great disadvantages, one of 

 which is its extremely complicated and extensive terminology. 

 It is probably owing to the extreme obscurity of the doctrine 

 that comparatively few investigators, apart from the originator 

 of the theory, have familiarized themselves with it and fully 

 understood its principles. As a result of this practically the 

 only valuable work along this line has been carried on under the 

 direct control of Roux himself, while in contrast with the com- 

 paratively scanty publications emanating from Roux's laboratory 

 an amazingly voluminous mass of literature has been supplied 



