"The muriatic acid, in combination with soda and potash, occurs both in the blood and in the urine; thus appearing to pass through the kidneys unchanged. This acid and its compounds formerly appeared to be of less importance in a pathological point of view than any other similar principles existing in the urine: but since the unexpected fact has been ascertained, that muriatic acid in a free state exists abundantly in the stomachs of animals during the process of digestion, I have attended a little more closely to the appearance of this principle in the urine, and am disposed to believe, in consequence, that it is the cause of the precipitation of lithic acid gravel from the urine more frequently than any other acid. I do not mean to say, that it is the _immediate_ cause of the precipitation of this acid; for in most instances, it acts like all powerful acids do under similar circumstances, namely, by liberating the weaker acids, which are thus enabled to act in their turn, and separate those having still weaker affinities than themselves. Thus, in the present instance, the muriatic acid may be supposed to separate the lactic, while the latter precipitates the lithic, &c. If this opinion be well founded, as I believe is the case, the muriatic acid may be considered of very great importance, not only in a pathological, but a physiological point of view; for if the muriatic acid, found in the urine in such instances, be supposed to have its origin in the digestive organs, we see at once the reason why the deposition of gravel is so liable to be influenced by the derangements in general, and more especially by the acidity, of the stomach." "The muriatic acid may be shown to exist in the urine by the white curdy precipitate insoluble in nitric acid, which is formed, when the nitrate of silver is added to it, after the sulphuric and phosphoric acids have been removed by the nitrate of barytes or lead." pp. 20 and 21. After finishing these introductory subjects, Dr. PROUT proceeds to the consideration of the diseases of the urinary organs themselves; which he divides into functional, mechanical, and organic. Under functional diseases, we have _first_, those, in which principles _soluble_ in the urine are morbidly deranged in quantity or quality, embracing three chapters; and _secondly_, those affections, in which principles _insoluble_ in the urine are morbidly deranged in quantity or quality, comprising six additional chapters. Under the first subdivision, the first chapter is on the affections, characterized by albuminous urine; the second, on diseases, in which an excess of urea is the characteristic symptom; and the third, on diabetes.