826 



Ringworm 



of the bacteria, plates can be made with high dilutions, or 

 drops of the fluid may be spread over potato, which is an 

 excellent medium for the culture. 



The culture, whether upon agar-agar, glycerin agar-agar, 

 glucose agar-agar, gelatin, or potato, occurs in the form of a 

 tuft of white mycelial filaments with aerial hypha, looking 

 like a tiny white powder-puff. Upon the surface of liquid cul- 

 ture-media the growth appears as a thick wrinkled pellicle 

 with aerial hypha of velvety appearance. As the cultures 



Fig. 280. Trichophyton tonsurans. Primary cultures twenty days' 

 old on maltose agar-agar. Natural size (Sabouraud). 



grow older the lower mycelial growth becomes yellowish and 

 wrinkled, but the aerial hypha maintain the velvety white ap- 

 pearance. Some of the colonies are mammillated, some are 

 crateriform. Gelatin is liquefied, the growth floating upon 

 the surface of the fluid. As the cultures become very old and 

 dry the velvety appearance is lost and the surface becomes 

 powdery. The powder detaches only when the growth is 

 touched, and does not shake off. 



Pathogenesis. The trichophytons are pathogenic for 

 man and for the lower animals. They spread from animal to 



