TRICHOPHYTON. 621 



the human skin and its appendages. T. microsporon 

 is the common fungus of tinea tonsurans of children, 

 especially of those cases which are rebellious to treat- 

 ment, and its special seat of growth is in the substance 

 of the hair. T. megalosporon (Fig. 83) is essentially 

 the fungus of ringworm of the beard and of the smooth 

 parts of the skin; the prognosis as regards treatment is 

 good. One-third of the cases of T. tonsurans of chil- 

 dren are due to trichophyton megalosporon. The spores 

 of T. microsporon are contained in a mycelium; but 

 this is not visible, the spores appearing irregularly 

 piled up like zoogloea masses; and, growing outside, 

 they form a dense sheath around the hair. The spores 

 of T. megalosporon are always contained in distinct 

 mycelium filaments, which may either be resistant when 

 the hair is broken up, or fragile and easily separating 

 up into spores. The two types when grown in artificial 

 cultures show distinct and constant characters. The 

 cultures of T. microsporon show a downy surface and 

 white color; those of T. megalosporon a powdery sur- 

 face, with arborescent peripheral rays, and often a yel- 

 lowish color. Although the morphological appearances, 

 mode of growth, and clinical effects of each type of tri- 

 chophyton show certain characters in general, yet there 

 are certain constant minor differences which point to 

 the fact that there are several different kinds or species 

 of fungus included under each type. The species in- 

 cluded under T. microsporon are few in number, and, 

 with the exception of one which causes the common 

 contagious " herpes" of the horse, almost entirely 

 human. The species of T. megalosporon are numer- 

 ous and fall under several natural groups, the members 

 of which resemble one another both from clinical 



