HIPPITRIC ACID is a compound of great interest both to the chemist and to the physiologist. It derives its name from its having been first dis covered iu the urine of the horse, and that fluid, or the renal secretion of the cow, affords its the best and readiest means of obtaining it. The crystals of hippuric acid are moderately large, colorless, but subsequently becoming milk-white, four-sided prisms. which are devoid of odor, but have a faintly bitter taste., They dissolve readily in boiling water and in spirit, but mat only sparinglySoluble in cold-water and iu ether.
Its chemical bearings show that hippuric acid is intimately associated with benzoic acid on the one hand, and with glycine (or glycocol) on the other.' The acid is a product of the metamorphosis of the bodily tissues, especially of herbivorous animals. It is a normal constituent of the urine of the horse, cow, sheep, goat, hare, elephant, etc., and
most probably is to be found in the urine of all vegetable feeders. In the human urine of healthy persons living on an ordinary mixed diet it occurs in very small quantity, but it is increased by an exclusively vegetable diet, and in the well-known disease diabetes.
Although hippuric acid usually occurs in mere traces in human urine, we can artifi cially produce it at will in the body, and cause it to be eliminated in comparatively large quantity by the kidney. If we swallow benzoic acid, it seems to take up glycine or the elements of glycine in its passage through the system, and thus to form hippuric acid, which appears abundautly in the urine. The hippuric acid occurring in the animal organism exists in combination with bases, and chiefly as hippurate of soda and hippurate of lime. The last-named salt can be obtained by the mere evaporation of the urine of the horse.