Cultivation 



799 



Morphology. — The trichophyton parasites form delicate mycelia 

 composed of somewhat slender septate hypha. They can best be 

 observed by extracting one of the hairs, including its root, from the 

 diseased area, or if the affection be upon a hairless part of the body, 

 by scraping off some of the epiderm, and mounting the material 

 between a slide and cover in a drop of caustic potash solution (20 

 per cent.). Under these circumstances the spores are conspicuous 

 and so numerous as to give the impression that they occur in rows 

 in a kind of structureless zooglea upon the outside of the hair. In 

 some cases, however, especially in Trichophyton megalosporon, the 

 hypha maybe observed with the spores 

 inside. The hypha measure from 2 to 

 8 iti in diameter, are usually simple, and 

 rarely divide. The spores are from 2 

 to 3 Ai in diameter in the Trichophyton 

 microsporon and 7 to 8 // in T. mega- 

 losporon. The former is the more 

 common upon the hairless, the latter 

 upon the hairy, portions of the skin. 

 Cultivation. — ^The organisms may 

 be secured in pure culture without 

 much difficulty, except for the annoy- 

 ing and almost constant presence of 

 the associated ■ bacteria of the skin. 

 By crushing the hair and scales in a 

 mortar with some dilute KOH solu- 

 tion, and then thoroughly distributing 

 the spores through the alkaline 

 medium which dissolves many of the 

 bacteria, plates can be made with high 

 dilutions, or drops of the fluid be 

 spread over potato, which is an ex- 

 cellent 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 

 myceHal filaments with aerial hypha, looking like a tiny white 

 powder-puff. Upon the surface of Hquid culture-media the growth 

 appears as a thick wrinkled pellicle with aerial hypha of velvety 

 appearance. As the cultures grow older the lower mycelial growth 

 becomes yellowish and wrinkled, but the aerial hypha maintain 

 the velvety white appearance. Some of the colonies are mammil- 

 lated, 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 



criotg off 



Pathogenesis.— The trichophytons are pathogenic for man and 



Fig. 323. — Invasion of a hu- 

 man hair by trichophyton: A, 

 Points at which the para,sitic 

 fungi coming from the epider- 

 mis are elevating the cuticle 

 of the hair and entering 'into 

 its substance. Magnified 200 

 diameters (Sabouraud). 



