ABSTRACT
When the blood of certain Crustaceans clots at a wound, the clot ultimately becomes black. This same blackening sometimes becomes troublesome in solutions of haemocyanin (in its natural serum) which are kept for any length of time in the laboratory. This will be shown to be the result of the action of a tyrosinase system in the blood, producing a black pigment, to which the general name melanin can be applied. Heim, in 1892, noticed black granules in the blood of Crustacea; these granules were soluble in mineral acids, producing a brown colour. He suggested that they were formed through the action of a tryptic ferment on some protein substrate in the blood. Furth (1903) first showed that the enzyme concerned in the reaction was a tyrosinase.
I am indebted to Dr Keilin for a private communication of unpublished results.
