THE BIOLOGY OF THE CELL SURFACE 



matter Is composed of proteins, carbohydrates and lipins 

 together with water, electrolytes and gases. It would be 

 necessary, unless life resides only in protein, and this has 

 not yet been proved, to obtain evidence to indicate that all 

 these constituents named as components of living matter in 

 some way combine as a single molecule. Further, with 

 respect to proteins, carbohydrates and fats, we have no 

 sufficient ground to warrant the conclusion that they exist 

 in living matter in the same form which they have when 

 they are Isolated. This is especially true of the proteins; 

 all of them known to us outside the living substance are 

 probably changed in their nature chemically and physically 

 by the methods of isolation. In the chemist's test-tube 

 the organic constituents of the living substance may repre- 

 sent merely end-products of something In the living. In 

 this, however, lies no reason for supporting the theory of a 

 blogen-molecule; rather should we try to refine our methods 

 of isolation, so that the results allow a more direct con- 

 clusion. If one says that the blogen-molecule depends 

 upon a certain milieu — if, for example, being protein-like 

 it depends upon fat and fat-like substances, sugars, various 

 electrolytes and water — we need the postulate that the life- 

 molecule is totally unlike molecules with which physical 

 science has to do. I have no wish to quarrel with words; 

 either the term molecule used in the expression, life-mole- 

 cule, carries the connotation ordinarily assigned It by 

 physical scientists or it embodies a non-physical conception. 

 As a concept consonant with physical science it stands open 

 to serious doubt; as a non-physical postulate it defeats Its 

 own purpose. 



What is said of the blogen-molecule may be said of the 

 gene-molecule, the hypothetical unit of which the chromo- 

 somes are assumed to be built. Like the former it too 

 appears incapable of self-maintenance — It grows by what 

 it feeds upon, the cellular matrix in which it lies; and more, 

 never stands apart from other genes in the same chromo- 



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