53 
Yoshida had called urushic acid, shows many resemblances to the 
polyatomic phenols. He therefore called this substance “laccol,” 
and in view of this analogy he was led to study the conduct of laccase 
toward a number of the polyatomic phenols and related compounds 
with the result that he found many of these to be oxidized under these 
conditions. Thus, hydroquinon is converted by laccase into quinon 
and quinhydron, with the absorption of oxygen ( 50 ). Thus, a 1 per 
cent solution of hydroquinon alone or with boiled laccase does not 
absorb oxygen from the air nor is it altered in any way. In the 
presence of a small amount of laccase, however, such a solution ab- 
sorbed 25.4 c. c. of oxygen in three hours. With tannin and pyrogallol 
the oxidation was always attended with the disengagement of con- 
siderable amounts of carbon dioxide. Thus, in two experiments 
oxygen was absorbed and carbon dioxide disengaged in the follow- 
ing amounts: 
Oxygen Absorbed. 
Carbon dioxide 
disengaged . 
(i) 
23.3 c. c. 
13.7 c. c. 
(2) 
29.8 c. c. 
16.4 c. c. 
He also found guaiacum to be a useful reagent for laccase, and by 
means of it he was able to detect the enzyme in many plants, such as 
potatoes, apples, peas, quinces, lucerne, clover, asparagus, turnips, 
chestnuts, and various rhizomes ( 57 ) . 
Bertrand and Bourquelot( 63 ), by the use of guaiacum, found laccase 
in a large number of species of mushrooms. Out of 18 species ex- 
amined at this time only two, Polyporus sulfur eus Bull, and Squa- 
mosus Huds., were found not to give the guaiacum reaction. Hence 
laccase is not confined to the chlorophyllous plants, but occurs in 
the nonchlorophyllous plants also. 
The oxidations occurring in the juice of the apple, observed in cider- 
making, were also studied about this time by Lindet ( 271 ) . This author 
also claims to have reached the conclusion, as early as 1893, that a 
soluble ferment governs this oxidation, and in a later article he ( 272 ) con- 
cludes that the changes of color occurring in fresh cider are due to the 
oxidation of tannin by a ferment, of the type of laccase, contained in 
the tissues of the apple. 
In the course of his investigations Bertrand found that laccase 
always contains small amounts of manganese and that its oxidizing 
power is proportional to the amount of manganese present; and 
further that oxidations accomplished by laccase are greatly acceler- 
ated by small amounts of manganese salts and that no other metal 
is capable of accelerating the oxidation brought about by laccase. 
In the course of these investigations the old observations by 
Schoenbein ( 378 ) that various fungi become colored in the air was also 
confirmed by Bertrand and Bourquelot ( 64 ) . They arrived at the 
