THE BEGINNINGS OF LIFE. 23 



whatever amount of power an organism expends in any 

 shape, is the correlate and equivalent of a power that 

 was taken into it from without. On the one hand, it 

 follows from the persistence of force, that each portion 

 of mechanical or other energy which an organism 

 exerts, implies the transformation of as much organic 

 matter as contained this energy in a latent state. And 

 on the other hand, it follows from the persistence of 

 force that no such transformation of organic matter 

 containing this latent energy can take place without 

 the energy being in one shape or other manifested/ 



We shall find it worth our while, however, to follow 

 up a little more fully the details of this most important 

 doctrine, as it will aid us so much in forming a true 

 conception as to the nature of Life. 



As pointed out by M. Gavarret x , most of the physi- 

 cal force which, in the form of light and heat, impinges 

 upon a plant, is consumed therein (travail interieur}. It 

 is stored up as potential force in the complex organic 

 substances entering into the composition of the plant ; 

 these being produced therein (under the influence of 

 the already existing living tissues) by the action of 

 physical forces upon the not-living constituents of the 

 earth, air, and water by which the plant was surrounded. 

 The animal, on the contrary, liberating and using these 

 forces which have been stored up by the plant after 

 assimilating its substance in the form of food expends 

 them in the production of that travail exterieur which 

 1 'Ph&iomenes Physiques de la Vie,' 1869, Paris, p. 73. 



