Long established clinical and histologic observations have made it apparent that certain hematogenous dermatoses selectively affect the pilosebaceous apparatus and thus have a predominantly follicular localization. Lichen scrofulosorum (or, more appropriately, tuberculosis lichenoides), lichen trichophyticus, acneform bromodermas, iododermas and tuberculodermas (for example, the rosacea-like tuberculid of Lewandowsky1) and certain eruptions due to arsphenamine and other drugs, appearing as a lichen spinulosus (Stauffer2), are examples of the many dermatoses in which a hematogenously distributed agent shows a certain predilection for affecting the follicles of the skin. Struck by this, many investigators have sought to explain this selectivity. J. Jadassohn3has repeatedly called attention to the fact that the anatomic and functional characteristics of the blood vessels surrounding the pilosebaceous invaginations were peculiarly conducive to a concentration of hematogenous substances, and particularly to a deposit of hematogenously distributed micro-organisms at these points. In the case of iododermas and bromodermas,