1906.] oa Tim PlujHical Basis of Life. 409 



acid. Here are solutions of two proteids, one from maize seeds, the 

 other from the white of egg. The former lacks, the latter possesses 

 this group. 



In order to represent the great varieties of living matter the 

 proteid molecules must be capable of xavj many variations of struc- 

 ture. That is, after all, mainly a (juestion of size — the larger it is 

 the greater the possibility of variations in detail ; and as the molecule 

 of proteid seems to contain from ten to thirty thousand atoms, whereas 

 the most complex molecule known to the organic chemist contains 

 less than a hundred, there is no lack in this respect. 



Proteids unquestionably are the material basis of life, but when 

 isolated after the death of the cell they are not living. They are 

 chemically stable bodies. They show no signs of the characteristic 

 chemical flux. It is therefore conjectured on experimental grounds 

 that the living molecule is built up of proteid molecules, that it is so 

 complex, so huge, as to include as units of its structure even such 

 large molecules as these. But when such very large molecules enter 

 into chemical combination with one another, whether by reason of 

 the great magnitude of the masses of matter in each in relation to 

 the magnitude of the directive forces, or because the molecules them- 

 selves, owing to their great size, to a certain extent cease to be 

 molecules at all in the physical sense, and possess the properties of 

 matter in- mass, it is at any rate certain that in their chemical com- 

 Ijinations they cease to follow the law of definite combining weights 

 Avhich is the basis of chemistry. The quantity of the substance A 

 which will combine with a fixed quantity of the substance B is 

 determined not only by the chemical nature of A and of B, but also 

 by the chance conditions of temperature and concentration of the 

 moment. This class of chemical compounds is within limits con- 

 tinuously adjustable to changes in its surroundings, Avhile at the 

 same time it resists those changes by reason of its inertia. Here is a 

 real adumbration in non-living matter of the chemical flux which is 

 the abiding characteristic of the matter of life. 



The biologist speaks of those molecular complexes as molecides^ 

 and in that he is wrong in so far as the word implies a dpfined struc- 

 ture, a chemical unit. The biogen, or chemical unit of living matter, 

 is not a fixed unit like the molecule of dead proteid ; it is an average 

 state. That we know from the chemical phenomena of living matter. 



Why should this be ? Consider what must happen if you make 

 the atomic building much larger than it already is in the molecule of 

 dead proteid. You already have a molecule so large as to be liable 

 to fracture on mere mechanical agitation. A molecule composed of 

 fifty proteid molecules would cease to be a molecule in the physical 

 sense : it would be matter in mass, defined by a surface ; it would 

 break up the Avaves of light, so radiant energy would profoundly 

 affect it. 



In a mass so large, a portion of the energy would of necessity be 



