290 An Introduction to Medical Mycology 



spora. The hair shaft is not invaded. The fungi in lesions of the smooth 

 skin are noted as short chains of spores; usually the amount of fungous 

 material is scanty. 



(d) Cultural characteristics.— Few fungi in culture are more easily 

 recognized. The rate of growth is moderately active, and in two weeks 

 there is a central umbo, which may be white, surrounded by a flat, felty 

 growth resembling suede. The cinnamon-brown color of the entire colony 

 is characteristic. If any furrows are present, they are usually concentric 

 rather than radial. The growth continues in an agar slant until the medium 

 is entirely covered. The margin of the colony is usually abrupt. Pleomor- 

 phic changes readily occur and are evidenced by the appearance of white 

 tufts on the surface of the colony. 



(e) Culture mount.— Numerous fuseaux are present. The walls are 

 moderately thick, and the ends are rounded. Racquet mycelium and 

 nodular organs may be found. Small round spores are to be seen in moder- 

 ate numbers. 



(f ) Filtered ultraviolet rays.— When observed in this light, infected 

 hairs fluoresce as light green stubs characteristic of all Microsporum infec- 

 tions. The fluorescence of the hairs may not be noted in an edematous 

 patch; in this case the diseased hairs may be below the surface. The cul- 

 tural growth is dull, clear and cinnamon-brown throughout. 



(g) Animal inoculation.— This organism may be transferred to the 

 young of several species of animals. 



(h) Differential diagnosis.— The microscopic picture may simulate that 

 of the other Microspora, but if the infected hair has been recently invaded, 

 short filaments in the hair shaft may suggest infection with A. schoenleinii. 

 The cultural growth is highly characteristic. The fuseaux are of slightly 

 different character and more numerous than with M. lanosum. Nodular 

 organs are not seen in other Microspora. 



4. MICROSPORUM FERRUGINEUM 



We have isolated this fungus only once. The patient, a Chinese child 

 born in Hawaii, had tinea capitis with little inflammation, the alopecia 

 spreading in concentric rings and progressively. We are unable to find 

 the child after one visit, so the response to therapy is unknown. According 

 to Frederick Reiss, the micro-organism is a common cause of tinea capitis 

 in China. We have received one specimen from American Samoa, where 

 it may be a frequent pathogen. 



(a) Microscopic features.— The sheath ol the invaded hair shows 

 slender filaments (about 3 microns in diameter) packed tightly together 



