Hi ON THE PHYSICAL BASIS OF LIFE 143 



whatever respecting the composition of actually 

 living matter, from that of the dead matter of 

 life, which alone is accessible to us. But ob- 

 jectors of this class do not seem to reflect that 

 it is also, in strictness, true that we know nothing 

 about the composition of any body whatever, as 

 it is. The statement that a crystal of calc-spar 

 consists of carbonate of lime, is quite true, if we 

 only mean that, by appropriate processes, it may be 

 resolved into carbonic acid and quicklime. If you 

 pass the same carbonic acid over the very quick- 

 lime thus obtained, you will obtain carbonate of 

 lime again ; but it will not be calc-spar, nor any- 

 thing like it. Can it, therefore, be said that 

 chemical analysis teaches nothing about the 

 chemical composition of calc-spar ? Such a state- 

 ment would be absurd ; but it is hardly more so 

 than the talk one occasionally hears about the 

 uselessness of applying the results of chemical 

 analysis to the living bodies which have yielded 

 them. 



One fact, at any rate, is out of reach of such 

 refinements, and this is, that all the forms of pro- 

 toplasm which have yet been examined contain 

 the four elements, carbon, hydrogen, oxygen, and 

 nitrogen, in very complex union, and that they 

 behave similarly towards several reagents. To 

 this complex combination, the nature of which has 

 never been determined with exactness, the name 

 of Protein has been applied. And if we use this 



