KNOWLEDGE of nail disease is indeed limited. Two textbooks* have been published on this subject in the last quarter of a century, but a study of the table of contents of both reveals merely a list of the many diseases in which concomitant nail findings have been reported. The descriptions are for the most part those of gross morphologic changes in the nails. Only a few isolated reports are available concerning the correlative histology of conditions that affect the nails, and the value of these reports is lessened by the lack of adequate histologic studies of the normal nail. As a matter of fact, most of us speak glibly of "nail disease" without having given thought whereof we speak. Some refer to paronychial disease with secondary change in the nails as nail disease; this is certainly confusing in view of the present concept of nail generation from the matrix (proximal