26 EVOLUTION AND ANIMAL LIFE 



things inanimate, we find structures and behavior among inor- 

 ganic things which cannot be readily distinguished in defining 

 words from structures and behavior that are usually taken as 

 characteristic of organisms. On the other hand we shall find in 

 organic nature the very same chemical elements, and for the 

 most part the same combinations of elements, th^t we find in 

 the great mass of inorganic world substance. So that some 

 biologists by a detailed and keen, if somewhat sophisticated, 

 analysis of the alleged differences between animate and inani- 

 mate matter show that these differences are not absolute, and 

 leave you with a stone in one hand and a grasshopper in the 

 other logically unable to define the fundamental difference 

 between the tAvo, and yet morally certain of this absolute 

 difference. 



As a matter of fact there is one distinction between living 

 matter and non-living matter which even the cleverest of the 

 modern physicochemical school of biologists has as yet been 

 unable to explain away. And that is the inevitable presence in 

 living matter and the inevitable absence in non-living matter 

 of certain highly complex chemical combinations of carbon, 

 hydrogen, oxygen, nitrogen, and sulphur, called proteids or 

 albuminous compounds. 



The actual presence of these chemical substances in living 

 matter is made manifest to us by the physicochemical behavior 

 of these substances: that is, by our observation or recognition 

 of their peculiar attributes. This behavior or these peculiar 

 attributes or activities are those fascinating ones which we are 

 accustomed to call the essential life processes. What these 

 activities are we indicate in a not very precise way by the 

 words organization, assimilation, growth, reproduction, motion, 

 irritability, and adaptation. These essential life processes we 

 have come by constant experience to associate always and only 

 wdth a substance called protoplasm. Huxley long ago called 

 protoplasm, therefore, the physical basis of life. 



But protoplasm we have found to be a complex of substances 

 or chemical compounds. Of these, a certain few are indispen- 

 sable and fundamental, while others may be absent or present 

 without affecting the particular capacities which make proto- 

 plasm the physical basis of life. This protoplasm too must be 

 organized in a particular way in order that Ufe m^ay persist in 

 the organism. It must appear in two conditions, and proto- 



