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FORMATION OF HIPPURIC ACID. 721
As the thorough investigations of Wiechowski teach, the synthesis
of hippuric acid does not stand in any direct relation to the extent of
protein metabolism; it varies, on the contrary, with the duration of
circulation of benzoic acid and the quantity of glycocoll present in
the body. The amount of the latter in intermediary metabolism is so
great that in rabbits, on the administration of benzoic acid, more than
one-half of the total urine nitrogen may exist as glycocoll. Magnus-
Levy l
found in rabbits and sheep up to 27.8 per cent of the total nitro-
gen as hippuric-acid nitrogen, and both investigators have found so much
hippuric-acid nitrogen that it could not be accounted for by the glycocoll
preformed from the proteins, which amounts to about 4-5 per cent of
the total nitrogen of the protein of the food and body.
In carnivora (dog) and man the conditions are different, according
to Brugsch and R. Hirsch, Feigin and Brugsch, as in these cases there
is no more glycocoll available for hippuric acid formation than is split
off from the proteins en hydrolysis. According to the investigations of
Lewinski 2
this does not seem to be correct, at least not for man. After
abundant introduction of benzoic acid in man about 34 per cent of the
total nitrogen may be excreted as hippuric acid and in a recent investiga-
tion he was able to obtain 50.5 grams pure crystalline hippuric acid
from the 24-hour urine of a man after feeding sodium benzoate.
The abundant production of hippuric acid in herbivora induced Abder-
halden, Gigon and Strauss to investigate the comparative supply of
certain amino-acids in carnivora and herbivora, and they found in cats,
rabbits and hens that the percentage quantity of glycocoll split off from
the entire organism (with the exception of the intestinal contents and
fat and feathers) by hydrolysis was the same, namely 2.33 to 3.34 per
cent of the proteins. In order to account for the large quantity of
glycocoll which can be eliminated as hippuric acid, we must admit of a
formation of glycocoll. That this occurs in animals fed with benzoic
acid has been recently proved by Abderhalden and Hirsch by very
conclusive experiments. It can be assumed that the benzoic acid com-
bines with higher amino-acids and that the hippuric acid is formed from
this combination. The investigations of Magnus-Levy to prove this
assumption, where he used benzoylated higher amino-acids, have not
Hupfer, Zeitschr. f. physiol. Chem., 37. See also Wiener, " Die Harnsiiure," Ergeb-
nisse der Physiol., 1, Abt. 1.
1
Wiechowski, Hofmeister’s Beitrage, 7 (literature); A. Mangus-Levy, Munch,
med. Wochenschr., 1905; Ringer, Journ. of biol. Chem., 10; Epstein and Bookman,
ibid., 10.
2
Brugsch and Hirsch, Zeitschr. f. exp. Path. u. Therap.. 3; Brunch. Maly’s
Jahresber., 37, 621, and Bioch. Centralbl., 8, 336; Feigin, Maly’s Jahresber., 86,
631; Lewinski, Arch. f. exp. Path. u. Pharm., 58 and 61.
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