316 APPENDIX. 



acid with his food, an acid crystallizing in needle-shaped 

 prisms, which had the general properties of benzoic acid, 

 and which he then took for benzoic acid. (Tiedemann's 

 Zeitschrift fur Physiologic, i., 142.) These crystals were 

 obviously hippuric acid, as plainly appears from the state- 

 ments, that they had the aspect of nitre, and, when sub- 

 limed, left a residue of carbon. But at that time hippuric 

 acid was not yet discovered ; and it is well known, that 

 till 1829, when these acids were first distinguished from 

 each other by Liebig, it was uniformly confounded with 

 benzoic acid. 



The recently published statement of A. Ure, that he 

 actually found hippuric acid in the urine of a patient who 

 had taken benzoic acid, recalled this relation, so remark- 

 able in a physiological point of view, and induced me to 

 undertake the following experiments, which, at the sug- 

 gestion of Professor Wohler, I made on myself. The 

 supposed conversion of benzoic acid into hippuric acid, 

 has, by these experiments, been unequivocally established. 



I took, in the evening before bedtime, about thirty-two 

 grains of pure benzoic acid in syrup. During the night I 

 perspired strongly, which was probably an effect of the 

 acid, as in general I am with great difficulty made to 

 transpire profusely. I could perceive no other effect, even 

 when, next day, I took the same dose three times ; in- 

 deed, even the perspiration did not again occur. 



The urine passed in the morning had an uncommonly 

 strong acid reaction, even after it had been evaporated, 

 and had stood for twelve hours. It deposited only the 

 usual sediment of earthy salts. But when it was mixed 

 with muriatic acid, and allowed to stand, there were 



