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 zodglea 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 
