Page:Transactions of the Royal Society of Tropical Medicine and Hygiene, volume 1.djvu/298

270 may form solid elevated dark red patches. In such situations the disease may be clinically indistinguishable from ordinary T. circinata. It is to be noted, however, that the rings have generally a thicker edge and the patches are coarser and larger than in ordinary Tinea circinata. It is to be noted also that in my experience mixed infections of dhobie itch and ordinary T. circinata do occur presenting the two fungi growing on the same patient, though on different regions of the body. Several such cases I described some years ago (see British Medical Journal, November, 1905).

Etiology.—For many years it has been known that dhobie itch is a trichophytic affection. In 1905, as the result of an investigation of numerous cases, I came to the conclusion that Tinea cruris, or dhobie itch, should be separated from the ordinary forms of Tinea corporis.

The Fungus.—In my experience there is more than one species of trichophyton which may give rise to dhobie itch: at least two species can be distinguished, and there are probably several varieties of each:—


 * 1. Trichophyton cruris (Castellani, 1905).
 * 2. Trichophyton perneti.

Trichophyton Cruris.—This is the commonest species. In Ceylon about 98 per cent, of the cases are due to it. Sabouraud has created a new genus for this fungus—the genus epidermophyton. Notwithstanding Sabouraud's great authority, it seems to me that there is no necessity to create a new genus, as the fungus presents all the principal characters of the other trichophytons of the megalosporon type. Sabouraud lays stress on the rapid degeneration which takes place in the forms found in the cultures, and other secondary characteristics which seem to me to be of insufficient importance to necessitate the creation of a new genus.