integument surrounding it. The pigment in the fungus and the profuse growth of the latter conceal, as a coat of paint might, the dark underlying natural pigment of the skin, which, moreover, in certain cases seems to be affected (either increased or decreased) by the action of the fungus. Castellani has recently studied the several forms of mycotic pityriasis as they occur in Ceylon. He recognizes three forms: Pityriasis versicolor flava, produced by Microsporon tropicum, a fungus having a thick, irregular, constricted mycelium; Pityriasis versicolor alba, produced by a very minute fungus with straight, short mycelia, Microsporon macfadyeni; and Pityriasis versicolor nigra— a variety I had described many years ago as occurring in South China— produced by Microsporon mansoni, which contains much dark pigment in the mycelial tubes, and which on culture in maltose-agar produces black hemispherical colonies.
The expression dhobie's itch, although applied to any itching, ringworm-like affection of any part of the skin, most commonly refers to some form of epiphytic disease of the crutch or axilla. There are at least three species of vegetable or bacterial parasites which in the tropics are prone to attack these situations—namely, the trichophytons or ordinary body ring-worms, the Microsporon minutissimum of erythrasma, and the germ of the disease I have described under the name pemphigus contagiosus.
The suffering to which some of the forms of dhobie's itch give rise is often severe. In hot, damp weather especially, the germs proliferate actively, producing, it may be, smart dermatitis. The excessive irritation thus set up leads to scratching and, very likely, from secondary bacterial invasion, to boils or small abscesses. The crutch, or axillæ, or both, are sometimes rendered so raw and tender that the patient may be unable to walk or even to dress. The irritation and itching are usually worse at night, and may keep the patient awake for hours. Even in the absence of treatment, when the cold season comes round the dermatitis and irritation subside spontaneously. The affected parts then become dry, pigmented, and scurfy,
