ORIGIN OF PIGMENT IN SKIN, AND THE NATURE OF CERTAIN PIGMENTED TUMORS ARISING IN THE SKIN.

Some years ago Karg transplanted skin from the negro to the white man, and vice versa. In both cases the grafts "took," and after a while the black skin lost its pigment and the white skin became black. The deepest layers of the epidermis contain peculiar spider-like branching cells full of pigment, and called "chromatophores." Similar cells also occur in the cutis. Karg believed, as is commonly taught, that these chromatophores are fibroblasts emigrating from connective tissue to the epithelium of the skin, where they deposit their pigment. When black pigment becomes white a reverse process is assumed to take place. Recently Loeb¹ of Chicago made some experiments with the skin of the guinea-pig, replacing black skin with white and white with black, and it was found that white grafts would not adhere indefinitely when placed upon colored skin, whereas black grafts invariably took well. These results Loeb found