95 
or by freezing, or by precipitation with alcohol and re-solution in 
water. He arrived at the conclusion, therefore, that oxidations in 
the animal organism are brought about by ferments or enzymes. 
Further studies on the oxidizing ferments were made by Pohl ( 329 ) 
with the view of determining whether the several oxidizing fer- 
ments described by various authors as occurring in animal and plant 
tissues are the same or different enzymes. He reached the conclu- 
sion that two essentially different kinds of oxidations occur in liv- 
ing tissues and that these are brought about by at least two dis- 
tinctly different ferments, one of which accelerates the oxidation 
of fatty (formic) and aromatic aldehydes, and the second brings 
about such oxidations as the production of indophenol-blue from 
an alkaline solution of a-naphthol and para-phenylene diamin. He 
found further that certain plant extracts have the power of accom- 
plishing the indophenol reaction, but are powerless to oxidize formic 
or salicylic aldehyde or mannite. An aqueous solution of tannin 
needles proved to be especially active. In this connection he also 
showed that amygdalin gives the indophenol reaction apparently 
independently of the action of any ferment. 
On the other hand, Spitzer ( 406 ) arrived at the conclusion that 
glycolysis (the disappearance of sugar in the blood) is only a special 
case of oxidation by blood and animal tissues, and that the glycolytic 
ferment of Lepine is probably identical with the oxidizing ferments 
in tissues capable of oxidizing aromatic alcohols and aldehydes. In 
support of these conclusions he cited, first, an observation by Sal- 
kowski ( 356 ) to the effect that under certain conditions blood can 
oxidize salic}dic aldehyde, and, secondly, some observations of his 
own to the effect that those tissues which can rapidly oxidize alco- 
hols and aldehydes can also destroy glucose. The results obtained 
in subsequent researches tend to confirm him ( see Spitzer ( 407 )) in the 
belief that the oxidizing ferments, especially of the animal organism, 
are substances of the same nature, viz., nucleoproteids, and that cer- 
tain of these owe their activity as oxygen-exciters to the organic 
iron which they contain. 
On the other hand, Abelous and Biarnes ( 7 > 8 ) observed that cer- 
tain globulins have the power to oxidize guaiacum, but are without 
action on salicylic aldehyde, and, as already pointed out, Raudnitz ( 338 ) 
proved that the substance in milk which causes the bluing of 
guaiacum in the presence of hydrogen peroxide is not identical with 
that which catalyzes the hydrogen peroxide. It was also pointed out 
by Lepine ( 262 ) and also by Jacoby ( 224 ) that the glycolytic ferment 
I I differs from the oxidizing ferment oxidizing salicylic aldehyde in 
several respects, especially in regard to the effect of temperature on 
the two ferments, the glycolytic ferment being destroyed at 58 ° C., 
whereas the oxidizing ferment under consideration is only destroyed 
