FOODS, IN RELATION TO RESPIRATION AND FEEDING. 347 
nure by which the increased Cereal is obtained; and again, this Cereal, ob- 
tained at the cost of, but with its lessened produce of nitrogen, is found in 
practice to be of equal, or of a more highly feeding value than the more 
highly nitrogenized Leguminous product which perhaps has been expended 
to produce it. It would thus appear, therefore, that the demands of the re- 
spiratory function which again, more than any other, regulate the consump- 
tion of food, would, in point of fact, not be satisfied in the use of the Legu- 
minous diet unless by a consumption or expenditure of an amount of nitrogen 
beyond that which the due balance of the constituents of food would seem 
to require ; whilst on the other hand, in the use of the Cereal grain, its better 
proportion of respiratory to nitrogenous constituents has only been attained 
by the sacrifice of nitrogen expended in its growth. It would seem, there- 
fore, that whether we would seek our supplies of respiratory food in the 
direct use of the highly nitrogenized Leguminous seeds, or in the better ba- 
lanced diet of the Cereal grains, in either case the end is attained only at the 
cost or expenditure of nitrogen; in the one case, by the consumption of a 
larger amount of it in the food than the due balance of constituents would 
seem to require, whilst in the other this due balance has not been attained 
without a loss of nitrogen during growth. ‘The claims of health and na- 
tural instinct generally leave little doubt which alternative should be adopted, 
in the case of human food at least; and it becomes us, therefore, to investi- 
gate and understand the practical bearings of these curious and interesting 
facts; for upon the principles they involve depend much for their success 
. those fundamental practices of the farm,—the feeding of our stock, for their 
double products of meat and manure, and the adaptation of our rotations. 
It would appear, then, from our experiments, that taking our current food- 
stuffs as we find them} it is their supply of the noz-nitrogenous, rather than of 
their nitrogenous constituents, which guides both the amount of food consumed, 
and of increase produced, by a fattening animal. When we consider the na- 
ture of the respiratory process, and the large share which its demands must 
necessarily have upon the consumption of food, it can scarcely appear sur- 
prising that consumption, at least, should be chiefly regulated by the supply 
in the food of compounds rich in carbon and hydrogen, rather than nitrogen. 
That the amount of inerease produced should also bear a closer relationship 
to the supply of these constituents than to that of the latter, does not perhaps 
at first sight seem so obvious, especially if we supposed, as some writers on 
this subject have done, that the amount of nitrogen in the current food of 
man and other animals was frequently insufficient to supply the amount re- 
quired for the production or restoration of the nitrogenous products of the 
animal organism. We believe, however, that a closer examination of the 
facts would show that this exceedingly rarely happens; and we think, more- 
over, as we have already intimated, that in fact, that portion of nitrogen which 
is stored up in the «nerease of a growing, and especially of a “fattening ” animal, 
is much less than is usually supposed. We cannot in any degree adequately 
discuss this question in this place; but when maintaining a greater relative 
importance of the mon-nitrogénous constituents of food than is usually ac- 
_ corded to them, it seems somewhat pertinent briefly to adduce some evidence 
in confirmation of our conclusions on this point. 
We propose, therefore, to give a very brief summary of one of our expe- 
riments, in which pigs were the subjects, which was undertaken chiefly for 
the purpose of ascertaining the composition of the increase of the fattening 
animal; but to obtain also, some clear evidence in reference to the much- 
debated question, whether or not more fatty matter is stored up in the 
animal, than is contained, as such, in its food. 
