LESSON 20.] AND I'UODLCINO TIU: FOOD OF ANIMALS. 165 



47"). P>iit starch, 8upir, and the like, do not make any part of the 

 flesh or liihric ul' anhnals. And (hat liir the obvious reason, tliat tlicy 

 consist of only the three elements carbon, hydrogen, and oxt/ijca ; 

 whereas the llesh of animals has nitrogen as well as these three ele- 

 ments in its composition. Tiie materials of the animal body, called 

 Fibrine in the lie>h or nnisclcs. Gelatine in the sinews and bones, 

 Cascine in tiie curd of milk, iVc, are all forms of one and the same 

 substance, composed of carbon, hydrogen, oxygen, and nitrogen. As 

 nitrogen is a large constituent of the atmosphere, and animals are 

 taking it into their lungs with every breath they draw, we might 

 suppose that they take this element of their frame directly from the 

 air. But they do not. Even this is furnished by vegetables, and 

 animals receive it ready-made in their food. And this brings us tc 

 consider still another and most important vegetable product, of » 

 different class from the rest (omitted till now, lor the sake of greater 

 simplicity) ; namely, what is called 



47G. Proteine. This name has been given to it by chemists, be- 

 cause it occurs under such a protean variety of forms. The Gluten 

 of wheat and the Legumine of beans and other Icjguminous plants 

 may be taken to represent it. It occurs in all plants, at least in 

 young and growing parts. It does not make any ])ortion of their 

 tissue, but is contained in all living cells, as a thin jelly, mingled 

 witli the sap or juice, or as a delicate mucilaginous lining. In fact, 

 it is formed earlier than the cell-wall itself, and the latter is moulded 

 on it, as it were ; so it is also called Protoplasm. It disappears from 

 common cells as they grow old, being transferred onward to new or 

 forming parts, where it plays a very active part in growth. Mixed 

 with starch, &c., it is accumulated in considerable quantity in wheat, 

 beans, and other grains and seeds, especially those which are most 

 nutritious as food. It is the proteine which makes them so nutritious. 

 Taken by animals as food, it forms their flesh and sinews, and the 

 animal part of their bones, without much change ; for it has the same 

 com[)osition, — is just the same thing, indeed, in some slightly diflerent 

 forms. To produce it, the plant employs, in addition to the carbonic 

 acid and wat(n- already mentioned as its general food, some ammo- 

 nia ; whicli is a <i)in|)onnd of hydrogen and 7iitrogen. Ammonia 

 (whi<li is llic same thing as hartshorn) is constantly escai)ing 

 i'llo tlic air in small (inantitics from all decomposing vegetable 

 and animal sul).-tances. I'.esides, it is pnxhiced in everv thinidei- 

 storm. Every flash of lightning causes some to be made (in '.he 



