During the period between the birth and maturity of animals, their flesh undergoes very considerable changes. For instance, when the animal is young, the fluids which the tissues of the muscles contain, possess a large proportion of what is called albumen . This albumen, which is also the chief component of the white of eggs, possesses the peculiarity of coagulating or hardening at a certain temperature, like the white of a boiled egg, into a soft, white fluid, no longer soluble, or capable of being dissolved in water. As animals grow older, this peculiar animal matter gradually decreases, in proportion to the other constituents of the juice of the flesh. Thus, the reason why veal, lamb are white, and without gravy when cooked, is, that the large quantity of albumen they contain hardens, or becomes coagulated. On the other hand, the reason why beef and mutton are brown, and have gravy , is, that the proportion of albumen they contain, is small, in comparison with their greater quantity of fluid which is soluble, and not coagulable.
The quality of the flesh of an animal is considerably influenced by the nature of the food on which it has been fed ; for the food supplies the material which produces the flesh. If the food be not suitable and good, the meat cannot be good either. To the experienced in this matter, it is well known that the flesh of animals fed on farinaceous produce, such as corn, pulse, &c., is firm, well-flavoured, and also economical in the cooking; that the flesh of those fed on succulent and pulpy substances, such as roots, possesses these qualities in a somewhat less degree; whilst the flesh of those whose food contains fixed oil, as linseed, is greasy, high coloured, and gross in the fat, and if the food has been used in large quantities, possessed of a rank flavour.
It is indispensable to the good quality of meat, that the animal should be perfectly healthy at the time of its slaughter. However slight the disease in an animal may be, inferiority in the quality of its flesh, as food, is certain to be produced. In most cases, indeed, as the flesh of diseased animals has a tendency to very rapid putrefaction, it becomes not only unwholesome, but absolutely poisonous, on account of the absorption of the virus of the unsound meat into the systems of those who partake of it. The external indications of good and bad meat will be described under its own particular head, but we may here premise that the layer of all wholesome meat, when freshly killed, adheres firmly to the bone.
Another circumstance greatly affecting the quality of meat, is the animal's treatment before it is slaughtered . This influences its value and wholesomeness in no inconsiderable degree. It will be easy to understand this, when we reflect on those leading principles by which the life of an animal is supported and maintained. These are, the digestion of its food, and the assimilation of that food into its substance. Nature, in effecting this process, first reduces the food in the stomach to a state of pulp, under the name of chyme, which passes into the intestines, and is there divided into two principles, each distinct from the other. One, a milk-white fluid, the nutritive portion, is absorbed by innumerable vessels which open upon the mucous membrane, or inner coat of the intestines. These vessels, or absorbents, discharge the fluid into a common duct, or road, along which it is conveyed to the large veins in the neighbourhood of the heart. Here it is mixed with the venous blood (which is black and impure) returning from every part of the body, and then it supplies the waste which is occasioned in the circulating stream by the arterial (or pure) blood having furnished matter for the substance of the animal. The blood of the animal having completed its course through all parts, and having had its waste recruited by the digested food, is now received into the heart, and by the action of that organ it is urged through the lungs, there to receive its purification from the air which the animal inhales. Again returning to the heart, it is forced through the arteries, and thence distributed, by innumerable ramifications, called capillaries, bestowing to every part of the animal, life and nutriment. The other principle the innutritive portion passes from the intestines, and is thus got rid of. It will now be readily understood how flesh is affected for bad, if an animal is slaughtered when the circulation of its blood has been increased by over-driving, ill-usage, or other causes of excitement, to such a degree of rapidity as to be too great for the capillaries to perform their functions, and causing the blood to be congealed in its minuter vessels. Where this has been the case, the meat will be dark-coloured, and become rapidly putrid; so that self-interest and humanity alike dictate kind and gentle treatment of all animals destined to serve as food for man.