67 
confirmation, especially in view of the failure of von Ffirth and 
Jerusalem ( 178 ) to obtain evidence of anti-tyrosinase, and the whole 
subject of anti-oxidases should be reinvestigated by means of Bach’s 
peroxidase. 
TYROSINASE. 
It has long been known that on exposure to the air certain of the 
higher fungi turn pink or red and finally black, whereas other species 
become blue. We have already seen that the latter change is due 
to an oxidizing ferment, laccase. That the reddening and final 
blackening of other species of mushrooms is due to the action of a 
specific oxidase was first suspected by Bourquelot and Bertrand ( 89 ), 
who in 1896 pointed out the existence in certain mushrooms, such as 
the Rassula foetens Pers., of a very active oxidizing ferment, probably 
different from laccase. They ( 87, 88 ) then showed that the blackening 
of Russula nigricans differs from the bluing of Boletus cyanescens by 
reason of the fact that the blackening of the crystalline chromogen 
contained in the former species is not accomplished by the laccase 
of the sap of the lac tree, whereas the blackening is undoubtedly due 
to an oxidation, as indicated by the fact that if one does not agitate 
the aqueous extract of the fungus the blackening takes place first in 
the upper layers of the liquid, and during the blackening oxygen is 
absorbed. Continuing these investigations Bertrand ( 53 ) proved the 
crystalline chromogen of Russula nigricans to be tyrosin. He also 
found that the beet root and the tubers of the dahlia and potato, like 
certain of the higher fungi, also redden and then turn black on ex- 
posure to the air. This change he now definitely proved to be an 
oxidation of tyrosin by atmospheric oxygen under the influence of a 
specific oxidizing ferment, to which he gave the name tyrosinase. 
From the roots and tubers of certain plants, such as the beet and 
dahlia, he was able to obtain in crystalline condition as much as 0.5 
gram of tyrosin from one quart of the expressed juice, an amount 
about corresponding to the solubility of the compound in pure water. 
The tyrosin thus obtained was identified 
reactions, and its composition determined by analysis. He also 
isolated tyrosin from Russula nigricans , and in this connection Bour- 
quelot and Harlay ( 90 ) give a drawing of a transverse section through 
the stipe of Russula nigricans , showing the rosettes of tyrosin crys- 
tals distributed more or less regularly throughout the tissue of the 
fungus. Bertrand also showed that the blackening of tyrosin is due 
to an oxidase and that this oxidase differs from laccase. Thus when 
a small amount of the aqueous extract of the russula, prepared in the 
cold, and a solution of tyrosin were brought together, the mixture be- 
came red, then inky black, and finally deposited a black precipitate. 
He showed that oxygen was absorbed at the same time; this was 
proved by simply allowing the tube in which the reaction was being 
by Hoffmann’s or Piria’s 
