996 THE HIGHER BACTERIA, MOLDS AND FUNGI 



and Dassonville of aseospore formation in Eidamella spinosa, a parasite 

 isolated from a dermatomycosis of the dog. In no other member of the 

 group, however, have ascospores been found. 



The fact is that ringworm-like diseases may be caused by various 

 fungi which show little resemblance to each other and that the 

 dermatophytes as a group are denned not by any common botanical 

 characteristics but by the type of lesions they produce. 



Our knowledge of the dermatophytes dates from Schoenlein's 

 discovery of the favus fungus in 1839. Two years later Gruby 

 discovered the fungus of ringworm and distinguished between the 

 large and small spored types. Since then many workers have con- 

 tributed to our knowledge of these parasites but by far the most 

 thorough and extended investigation has been made by Sabouraud. 38 



Cultural Characteristics. The more important varieties of 

 dermatophytes have been cultivated and show certain common char- 

 acteristics. All of them grow as leathery masses of closely inter- 

 woven hyphse. From a point of inoculation on solid media they 

 spread out symmetrically over the surface at the same time sending 

 down numerous short branches which penetrate the substrate and 

 bind the growth firmly to it. As the membranous disc extends 

 peripherally the central mycelium continues to grow increasing in 

 thickness and forcing the less adherent portions upward. This 

 produces on the surface a series of humps and ridges, with cor- 

 responding hollows and grooves on the under side, which often form 

 striking geometrical patterns. The surface may be smooth and 

 hard but most species sooner or later develop a duvet a covering 

 of aerial hyphse which according to their length give the surface 

 a powdery or velvety or hairy appearance. The majority develop 

 a yellow or brown pigment and some are characterized by brilliant 

 red and violet colors which appear late and are most marked in 

 those portions of the membrane which are raised above the surface 

 of the medium. 



The rapidity of growth varies greatly in the different species but their 

 evolution is always a matter of weeks. Some varieties such as the microspora 

 attain a diameter of ten centimeters or more. Others do not extend beyond 

 one or two centimeters from the center, but may pile up a mass a centimeter 

 in thickness. 



86 Sabouraud, E., Les Teigncs, Masson et Cie., Paris, 1910. 



