THE CRITERIA OF LIVINGNESS 103 



istics of living creatures. Hence this inquiry into the criteria 

 of livingness. The bearing of this on modern Natural The- 

 ology is that an easy-going concept of ' organism ' is a dead 

 fly that may spoil many an ointment. 



SUMMARY. 



If we are to reach a coherent view of Nature, such as could be 

 included in a philosophy, we must arrive at some definition of the 

 characteristics which mark off living organisms from their not-living 

 surroundings. In the present state of science this definition cannot 

 be more than tentative, but it must be continually attempted. 



Living may be described as a twofold relation of action and re- 

 action between organisms and their environment, and living crea- 

 tures are always active towards two main results, self-maintenance 

 and the continuance of their race. But the difficult question is: 

 What are the insignia of living creatures? 



The first is the power of persisting in a complex specific metabo- 

 lism, and in a corresponding specific organisation, (a) The essential 

 metabolism of life has to do with the up-building and down-break- 

 ing of protein substances in a colloid state, (b) Each living 

 creature has its own chemical individuality and its own specific 

 microscopic and ultra-microscopic architecture, (c) Part of the 

 secret of life is a correlation of chemical processes so that in 

 spite of ceaseless change the organism persists in its integrity 

 for days or years or centuries. It is always burning away; but 

 it is not consumed. 



Secondly there are the capacities of (a) growth, of (b) re- 

 production, and of (c) development a triad of qualities, (a) 

 Organic growth, an increase in the amount of organised living- 

 matter, is at the expense of materials different from those which 

 compose -the growing substance; it implies active assimilation 

 rather than passive accretion; it is very definitely a regulated 

 process. (b) The power of spontaneous division leading on, 

 directly or indirectly, to the origin of new individualities is 

 one of the momentous distinctions between the living and the 

 not-living, (c) Development is the actualisation of the intrinsic 

 manifoldness of the liberated fragment, sample, or cell, and may 

 be brought into line with the process of repairing the specific 

 organisation. 





