84 THE PHILOSOPHY OF BIOLOGY 



from those which exist in inorganic nature in their 

 greater complexity. It was also seen that physico- 

 chemical reactions occurred in living substance ana- 

 logous with, or quite similar to, those which could be 

 studied in non-living substance. The conclusion, then, 

 was irresistible that the life of the organism was merely 

 a phase in the evolution of matter and energy, and 

 differed in no essential respect from the physico- 

 chemical activities that could be observed in the non- 

 living world. 



These conclusions were stated so well by Huxley 

 in his famous lecture on ' The physical basis of life," 

 over forty years ago, that all subsequent utterances 

 have been merely reiterations of this thesis in a less 

 perfect form. The existence of the matter of life, 

 Huxley said, depended on the pre-existence of cer- 

 tain chemical compounds carbonic acid, water, and 

 ammonia. Withdraw any one of them from the world 

 and vital phenomena come to an end. They are the 

 antecedents of vegetable protoplasm, just as the latter 

 is the antecedent of animal protoplasm. They are all 

 lifeless substances, but when brought together under 

 certain conditions they give rise to the complex body 

 called protoplasm ; and this protoplasm exhibits the 

 phenomena of life. There is no apparent break in the 

 series of increasingly complex compounds between 

 water, carbon dioxide, and ammonia, on the one hand, 

 and protoplasm on the other. We decide to call 

 differen tkinds of matter carbon, oxygen, hydrogen, 

 and nitrogen and to speak of their activities as their 

 physico-chemical properties. Why, then, should we 

 speak otherwise of the activities of the substance 

 protoplasm ? 



" When hydrogen and oxygen are mixed in certain 

 proportions and an electric spark is passed through 



