Cultivation 



753 



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 may be observed with the spores 

 inside. The hypha measure from 2 to 

 8 M in diameter, are usually simple, 

 and rarely divide. The spores are 

 from 2 to 3 M in diameter in the Tri- 

 chophyton microsporon and 7 to 8 ju 

 in T. megalosporon. 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 annoying and 

 almost constant presence of the associ- 

 ated bacteria of the skin. By crushing 

 the hairs and scales in a mortar with 

 some dilute KOH solution, and then, 

 after thoroughly distributing the spores 

 through the alkaline medium which dis- 

 solves many 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 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 

 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. 



Fig. 315. Invasion of a hu- 

 man hair by trichophyton: A, 

 Points at which the parasitic 

 fungi coming from the epider- 

 mis are elevating the cuticle 

 of the hair and entering into 

 its substance. Magnified 200 

 diameters (Sabouraud). 



