72 
white. These facts serve to corroborate the hypothesis that tyro- 
sinase is responsible for the production of cutaneous pigments in man 
and animals. 
In order to demonstrate the presence of tyrosinase, the ink sac 
(glande du noir) of the cuttle fish was removed and macerated with 
chloroform water and filtered through a Cliamberland filter. Under 
these conditions the fine granules of pigment are retained by the 
filter and a clear solution of the ferment is obtained which exhibits 
the same color changes with tyrosin as is shown by an extract of 
russula. Gessard was also able to demonstrate the presence of tyro- 
sinase in the commercial product known as sepia envessie — crude sepia. 
This is simply the dried gland with its contents and is employed in the 
preparation of the refined coloring matter of the same name, sepia. 
In the course of this investigation he also showed that the anti-tyro- 
sinase serum ( 182 ) obtained by the repeated injection of a rabbit with 
vegetable tyrosinase is powerless to hinder the action of the animal 
tyrosinase on tyrosin, indicating that, despite the similarity of the 
two varieties of tyrosinase in their action on tyrosin, they are not 
precisely alike in all respects. (See also Gessard, 183 .) 
Similarly in his studies on the formation of the melanotic pigments 
in tumors of the horse, this author ( 184 ) calls attention to the fact that 
a general chemical and physical relationship has long been recognized 
as existing between the black pigments of the eye and skin and that 
of the cuttle fish (Seich) and other molluscs. It is quite likely, there- 
fore, that our knowledge of the formation of this pigment in the case 
of the cephalopods will hold equally well for its production in other 
animals. The abnormal production of melanotic pigments in liep 1 by 
or diseased tissues of man is rare, but more common in those, of ^.e 
horse, in which case its production is of less formidable significance. 
Melanotic tumors are especially common on the white horse, and 
these furnished the material for Gessard's investigations. He has 
found that in the production of the melanotic pigment of such tumors 
the same agencies are at work as in its production in the ink sac of 
the cuttle fish, viz, a chromogen and an oxidizing ferment. From 
such tumors he was able to obtain tyrosin by appropriate methods, in 
crystalline condition, and aqueous extracts thereof were found to give 
with tyrosin the color changes characteristic of tyrosinase. The 
author concludes therefore that tyrosin is the chromogen whose 
oxidation by tyrosinase gives rise to the pigment in melanotic tumors 
and wherever else such pigments are met with in the animal economy .• 
He is also of the opinion that the color of the negro is due to the 
reaction which gives rise to production of the ink of the cuttle fish 
(Seiche) and the black pigment of mushrooms. While such is doubt- 
less the case, we are still a long way from an understanding of the 
physiological cause which gives rise to tyrosinase in the epiderp. 
