ON THE PHYSICAL BASIS OF LIFE 105 



in his bath of smelling-salts, though it would be surrounded 

 by all the constituents of protoplasm. Nor, indeed, need 

 the process of simplification of vegetable food be carried so 

 far as this, in order to arrive at the limit of the plant's 

 thaumaturgy. Let water, carbonic acid, and all the other 

 needful constituents be supplied except nitrogenous salts, 

 and an ordinary plant will still be unable to manufacture 

 protoplasm. 



Thus the matter of life, so far as we know it (and we have 

 no right to speculate on any other), breaks up, in conse- 

 quence of that continual death which is the condition of its 

 manifesting vitality, into carbonic acid, water, and nitrog- 

 enous compounds, which certainly possess no properties 

 but those of ordinary matter. And out of these same forms 

 of ordinary matter, and from none which are simpler, the 

 vegetable world builds up all the protoplasm which keeps 

 the animal world a-going. Plants are the accumulators of 

 the power which animals distribute and disperse. 



But it will be observed, that the existence of the matter of 

 life depends on the pre-existence of certain compounds; 

 namely, carbonic acid, water, and certain nitrogenous 

 bodies. Withdraw any one of these three from the world, 

 and all vital phenomena come to an end. They are as 

 necessary to the protoplasm of the plant, as the proto- 

 plasm 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 produce water; nitrogen and other 

 elements give rise to nitrogenous salts. These new com- 

 pounds, like the elementary bodies of which they are com- 

 posed, are lifeless. But when they are brought together, 

 under certain conditions, they give rise to the still more 



