170 



INFECTIONS CAUSED BY MOLDS 



of the acuminate type, but when first isolated they are of a deep 

 violet color. Many strains lose the pigment upon continued cultiva- 

 tion. Colorless sectors frequently appear in the pigmented colonies, 

 together with sectors of transitional color. A number of varieties 

 have been named according to these various differences. Few spores 

 are formed in the cultures. Some strains, after cultivation, lose the 



Fig. 83. Ringworm of the smooth skin showing concentric rings, approaching 



the imbricate type. 



typical glabrous wrinkled appearance and produce a short aerial 

 mycelium. On this mycelium a few typical dermatophyte conidia 

 can sometimes be found. Fungi of the endothrix group have a low 

 degree of virulence for laboratory animals producing no lesions or 

 only localized lesions which soon heal. 



Neoendothrix Species of Trichophyton. Neoendothrix species of 

 Trichophyton are transitional between the ectothrix and endothrix 

 groups as far as the relationship 'of the fungus to the hair is con- 

 cerned. The condition in the early invasion of the hair by an endo- 

 thrix species in which there are hyphae outside the hair shaft as well 

 as within persists in this group. The infections produced are also 

 transitional between those caused by the human and animal types of 

 Trichophytons; they show some tendency to inflammatory reaction, 



