FOOD OF PLANTS. 295 



cal degradation is only postponed, taking place in the body 

 of the offspring instead of that of the parent. In all cases 

 animals are thus, essentially, proteid consumers or wasters, 

 and breakers down of complex bodies; the carbon, hydro- 

 gen and nitrogen which they take as foods in the form of 

 complex unstable bodies, ultimately leaving them in the 

 simpler compounds, carbon dioxide, water, and urea; 

 which are incapable of either yielding energy or building- 

 tissue for any other animal and so of serving it as food. 

 The question immediately suggests itself, How, since animals 

 are constantly breaking up these complex bodies and can- 

 not again build them, is the supply kept up ? For exam- 

 ple, the supply of proteids, which cannot be made artificially 

 by any process which we know, and yet are necessary foods 

 for all animals, and daily destroyed by them. 



The Food of Plants. As regards our own Bodies the 

 question at the end of the last paragraph might perhaps be 

 answered by saying that we get our proteids from the flesh 

 of the other animals which we eat. But, then, we have to 

 account for the possession of them by those animals; since 

 they cannot make them from urea and carbon dioxide and 

 water any more than we can. The animals eaten get them, 

 in fact, from plants which are the great proteid formers of 

 the world, so that the most carnivorous animal really de- 

 pends for its most essential foods upon the vegetable king- 

 dom; the fox that devours a hare in the long run lives on 

 the proteids of the herbs that the hare had previously eaten. 

 All animals are thus, in a certain sense, parasites; they 

 only do half of their own nutritive work, just the final 

 stages, leaving all the rest to the vegetable kingdom and 

 using the products of its labor; and plants are able to meet 

 this demand because they can live on the simple compounds 

 of carbon, hydrogen, and nitrogen eliminated by animals, 

 building up out of them new complex substances which 

 animals can use as food. A green plant, supplied with am- 

 monia salts, carbon dioxide, water, and some minerals, will 

 grow and build up large quantities of proteids, fats, starches, 

 and similar things; it will pull the stable compounds eli- 

 minated by animals to pieces, and build them up into com- 



