Volume 1

A text-book of human physiology : including histology and microscopical anatomy with special reference to the requirements of practical medicine / by L. Landois ; translated from the seventh German edition with additions by William Stirling.

Landois, L. (Leonard), 1837-1902. Lehrbuch der Physiologie des Menschen. English

Date:: 1891

Credit: A text-book of human physiology : including histology and microscopical anatomy with special reference to the requirements of practical medicine / by L. Landois ; translated from the seventh German edition with additions by William Stirling. Source: Wellcome Collection.

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$Fig. 315. Hippuric Acid. in the cuticular coverings of the food. That liippnric acid, in part at least, is formed in the kidneys, i.e., by the cells of the renal tubules, is shown by the following considerations :—If arterialised blood, containing benzoic acid and giycin, or even benzoic acid alone, be passed through the blood-vessels of a fresh, living, excised kidney, a so-called surviving kidney, hippuric acid is found in the blood after it is perfused. Even after forty-eight hours, if the kidney be kept cool, the synthesis takes place. The kidney in this case also must not be dead, but a ^'surviving one. If the kidney be kept too long, the conjugation does not take place. If the fresh surviving kidney be chopped up, and kept at the temperature of the body with benzoic acid and glyco- €oll, hippuric acid is formed. Oxygen seems to be necessary for the process, for, if blood or serum containing carbonic oxide be used, there is no formation of hippuric acid.] [If the liver be excised in frogs, and benzoic acid, or better, benzoic acid and glycocoll, be injected into the dorsal lymph-sac, hippuric acid is found in the tissues and secretions. Thus the liver is not the locality, or exclusive locality, in the frog, where the synthesis occurs. But in the frog, it may be formed after extir- pation of the kidneys. It is only in the dog that its exclusive formation in the kidney has been proved (Bunge and Sclimiedeberg).'] [There is one difficulty about the matter, viz., that giycin, as such, has not been found in the tissues. It is probable, however, that it is formed in various meta- bolic processes, and is as rapidly combined with some other body. It may be formed in this way in the kidney, and immediately combine with l^enzoic acid to form hippuric acid.] According to this view, it is derived cliiefly from the food of herbivorous auinmls, and lience it is absent from the urine of sucking calves, as well as after feeding with grain devoid of husk. But it is also formed in the body from the proteids. In the dog, the formation of hippuric acid occurs in the kidney {Schmiecleherg and Bunge), and in the frog also outside the kidney. Kühne and Hallwachs thought it was formed in the liver, and Jaarsveld and Stockvis in the kidney, liver, and intestine. The observation of Salomon that, after excision of the kidneys in rabbits, and injection of benzoic acid into the blood, hippuric acid was found in the nuiscles, blood, and liver, goes to show that it must be formed in other organs beside the kidneys. The power of changing benzoic acid introduced into the human body into hippuric acid may even be abolished in disease of the kidney. Under certain circumstances it seems that hippuric acid, already formed, may be again decomposed in the tissues. It is greatly increased after eating pears, plums, and cranberries ; in icterus, some liver affections, and in diabetes. Preparation.—Add milk of lime to i\\G fresh urine of horses or cows to form calcic hippnrate. Filter, evaporate the filtrate to a small bulk, and precipitate the hippuric acid with excess of hydrochloric acid. To purify the hippuric acid, crystallise it several times from a hot watery solution. Cynuric Acid CooHijN'^Oe 4-HoO occurs in the urine of dogs {J. v. Liebig). Allantoin, C^H^N^Oy, which occurs in the amniotic fluid of the cow, is found in minute traces in normal urine after flesh food, and is more abundant during the first weeks of life and during pregnancy. [It to a large extent replaces urea in the urine of the foetus.] After large doses of tannic acid the amount is increased (ScJiottui), while, in dogs, feeding with uric acid also increases it {Salkowski). Properties.—It forms shining, prismatic crystals ; from the urine of sucking calves it crystallises in transparent prisms. It is decomposed by ferments into urea, ammonium oxalate, and carbonate, and another as yet unknown body. Preparation—(a) the urine is precipitated$