THE ORIGIN OF LIVING MATTER 529 



certainly true, that many so-called vital events take place in 

 nonliving systems. 



We can distinguish living matter from nonliving only by 

 selecting a number of properties all of which living matter 

 possesses, but only one or two of which are possessed at a time 

 by any one nonliving system. Four such properties are absence 

 of equilibrium (living matter is never in a state of equilibrium, 

 for equilibrium means death, while all nonliving systems ulti- 

 mately attain such a state); adjustment (living matter is always 

 adjusting itself to its environment, while nonliving matter rarely 

 does so, though it may respond to certain environmental factors 

 such as gravity) ; heterogeneity (this is attained to a high degree 

 by living matter and never so much so by nonliving matter); 

 and the maintenance of a definite form (this is sometimes dis- 

 turbed in living matter and, on the other hand, regularly and 

 perfectly attained by nonliving matter, e.g., crystals; but as a 

 whole it is more characteristic of life). 



Having failed to find any one property that distinguishes the 

 living from the nonliving, we may now inquire if there is any one 

 material substance typical of life. Early biologists, influenced 

 by the vitalism of their time, recognized special vital bodies in 

 protoplasm which give to it the properties of life. The French 

 naturalist Buffon conceived of gigantic living molecules termed 

 "biogens." Haeckel, Darwin, and others postulated similar 

 units, as has been noted (page 9). The distinction between 

 living and nonliving matter would, on the basis of these older 

 hypotheses, lie in the possession of special vital bodies by the 

 living substance. But such speculative ideas are no longer 

 seriously considered, though they are not far removed from some 

 modern thoughts. Numerous physiologists have expressed the 

 belief that a definite substance or group of substances represents 

 the ultimate living material. Leathes states that proteins are 

 generally considered the most important components of proto- 

 plasm, and Pauli lays emphasis on them as substances that 

 possess many of the characteristics of living matter. Thus, 

 the opinion prevails that the ultimate living substance is a 

 protein complex. The constituents of this complex may be 

 of the nature of enzymes. Many have commented on the 

 striking similarity between enzymes and living matter. The 

 French microbiologist Duclaux stated that the bacterial cell 



