CHAP, iv.] OF THE GENERAL CONDITIONS OF GROWTH. 297 



act of assimilation and that of disassimilation. " Condorcet had 

 already written : " Would it be absurd now to suppose that the 

 perfectionment of the human species may be regarded as sus- 

 ceptible of indefinite progress, that a time must come when 

 death will only be the effect either of extraordinary accidents, 

 or of the more or less gradual destruction of the vital forces, and 

 that finally, the duration of the average interval between birth 

 and this destruction has no assignable term ? Doubtless, man 

 will not become immortal ; but may not the distance between 

 the moment when he begins to live and the ordinary epoch 

 when naturally, without illness, without accident, he experiences 

 the difficulty of existing, be ceaselessly increased ? " l 



To dare now to assert that it is not impossible to conquer 

 death, the great enemy, is to expose ourselves to an accusation 

 of madness. The animist and vitalist doctrines fail ; they have 

 lost all credit with science ; but a yoke borne for a long time 

 always leaves a permanent impress, and, in the domain of 

 opinion, the effect often long survives the cause. For centuries 

 life has been considered as a mysterious, miraculous fact, beyond 

 all investigation. Each organism was regarded as a monarchy 

 despotically governed by a metaphysical entity. It was believed 

 that the problem of life must eternally defy the power of human 

 science. It was &fatum, against which it was useless to struggle. 

 Such is still the prevailing opinion ; but it exists only by force 

 of habit. The phenomenon of life has been analysed. We know 

 that it is the result of simple molecular exchanges, comparable 

 to those that take place in an electric pile. That there is in the 

 vital phenomena something immutable, predestined, no one can 

 now maintain. Every living being conserves itself as long as 

 there is in it a certain nutritive equilibrium, as long as assimi- 

 lation and disassimilation are almost equally balanced. Now it 

 is certain that the duration of this equilibrium depends upon 

 an infinity of causes, internal and external. Of two children 

 born, one may live ar hour, the other half a century. There is 

 1 Coadorcet, Progres de I'Esprit Humain. 



