180 CLASSIFICATION OF THE MICRO-ORGANISMS. 



teristic morbid symptoms in fowls; mice, rabbits, and 

 various other animals were not affected. 



Mouse favus has been repeatedly studied, and quite 

 recently in the author's laboratory. Nicolaier demon- 

 strated that the disease could be transmitted by the appli- 

 cation of scales to patches of the skin of healthy mice 

 previously scraped with a knife and denuded of epider- 

 mis. After about eight days a crust is formed about 

 the size of a lentil, whitish yellow, and pitted in the 

 middle; this crust constantly enlarges till it finally 

 comes to occupy the whole forehead and ears, spreads over 

 the eyes and covers the head of the animal with a 



Fig. 18. Cultivation of Mouse Favus. 

 , mycelial threads X 300 ; b, a thread more highly magnified X 700, 



whitish grey dry mass of a laminated character which 

 forms a thick layer on the skin. Small crusts planted 

 on acid nutrient agar, or on potatoes impregnated with 

 tartaric acid, and kept at 30 35 C., give rise after 

 repeated recultivations to a pure cultivation of a fungus 

 which forms a thick low mycelium, at first of a pure white 

 colour, with very closely packed, delicate hyphse, so that 

 the whole mass (particularly on potatoes) looks like a 

 crust of sugar. At a later period the surface of the 

 mycelium assumes a red or reddish-brown colour. In 

 microscopical preparations of the favus crusts, or of cul- 



