HIPPURIC ACID, HIPPURATES AND LACTATES. 381 



If from any cause the urine become excessively acid after its emission, a 

 deposit of uric acid is likely to occur. The addition of a very small quantity 

 of almost any acid is sufficient to decompose the urates, when the uric acid 

 appears, after a few hours, in a crystalline form. 



Uric acid, probably in combination with bases, was found in the substance 

 of the liver in large quantity by Cloetta (1858), and his observations have 

 been confirmed by recent authorities. The urates also exist in the blood in 

 very small quantity and pass ready-formed into the urine. The fact that 

 the urates exist in the liver has led to the opinion that this organ is the prin- 

 cipal seat of the formation of uric acid (Meissner). However this may be, uric 

 acid certainly is not formed in the kidneys, but is simply separated by these or- 

 gans from the blood. Meissner did not succeed in finding uric acid in the mus- 

 cular tissue, although the specimens were taken from animals in which he had 

 found large quantities in the liver. The urates, particularly sodium urate, 

 are products of disassimilation of the nitrogenized constituents of the body. 



The daily excretion of uric acid, given in the table, is six to nine grains 

 (0-39 to 0-58 gramme), the equivalent of nine to fourteen grains (O58 to 0'9 

 gramme) of urates estimated as neutral sodium urate. Like urea, the pro- 

 portion of the urates in the urine is subject to certain physiological varia- 

 tions. 



Hippuric Acid, Hippurates and Lactates. The compounds of hippuric 

 acid (C 9 H 9 N0 3 ), which are so abundant in the urine of the herbivora, are 

 now known to be constant constituents of the human urine. Hippuric acid 

 is always to be found in the urine of children, but it is sometimes absent 

 temporarily in the adult. The hippurates have been detected in the blood 

 of the ox by Verdeil and Dolfuss, and they have since been found in the blood 

 of the human subject. There can be scarcely any doubt that they pass, 

 ready-formed, from the blood into the urine. As to the exact mode of origin 

 of the hippurates, there is even less information than with regard to the 

 origin of the other urinary constituents already considered. Experiments 

 have shown that the proportion of hippuric acid in the urine is greatest after 

 taking vegetable food ; but it is found after a purely animal diet, and proba- 

 bly it also exists during fasting. The daily excretion of hippuric acid is 

 about 7'5 grains (0-486 gramme), which is equivalent to about 8- 7 grains 

 (0-566 gramme) of sodium hippurate. 



Hippuric acid itself, unlike uric acid, is soluble in water and in a mixture 

 of hydrochloric acid. It requires six hundred parts of cold water for its 

 solution, and a much smaller proportion of warm water. Under pathological 

 conditions it is sometimes found free in solution in the urine. 



Sodium, potassium and calcium lactates exist in considerable quantity in 

 the normal urine. They are undoubtedly derived immediately from the 

 blood, passing ready-formed into the urine, where they exist in simple watery 

 solution. According to Robin, the lactates are formed in the muscles, in the 

 substance of which they can readily be detected. Physiologists have little 

 positive information with regard to the precise mode of formation of these 

 salts. It is probable, however, that the lactic acid is the result of transforma- 

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