HYPHOMYCETES 545 



more frequently than in adults. The disease is characterized clinically 

 by the formation of inflamed scab-areas or patches on the skin imme- 

 diately surrounding hairs and these patches exhibit a decided tendency 

 to spread. They itch intensely and within them the hairs fall out. 

 Usually the inflammation is not accompanied by exudation, but in 

 very severe cases pustule formation may occur. The disease is con- 

 tagious and is transmitted by towels, the hands, hairdressers' utensils 

 and very commonly in the tropics through laundry. The initial lesion 

 appears in the outer layers of the skin and extends downward through 

 the hair follicle and then invades the inner layers of the hair itself, 

 through which both the mycelia and spores develop in large numbers. 



The organism, Trichophyton tonsurans, was described by Gruby 

 and by Malmsten in 1845. Several subvarieties have been described, 

 but their differential characteristics are imperfectly established. It 

 is readily demonstrated in the hair bulb by adding a few drops of 

 NaOII solution, gently heating and examining under the microscope. 1 

 The mycelial filaments appear in the bulb and penetrate for some 

 distance along the hair shaft. The spores are usually restricted to 

 the outer layers of the hair. 



The mold grows readily upon neutral agar and gelatin, the latter 

 becoming liquefied. After a few days' incubation, multicellular 

 mycelia with their nodal thickenings within which chlamydospores 

 develop appear and frequently the colony becomes pigmented 

 brownish after prolonged cultivation. Plant 2 states that there are 

 two varieties of Trichophyton tonsurans, one, less common, produc- 

 ing relatively large spores, the other producing smaller spores. Guinea- 

 pigs may be successfully infected with cultures of the organisms 

 grown on artificial media; a small area on the back is epilated and the 

 culture rubbed in. The lesions are self-limited and usually heal 

 spontaneously after a few weeks. 



Pityriasis Versicolor. Pityriasis versicolor is a disease of .the 

 epidermis which differs from favus and ringworm anatomically in 

 that the infecting organisms neither penetrate the deeper layers of 

 the skin, nor do they cause any noteworthy alterations in the skin or 

 hair. Usually the epidermis of the chest, abdomen, joints and axilla 

 are involved, rarely the neck. The disease is observed in the uncleanly 



1 Water should not be added after the addition of the NaOH, else the hair will very 

 quickly crumble. 



2 Plant removes a hair to a sterile moist chamber, seals the cover glass with melted 

 paraffin and incubates for several days. When the spores have germinated the mycelia 

 may be removed and cultivated upon agar or gelatin. 



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