ON HIPP URIC ACID AND ITS TESTS. 
337 
ART. LXIII. — ON HIPPURIC ACID AND ITS TESTS. 
BY ALEXANDER URE, M. D. , A< M. 
Bead the 9th of June, 1841. 
In a paper communicated by me to the Medico-chirurgical 
Society in the month of January last, it was pointed out, for 
the first time, that when a certain portion of benzoic acid, or 
of a soluble benzoic salt, is introduced into the human 
stomach, a remarkable change takes place in its passage 
through the kidney. The urine voided in the course of a 
couple of hours after its ingestion, amounting usually to five 
or six ounces, will be found, upon adding a twelfth part of 
muriatic acid, to yield by and by a copious precipitate of 
beautiful rose-pink acicular crystals. These, when examined 
by the microscope, exhibit the form of a four-sided prism, 
terminated by a dehedral summit. Now this is precisely 
the crystalline character of an acid peculiar to the urine of 
the horse, cow, and other graminivorous animals, and to 
which, for that reason, Liebig has assigned the name of 
hippuric. 
By this single interchange of elements, capable of being 
effected only by the aid of vital chemistry, we have an or- 
ganic product, uric acid, containing eight atoms of azote and 
ten of carbon, replaced by one, hippuric acid, containing no 
less than eighteen of carbon and only two of azote ! In pur- 
suing the above investigation a step further, it was ascertained 
that no trace whatever of uric acid or any of its salts could 
be discovered in the urine in question. In point of fact it 
had been wholly superseded by the other acid. 
The important circumstance connected with this research, 
as bearing upon medical practice, is that the salts which this 
new acid forms with the ordinary bases occurring in the ani- 
mal fluids, as soda, ammonia, and potash, are all of easy solu. 
Vol. vh. — No. iv. 43 
