Page:Tropical Diseases.djvu/944

888 far as Burma, and northward as far as Foochow and Formosa on the coast of China. In many of the islands of the South Pacific it affects a large proportion of the inhabitants; in some islands quite one-half. There is good reason to believe that its area of distribution is gradually extending. Thus Turner and Koniger tell us that it was formerly unknown in Samoa and Bowditch Islands, where it is now very prevalent. Daniels informs me that it was introduced for the first time into Fiji by some Solomon Islanders in 1870; by 1872 it had become general among the Fijians. It was recently introduced into Tahiti, and rapidly spread there among the natives. We now hear of it in tropical Africa. Recently it has been described by Paranhos and Leme as occurring in the interior of Brazil. Once introduced, it spreads very rapidly in countries with a damp, equable climate and a temperature of 80° to 90° F. Very high or very low temperatures and a dry atmosphere are inimical to its extension.

Symptoms.—Tinea imbricata is easily recognized. At first it may be confined to one or two spots on the surface of the body; usually, in a short time, it comes to occupy a very large area. It does not generally affect the soles and palms, although it may do so; nor is the scalp a favourite site. Baker, confirmed by Tribondeau, remarks that it avoids the crutch, the axillæ, and, contrary to Castellani's experience, the nails. With these exceptions it may, and commonly does, sweep over and keep its hold on nearly the entire surface of the body; so that after a year or two a large part of the skin is covered with the dry, tissue-paper-like scales, arranged in more or less confused systems of concentric parallel lines, absolutely characteristic of the disease.

An inoculation experiment readily explains the production of the scales, their concentric parallel arrangement, and the mode of extension of the patches. About ten days after the successful inoculation of a healthy skin with tinea imbricata, the epidermis at the seat of inoculation is seen to be very slightly