Achorion Schonleinii, Schonlein (1839). 



THE FUNGUS OF FAVUS. 



Origin. — Found in the scaly a'ccumulations on the skin 

 of persons afflicted with favus. Similar, if not identical 

 organisms occur in the favus of the dog, cat, rabbit, mouse, 

 chicken, etc. It is closely related to the Oidium lactis. 



Form. — Apparently belongs to the moulds that produce 

 oidia. The mycelium when actively developing consists of 

 stellate threads which are not septate. The individual 

 hyphae vary considerably in thickness and usually fork. 

 The ends are swollen and, moreover, peculiar yellowish 

 lateral buds or corpuscles are seen. When the culture be- 

 comes old the threads divide into oval elements (oidia) 

 vsrhich remain attached. In the deeper layers of the culture 

 medium, moss-like ramifications are found. 



Fruit-organs. — No true fruit-organs observed, but on 

 special media, as on blood-serum at 30°, conidia or spores 

 are said to form. 



Anilin dyes. — Stain well; so does Gram's method. 



Growth. — Is rather slow and requires a week or more. 

 It is at first grayish- white, then yellowish. On the uS|Ual 

 media it tends to grow below the surface and only a feeble 

 development occurs in contact with the air. 



Plates. — On gelatin, the colonies grow slowly and fofm whitish, 

 stellate masses which liquefy the gelatin. No conidia present. 



Stab culture. — Growth is very poor in the lowpr part of the gelatin 

 tube. On the surface it forms a white covering, the lower side of 

 which is light-yellow. On potato it forms thick scales. 



Streak cultv/re. — On agar it forms a closely adherent, dry, folded, 

 whitish mass. 



Temperature. — Dies out at the ordinary temperature. 

 The optimum is about 30°. 



Behaviorto gelatin. — Slowly liquefied; becomes reddish. 



Pathogenesis. — Inoculation with a pure culture produces 

 typical favus in man. It is usually localized on the scalp. 



The favus fungus is closely related to that of Herpes 

 tonsurans — the Tricophyton tonsurans (1845); and to that of 

 Pityriasis versicolor — the Microsporon furfur (1846). 



In order to isolate the organism in pure culture it is 

 advisable to crush the scales in a sterile mortar with ster- 

 ile sand. This finely divided powder is then used to make 

 dilution cultures on ordinary agar. As many as nine dif- 

 ferent varieties of Achorion have been described. 



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