482 
On the Composition of Oxen, S'lcep, and. Figs, 
that of pigs, a considerable amount of fat will frequently be 
formed in the body from other constituents of tlie food. As has 
been seen, however, only about half as much fat, or total dry 
increase, is obtained from 100 of the dry substance of the fatten- 
ing food of oxrn and sheep, as of that of pigs. There will, ia 
fact, be a far less proportion of the dry matter of the food of the 
former than of the latter animals, appropriated in the (so to 
speak) direct production of increase. 
It appears then, that a considerable proportion of the fat — of 
which the increase of the so-called fattening animals so largely 
consists — may he formed in the hodij from other constitue/ds of the 
food. Of the nitrogenous compounds, on the other hand, it is 
probable that frequently as little, and even less, than 5 per cent, 
of the whole consumed will be found finally stored up in the 
increase of the animal. In fact, if the animals are to store up 
as much as they can do of matters not containing nitrogen, a 
very large amount of nitrogen must pass through the body, 
beyond that which is finally retained in the increase. 
Since it is found, that by far the larger proportion of the solid 
increase of the fattening animals is re^Wy fat itself; — since it is 
probable, that at least a great part of the fat stored up in the 
body is derived from starch, and other ?i07i-nitrogenous constitu- 
ents of the food ; — since so large an amount of non-nitrogenous 
constituents is required to meet the respiratory demands of the 
system ; — and since the current fattening foods contain so very 
much more of nitrogen than is eventually retained in the in- 
crease — it can hardly excite surprise that the comparative value 
of foods, as sucli, does not depend upon their percentage of 
nitrogenous compounds. Practically — provided the amount of 
nitrogenous compounds be not actually deficient, which in or- 
dinary fattening foods is seldom the case — the amount of in- 
crease is much more frequently dependent on the proportion in 
the food of the digestible and assimilable 7/o»-nitrogenous com- 
pounds, than on that of the nitrogenous ones. It would, in fact, 
be more nearly true to say, that in our current food-stuffs, the 
digestible and assimilable non-nitrogenous constituents are ge- 
nerally in relative defect, than to say that the digestible and 
assimilable nitrogenous compounds are so. 
As, however, the manure from highly nitrogenous foods is the 
most valuable, it frequently becomes the interest of the farmer, 
having regard to it, to purchase and use those having the 
higher amounts of nitrogen. 
The comparative values of food-stuffs, even as such, are, however, 
not to be unconditionally determined by the percentage of either 
the total nitrosrenous or total non-nitro^jenous constituents. The 
