THE PATHOGENIC FUNGI AND YEASTS 435 



yet there are certain constant minor differences which point to the fact 

 that there are several different kinds of species of fungus included under 

 t'jirli type. The species included under T. microsporon are few in 

 number, and, with the exception of one which causes the common con- 

 tagious "herpes" of the horse, almost entirely human. The species of 

 T. megalosporon are numerous and fall under several natural groups, 

 the members of which resemble one another both from clinical and 

 mycological aspects (Fig. 136). Many animals are subject to the growth 

 upon their skins of particular species of T. megalosporon. 



Achorion Schoenleinii (Favus). 



Favus is due to a fungus discovered by Schoenlein in 1839, and called 

 by Remak Achorion schoenleinii. The disease is communicated by 

 contagion, the fungus being often derived from animals, especially 

 cats, mice, rabbits, fowls; and dogs are also subject to it. It grows 

 much more slowly than the ringworm fungus, and is, therefore, not so 



FIG. 137 



A portion of a favus-infected hair ; magnified. 



easily transmitted. Want of cleanliness is a predisposing factor. The 

 fungus seems to find a more favorable soil for its development on the 

 skin of persons in weak health, especially from phthisis, than in others. 

 Pathologically, the disease represents the reaction of the tissues to 

 the irritation caused by the growth of the fungus. The spores generally 

 find their way into the hair follicles, where they grow in and about the 

 hair (Fig. 137). The favus fungus grows in the epidermis, the density 

 of the growth causing pressure on the parts below, thus crushing out 

 the vitality of the hair and giving rise to atrophic scarring. The dis- 

 ease shows a marked preference for the scalp, but no part of the skin 

 is exempt, and even the mucous membranes are liable to be attacked. 

 Kaposi has reported a case in which a patient suffering from universal 

 favus died, with symptoms of severe gastrointestinal irritation, which was 

 found after death to be due to the presence of the favus fungus in the 

 stomach and intestine. On the scalp it first appears as a tiny sulphur- 

 yellow disk or scidulum, depressed in the centre like a cup and pierced 

 bv a hair. This is the characteristic lesion. The cup shape is attributed 



