URINE is the fluid which is secreted or sepacated by the kidneys from the blood, and if is the principal means of removing the worn-out tissues, especially the nitrogenous and saline matters, from the system. It is a very complex fluid, and its composition varies considerably in different classes of animals, and mainly in accordance with the nature of the food.
Healthy human urine, when freshly discharged, is a clear fluid of a bright amber color, a bitter, saltish taste, and a peculiar aromatic odor. Its normal reaction is add, and its specific gravity ranges from 1.015 to 1.025. From a table published in Day's Physiological Cheinistry.p. 352, it appears that an adult man of ordinary weight (about eleven stones) secretes in 24 hours about 52 fluid ounces (or rather more than two pints and a half) of urine, the range extending from 40 to 70 ounces; and that these 52 ounces yield. on evaporation, 935 grains of solid constituents, the remainder being water, which is expelled by heat. Of these 935 grains, 520 (or more than an ounce) are composed of urea (q.v.), and 296 of chloride of sodium (or common salt), while the remaining 149 grains are made up of uric acid (q.v.), hippurie acid (q.v.), sulphuric acid, 32 grains; phosphoric :mid, 54 grains; earthy phosphates, 15 grains, ammonia (in the form of hydro chlorate), 11 grains; with smaller quantities (in most cases mere traces) of creAtinine (q.v.) and creatine xauthine, hypoxanthine, coloring matters, mucus (from the walla of the bladder), iron, silica, and fluorine. The livid else hoids an undetermined quantity of gases (carbonic acid and a little nitrogen) in solution. The most characteris tic and important of these ingredients is the urea, the daily excretion of which is modi fi3a by various circumstances. On a purely animal diet, Lehmann found that he secreted two-tiftlis more urea than when he was living on an ordinary mixed diet; while on a mimed diet there was secreted almost one-third more than on a purely vegetable diet; while finally, on a non nitrogenous diet, the amount of urea was less than half the quan tity secnated daring a mixed diet. The free use of common salt increases the daily exere tiJa of urea, in consequence. doubtless, of its augmenting the rapidity of the destructive action always going on in all the tissues; while alcohol, lea, coffee, and tobacco (whether smoked or chewed) diminish the daily quantity. The only medicine which increases its quantity to any marked degree is liquor polavie. The daily quantity is increased in many diseases (typhoid fever and many other acute diseases, especially inflammation of the men:bra:les of the brain), while in Bright's disease and a few other disorders, it is dimin ished. The daily amount of excreted uric acid, like that of urea, varies with the nature
of the Rind. Thus, for instance, prof. lIaughton found that the mean daily quantity of uric acid excreted h ten ny meat-caters and wine-drinkers was 4.5 grains, while vegetarians yielded an average of only 1.48 grains, part of which, moreover, was hippuric acid. As an excess of uric acid is likely to give rise to gravel or stone, it should be generally known that the free ingestion of water diminishes its excretion, while at the same time it increases. the amount of urea, into which the uric acid is probably transformed by oxidation. The daily amount is diminished by strong bodily exercise, and hfcreased by repose; the reverse of what holds good in relation to the urea. The amount is increased woen the digestive functions are disturbed, as after the use of indigestible food or excess of alcoholic Lt•inks; in those con litious of the system which are associated with much disturbance of the functions of respiration and circulation; and in disorders accompanied with severe feb rile symptoms, such as acute rheumatism. Its entire absence seem] compatible with perfect health. With regard to hippuric acid there has been much discussion, not only as to the quantity iu which it occurs, but as to whether it actually exist in healthy urina. Thus, Weissman. a German chemist, finds that on a mixed diet he secreted more than 40. grain; of this acid daily, and on a purely animal diet, only 12 grains. Duchek and deny that it is a constant ingredient of healthy human urine; and prof. Haughton only in_!t with it once in the urine of ten men. Dr. Bence Jones, a very trustworthy chemist, foam] that a man, A, weighing 152, lbs., and a man, B, weighing 202 lbs., living on a. mixed diet, excreted daily, on an average, 4.9 and 6.5 grains of hipparic acid, the corres paitling quantities of uric acid being 7.7 and 12.6 grains. In eases of jaundice, no traces of hippuric acid are present, even after the administration of benzoic acid,* which is usually converted in the system into hippuric acid. Hence it may be inferred that a healthy condition of the urine is essential to the formation of this acid in the system. Nothing is known with certainty regarding the diseases in which this acid is secreted to excess. The only other characteristic ingredient of the urine is its coloring ?natter. Prof. Harley believes that he has isolated the normal urine-pigment, to which he applies term uralacmatin; and from its always containing iron, and on other grounds, he regards it as modified hrematin or blood-pigment. Mr. Schanck has also shown that indigo-blue, in very small quantity, is almost always present.l.