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716 URINE.
COOTT
Oxalic Acid, C2H2O4, or •
, occurs under physiological conditions
COOH
in very small amounts in the urine, about 0.02 gram in twenty-four hours
(Furbringer x
). According to the generally accepted view it exists in
the urine as calcium oxalate, which is kept in solution by the acid phos-
phates present. Calcium oxalate is a frequent constituent of uninary
sediments, and also occurs in certain urinary calculi.
The origin of the oxalic acid in the urine is not well known. Oxalic
acid when administered is eliminated unchanged, at least in part, by
the urine;2
and as many vegetables and fruits, such as cabbage, spinach,
asparagus, sorrel, apples, grapes, etc., contain oxalic acid, it is possible
that a part of the oxalic acid of the urine originates directly from the
food. That oxalic acid may be formed in the animal body as a metabolic
product from proteins or fats follows from the observations of Mills
and Luthje and others, who found that in dogs on an exclusively meat
and fat diet, as also in starvation, oxalic acid was eliminated by the urine.
The oxalic acid which is eliminated in increased quantity with a diminished
oxygen supply and an increased protein catabolism, as found by Reale
and Boeri, and also by Terray, is supposed to be derived partly from
the greater destruction of proteins. Pure protein does not, accord-
ing to Salkowski and Wegrzynowski 3
increase the quantity of oxalic
acid eliminated; on the contrary, after meat feeding the amount of this
acid is increased, due in part to the meat containing oxalic acid (Sal-
kowski). Gelatin and gelatin-yielding tissues seem to increase the
excretion of oxalic acid, and the same is also true for fats or at least
glycerin (Wegrzynowski). After feeding nucleins no constant increase
in the elimination of oxalic acid has been observed. The statements
as to the action of carbohydrates are contradictory. The production of
oxalic acid due to an incomplete combustion of the carbohydrates has also
been suggested, and the work of Hildebrandt and P. Mayer seems to
indicate this under abnormal conditions. According to Darin,4 in rabbits
an increased elimination of oxalic acid occurs after the introduction of
glycollic or glyoxylic acids, and the oxalic acid seems in many cases to
be an intermediary product of metabolism, which is further burnt. We
cannot exclude the possibility of the formation of oxalic acid in the
oxidation of uric acid in the animal body, yet we have no positive proof
1
Deutsch. Arch. f. klin. Med., 18. See also Dunlop, Journ. Path, and Bacterid., 3.
2
In regard to the behavior of oxalic acid in the animal body, see page 773.
3
Reale and Boeri, Wien. med. Wochenschr., 1895; Terray, Pfliiger’s Arch., 65;
Salkowski, Berl. klin. Wochenschr., 1900; Wegrzynowski. Zeitschr. f. physiol. Chem.,
83 which contains the literature.
4
Journ. of biol. Chem., 3, 57.
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