HYPHOMYCETES 



643 



studied later, by Sabouraud. 1 The fungi consist of finely interlaced 

 narrow septate mycelia, within which characteristic swellings appear. 

 From these swellings, chlamydospores develop. Hypha?, both aerial and 

 deep, grow out of the mycelial threads, on the ends of which ascospores 

 may develop. In the diseased skin, the fungi grow chiefly within the 

 hair sheath, causing an area of secondary inflammation about the base 

 of the hair. The infection probably begins first in the epidermis sur- 

 rounding the hairs, from which it then spreads into the hair bulb and 

 thence grows up into the substance of the hair in which mycelial threads 



FIG. 152. ACHORION SCHOENLEINII. Section of favus crust. Stained by 

 Gram. (After Fraenkel and Pfeiffer.) 



and spores develop in large numbers. The demonstration of the micro- 

 organism from a case can easily be accomplished by epilating an af- 

 fected hair, making sure that the hair bulb has been removed. This 

 is then immersed under a cover-slip in a drop of sodium hydrate or 

 potassium hydrate solution and examined under the microscope. In 

 this way enormous numbers of short mycelial threads and spores may 

 be seen to lie within the bulb. Many varieties of these fungi have been 

 described from different cases. Their interrelationship is not entirely 

 clear. In general, a division is made between those which develop large 

 spores and a more common small-spored variety. 



1 Sabouraud, Ann. de dermat. et de syph., 3, 1892, and 4, 1893. 



