FAVUS 



537 



epithelial squames, sometimes accompanied by an intra-epidermic, 

 very often circumpilary, suppuration. As in the conditions 

 previously described, the hair becomes invaded, the shaft being 

 especially affected, but the hair infection is of subsidiary im- 

 portance. The feature of the affection is the destruction of skin 

 structures (e.g., hair follicles), this leading, when recovery takes 

 place, to the affected part assuming a cicatricial character. 

 This is apparently consequent on a pressure atrophy of the 

 tissues brought about by the formation of the scutula. Some- 

 times a granulomatous affection of the skin is observed, which 

 may be due to secondary infections. Preparations from the crusts 

 (Fig. 16 8) show the presence of spores and mycelial threads, whose 



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FIG. 166. Favus hair showing air channels left by mycelium, x 300. 



elements vary much in size and shape, but which are generally 

 larger than those of the trichophyta. The affection of the hairs 

 is severe, and the track of the mycelium is often marked by the 

 presence of comparatively large air bubbles (Fig. 166). The 

 commonest fungus present is the Achorion schonleinii (Fig. 167a), 

 but a great number of varieties occur, and again the lower animals 

 (fowl, mouse, dog, cat (Fig. 167c)) are affected. These can be 

 readily cultivated on Sabouraud's media. 



Of the less common skin fungi, Epidermophyton inguinale, 

 found in eczema marginatum, deserves mention. In preparations 

 of the epithelial scales the organism presents itself in complex 

 undulating threads consisting of short elements 4 to 5 ft broad 

 and 4 to 12 /x long. Its characters mark it off from the 

 organisms described. The hairs in the diseased area|remain 

 unaffected, but the organism is closely allied to the trichophyta, 



