920 Favus. 



appeared, in size like a one-cent piece, on the periphery of which small quickly 

 drying vesicles could be seen, in 3 to 4 weeks little sulphur-yellow or whitish yellow 

 nodules developed in place of the discs, and from these elevated hempseed-sized, rough 

 deposits of scales which on falling off left shallow depressions. In cattle, horses and 

 asses, spots were formed like those of herpes tonsurans, and after scraping away of 

 the grayish scales which generally formed, the development of the little favus shields 

 could be observed. 



Natural infection probably occurs mostly by immediate con- 

 tact, more rarely indirectly. Obviously cats are cliiefl}^ infected 

 when catching diseased mice or rats, which rather frequently 

 suffer from favus. More rarely the disease of cats is contracted 

 from persons aifected with favus. Dogs infect themselves in 

 the same way as cats, but besides may acquire the disease from 

 coming in contact with affected cats. 



Susceptibility. Youth is seemingly an important predis- 

 posing factor, as is shown by the transmission experiments of 

 Saint-Cyr and Schindelka. Of equal importance in this respect 

 is the species of the animal, for among domestic mammalians 

 the disease has been definitely demonstrated only in cats, dogs 

 and rabbits. Predisposing causes are probably also found in 

 maceration of the skin and in bad nutrition of the animals. 



Transmission of favus from animals to persons has been noted many times 

 (Saint-Cyr, Sherwell, Draper, Horand ; Anderson, Smith) and chiefly resulted from 

 fondling, handling or treating sick animals. 



Pathogenesis. The achorion as a rule localizes in mammals 

 in the orifice of the hair follicle, whence it develops further in the 

 interior of the hair follicle as well as over a large part of the 

 extrafollicular portion of the hair (Unna, Mibelli, Walsch) and 

 penetrates also between the tissues of the epidermis. On the 

 other hand it seems questionable whether it can pass to the liv- 

 ing Malpighian layer, and, still more, to the cutis vera. In the 

 hairs the fungus is found chiefly between the hair cortex and 

 the hair cuticle ; it penetrates, however, frequently into the hair 

 cortex without causing splitting up of the hairs. The hair bulb 

 is never attacked or only exceptionally (Unna, Mibelli, Walsch, 

 Jarisch). The fungous growth gradually leads to the formation 

 of a small sulphur-yellow point covered w^ith epidermis cells 

 which gradually changes to a lentil-sized, elevated, disc-like 

 crust, which is depressed in the center (scutulum — small disc, 

 dish-shaped scab; godet [French]), probably because the de- 

 velopment of the fungous colony soon becomes less in the middle 

 of the scab, the conditions of growth being unfavorable there, 

 active growth going on at the periphery (Unna). Except for 

 a few epidermis cells, the crust consists almost exclusively of 

 fungous elements over w^hich the epidermis covering is broken 

 on further growth, and the crusts which develop close to one 

 another become larger by coalescence and enclosing, according 

 to their size, several lusterless, dusty looking hairs. In the im- 

 mediate neighborhood of the scutulum a wall arises consisting 

 of leucocytes (Walsch) while the atrophy of the skin tissue 



