446 MEDICAL MYCOLOGY 



caused by T. tonsurans, the hair is folded and refolded in the scale. It is 

 yellowish gray and extends about 5 mm. beyond the scalp. Many normal 

 hairs are scattered over the infected area. In more atypical cases, the hair 

 may be straight, yellowish gray, 2-3 mm. above the scalp, suggesting the mi- 

 crosporic type but lacking the spore sheath, or the lesions may be covered 

 with a thick layer of impetiginous, crusts, or half impetiginous, half fat. 



Some lesions are slightly infiltrated while others show no erythema but 

 large black hairs, broken in the skin and enlarged so that the follicle is pro- 

 truding. The follicular orifices may be marked by an isolated red point, the 

 beginning of folliculitis, or the folliculitis may become suppurative and each 

 hair the center of a pustule, the whole lesion forming an elevated, red, ulcer- 

 ated plaque, and giving the appearance of a true kerion, which may be benign 

 or severe and terminate with or without a scar. In these latter variations it 

 may be found on adults, but it is predominantly a disease of children. The 

 more active the suppuration, the shorter the probable duration of the disease. 

 The dry lesions often last for several years if not treated ; the lesions, marked 

 by red points where the follicle is invaded, disappear in 6-7 months while the 

 suppurative lesions are cured in 6-8 weeks. Although growth of new hair is 

 very slow, bald areas are rare following tinea tonsurans except in scar forma- 

 tion following kerion and where the careless application of irritants to secure 

 prompt depilation has caused irreparable damage. 



On the infected hair the hyphae are parallel, composed of isodiametric 

 cells, often called spores by dermatologists. These cells may be large, about 

 8/i, or small, about 3/* in diameter, spherical, ovoid, or eylindric. Hyphal 

 branching is rare and strictly dichotomous, the forks pointing downward. 

 When the li^qDhae are confined to the interior of the hair, as is usual in tinea 

 tonsurans (Fig. 77, 1), the fungTis is said to belong to the TricJiophyton endo- 

 thrix type. AVhen the fungus produces a mass of mycelium surrounding the 

 hair without penetrating it, as frequently occurs in lesions of the beard, the 

 fungus is said to belong to the Trichophyton ectothrix type (Fig. 77, 2). These 

 types are alike in the very young stages. In a third type the mycelium is 

 mostly within the hair as in the true T. endothrix type, but a few hyphae still 

 grow along the outside of the hair; this is called the Trichophyton neoendothrix 

 type. The second type is further differentiated into the large spored tyipe with 

 spores 5-8ju, in diameter and a small spored tj^pe, with cells 3-4/a, the former 

 sometimes referred to as T. ectothrix megaspore (often shortened to T. ecto- 

 thrix) and T. ectothrix microsporoid (often shortened by French writers to 

 T. micro'ide type). 



As in the Microsporum type, the homy layer of the epidermis is first in- 

 vaded, the hyphae growing along this until the mouth of a follicle is reached. 

 They then grow along the follicular epidermis, producing a slight mycelial 

 collar. Penetration of the hair is prompt and similar to that in Microsporum. 

 As soon as a hyphae has penetrated, it branches dichotomously and grows 

 downward. While it is just under the cuticle of the hair, it is easily stained, 



