VIL] ON THE PHYSICAL BASIS OF LIFE. 117 



phorus, sulphur, and the like, would as infallibly die as the animal 

 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 with ammonia, 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 consequence of 

 that continual death which is the condition of its manifesting 

 vitality, into carbonic acid, water, and ammonia, 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 ammonia. Withdraw any one of these 

 three from the world, and all vital phenomena come to an end. 

 They are related 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 produce water; 

 nitrogen and hydrogen give rise to ammonia. These new com 

 pounds, 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 complex body, proto 

 plasm, and this protoplasm exhibits the phenomena 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 



