DEFINITION Under this head may be described a malignant disease of the nail-bed marked by the formation of nodules of neoplastic tissue about the border and beneath the nails. The growth is characterized by the formation of melanin and a tendency to spread by way of the lymphatics. Hutchinson called this condition melanotic whitlow, a designation obviously inapt in the more advanced cases. I have adopted the term "melanoblastoma," in harmony with the teachings of Mallory, in order to emphasize the fact that, genetically, they are different both from the sarcomas and carcinomas. INCIDENCE The condition is rare, though obviously not so rare as the literature would indicate. The reported cases do not much exceed twenty. It has been my privilege to treat two of these patents, and, since American literature is all but devoid of case reports, a presentation of my cases, together with a general summary of the