HISTOCHEMICAL OBSERVATIONS ON MELANIN PRODUCTION IN THE SKIN

Abstract

For a quarter of a century studies of the problem of human pigment have been dominated by the histochemical reaction of Bloch, the dopa reaction. The importance of this reaction lies in the apparently established fact that its production denotes for the cell in question (we here ignore nonspecific reactions seen in leukocytes and sweat gland parenchyma) the capacity to make physiologic melanin. This significance for this reaction has been achieved through an endless number of studies with both animal and human skin, revealing a positive correlation between positive dopa reactions and the recognized capacity of the reacting epidermal cells to form physiologic melanin. Even more convincing has been the stronger positive correlation between the negative dopa reactions and the failure through functional perversion and damage of identical sites of skin to form pigment as disclosed clinically and histologically. While there has been this general acceptance of the dopa reaction