ND THAT OF ITS FOOD.

I have already stated that the results of the admirable investigations
of Lawes and Gilbert prove that the non-nitrogenous constituents of the
carcasses of oxen, sheep, and pigs exceed in weight their nitrogenous
elements. This fact is suggestive of many important questions. What
relation is there between the composition of an animal and that of
its food? Should an animal whose body contains three times as much
fat as lean flesh, be supplied with food containing three times
as much fat-formers as flesh-formers? To these questions there is
some difficulty in replying. There _is_ a relationship between the
composition of the body of an animal and that of its food; but the
relationship varies so greatly that it is impossible to determine with
any degree of accuracy the quantity of fat-formers which is required to
produce a given weight of fat in animals, taken _in globo_. If, however,
we deal with a particular animal placed under certain conditions, it is
then possible to ascertain the amount of fat which a given weight of
non-plastic food will produce. For the greater part of our knowledge
on this point, as on so many others, in the feeding of stock, we are
indebted to Lawes and Gilbert. In the case of sheep fed upon fattening
food these inquirers found that every 100 lbs. of dry[10] non-nitrogenous
substances consumed by them produced, on an average, an increase of 10
lbs. in the weight of their fat. In the case of pigs, also, supplied
with food, the proportion of non-nitrogenous matters appropriated to
the animal's increase was double that so applied in the bodies of the
sheep. As the food supplied to these animals contained but a very small
proportion of ready-formed fat, it was inferred that four-fifths of the
fat of the increase was derived from the sugar, starch, cellulose, and
pectine bodies.

These tables exhibit in a condensed form the results of one of the
elaborate series of experiments in relation to this point carried out
by Lawes and Gilbert:--

ESTIMATED AMOUNT OF CERTAIN CONSTITUENTS STORED UP IN _INCREASE_,
FOR 100 PARTS OF EACH CONSUMED IN FOOD BY FATTENING SHEEP.

+--------------------------------------------------------
| KEY:
| A.--No. of Animals.
| B.--Mineral matter (ash).[11]
| C.--Nitrogenous compounds (dry).
| D.--Non-nitrogenous substa