are correct. That urea and lithic acid are (in a great measure) the result of the transformation of the tissues, and vary (cæteris paribus) with the rapidity of decomposition; and that the quantity of lithic acid is increased by a deficient supply of oxygen,-may be readily conceded but that urea and lithic acid have no other origin than the transformation of the tissues, is certainly incorrect; and that non-azotized articles of food favour the production of lithic acid, by combining with the oxygen, is purely hypothetical, and contradicted by facts. 328. Majendie states that uric acid disappears from the urine of carnivorous animals, fed for about three weeks on non-nitrogenized food. Another fact mentioned by Professor Liebig to Dr. Bird, as having been lately observed at the hospital at Wurzburg, is to the same effect:"A girl labouring under what appears to have. been some form of hysteria, refused all food, excepting apples; of which she devoured an enormous quantity. On examining her urine, it was found to be alcaline; and contained a large quantity of hippuric, but no uric acid;—like the urine of a horse or cow."* Hippuric acid contains eighteen equivalents of carbon, but only one of nitrogen. 329. It even seems more consistent with Liebig's own views to conclude that, as much oxygen is liberated by the chemical changes which take place during the digestion of non-azotized food (200), this very excess of oxyen may be employed in the conversion of uric acid into urea. His observations respecting concretions * URINARY DEPOSITS." P. 50. of lithic acid never having been found in carnivorous animals in the wild state, is equally applicable to herbivorous animals, when free and uncontrolled in their habits; because they then live upon such substances as are adapted to their organization, and are not tempted, by artificial preparations, to take more than the wants of the system require. But man acts in a far different manner: he freely indulges in all the varieties of artificially prepared food, which are contrived rather to gratify the palate than to satisfy the natural appetite; and instead of preventing the injurious effects of repletion by labour and exercise, he too frequently increases the evil by indulgence in sloth and inactivity. The excess of non-azotized food, in such circumstances, may be deposited as fat (200 &c.); but the excess of azotized principles in the blood, is not converted into muscle and other tissues: it must therefore be removed with the excretions, and pass off either by the kidneys or the skin; and this must ever be the case, when the supply exceeds the demand. 330. If no more nutriment be received into the system than is requisite to supply its wants, no azotized principles (it is probable) will appear in the urine, except such as have first formed a part of the animal fabric; but whenever an excess of food is ingested, there will be an accumulation of nutrient principles in the blood, unless means be adopted to prevent it. It is very probable that the fibrin of the blood, like the solid tissues, has a limited term of existence as such; and that it must મંદ either be converted into solid tissue, or must undergo a change of composition." In the healthy state of the system, there is a constant demand for as much fibrin as the blood supplies; consequently there is no waste: but if the supply is greater than the demand, how can the excess be removed, except through the excretory organs especially concerned in carrying off the superfluous and effete azotized matters of the system;namely, the kidneys and the skin? Liebig states, that the superfluous food of the luxurious is converted into various gases. This, no doubt, is partly the case; but the whole excess of azotized substances, is certainly not thus disposed of; for the excretions from the kidneys, skin, &c., vary (in character and amount) with the quality and quantity of the food. 331. Dr. Prout has shown, that a considerable difference exists between the urina sanguinis, or urine resulting from the secondary assimilating process; and the urina potus vel chyli vel cibi, or urine of primary assimilation. "There are few persons", says he, "in whom the urine of assimilation does not deviate (more or less) from the healthy standard,-both in specific gravity and quantity; and the degree and nature of the differences, often throw much light on the derangements of the assimilating organs. The urine of the blood in general is more uniform in its properties; but when it does vary remarkably from the standard of health, the deviation generally denotes some deep-seated and constitutional disease of an unfavourable character." And again: -"With respect to diet, quantity is often of infinitely greater importance than quality. Thus a full meal whether of animal or vegetable* matters, or of a mixture of the two-will usually produce a deposition of gravel, in predisposed individuals, in whom a spare meal of the very same materials is not followed by such deposits." 332. If Liebig were correct in stating, that the urinary deposits result solely from decomposition of the tissues, they ought to vary little (in quantity or quality) from day to day, except when transformation is hastened by museular exercise, disease, &c.; whereas it is a well known fact, that excess of azotized food greatly increases these deposits, when little exercise has been taken to promote disintegration it is, therefore, reasonable to conclude, "that the superfluous azotized matter ingested, passes off in the form of urate of ammonia, without becoming part of the tissues at all." 333. "There can be no question", says Dr. Golding Bird, "that all the phenomena of health and disease, point out the probability of there being a double origin of this substance (uric acid);—one from the nitrogenized elements of tissues, and the other from the elements of food, rich in nitrogen, which escape the completion of the process of primary assimilation. No experience yet collected, justifies our assuming that uric acid bears any definite relation (in quantity) to urea: in all probability, Dr. Prout's opinion that the latter is derived from the metamorphoses of a different set of tissues (the gelatinous), from those yielding the former (the albuminous), *If vegetable food only be taken, the effect here spoken of is doubtful, unless one or more of the excreting functions be much out of order. 66 is correct; although it obviously does not admit of positive proof."* A diminution of albuminous matter in the food, therefore, so as to afford no more than the necessary supply to the tissues, is the most likely remedy in the lithic acid diathesis; and it has universal experience in its favour. "Who", says Dr. Graves, "ever heard of a case of gout among the potato-eating peasantry of Ireland?" And who", observes a writer in the British and Foreign Medical Review,t "ever heard of one among the oatmeal-feeders of Scotland, or the ricefeeding Hindoos;-low as is their oxygenation, in consequence of the warmth of the surrounding medium. Every practitioner must have met with examples, in which a simple reduction in the quantity of animal food ingested, has caused an immediate disappearance of the lithic acid from the urine. Sometimes it is necessary to push this reduction to a still greater extent: thus, we have known an instance in which no decided benefit was obtained, until the patient was restricted to the Hindoo diet of rice and capsicums; which produced a complete cure. Upon Dr. Jones's principles, this ought to have produced the most serious aggravation; for the diet which he recommends, is one from which starch and other non-azotized substances are almost completely excluded.” 334. The following experiments fully confirm these remarks. Careful analyses were made of the urine from two persons, A and B; the former having lived, during several years, on an exclusively vegetable diet; the latter temperately on a mixed diet, excepting five days previously "URINARY DEPOSITS." P. 47. + No. XXX. April 1823. |