ANIMAL GRAFTS AND REGENERATIONS. 253 



might not undertake to modify directly the existing com- 

 position of anatomical elements. 



This latter conception, which sets the bounds of physi- 

 ological determinism at a far greater distance than the 

 former does, is also capable of verification by experiments. 

 Just as we act upon phenomena of evolution, we may, by 

 processes of methodical and persistent boldness, disturb 

 the order of the operations of nutrition. The method we 

 have followed in our own researches on this subject con- 

 sists in suppressing certain essential principles of nutrition, 

 and substituting for them new immediate principles, more 

 or less similar. But the immediate principles that are nu- 

 tritious are found mingled with the substances of food in 

 the conditions most favorable to assimilation. The mineral 

 salts in them are intimately combined with azote matters. 

 In order, then, to replace these mineral salts of common 

 food with others, phosphate of lime, for instance, with phos- 

 phates of a different kind, it is necessary not merely to dis- 

 engage the food as much as possible from the salts that we 

 wish to reject, but also to associate with it in the closest 

 manner the new salts which we intend to fix in the system ; 

 that is to say, we must introduce them into it under the 

 form fittest for assimilation, and most capable of overcom 

 ing the natural resistance of the organism. It is also clear 

 that it is best to experiment on young animals, in which 

 the action of assimilation is most intense. Under such 

 conditions, and by such processes, we reach the end of 

 modifying the order and kind of the immediate principles 

 in organized substance. Personal experiments permit us 

 at least to assert this, as far as it regards the bony tissue, 

 and thus far we have seen nothing that compels us to doubt 

 our power of producing at length, by gradual transforma- 

 tions, following upon certain contrivances of nutrition, or- 

 ganisms of a new and harmonious equilibrium, from the 

 point of view of the system of immediate principles. In 



