344 CLINICAL BACTERIOLOGY. 



ings from others, less commonly through animals. On 

 the whole, the disease is but slightly contagious. Whether 

 an especial predisposition on the part of the skin is neces- 

 sary for the vegetation of the favus-fungus is doubtful. 

 Youth appears especially predisposed to favus. 



Infection with favus probably occurs only when the 

 fungus is deposited upon a macerated area of the epidermis 

 or gains entrance into a hair-follicle. The morbid process 

 takes place beneath the epidermis. It does not extend 

 deeply, and the favus-fungus only exceptionally -reaches 

 the subcutaneous connective tissue. In rare instances 

 favus has been observed upon the mucous membrane of 



Fig- 77- Trichophyton, X 450, as found in epidermic scrapings of ringworm, showing 

 mycelium and spores (after Duhring). 



the stomach. Under these circumstances it is probable 

 that the fungus has been swallowed, as opportunity is 

 scarcely ever afforded for embolic dissemination. 



The diagnosis of favus is made upon both clinical and 

 microscopic data. Culture is not necessary therefor. If 

 it is desired to make a culture, the scutulum is rubbed up 

 in a sterile mortar with sterile silicic acid, and plates are 

 made. 



Herpes Tonsurans. The various forms of herpes ton- 

 surans upon the hairy scalp and upon parts of the body 

 free from hair are, like parasitic sycosis, eczema margina- 

 tum, onychomycosis trichophytina, and a number of other 

 affections of the skin, due to the presence of the tricl 



