We use the flesh of the vegetable-feeding mammals and birds that are most easily obtainable, and many kinds of fish. The invertebrate animals, mostly shellfish, needly hardly be mentioned in a physiological dietary, and are not spoken of as meat.
As it comes from the butcher, meat consists of many of the animal tissues, the chief ones being flesh (muscle tissue), fat and some sinews (fibrous tissue). The fleshy or lean part of meat is chiefly made up of nitrogenous materials, and contains: (I) Several proteids, chiefly the globulin, myosin; (2) gelatine yielding substances; (3) carbohydrates, as inosit and grape sugar; (4) small quantities of fat: (5) several inorganic salts; (6) extractives.
Meat may be eaten raw, but, as it is impossible to impart to it the various flavors which our artificial tastes demand without some special preparation, it is generally cooked before use. Moreover, the not infrequent occurrence in muscle of parasites which would prove injurious if swallowed alive, makes the exposure of meat to a temperature high enough to ensure their destruction advisable.
Apart from pleasing the taste, it is of great importance so to prepare meat as to preserve in it all the nutrient parts, many of which are soluble in water, and therefore are apt to be removed if that solvent be injudiciously used. Thus, the process of roasting, in which all its nutrient parts are retained, ought to be more satisfactory than boiling, by which the salts, extractives, carbohydrates, gelatine, and some albumin may be dissolved by the water. However, if the meat be plunged into water which is already boiling, the proteids near the surface are rapidly coagulated, and the water cannot reach the central parts in sufficient quantity to remove even the soluble ingredients. The whole of the albuminous parts may be thus coagulated as the temperature of the inner parts rises to boiling point. In treating meat to obtain "stock" (bouillon) for the foundation of soups, the opposite procedure is adopted. Cold water is used, and the temperature slowly and gradually raised, but not quite to boiling point, in order that as much as possible of the soluble materials may be extracted, and a tasteless friable muscle tissue remains ("bouilli "). As the fluid is generally allowed to boil in order to clear it, much of the proteid material which was dissolved in the earlier stage is coagulated and removed with the scum. Although "stock" cannot contain any great proportion of the most important constituents of meat, it is of much value as a nutriment in medical practice, possibly on account of some stimulating action of its ingredients upon the motions of the intestines and heart. A strongly albuminous extract of meat, "beef-tea," may be made by digesting flesh in a small quantity of water, keeping the temperature below that at which albumin coagulates, and adding vinegar and salt to facilitate the formation of syntonin and the solution of myosin. The salt can be then removed by dialysis.