ON THE PHYSICAL BASIS OF LIFE 109 



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 assimilation with other ani- 

 mals, 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 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 can- 

 not 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. 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 mil- 

 lion 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 



