Agricultural Chemistry. — Pig Feeding. 



539 



very different principles ; and simply takes cognizance of the 

 relations of supply and demand. Thus, air, water, and other 

 natural agents, from their vast importance in sustaining animal 

 and vegetable life, have a high value in a physiological or scien- 

 tific point of view ; but, from the relations of supply and demand, 

 they are of little accounted money value. And so it is with 

 the nitrogenous compounds of food ; the functions which they 

 alone can fulfil in the animal body are of the utmost importance ; 

 but in relation to the demand for them, it would seem, that our 

 current food stuffs are much more likely to be deficient in certain 

 other elements. Indeed, it would be difficult adequately to 

 account for the comparatively high commercial value of the 

 foods which contain a comparatively large proportion of certain 

 720?z-nitrogenous compounds, except by supposing, that these, 

 compared with the nitrogenous ones, were in less abundance in 

 relation to the demands of the animal system for them. 



It is not indeed, only in our current fattening foods., that the 

 amount of certain elaborated and digestible non-nitrogenous 

 constituents, rather than that of the nitrogenous ones, chieflj^ 

 determines their relative value ; for, a careful consideration of 

 many human dietaries has led us to similar conclusions. When 

 we remember too, that in using sugar, we do so at the cost 

 of the rejection of all the nitrogenous compounds of the sugar- 

 cane — and, in addition, of heavy money charges — it would seem 

 improbable that it would become an article of diet of such grow- 

 ing necessity in all ranks of society, if our own home-produced 

 foods were chiefly deficient in the nitrogenous constituents. 

 Again, in the much higher price of butter than cheese, and of 

 those cheeses which contain a large proportion of butter than 

 those which are richer in nitrogen, it would seem to be further 

 illustrated, that the demands of the body in relation to the 

 supplies within its reach, are measured more by the amounts in 

 the food, of the non-nitrogenous, than of the nitrogenous con- 

 stituents. It would perhaps not be difficult to trace the undue 

 estimates which, from scientific considerations merely, have 

 been made as to the relative value of nitrogen and of mineral 

 substances in manures, to a source somewhat similar to that 

 Avhich has given to the nitrogenous compounds of food, such a 

 high theoretical value. For, as it is the mutual relationship of 

 supply and demand of the nitrogenous and non-nitrogenous 

 constituents of food, which must chiefly determine their relative 

 values— so it is the relationship of supply and demand of the 

 nitrogenous and mineral constituents of manures, that must 

 give to them also their respective comparative values. 



In conclusion, whilst we must not be understood, as in any 

 way depreciating the value of a somewhat liberal supply of the 



