It has been known for many years that tinea circinata in various forms may occur on the hands and feet, as on any other part of the body, and it is not my purpose to touch on these eruptions except incidentally. But, aside from these, there is a variety of lesions whose etiology has remained obscure but whose secrets are being revealed by careful research. As far back as 1860, Hebra gave a description of tinea cruris, or eczema marginatum, which has never been excelled in its minute precision. He stated at the same time that this same eruption may occur, though rarely, on other parts of the body, including the extremities. It is now recognized that tinea cruris is invariably parasitic and caused by some form of tinea, usually a distinct species, theEpidermophyton, and it is the demonstration of this organism in an increasing number of cases of