1905 - 6 .] Excretion of Allantoin in Thymus Feeding. 
97 
Mendel and White (13) injected lithium urate in doses of 1 
gramme into the veins of dogs, and they record the appearance of 
allantoin in the urine. The appearance was not constant, and the 
amount was small in all cases, being somewhat larger when the 
injection was made into the portal vein. When it is remembered 
that mere autolysis of the liver causes the production of allantoin 
(Pohl) (5), the significance of these experiments in indicating a 
production of allantoin for uric acid is decreased. It might be 
urged that the allantoin underwent further change in the organism, 
but the fact that allantoin, when injected, is nearly all recovered 
in the urine, invalidates such an explanation. The origin of 
allantoin from uric acid is, therefore, by no means satisfactorily 
established. 
The possible relationship of allantoin to uric acid and the purin 
bases tends to connect it with the metabolism of the nucleins, and 
evidence has been adduced by Mendel, Underhill, and White (14), 
that in the dog it is formed from this source. By injecting 
preparations of nucleic acid, prepared from different sources, into 
the blood vessels, intraperitoneally and subcutaneously in dogs, 
they caused the appearance of allantoin in the urine. The 
symptoms produced by these injections were fairly marked, and 
the possibility must be borne in mind that the appearance of 
allantoin maybe ascribed to a toxic action, just as the increased 
excretion of uric acid, observed by Loewi (15), is, after the 
subcutaneous injection of sodium nucleate, ascribed by them to a 
toxic effect. 
While the effects of administering the purin bodies, either free 
or still combined in nucleic acid, upon the production of allantoin 
is by no means distinct, the administration of thymus gland 
substance is always very pronounced. Minkowski and Cohn (10) 
discovered, independently, that allantoin may be excreted in the 
dog as an end-product in the metabolic processes which give rise 
in man to uric acid after thymus feeding, and an enormous rise 
in the excretion of allantoin in the dog under the administration 
of thymus gland was discovered by Salko^ski. This is generally 
explained as the result of the katabolism of the nucleins con- 
tained, but so far this theory has not been tested by actual 
experiment. 
PEOC. ROY. SOC. EDIN. — YOL. XXVI. 
7 
