This section is from the book "Meals Medicinal", by W. T. Fernie. Also available from Amazon: Meals Medicinal: With "Herbal Simples" Curative Foods From the Cook in Place of Drugs From the Chemist.
"As food," writes Dr. Yeo, "animal kidneys are of close, firm texture, and when much cooked become very hard, and difficult of digestion." Steep's kidneys contain about seventeen per cent of albuminates, and two per cent of fat. They may be grilled, fried plain, or egg-and-bread-crumbed beforehand. Ox kidney, even when thoroughly cooked, requires a good mastication, and a strong digestion, having moreover a strong flavour of its own. The calf's kidneys may be minced, and braised, going well with a brown sauce. Dr. Haig attributes to the sheep's kidney as food three and a quarter per cent of uric acid. Some of the earliest mediciners, with an empirical instinct gave donkey's kidneys for curing diseases of the same organs in their human patients; and recent medical science justifies such a proceeding, according to the expounded principles of curative animal extracts. Lately, in thirty-five sick persons labouring under various diseased states of the kidneys, an internal administration of fresh, healthy animal kidney in small quantities, or of an extract prepared carefully therefrom, has proved of undoubted curative value, as faithfully recorded by attendant physicians.
Urea, and uric acid as eliminated by the kidneys, are now proved by many facts to serve protective purposes within the human system. These are chiefly products from animal foods, and are antagonistic to the tubercular disposition towards consumptive disease of the lungs. But they are favourable to the development of gout, the said two diseases being opposed to each other; for the former, it is proper to give a liberal allowance of nitrogenous proteids, sweets, fats, butter, beer, and the like; but for the latter just the reverse, only a little meat, and that principally of the white sort, plain fish, fruits, vegetables, and milk foods. It is a known fact that vegetarians, and sedentary persons whose tissues are always laden with carbonates, are examples of the structures which most readily foster consumptive germs, and that these persons become materially benefited by increasing their nitrogenous nourishment. Furthermore, in gouty conditions it is desirable to augment the combustion of the materies morbi by active exercise, as Abernethy taught in a practical manner when he made his gouty patients dance on hot plates.
Whereas it has been until within the last few years supposed that the sole function of our kidneys is to excrete urine from the system, doctors now understand that these organs perform another important duty of pouring from themselves important matters into the blood, lacking which the general body has its welfare seriously impaired; and the vital fact has been learnt that if healthy animal kidney substance be given under these conditions, then the disturbed balance of soundness is restored to the patient. Therefore, for meeting this object our manufacturing chemists supply animal kidney substance ready to hand as a dry powder, or in tabloid form. But still better is the fresh healthy animal kidney as furnished opportunely by the cook. A liking for sheep's kidneys is not confined to the human gourmet. For instance, we are told by Dr. John Brown, of Edinburgh (1860), in Our Dogs, that "Jock, of the Orkneys, though beloved by his master, took to evil courses, extracting the kidneys from the best young rams of the flock, and driving whole hirsels down steep places into the sea, till at last all the guns of Westray were pointed at him, and blew him into space as he stood at bay under a huge rock on the shore." Curiously enough, the term kidney was at one time a cant word for a servant in waiting.
Thus The Tatler has told, "it is our custom upon the first coming of the news to order a youth who officiates as the kidney of the coffee house to get into the pulpit, and read every paper with a loud and distinct voice".