IIYPHOMYCETES 617 
with an alkaline reaction and e^•en a relati\-ely strong acid reaction 
(organic acids, not mineral acids), will usnally permit of their mnl- 
tiplication. Even on very dry media development takes place. 
Pathogenic Molds. ^—Fams.—Fa.vus or tinea favosa is a skin disease 
limited chiefly to the hairy parts of the body; more frequently the 
head alone is involved, but the disease may spread over the entire 
sm-face of the body. It is not limited to man— dogs, cats, mice and 
rabbits are also susceptible. The disease is contagious and is trans- 
mitted from man to man or from animal to man by contact. Unclean- 
liness is a potent predisposing factor, but individuals with lowered 
vitality, as poorly nourished children and consumptiAes, appear to 
be relatively more readily infected than the more robust. The organ- 
ism spreads slowly and the disease is a chronic one, difficult to influence 
by treatment. The initial lesions are small red pimples, which soon 
enlarge somew^hat, forming gray or sulphur-yellow crusts groupetl 
F)G. 92. — Penicillium; conidiophorcs, sterigmata and conidia. 
around the base of hairs. These crusts, known as scutella (singular 
scutellum), slowly increase in size peripherally and tend to coalesce. 
If a scutellum is removed it is found to be somewhat thicker in the 
center and cup-shaped. Examined under the microscope it consists 
of a dense, matted mycelium which in the center may be so compact 
as to obscure the individuality of the filaments; at the periphery the 
growth is less luxuriant and the individual filaments are clearly defined. 
Spores are very numerous at the center of the scutellum, but at the 
periphery they are much fewer in numbers. The hair enclosed by the 
colony of mold is destroyed. 
The organism, Achorion schonleinii, was first observed by Schonlein 
in 1839. It is readily cultivated at room temperature upon gelatin, 
or better, upon agar at 30° to 35° C. Media with a neutral or slightly 
alkaline reaction are more favorable for its development than acid 
' Sabouraud: Les Teignes, Paris. Pinoy: Les Champignons pathogen^s. Bull. 
Inst. Pasteur, 1903, 1, 761, 809. 
