298 



APPLIED BACTERIOLOGY 



Tricopliytoii Tonsurans. 



This fungus, which is the cause of herpes tonsurans, 

 ringworm, onychomycosis, and certain other affections, was 

 first described by Malsten, a Swedish microscopist, and 

 about the same time by Gruby. 



The organism, which belongs to the oidium group, was 

 first cultivated by Leslie Roberts, who obtained growths in 

 broth to which malt extract and sugar had been added, 

 growth occurring in twenty-four hours. A pure culture 



Fig. 25. — Trichophyton Tonsurans. (Mycelia and segmented 

 filaments.) 



may be obtained from an affected hair by making, an agar 

 plate and incubating it for three days at blood-heat, when 

 the colonies will make their appearance as whitish spots. 

 When grown on gelatine, the medium is liquefied. To 

 diagnose a case of ringworm, it is generally sufficient to 

 examine one of the suspected hairs under a low power 

 (a quarter-inch), when it will be found to be covered with 

 spores. To facilitate examination, the hair may first be 

 soaked in 40'0 per cent, caustic potash, and then in alcohol 

 and ether. If the patch itself is examined, spores will be 

 found on the surface, while a little below will be seen a 

 matted mass of mycelial branching. The organism may 



