TRICHOPHYTONEAE 445 



of tinea tonsurans may show after an inflammatory phase. Growth of the 

 new hair is much slower than that of normal hair so that the site of the lesion 

 can long be distinguished by the smaller number of hairs per square centi- 

 meter. Microsporic tinea tonsurans is much more common on boys than girls, 

 but it is sufficiently contagious for practically all the other members of a 

 family who are of a suitable age, to contract the disease from the one origi- 

 nally infected. It spreads easily in primary schools, and only the strictest 

 isolation and inspection can prevent its running for several years. 



In the early stage an examination of the horny layer of the epidermis 

 shows mycelium l-3yu, in diameter, hyphae curved and undulate, with many 

 short lateral branches, septa rarely visible in unstained preparations. When 

 the mycelium reaches the mouth of a follicle, it follows the follicular epidermis 

 downward. It then grows out into the space between the epidermis and the 

 hair, forming a mycelial mass (suggesting an early stage of a favic scutulum), 

 composed of hyphae, 6-7 cells, each 12-15/x long, and some loose spores. When 

 the hair is reached, some hyphae penetrate the hair itself and grow downward 

 in flexuous curves (nearly straight in very old hairs after the tendency to heal 

 has begun). Sometimes they nearly fill the hair with their bifurcations. 

 Other hyphae grow downward along the outside of the hair from which hyphal 

 branches grow outward to form the spore layer which is so characteristic 

 in these lesions. The spores apparently arise by frequent dichotomy and cell 

 division in the hyphae, producing compact masses of spores on the outside of 

 the hair. The cells are somewhat deformed by mutual pressure. It is also 

 probable that branches from the hyphae within the hair grow outward to 

 contribute to this spore sheath. 



In handling the hairs, this spore sheath is often knocked oft' and the hair, 

 which then appears dull grayish yellow, under the microscope shows only a 

 few scattered spores over its surface which is roughened and cracked like 

 the bark of an elm. Within the hair, a few flexuous irregularly septate 

 hyphae, 2-3/* in diameter, may be seen. The spore sheath penetrates the fol- 

 licle only one or tAvo millimeters, thinning out toward the root. On the root 

 itself only a few scattered islets of spores may be seen. The hyphae within 

 the hair become increasingly abundant, ending in a fringe (of Adamson). 

 Rarely the eyelids and lashes are attacked (Arijewitsch 1930), 



In the second type of tinea tonsurans caused by Trichophyton, the erj^the- 

 matous spot disappears very quickly and is followed by a scaly crust, about 

 a millimeter thick, of yellowish scales with adherent hairs. The lesions are 

 abundant (often over 100 to a scalp), small and very scattered over the sur- 

 face, often only 2 or 3 hairs being infected in each lesion. The infection often 

 spreads by autoinoculation to the glabrous skin where it either produces small, 

 amorphous, abortive, erythematous patches which soon disappear, or more 

 rarely a circinate lesion. In the first or Sabouraudia subtype caused by T. Sahour- 

 audi {T. acuminatum) the hair breaks off sharply at the follicular orifice and 

 is thick and black. It resembles a comedo in appearance. Comparatively few 

 normal hairs are found in the lesion. In the second or Malmstenia subtype 



