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FOODS, IN RELATION TO RESPIRATION AND FEEDING. 345 
of it in the second section of Series i, where the Indian corn predomi- 
nated, and where the nitrogenous constituents consumed were only about 
half as great as in the pens | and 2, are generally as small, or even smaller, 
than in these two pens. It is not, then, that there was in reality a very great 
productiveness in gross increase from a given amount of food in these two 
pens, but rather only that with the large supply of available nitrogenous con- 
stituents in the Leguminous seeds, a certain amount of the non-nitrogenous 
constituents have been substituted by it. It was observed, too, that although 
all the pigs were very fut, excepting the few with an excessive allowance of 
bran, yet those apparently grew more, where, with no deficiency of other 
matters, the nitrogenous constituents were very liberally supplied. Hence 
the gross increase obtained might be somewhat more nitrogenous with the 
large supply of nitrogenous food; but it would in that case, according to 
some experiments of our own, contain a larger proportion of water, and less 
of solid matter, than where more fat had been produced. 
But, with the very great regularity of non-nitrogenous equivalent con- 
sumed throughout this large series of pig experiments ¢o produce a given 
amount of inerease, we have, in the column of total nitrogenous substance, 
on the other hand, a difference in the amounts required, in the proportion of 
from one to two, or three, or even more; though, since all the foods used in 
these experiments were ripened vegetable products, a very trifling error, if 
any, can arise from representing, in all cases, the whole of the nitrogen as 
existing as proteine compounds. And, there is throughout, a generally 
larger amount of total organic substance required to yield a given amount of 
gross increase, the larger the proportion in that substance of the nitrogenous 
constituents. 
It is seen, as has been already noticed, that where the amount of nitrogen 
consumed in these pig experiments to produce a given amount of gross in- 
crease is comparatively large, it is where a large proportion of the Legumi- 
nous seeds have been employed. Some writers who have taken the per-cent- 
age of nitrogenous compounds as the measure of feeding value, have recog- 
nised, and endeavoured to explain in various ways, the fact that the records 
of practical feeding experiments do not award to the Leguminous seeds a 
feeding value in proportion to their richness in nitrogen ; and they have con- 
cluded, that it is the accepted indications of the practical experiments, and 
not the theoretical conclusiens, that are at fault. Thus, it has been objected | 
against the teachings of such experiments, that the variations in the compo- 
sition of the same description of food used in different cases has not been 
determined ; that the test has been the gross increase or loss in weight; that 
the increase may be only fat formed from starch, &c.; that the loss in weight, 
if any, may be the result of activity, and not of defective dict; that the food 
in the different cases has been employed in different states, that is, coarse or 
fine, raw or prepared; that the animals have been variously cireumstanced as 
to temperature, exposure and activity; that individual animals have very 
various tendencies to increase, and so on. Now we believe that not one of all 
these objections can vitiate the comparisons which we have made, unless, in- 
deed, in some degree, the one which refers to the difficulty of determining 
whether the gross increase obtained be composed chiefly of fat formed from 
the starch and oily series of compounds ; or whether of flesh from the nitro- 
genous ones. We believe, indeed, from the many direct experiments which we 
have made, that in reality, the composition of our domestic animals generally, 
but especially that of the gross increase of the so-called “ fattening” animals, 
consists of a much larger proportion of fat than is usually supposed. We 
have instituted very extensive and laborious investigations in regard to this 
point, the details, or even the general results of which must be reserved for 
