PARASITE OF PITYRIASIS VERSICOLOR 669 



colonies like thin concave discs, dry and whitish, have grown on the surface. 

 Later they become confluent, cover the whole of the surface of the liquid and 

 climb up the sides of the vessel. Some of the colonies fall to the bottom of 

 the tube and form a rather scanty deposit. 



Potato. On potato, a thin whitish growth appears and later becomes 

 prominent, brownishrpink in colour and sprinkled with white. 



Milk. The surface of the medium is covered with a pinkish- white growth. 

 The milk is not coagulated. 



XV. DISCOMYCES HOFMANNI. 



Syn. Oospora hofmanni. Nocardia hofmanni Trevisan. Micromyces 



hofmanni Max Griiber. 



Max Griiber isolated from air a streptothrix, Discomyces hofmanni, which 

 is very like Discomyces bovis, but when inoculated into rabbits produces a 

 local abscess which resolves spontaneously. Growth in artificial culture 

 media begins at 22 C. : glucose-agar is the best medium : no growth takes 

 place on potato and ordinary gelatin. 



XVI. THE POLYCHROME DISCOMYCES OF VALL^E. 



This streptothrix, found by Vallee in the blood of an horse which had died 

 of an acute pasteurellosis, does not infect either laboratory animals or the 

 larger animals, but in broth cultures forms a toxin which is fatal to rabbits 

 and guinea-pigs. 



It is a strict aerobe and grows on all the ordinary culture media. Cultures 

 on peptone media are salmon red : on glycerin media, yellow : on potato 

 the organism forms a pellicle which is at first pinkish-grey, and, as it becomes 

 older, red. 



SECTION n. THE GENUS MALASSEZIA. 

 1. Malassezia furfur. 



Syn. Microsporum furfur. 



Pityriasis versicolor (Tinea versicolor) is due to a fungus, Malassezia furfur, 

 discovered by Eichstedt. 



Methods of examination. Detach a few of the epithelial scales from a 

 patch of pityriasis by lightly scraping the latter with the edge of a slide, 

 soak them in a few drops of a warm 40 per cent, solution of potash on a slide 

 and examine them in the solution (p. 690). The scales may also be treated 

 with acetic acid and mounted in glycerin tinted with eosin. 



Masses of the fungus will be seen lying in the interstices between the 

 epithelial cells. The parasite consists of mycelial filaments and rounded 

 corpuscles : the corpuscles are spherical, measuring 3-5/x in diameter, and are 

 enclosed in a cuticle of cellulose arranged spirally : the mycelial filaments 

 are short, measuring 3-4/u in diameter, septate, somewhat wavy, slightly 

 branched, sometimes placed end to end and often bent on themselves in the 

 form of a V. 



Very little is known of the development of Malassezia furfur. 



Cultures. Malassezia furfur is a difficult organism to grow though cultures 

 have been obtained by Spielschka and by Matzenauer. Media containing 

 glycerin are the best for the purpose (Kotliar). On glycerin-agar at 37 C. 

 small wrinkled pale yellow colonies are formed, and these may attain the 



