116 LAY SERMONS, ESSAYS, AND REVIEWS. [vii. 



Hence it appears to be a matter of no great moment what 

 animal, or what plant, I lay under contribution for protoplasm, 

 and the fact speaks volumes for the general identity of that 

 substance in all living beings. I share this catholicity of assimi 

 lation with other animals, all of which, so far as we know, could 

 thrive equally well on the protoplasm of any of their fellows, or 

 of any plant ; 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 proto 

 plasm ; 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 substance of dead 

 protoplasm to the higher power, as one may say, of living proto 

 plasm ; 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 

 upon the uncompounded elements of protoplasm. A plant 

 supplied with pure carbon, hydrogen, oxygen, and nitrogen, phos- 



