The animal food which digests in the stomach with the least irritation, though not the most quickly, is the white meat of all animals, and the meat of the younger ones. White and young meats abound in jelly, which forms also a considerable proportion of the membranes, tendons, and cartilages. Jelly, though soluble in water, is not affected by alcohol; and, while it resembles albumen, yet differs greatly from it. Jelly contains a larger proportion of earth than albumen, and the further an animal is advanced in life, so much more are its fluids loaded with earth. Jelly also contains an alkaline phlegm of an animal nature which readily putrifies, with a larger proportion of carbone, the predominant principle of vegetable substances. To these it adds hydrogen and azote; the last of which abounds more in the coagulable Iymph of the blood, and still more in the fibrin. See Blood.

Birds have been considered as of more easy digestion than mammalia. This however is not unexceptionably true. Even in the gallinaceous tribe there are some. exceptions; but it may be admitted in general, that the young of the feathered race are easily digestible. The parts of the bird most so are those most used; as the wings of the wilder kind, and the legs of the tame ones. Birds also differ in their digestibility, as they are more or less alkalescent, or more or less oily. Alkalescence is a term introduced into diaetetics, on a principle neither correct in a chemical nor a physiological view; yet it may be admitted as a naturalised foreigner, without examining its pretensions. Wild animals are styled alkalescent; as woodcocks, snipes, moor-fowl, etc. among birds; hares, red-deer, etc. among the mammalia. These are perhaps justly considered as more easily and quickly digestible than the tamer animals of a similar kind: when they have been some time pursued, they become aliments still more easily assimilated. It is said, we know not with what truth, that bulls baited become wholesome food; and that an act of parliament exists, which directs, that no bull should be killed without being thus previously irritated and tormented.

On the other hand, the oily birds, the anseres for instance, are gross and indigestible, though only when full grown. We dare not say, that in earlier periods they are very easily subdued by the stomach, though, on the whole, they are then a mild, and generally harmless, nutriment.

Quadrupeds differ in their digestibility from various circumstances. In general, the pecora afford mild nutriment, though food is taken from the other orders also; but the particular animals we shall afterwards separately enumerate. The size of the animal, independent of its age, appears of consequence, as of the larger animals the fibres are coarse and more indigestible. The mode of life, and the exercise, are of importance in this view. An animal living according to its own nature is a more nourishing, though not always a more delicious food, than one crammed or pampered. A grass lamb is more digestible and nourishing than house lamb; a black turkey, that roosts on trees and feeds on chesnuts and acorns, superior to that fattened in the coop. The ground on which they feed, the food they eat, and the air they breathe, necessarily alter their nutritious, and consequently their digestible, powers. We know the fatal disease, the rot in sheep, which arises.from the air, probably from hydrogenous gas, since sheep will catch the infection in a single night; and we can easily conceive, that, in a slighter degree, the same disease, though less obvious, may injure their nutritious powers. Sheep, fed on turnips, arc less nutritious than those which have grazed on the finer turf of more elevated districts. The cow, fed on oil-cakes, gives an ill-tasted milk, while its flesh is Coarse and indigestible.

A circumstance influencing the digestibility of animal food, not generally noticed, is what the graziers call the proving state. When an animal is improving in condition, the meat is tender and easily digestible: when its condition is growing worse, though equally fat, and in appearance promising, it is tough and not easily assimilated. This peculiarity proceeds further; and, in proportion to the rapidity of the improvement, the meat is preferable in flavour and solubility. Thus an ox, worked to the lowest degree of emaciation, affords, when quickly fattened, the best beef. This, we have said, is independent of the fatness. Fat meat, however, is more nourishing, though in weak stomachs not so easily digestible. Savages are fond only of the fattest meats, and they style lean cattle bread meat: we have heard a similar expression among the rustics in our own remote provinces, so universal is the opinion derived from experience. The marrow of meat, though resembling the fat, is not equally difficult of digestion: by some authors it is arranged, we suspect with reason, among the most digestible substances.

Another circumstance which influences the solubility of meats is castration. The flesh of the ox is more digestible than that of the bull; of the wether than of the ram; of the capon and the pullard rather than the cock or the hen. In reality the meat approaches that of the female, though more firm, and probably of a higher flavour. If to this there is any exception, it is in the capon, whose flesh is more moist and soluble than that of the hen. The preservation makes some difference in this respect. Animal food, kept till putrefaction ap-/iroaches, is more soluble than at an earlier period. We have said "approaches,"for, when in the slightest degree arrived, it generally excites nausea, unless the stomach be stimulated, and the further progress of putrefaction prevented by the warmest condiments. Meat preserved by freezing, and gradually thawed, is in the state of that well kept. By salt and smoke it is hardened, and rendered more indigestible; by sugar we think it is preserved in nearly as soluble a state as by cold. The mode of cookery also affects the solubility of animal food. Boiling renders it more digestible than roasting; and this than baking or frying. Various fancies have prevailed on this subject, and different modes have been recommended according to the inclinations of different authors; for physicians usually advise what they themselves like. In general, however, in roasting, baking, and frying, the oily parts are rendered empyreumatic; and a substance of this kind is very indigestible. If, of roasted meat, the inside parts are only taken, the difference is not considerable; but in baking and frying, the gravy is retained, and a change similar to the empyreuma of oily substances takes place. This is known from the preference given to the superior flavour of meat, dressed in these manners.