Hi ON THE PHYSICAL BASIS OF LIFE 149 



world. A fluid containing carbonic acid, water, 

 and nitrogenous salts, which offers such a 

 Barmecide feast to the animal, is a table richly 

 spread to multitudes of plants ; and, with a due 

 supply of only such materials, many a plant will 

 not only maintain itself in vigour, but grow and 

 multiply until it has increased a million-fold, or a 

 million million-fold, the quantity of protoplasm 

 which it originally possessed ; in this way building 

 up the matter of life, to an indefinite extent, from 

 the common matter of the universe. 



Thus, the animal can only raise the complex 

 substance of dead protoplasm to the higher power, 

 as one may say, of living protoplasm ; while the 

 plant can raise the less complex substances 

 carbonic acid, water, and nitrogenous salts to the 

 same stage of living protoplasm, if not to the same 

 level. But the plant also has its limitations. 

 Some of the fungi, for example, appear to need 

 higher compounds to start with ; and no known 

 plant can live upon the uncompounded elements 

 of protoplasm. A plant supplied with pure car- 

 bon, hydrogen, oxygen, and nitrogen, phosphorus, 

 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 



