VARIOUS THEORIES OF THE ORGANISM 19 



In his book on the physical chemistry of the cell and tissues, 

 Hober ('n, pp. 553-55) asserts that we have absolutely no grounds 

 for believing that the metabolic process is based on the lability of a 

 complex organic component of the protoplasm. When we attempt 

 to solve the problems of metabolism with the aid of this hypothetical 

 labile molecule, we find ourselves in a cul de sac from which the 

 only possible way out is retreat. According to Hober, and most 

 authorities now agree with him, there is no kind of proteid essen- 

 tially different from that with which we are familiar in the labora- 

 tory. If proteids are readily broken up in the organism, it is not 

 because in some way they have acquired a peculiar property of 

 lability which they do not possess elsewhere, but for very different 

 reasons; the conditions in the organism are different from those in 

 the test-tube. Hober maintains that the fundamental charac- 

 teristic of the process of metabolism is to be found in the combined 

 and correlated activity of certain definite substances in certain 

 definite quantitative relations. 



This conception of metabolism has gained ground rapidly of 

 late and for various reasons. In the first place, evidence in its 

 favor has been rapidly accumulating, and there is not a shred of 

 experimental evidence in support of the labile molecule hypothesis. 

 It is all the time becoming more evident that life does not consist 

 in any one process nor depend on a particular kind of molecule, 

 but that it is the result of many processes occurring under con- 

 ditions of a certain kind and influencing each other. Moreover, 

 such a conception has a logical advantage over the hypothesis of 

 the labile molecule in that it does not involve assumptions which 

 are outside the range of scientific investigation and which we can 

 therefore never hope to prove or disprove. 



If we accept this idea we must abandon the assumption of a 

 living substance in the sense of a definite chemical compound. 

 Life is a complex of dynamic processes occurring in a certain field 

 or substratum. Protoplasm, instead of being a peculiar living sub- 

 stance with a peculiar complex morphological structure necessary 

 for life, is on the one hand a colloid product of the chemical reac- 

 tions, and on the other a substratum in which the reactions occur 

 and which influences their course and character both physically and 



