ICHTHYOSIS or XERODERMA, a general thickening of the whole skin and marked accumulation of the epidermic ele ments, with atrophy of the sebaceous glands, giving rise to a hard, dry, scaly condition. This disease generally first appears in infancy, and is probably congenital. It differs in intensity and in distribution, and is little amenable to treatment. A somewhat similar condition (leukoplakia) affects the tongue in syphilitic subjects and cancer may start in one of the patches.