324 REPORT—1852. 
a large series of aliments from the animal kingdom by MM. Schlossberger 
and Kemp. Dr. Anderson also, in his valuable Report on the Composition of 
Turnips, grown under different circumstances and in different localities, has 
taken their per-centage of nitrogen as the measure of their comparative feed- 
ing value. 
The views which have thus led to a vast number of analyses of foods, as 
well as the information supplied by the analyses themselves, have contributed 
much to the advancement of our knowledge of the chemistry of food. It has 
however been found, that the indications of tables of the comparative values 
of foods, founded on the per-centages of proteine compounds, were frequently 
discrepant with those which common usage or direct experiment affords. 
These discrepancies have not escaped the attention of the authors of the theo- 
retical tables ; but they have attributed them rather to the erroneous teachings 
of common practice or experiments on feeding, than to any defect in the theo- 
retical method of estimation. On all hands, however, it has been admitted, 
that further direct experiment bearing upon this important subject was much 
needed ; and it is the acknowledgement of this necessity that seems to justify 
the publication, under the auspices of the British Association, the results of 
this kind which we have now to submit. 
The question to which we shall first call attention, is, whether, in the use 
of our current foods, under ordinary circumstances, but especially in the case 
of animals fattening for the buteher, the amount of food consumed, and that 
of increase produced, have a closer relationship to the supplies in such foods 
of the nitrogenous, or of the mon-nitrogenous constituents? That is to say, 
whether the sum of the requirements of the animal system is such, that, in 
ordinary circumstances, and in the use of ordinary articles of food, the 
measure of the amount taken, or of the increase produced, will be regulated 
more by the supplies of the “Plastic,” or of the more peculiarly respiratory and 
fat-forming constituents. According to the views upon which all the tables 
of the comparative values of foods are constructed, it is the supplies of the 
plastic elements of food chiefly, that should regulate both the consumption, 
and the increase in weight, of a fattening animal. If, however, we bear in 
mind the views which are generally entertained as to the influence of respi- 
ration on the demands of the system for the oxidizable elements of food, it 
would appear more consistent to suppose that the measure, at least of the con- 
sumption of food, would be chiefly regulated by its supplies of those elements. 
In the experiments to which we shall call attention, sheep and pigs have 
been the subjects. As, however, their object has partly been the solution of 
certain questions of a more purely agricultural character than those now 
under consideration, the details, as to the selection of the animals, and the 
general management of the experiments, will be given more appropriately in 
another place. Indeed, the particulars of some of the experiments with 
sheep, so far as their agricultural bearings are concerned, have already ap- 
peared in the Journals of the Royal Agricultural Society of England; and 
those of the rest, and also of the experiments with pigs, will probably do so 
shortly. It should here be stated, however, that the general plan has been 
to select several different descriptions of food, containing respectively various 
amounts of nitrogenous and non-nitrogenous constituents, the proportions of 
which were ascertained by analysis. ‘To one or more sets of animals to be 
compared, a fixed and limited amount of food of a high or of alow per-centage 
of nitrogen, as the case might be, was allotted, and they were then allowed to 
take ad libitum of another or complementary food. In this way, in obedience 
to the instinctive demands of the system, the animals were enabled to fix for 
themselves, according to the composition of the respective foods, the quantities 
of each class of constituents which they required. 


