104 
only 0.039 to 0.048 gram. It was afterwards shown by TTeintraud 
( 445 ) that following a diet rich in nucleins, as for example, the calf’s 
thymus, the uric acid in the urine is considerably increased, whereas 
according to Hess and Schmoll ( 2n ) a similar increase in the uric 
acid does not follow a nuclein-free proteid diet. 
On the other hand it is of interest to note in this connection that 
uric acid itself can be destroyed to a certain extent in the organism, 
and that following the administration of uric acid by the mouth in 
men and dogs only a small part of it is recoverable from the urine 
( see Minkowski, 302 ) . It has also been shown by Minkowski that hypo- 
xanthin causes a distinct increase in the output of uric acid, and that 
meat extract which contains considerable amounts of this substance 
has a similar influence on the uric acid excretion. That certain purin 
bases are formed by the decomposition (autolysis) of the nucleins 
was shown by Horbaczewski ( 218 ’ 219 ) . This author allowed a mixture 
of spleen pulp and water to stand at 50° C. From this slightly 
putrid mixture he was able to isolate large amounts of xanthin 
and hypoxanthin, whereas from the fresh extract of spleen only 
traces of these purins were obtainable. After shaking the slightly 
putrid mixture with air he obtained no xanthin or hypoxanthin, 
but only uric acid. Similar results were obtained by adding blood 
or hydrogen peroxide to the slightly putrid spleen pulp. It is evi- 
dent from these results that the nucleins of the spleen are the precur- 
sors of the purins. 
On repeating Horbaczewski’s work, Spitzer ( 409 ) showed that uric 
acid is formed in aqueous extracts of spleen pulp through which is 
passing a current of air and in which putrefaction is prevented by 
chloroform or thymol, and that contrary to the opinion of Horbac- 
zewski, xanthin and hypoxanthin can be readily converted into uric 
acid by the action of a current of air on an aqueous extract of spleen 
containing these substances at 50° G. Similar results were obtained 
with the liver, but other organs, such as the kidney, pancreas, and 
thymus, were found to be much less active in their power to accom- 
plish this oxidation. Similar results were obtained by Wilner ( 452 ), 
who arrived at the conclusion that in the liver, not only of birds but 
also of certain mammals, there are produced large amounts of uric 
acid. He also showed that the addition of hypoxanthin to liver 
extracts causes a great increase in the quantity of uric acid obtain- 
able from the extract. 
Evidently, therefore, the oxidation of xanthin and hypoxanthin 
is accomplished in vivo and in vitro through the instrumentality of 
an oxidizing ferment. This ferment has been made the subject of 
an exhaustive investigation by Burian ( 107 ) and named by him xan- 
thin-oxidase. By following Spitzer’s method and using one part 
of macerated liver to two parts of chloroform water he was able , 
to obtain clear extracts of xanthin-oxidase containing only very 
