HIPPUKATES AND LACTATES. 203 



urine seems to have been first established by Liebig ; l and 

 his researches have since been confirmed by numerous other 

 observers. Lehmann, particularly, has been able to find 

 this acid in his own urine, not only when on a purely vege- 

 table diet, but during the use of a mixed diet. He is of the 

 opinion that this principle frequently escapes observation 

 when the urine has been evaporated too rapidly. 3 



The hippurates have been detected in the blood of the 

 ox by Yerdeil and Dolfuss, 3 and have since been found in 

 the blood of the human subject ; 4 and there can be scarcely 

 any doubt that they pass, ready-formed, from the blood into 

 the urine. With regard to the exact mode of origin of the 

 hippurates, we have even less information than upon 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 probably also 

 exists during fasting. "We must be content at present simply 

 to class the hippurates among the products of disassimila- 

 tion, without attempting to specify their exact mode of origin. 5 

 The daily excretion of hippuric acid amounts to about Y'5 

 grains ; 6 equivalent to about 8*7 grains of hippurate of soda. 



Hippuric acid itself, unlike uric acid, is quite soluble in 

 water and in a mixture of hydrochloric acid. It requires 

 six hundred parts of cold water for its solution, and a much 

 less proportion of warm water. Under pathological con- 

 ditions, it is sometimes found free in solution in the urine. 



1 LIEBIG, Sur facide contenu dans Furine des quadrupedes herbivores. Annales 

 de chimie et de physique, Paris, 1830, tome xliii., p. 188, et seq. 



2 LEHMANN, Physiological Chemistry, Philadelphia, 1855, vol i., p. 179. 



3 ROBIN ET VERDEIL, Chimie anatomique, Paris, 1853, tome ii., p. 446. 



4 MILNE-EDWARDS, Lemons sur la physiologic, Paris, 1857, tome i., p. 201. 



5 The reader is referred to works treating specially of the urine, for specu- 

 lations concerning the origin and pathological relations of hippuric acid. An 

 analysis of numerous observations on this subject has been made by Parkes. 

 (Composition of the Urine, London, 1860, pp. 13, 29.) 



6 THUDICHUM, A Treatise on the Pathology of the Urine, London, 1858, p. 

 416. 



