266 the president's address. 



nature but gradually assume a character which distinguishes 

 them more or less from ordinary physical and chemical processes 

 and perhaps justifies us in speaking of them as vital. 



That there should be perfect continuity between not-living and 

 living matter on the one hand, and between physico-chemical and 

 vital processes on the other, is clearly demanded by the doctrine 

 of evolution. Moreover we know that, at the present day, 

 inorganic matter is constantly being converted into living proto- 

 plasm, though only by the peculiar organising activities of 

 living bodies. All organisms assimilate materials derived from 

 their environment in order to build up their own bodies, and it 

 is largely this power of assimilation that distinguishes them from 

 bodies that are not alive. Daring life the organism conquers its 

 environment and appropriates such portions of it as it requires. 

 Death is the conquest of the organism by the environment, 

 accompanied by re-annexation on the part of the inorganic world 

 of all that the organism had appropriated during its lifetime. 



The chemist has no difficulty in analysing the complex col- 

 loidal constituents of dead organisms into a descending series 

 of less and less complex substances, ending with the so-called 

 elements themselves. He has also, to a very great extent, accom- 

 plished the reverse process, and has already carried his constructive 

 operations as far as the synthesis of polypeptides, from which 

 point to the proteids themselves is but another step. He has no 

 right to assume, however, that when he has actually taken this 

 step and, further, mixed his proteids with the other substances 

 known to occur in living protoplasm, he will have produced 

 anything that is actually endowed with life. We may even say, 

 without much exaggeration, that the chemist, as such, has no 

 knowledge of protoplasm at all, for it is impossible to analyse 

 protoplasm while it is alive, and as soon as you kill it it ceases 

 to be protoplasm. 



Even the simplest living things known to us behave in a 

 manner which cannot, at any rate in the present state of our 

 knowledge, be explained entirely in terms of chemistry and 

 physics. The living organism itself plays the part of the chemist 

 and the physicist, and we cannot explain the chemist or physicist 

 in terms of the chemical and physical operations which he per- 

 forms in his laboratory. Out of a multitude of possibilities the 

 living organism selects those materials and those modes of action 



