ON THE PHYSICAL BASIS OF LIFE 111 



end. They are as necessary to the protoplasm of the 

 plant, as the protoplasm of the plant is to that of the 

 animal. Carbon, hydrogen, oxygen, and nitrogen are 

 all lifeless bodies. Of these, carbon and oxygen unite 

 in certain proportions and under certain conditions, to 

 give rise to carbonic acid; hydrogen and oxygen pro- 

 duce water; nitrogen and other elements give rise to 

 nitrogenous salts. These new compounds, like the 

 elementary bodies of which they are composed, are 

 lifeless. But when they are brought together, under 

 certain conditions, they give rise to the still more com- 

 plex body, protoplasm, and this protoplasm exhibits 

 the phsenomena of life. 



I see no break in this series of steps in molecular 

 complication, and I am unable to understand why the 

 language which is applicable to any one term of the 

 series may not be used to any of the others. We think 

 fit to call different kinds of matter carbon, oxygen, 

 hydrogen, and nitrogen, and to speak of the various 

 powers and activities of these substances as the proper- 

 ties of the matter of which they are composed. 



When hydrogen and oxygen are mixed in a certain 

 proportion, and an electric spark is passed through 

 them, they disappear, and a quantity of water, equal 

 in weight to the sum of their weights, appears in their 

 place. There is not the slightest parity between the 

 passive and active powers of the water and those of the 

 oxygen and hydrogen which have given rise to it. At 

 32 Fahrenheit, and far below that temperature, oxygen 

 and hydrogen are elastic gaseous bodies, whose particles 

 tend to rush away from one another with great force. 

 Water, at the same temperature, is a strong though 

 brittle solid whose particles tend to cohere into definite 

 geometrical shapes, and sometimes build up frosty imi- 



