208 LIFE AND DEATH. 



tion alike raise problems of the highest importance. 

 Does the part become regenerated just as it was 

 formed at first ? Does the regeneration repeat the 

 ontogeny? Is it true that a lost organ is never re- 

 generated (the kidney for instance) ? Does the- 

 symmetrical organ enjoy a compensating and hyper- 

 trophic development, as Ribbert has asserted ? And 

 further, if the organ be removed and transplanted to 

 another position, can it be grafted there, as Y. Delage 

 maintains? These are very important questions; but 

 if we dwell upon them, we shall be diverted from our 

 immediate object. Our task is to look at these facts 

 from the point of view of their significant and char- 

 acteristic meaning in vitality. Flourens invoked on 

 their behalf the intervention of vital forces, plastic 

 and morplioplastic. But, as we shall see later, these 

 phenomena of cicatrization, of reparation, of re- 

 generation, these more or less complete efforts for 

 the re-establishment of the specific form, although 

 they are found in all living beings in different degrees, 

 are not exclusively confined to them. We find them 

 again in some representatives of the mineral world — 

 in crystals, for instance. 



