Dr. Oscar Loew 51 
filtered liquid will become blue very soon. 
This shows an exceptional case, namely, that 
the oxidase (laccase) is present in an insoluble 
state and perhaps held in combination with an 
insoluble protein." Upon standing, the blue 
colour, obtained with the unfiltered liquid, will 
gradually disappear, except on the surface, but 
on adding a few more drops of the reagent 
and shaking, the intense blue colour reappears. 
This phenomenon is due to the presence of a 
reducing compound in the juice. 
In testing for a second oxidizing enzyme, the 
peroxidase, the tissue of the seed, crushed 
with a little water, was heated for five minutes 
to 75° C. and one portion of this liquid was 
filtered ; the other not. The test with guaia- 
cum tincture yielded no blue reaction in either 
liquid, proving that the oxidase was killed, 
while on addition of a little peroxide of 
hydrogen the unfiltered juice gave an intense 
blue reaction and the filtered juice showed 
only a trace. This difference proves that the 
peroxidase, like the oxidase, was present, but 
retained as an insoluble compound—an ex- 
ceptional case. 
Reactions with guaiacol were also tried. 
This substance produced no colouration when 
applied by itself, but in conjunction with 
hydrogen peroxide a red colour turning to 
brown was soon produced in both the hard 
1 This recalls the existence of a soluble and insoluble 
form of catalase. 
