EVOLUTION AND MUTABILITY OF MATTER^ 265 



true that M. H. Bouasse protests in the name of the 

 physico-mathematicians against the employment of 

 these figurative expressions. But has he not himself 

 written "a twisted wire is a wound-up watch," and 

 elsewhere, " the properties of bodies depend at every 

 moment upon all anterior modifications "? Does not 

 this imply that they retain in some manner the 

 impression of their past evolution ? Powerful de- 

 formative agencies leave a trace of their action ; they 

 modify the body's condition of molecular aggregation, 

 and some physicists go so far as to say that they even 

 modify its chemical constitution. With the exception 

 of M. Duhem, the disciples of the mechanical school 

 who have studied elasticity admit that the effect of an 

 external force upon a body depends upon the forces 

 which have been previously acting on it, and not 

 merely upon those which are acting on it at the 

 present moment. Its present state cannot be antici- 

 pated, it is the recapitulation of preceding states. 

 The effect of a torsional force upon a new wire will 

 be different from that of the same force upon a wire 

 previously subjected to torsions and detorsions. It 

 was with reference to actions of this kind that 

 Boltzmann, in 1876, declared that "a wire that has 

 been twisted or drawn out remembers for a certain 

 time the deformations which it has undergone." 

 This memory is obliterated and disappears after a 

 certain definite period. Here then, in a problem of 

 static equilibrium, we find introduced an unexpected 

 factor — time. 



To sum up, it is the physicists themselves who 

 have indicated the correspondence between the con- 

 dition of existence in many brute bodies and that in 

 many living bodies. It cannot be expected that 



