434 



BACTERIA PATHOGENIC TO MAN 



on artificial media and in their pathological effects on 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 treatment, and its special seat of growth is in the substance of the 

 hair. T. megalosporon (Fig. 135) is essentially the fungus of ringworm 

 of the beard and of the smooth part of the skin; the prognosis as regards 

 treatment is good. One-third of the cases of T. tonsurans of children 

 are due to trichophyton megalosporon. The spores of T. microsporon 

 are contained in a mycelium; but this is not visible, the spores appearing 



FIG. 136 



These two half-plates show three months' growth on peptone-maltose agar of two megalosporon 

 varieties of the ringworm fungus. Natural size. 



irregularly piled up like zooglosa 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 breaking 

 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 

 surface, with arborescent peripheral rays, and often a yellowish color. 

 Although the morphological appearances, mode of growth, and clinical 

 effects of each type of trichophyton show certain characters in general, 



