156 NUTRITION. 



posit brought within the reach of animal necessities in periods when the 



ordinary supplies cease. 



It belongs to that class of food which has reference to respiration. 

 There are two classes, the first has reference to the repair and nutriment 

 of the body, and the other has reference to animal heat by combustion — 

 the first called by Liebig the plastic elements of nutrition — the second 

 the elements of respiration. 



First class. 1, Vegetable fibrin; 2, Vegetable albumen; 3, Vegeta- 

 ble casein ; 4, Animal flesh and blood. 



Second class. Fat, Starch, Gum, Cane sugar. Loaf sugar, Milk, Su- 

 gar, Mucilage. Wine, Beer, Spirits. 



This then is in general its use, and for details, we must refer you to 

 Liebig. 



We ask, finally, what are the circulations between these kingdoms 

 by which tliey minister to each other. It is not to be denied that if, on 

 the one hand, the vegetable kingdom contributes to the support of the 

 animal kingdom — on the other, the animal contributes to the support of 

 the vegetable. If, moreover, animal and vegetable life depends upon the 

 atmosphere, it is true that it too receives contributions from its benefi- 

 ciaries by which it is upheld in its power. The remarks already made 

 render it intelligible and satisfactory, that vegetables contribute essen- 

 tially and largely to the supply of animal necessities, but is the favor 

 returned — is the debt in any way cancelled ? The appropriate answer 

 here, we presume, is that animals furnish in various ways substances 

 which are necessary to vegetation. Carbonic acid, ammonia, various 

 saline combinations with water, are all instrumental in the development 

 of vegetable life. The deterioration of the atmosphere and animal pro- 

 cesses is remedied by supplies from the vegetable world. 



A recent French writer, says Fownes, in his Chemistry as exempli- 

 fying the wisdom and goodness of God, has contrasted the opposite 

 functions of plants and animals in a very pleasing manner : 



The vegetable The aniinal 



Produces the neutral azotized Consumes the neutral azotized 

 substances, substances, 



" " fatty substances, " " fatty substances. 



" " sugar starch and gum, " " sugar, starch, &. gum. 



Decomposes carbonic acid. Produces carbonic acid, 

 "• water, " water, 



" ammoniacal salts, " ammoniacal salts. 



Disengages oxygen, Absorbs oxygen, 



Absorbs heat and electricity. Produces heat and electricity, 



Is an apparatus of reduction. Is an apparatus of oxidation, 



Is stationary. Is locouiotive. 



