100 
for the estimation of salicylic acid are far from exact. In their own 
work they adopted the method of Elion of estimating the salicylic 
acid formed during the oxidation by means of bromine. They have 
also arrived at the conclusion that the salicylic acid appears to com- 
bine in part at least with certain substances present in the extracts 
and hence would be likely to escape detection in most of the methods. 
They agree with Abelous and Aloy ( 4 ) that the acid is only produced 
rapidly in the absence of oxygen. The quantity of salicylic acid 
produced in a given time also varies with the concentration of the 
aldehyde and the amount of extract employed, the former being the 
preponderating factor in determining the velocity of the reaction. 
They observed, further, that the oxidizing power of extracts of the 
liver diminishes spontaneously when such extracts are left to them- 
selves, especially at higher temperatures. According to these authors, 
the results thus far reached in the study of this oxidation do not 
warrant the conclusion that the oxidation in question is accom- 
plished by a ferment acting in the absence of air. About all that 
can be said is that a certain amount of oxidizing material is present, 
but this being limited the amount of salicylic aldehyde oxidized by 
a given quantity of extract is also limited, while the oxidase is a true 
catalyst, probably of a mineral nature, and as such ought to be able 
to accomplish the oxidation of practically unlimited quantities of 
material. According to these authors the presence of such substances 
has not been proven in such animal extracts as those under immediate 
consideration, nor is it necessary to assume their presence in order to 
account for the phenomena observed. 
THE INDOPHENOL OXIDASE; THE ROHMANN-SPITZER REAGENT. 
In his study of the oxygen requirements of the organism it was 
shown by Ehrlich ( 157 ), in 1885, that the intravenous injection of a- 
naphthol and para-phenylene diamin results in the formation of indo- 
phenol in the tissues of the animal. So also Wurster ( 466 ) showed 
that di- and tetramethyl-para-phenylene diamin are reagents for 
active oxygen, and that in the animal organism these substances are I 
converted into blue coloring matters. Acting upon these suggestions, 
Rohmann and Spitzer( 351 ) have made use of a reagent consisting of 
equal amounts of a-naphthol and para-phenylene diamin, in a 
dilute solution of sodium carbonate (three molecules of sodium car- 
bonate to one molecule of each of the organic compounds), for the 
investigation of the oxidizing power of the various animal tissues. 
Various other related substances can be employed in the preparation 
of the reagent ; thus dimethyl-para-phenylene diamin ( 453 ) can be used : 
instead of para-phenylene diamin. They also showed that other 
coloring matters result from, the oxidation c'f suitable mixtures by 
the action of various animal tissues. Thus they succeeded in -show- 
