105 
small amounts of purin bases. On digestion in a current of air these 
extracts alone gave practically no uric acid. They were found, how- 
ever, to oxidize xantliin and hvpoxanthin rapidly in a current of air. 
By means of these preparations of xanthin-oxidase he was able to 
confirm the previous observations of Spitzer and Wilner and to show 
that, as is the case with many ferments, the conversion of xanthin 
and hvpoxanthin under the influence of the ferment is a reaction of 
the first order. He showed also that the xanthin-oxidase is not con- 
sumed in the process, but is capable of oxidizing fresh quantities of 
xanthin and hvpoxanthin in the presence of oxygen. Hence it 
would seem to be a true ferment. This is evident from the fact that 
no noteworthv falling off in the coefficient of the velocitv of the 
reaction was observable. 
On the other hand, the reverse process, viz, the reduction of uric 
acid to other purin bodies does not take place to any noticeable 
extent. He is of the opinion therefore that xanthin-oxidase is respon- 
sible for the production of uric acid from purin bases in the living 
animal. Contrary to the observations of Wilner ( 452 ) he found 
that in the absence of purin bases, tartronic and dialuric acids cause 
no production of uric acid with his extracts of xanthin-oxidase. He 
concludes therefore that these substances can act only by accelerat- 
ing the action of the xanthin-oxidase on purin bodies already present 
in the liver extracts. Neither can xanthin-oxidase convert guanin 
or adenin directly into uric acid, but, as has been found by Jones and 
Austrian ( 230 > 231 ), these substances must first be desamidized by the 
action of guanase and adenase, whereby they are converted into 
xanthin and hvpoxanthin, respectively, before their oxidation into 
uric acid can occur. The occurrence and distribution of these fer- 
ments have been exhaustively studied by Jones and Austrian ( 230 > 231 ) 
and also by Schittenhelm ( 365 ) and others. A very good idea of 
their distribution in the liver of various animals is afforded by the 
following diagram, which is given in certain of Jones’s original con- 
tributions to the subj ect : 
Guanin Adenin 
o 
m 
Uric Acid 
◄ 
TO 
Xantliin 
m 
<3 
T<1 
Hvpoxanthin 
Xanthooxidase 
Ox Liver. 
Pig’s Liver. 
T 
Rabbit’s Liver. 
i 
T 
Dog’s Liver. 
