134 LAY SERMONS, ADDRESSES, AND REVIEWS. [vil 



but here the assimilative powers of the animal world 

 cease. A solution of smelling-salts in water, with an 

 infinitesimal proportion of some other saline matters, 

 contains all the elementary bodies which enter into the 

 composition of protoplasm ; but, as I need hardly say, a 

 hogshead of that fluid would not keep a hungry man from 

 starving, nor would it save any animal whatever from a 

 like fate. An animal cannot make protoplasm, but must 

 take it ready-made from some other animal, or some 

 plant — the animal's highest feat of constructive chemistry 

 being to convert dead protoplasm into that living matter 

 of life which is appropriate to itself. 



Therefore, in seeking for the origin of protoplasm, we 

 must eventually turn to the vegetable world. The fluid, 

 containing carbonic acid, water, and ammonia, 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 sub- 

 stance 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 

 ammonia — 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 

 upou the uncompounded elements of protoplasm. A 

 plant supplied with pure carbon, hydrogen, oxygen, 

 and nitrogen, phosphorus, sulphur, and the like, would 

 as infallibly die as the animal in his bath of smelling* 



