The articles used as food for horses have been submitted to chymical examination, with the purpose of ascertaining the amount of nutritive matter yielded by each in proportion to its bulk.

The Nutritive Matter of plants consists of starch, sugar, gluten, and extract. These four substances exist together in varying proportions. In some vegetables, as carrots, the sugar is most abundant; in many, as in the different kinds of grain, starch predominates. Gluten abounds in grain and pulse, while it is deficient in the most of grasses. Extract is wanting in grain and several of the roots, while beans, peas, herbage, plants, and grasses, possess a considerable quantity.

It is not known whether a certain quantity of any one of these substances will produce the same effect as an equal quantity of any other; starch, and sugar, though both nutritive articles, are very different in many respects, and it is not likely that the one can perform all the functions of the other. But this subject, so far as I know, has not been put to trial. I am disposed to believe that each of the nutritive matters performs its own duty; that life may be maintained for a time by any one of them; that certain combinations will produce results different from other combinations; and that it is very desirable to know the power of each individual substance, and the power of every possible combination, which must vary according to the number of the nutritive matters, and their relative proportions.

The animal economy exists in very different states at different times. It is almost certain that in all states it demands and consumes more than one of the nutritive articles; but it is probable that in particular states there is a predominating demand for sugar, in another for starch, and so on. From one or two circumstances, it would appear as if sugar were useful or necessary for making fat, while a large quantity may be pernicious if severe labor forbid the formation of fat. Diabetes may perhaps be explained upon this supposition. Mowburnt hay, which contains a large quantity of sugar, may be eaten with impunity by idle or half-worked horses. It is said to make them fat. But in the coaching-stables it is a destructive poison. The sugar enters the circulation, but the system can not appropriate it, and the kidneys have to labor incessantly in order to eject it with the urine, a large quantity of which must be made to carry off the sugar. This is entirely a conjectural explanation, the truth or error of which can not be proved without experiments.

If it were possible to learn what combinations are merely fattening, what invigorating; what producing bone, what flesh, what milk; and what the signs which indicate a demand for one substance more than for another, the feeding of horses and other animals would become a science. It is possible that we often err in giving that which is rejected at the time, but which might be highly acceptable in some other state of the system. If we knew, for instance, what combination of gluten, starch, and sugar, were invigorating and what fattening, it would be absurd to give the former to an ox while preparing for the butcher, or the latter to a racer while preparing for the course. The ox wants no vigor, and the racer wants no fat. That which is not wanted may be inconvenient, or it may be rejected as useless, the system of the animal not demanding it, or his habits forbidding its appropriation. It will be long, however, ere the feeding of live stock becomes a matter of such accuracy, and perhaps it is not attainable.

But it may be good to remember that what the chymists term nutritive matter, is composed of four substances, which do not each produce the same effect; that in combination, it is probable the effects vary according to the proportions in which the substances operate together; and that, in particular states of the system, one or two may be in greater request than the others.

Besides the Nutritive Matter, food contains other substances. Roots, and herbage undried, contain a large quantity of water; and new grain and new hay have more than the old. In many articles there is much woody fibre, which passes through the stomach and bowels like inert matter, having no nutritious nor any medical property. This, however, is useful; for, to be in health, it is necessary that the stomach and bowels suffer a moderate degree of distention, which is most cheaply, and perhaps most safely produced by the woody fibre. Bean straw, I believe, furnishes more in proportion to its bulk than any other fodder : grains and roots have not much. Hay stands next to straw. It is probable that several kinds of food, possibly all the kinds, contain some ingredients neither inert nor nutritious, but still very useful. To digest the food, the stomach must be in a particular state; the food itself excites that state; but it is not likely that every portion or ingredient of the food is equally able to rouse the digestive process. In some articles a bitter ingredient is found, which is supposed to stimulate the stomach, and other portions of the digestive apparatus to action.

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