Page:Popular Science Monthly Volume 22.djvu/409

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For comparison with these ratios of the nutritive constituents of animal foods, wheat-flour bread was selected as one of the most important of the representative articles of vegetable food. The fat in the bread itself, estimated at one per cent, which is probably above the average, was reckoned in its equivalent of starch, and the ratio of nitrogenous and non-nitrogenous constituents was then found to be 1 to 6·8. Of the animals fattened for the butcher's use, the fat calf, only, gives a smaller proportion of non-nitrogenous constituents than the bread; the fat ox has nearly the same, and the other animals very much more. The averages also show that beef, mutton, and pork, on the whole, are not deficient in carbo-hydrates or non-nitrogenous nutritive constituents. After a full discussion of the subject, Drs. Lawes and Gilbert come to the conclusion that the great advantage of a mixed bread and meat diet, over one of bread alone, does not depend on the nitrogenous substance, but rather in substituting fat for a portion of the starch of vegetables. From the greater value of fat as a source of energy, and the general advantages of a variety of nutritive elements in the composition of a diet, this view of the influence of animal food seems to be well founded.

The limits of this article will not allow us to notice the experiments with sewage, and the feeding value of sewage-grown crops in the production of meat and milk; or the milling products of grain grown under a variety of conditions, and other special subjects of investigation, that have been included in the work at Rothamsted. .

It is perhaps worthy of notice that nitrogen was the prominent object of interest in the Rothamsted field experiments, while the carbo-hydrates or non-nitrogenous constituents of the food seemed to