226 ON VARIABILITY AND ADAPTATION 



resemble phenomena of surrounding inanimate nature ; they 

 differ from those only in degree, not in kind. There is not one 

 vital activity which can be mentioned that demands for its 

 explanation something over and above chemical change ; 1 and, 

 to this extent, inanimate and animate nature are one. There is, 

 however, an apparent, most important difference between the 

 results of vital and non-vital phenomena. This has been well 

 put by Earl. " Every living organism may be regarded as a 

 centre at which energy is being constantly transformed. It is 

 by the nature of this transformation that we recognize it as a 

 living organism. But," he continues, " the continuous operation 

 of these transformations in the region of the organism is dis- 

 tinctive. In all exchanges of energy between inanimate bodies 

 there is a speedy attainment of equilibrium, whereas the organism, 

 so long as it lives, is incessantly disturbing the equilibrium 

 which would otherwise arise between itself and its environment. 

 In other words, living organisms are not ordinary conservative 

 systems, and the extent to which they diverge from the principle 

 of the conservation of energy is another indication to us that in 

 the organism we come in touch with phenomena which are not 

 yet, at all events, reduced to physical laws." 



I wish to discuss how far this statement is true, for, if true, 

 it immediately defines the difference between phenomena of 

 animate and inanimate creation. It will be best, I think, to 

 study the subject by analysing that property of living matter 

 which is the most evident outcome of the incessant disturbance 

 of equilibrium above mentioned — I mean growth. 



If we seek to test the relative importance of the various forms 

 in which vital activity manifests itself — motion, sensation, 

 assimilation, excretion, reproduction — we are bound to see that 

 one and all of these subserve growth. If the individual moves, 

 an ultimate analysis shows that the primary object in motion 

 is either to obtain more food, or, more accurately, the primary 

 result of that movement is to approach and assimilate food-stuffs, 

 and that food obtained is of benefit as it can be used for further 

 growth ; or is to place itself at a greater distance from disintegra- 

 tive forces. The same is true also with regard to sensation. 



1 Even memory has been explained by Hering and others as a reproduction 

 under particular stimuli of particular relationships between particular mole- 

 cules, so that now they set in order an identical series of reactions in the cerebra 

 cells. 



