Cow-heel, calf-head, sheep-head, and trotters, afford examples of this kind of aliment, which, unless ex tremely IA ell boiled, is far from being easily digested.
The gelatine of bones is digestible and alimentary, only after it has been extracted and dissolved in water.
Tripe, the stomach of ruminating quadrupeds, is nearly allied to the white membranous parts, in composi tion and alimentary properties. The stomach, however, circulates more red blood, contains besides a certain portion of muscular fibre, is more annualised, and fur nishes accordingly a more savoury aliment, perhaps a more nourishing one, than those parts entirely formed of gelatine.
We find it more difficult to estimate the alimentary qualities of the glandular parts of animals. The spleen and kidneys are enumerated by Celsus, with those ali ments which afford a bad, and the liver with those which yield a good juice. All that we can venture to say on this subject, is, that the glandular parts of young animals, if freed from the odour of their peculiar secretion, are agreeable, and sufficiently nutritive aliments. The pan creas, or sweet-bread, is the most delicate, the least sti mulating, and perhaps the most digestible. The spleen is a coarse, and not very digestible aliment. The brain too is heavy, and apt to disagree with some stomachs. The liver, especially that of young animals, and ol some birds, is by many esteemed a great delicacy, and appears to be very wholesome. The liver of many fishes abounds in oil.
The muscular flesh, which constitutes indeed the chief part of our food derived From the animal kingdom, ap pears to be, upon the whole, the most nourishing, the most wholesome, and the most easily digested of any.
Its advantages in these respects, may well be attribut ed to its peculiar composition,—a just assemblage of all the alimentary principles. For the flesh, besides con taining the largest quantity of fibrine, has also a due pro portion of gelatine, albumen, and fat. And indeed the alimentary properties of different kinds of flesh, appear to depend, in a great measure, on the proportions and aggregation of these principles. Thus, the flesh of
young animals contains more gelatine, and less fibrine, than that of the full grown and older, and yields at the same time a lighter nutriment, and of less easy diges tion. Very old, hard, tough flesh, contains again too little gelatine and fat; the fibrine has become firmer and less soluble; and therefore such meat is less suc culent, less digestible, and less nutritive, than the same kind of flesh in its prime. By boiling, the gelatine and a portion of albumen arc extracted, and hence, perhaps, it is that boiled meat is less nourishing and digestible than roasted flesh, which retains all its principles.
Muscular flesh contains also a larger quantity of red blood, front which indeed it derives its colour, than any of the other parts of animals commonly employed as aliment. Whether or not any of its alimentary quali ties may depend on this circumstance, we cannot con fidently say. But red-coloured flesh is certainly a stronger and more nourishing food than the white-co loured muscle—the flesh of the ox, for example, than that of the rabbit.
Chemists have detected another principle in muscular flesh, to which they have given the name of extractive. This principle is soluble in alcohol, of a brownish red colour, an aromatic odour, and strong acrid taste.
The particular flavours of flesh have been attributed to this principle, which may probably add also to its stimulant properties, if not to its nutritive.
We may remark in this place too, that a peculiar strong and disagreeable flavour is communicated to the flesh of many male animals by the seminal fluids.
This is one reason why the flesh of these animals is so much improved by castration. The flesh of the cas trated animal is free from this flavour, it becomes ten derer also, and generally fatter.
The muscular parts arc the organs by which all the motions of animals are performed, and there is a particu lar state of their contraction, called their tone, which seems to continue even for some time after a vigorous animal has been slaughtered—a sort of permanent con traction, which approximates the fibres of the muscles.