352 REPORT—1852. 
nous compounds also. He also experimented with pigs, in a manner somewhat 
similar to that adopted by ourselves; and it is a curious circumstance, that 
his store, or lean pig, contained almost identically the same per-centage of 
fat as our own. ‘The foods he employed were, however, far inferior in fatten- 
ing quality. Hence, though his experiments extended over a much longer 
period of time, the per-centage of fat in his fat pig was scarcely 5 per cent. 
higher than in his lean one; whilst almost the whole of this izereased fat had 
been supplied by fatty matter in the food. It was indeed mainly upon a 
calculation of the fat which had been supplied in the food of the store pig, 
that he found the evidence of the formation of fat in his experiments with 
pigs. M. Boussingault is disposed to believe, that the nitrogenous con- 
stituents of food probably have some considerable influence in the formation 
of fat in the animal body. We have ourselves called attention to the fact, 
that a large supply of the nitrogenous constituents of the food would seem 
to replace a relative deficiency of other constituents. The amount of increase 
is found, however, to bear a rapidly decreasing ratio to the amount of nitrogen 
in the food when this exceeds a somewhat narrow limit ; whilst the composition 
of such increase would appear to contain a less proportion of fat. Whether 
therefore any effect of an excess of nitrogenous compounds in the produc- 
tion of increase be due merely to the amounts they contain of certain non- 
nitrogenous elements, or to the influence of the nitrogenous compounds them- 
selves as such, in increasing the activity of some of the vital processes, and thus 
aiding the production of fat, or whether any increase due to the nitrogenous 
constituents in the food is more generally not fat at all, may be considered 
to be an open question. 
In the experiments made by M. Persoz, geese were the animals he operated 
upon, and maize the food employed. He found a decided formation of fat; 
and apparently from the starch series of compounds. 
We repeat, then, that we believe that the formation of fat in the animal 
body, even to a considerable and practically important extent, and most 
probably from the starch series of compounds, may now be considered to be 
clearly proved. It would appear, therefore, that the theoretical opinions of 
Baron Liebig on this point are fully borne out. 
We have thus far only alluded to the feeding of fattening animals ; and we 
think that the results which have been brought forward clearly indicate, that 
with them at least, as our current food-stuffs go, both the amount consumed, 
and the inerease produced, are regulated more by the supplies of the more 
peculiarly respiratory and fat-forming constituents, than of the flesh-forming 
or nitrogenous ones. We have, however, calculated many human dietaries ; 
and this branch of the subject we hope to enter upon more fully on some future 
occasion. ° We may, however, remark in passing, that from the results of this 
inquiry, as well as from a consideration of the management of the animal 
body undergoing somewhat excessive labour, as for instance, the hunting 
horse, the racer, the cab-horse, and the fox-hound, and also pugilists and 
runners, we are led to believe, that in the cases, at least of ordinary exercise 
of force, the exigences of the respiratory system keep pace more nearly with 
the demand for nitrogenous constituents of food than is usually supposed ; 
and in fact, that the exigences of the animal body are much more correctly 
stated in the following sentences by Professor Liebig, than in those wherein 
he has attached so much more of importance to the amounts of the nitro- 
genous constituents, as the measure of the comparative value of foods. 
At page 314 of the 3rd edition of his Chemical Letters, he says :— 
««* * * Tt is evident that the amount of nourishment required by an animal 

