68 
carried out to remain quiet, whereby these color changes were first 
observed to occur on the upper surface of the liquid. In a vacuum 
or under a bell jar, resting in a watch glass on the surface of mercury, 
the mixture acquired a faint rose tint, since it was impossible to re- 
move all traces of oxygen therefrom, but they showed no further 
deepening of color no matter what the duration of the experiment. 
With a boiled extract of russula no change of color was observed. A 
repetition of these experiments on the boiled juice of the beet, or with 
tyrosin of animal origin (from the horse), or of vegetable origin (from 
the dahlia or russula), or with the oxidase obtained from the beet or the 
dahlia, always led to the same results. Finally, in order to prove that 
the oxidation of tyrosin could not be accomplished by laccase, the fol- 
lowing experiment was carried out: A certain amount of extract of 
russula was introduced into a vacuous flask, and then some tyrosin 
added. The flask containing these substances was then allowed 
to stand for twenty-four hours, at the end of which- time no change 
of color had occurred. The contents of the flask were then heated 
to 100° C. for ten minutes in order to destroy all enzyme action. The 
flask was then opened and its contents exposed to the action of the 
air, but the tyrosin remained unaltered even after the addition of 
ordinary laccase. Hence the blackening of tyrosin is not due to the 
successive action of two ferments but solelv to that of tvrosinase in 
%J 
the presence of oxygen. He then points out that independently of 
their special interest, these observations go to show that laccase is 
not the only oxidizing ferment existing in the vegetable world but 
that on the contrary, it should be regarded as a type of a series of 
analogous substances to which he had already given the generic name 
of oxydases. (See p. 54.) 
While perhaps not so widely distributed in nature as laccase, tyro- 
sinase has been found in a large number of plants and animal species. 
Bourquelot and Bertrand ( 87> 88 ’ 89 ) found it in a large number of 
fungi, and also in phenogams. According to Lehmann ( 26 °) and 
Lehmann and Sano ( 261 ) tyrosinase is found in a number of species of 
bacteria, notably in B. jluorescens nonliquefaciens , and also in B. 
phosphorescens , B. putridens, and Actinomyces chromogens. As a 
general thing, wherever we find tyrosinase in plant tissues, we are 
apt to find laccase. The converse of this, however, does not hold 
generally — that is, we do not find tyrosinase wherever we find lac- 
case. For example, in Russula delica, Lactarius piperatus , and in the 
tubers of the dahlia and potato, we find both tyrosinase and laccase, 
whereas in the silk of the green corn ( Zea mays ) we find laccase but 
no tyrosinase. 
Tyrosinase is also widely distributed in the animal kingdom, 
where it plays an essential role in the formation of animal pigment 
(melano genesis) . The following are the more important investigations- 
bearing on this point: The blackening (melanose) of the Flood 
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