CHEMISTRY AND PROTOPLASM 191 



living plasmogen. To construct plasmogen itself is a 

 task for the chemists of the distant future. In early 

 geological ages plasmogen came into being ; it has gone 

 on ever since "nourishing" itself, maintaining itself, 

 growing and spreading over the earth. It is improbable 

 that the conditions which led to its formation have ever 

 recurred. All subsequent plasmogen has been formed 

 by the growth and increase of that first sample of it, 

 which once in a remote period of the earth's history was 

 built up by chemical conditions, which came to an end 

 as soon as they had produced it. 



The only process in nature of which we know, which 

 resembles the " building " action of plasmogen, the 

 ultimate molecule of life, buried in the cell's protoplasm, 

 is the selective action of crystals, which draw to them- 

 selves from a solution or magma of all sorts of chemical 

 bodies those molecules of a chemical nature identical 

 with their own, and build them up into special and 

 definite crystalline forms. But there is a very wide gap 

 between this process and even the mere assimilation by 

 living matter of the organic elements, so as to raise them 

 from a lower to a higher grade of chemical complexity 

 of combination. And over and above this we have 

 added, in the case of living material, to the mere power 

 of assimilation and growth the almost unthinkable com- 

 plications and variations of specific form and quality, 

 and yet further of individual form and quality, which 

 are determined by special complications and variations 

 of the plasmogen, that unique compound concealed in 

 the cell-protoplasm. 



We cannot at present, if ever, picture to ourselves 

 adequately the mechanism of plasmogen, though the 

 attempt has been, and must be, made. But we can 

 watch its workings closely ; we can ascertain the con- 

 ditions which promote, check, or modify its activity ; in 



