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THE PARASITES OF RINGWORM 



Sabouraud as Tricophyton ectothrix or Tricophyton pyogenes, is of animal 

 origin. In the horse it causes a suppurating folliculitis. In the human adult 

 it produces sycosis or mentagra and onychomycosis : in children it gives 

 rise to tinea kerion. 



Tricophyton mentagrophytes is pyogenic and the lesions are accompanied 

 by dermatitis. 



It is an endo-ectothrix parasite and grows both within and outside the 

 hair, forming a sort of collar around the base and affecting the epidermal 

 covering of the skin more than the hair itself. The infected hairs are broken 

 and somewhat bent at the free end giving to the affected area a rather charac- 

 teristic untidy appearance. 



1. Microscopical appearance. In order to find the parasite the small 

 downy hairs at the periphery of the affected area should be examined, and 

 not the dead full-grown detached hairs. Epilate the downy hair together 

 with the epidermal cone from which it emerges and treat with potash. On 

 examining the preparation under the microscope it will be seen that the 

 mycelial spores form a compact mass in the epidermal covering of the hair. 

 The spores of T. mentagrophytes are, as a rule, larger than those of T. 

 endotkrix : some may reach a diameter of 15-1 8/x. 



FIG. 326. Unstained preparation of large-spored ringworm (T. megalosporum 

 endo-ec.tothrix). The fungus is outside the hair. (From a photograph kindly 

 lent by Dr. H. G. Adamson.) 



When the parasite cannot be found on the hair the pus from a vesicle which 

 has not yet opened should be collected and a small drop examined unstained. 

 In the pus, a small number of spores having the same characters as those in 

 the hair will be seen ; by using an Abbe condenser a quantity of very slender 

 and very short mycelial debris can be found which would escape observation 

 when only ordinary light is used. It is difficult to stain preparations satis- 

 factorily : fuchsin and eosin give the best results. 



2. Cultural characteristics. On beer-wort agar, which is the best medium, 

 the culture forms in the first instance a fine white downy tuft which after 



