1006 THE HIGHER BACTERIA, MOLDS AND FUNGI 



arranged in clusters. A few species (Tr. violaceum) which bear no 

 conidia are, however, included in the genus. On artificial media 

 the growths are much buckled and raised as compared to the flat 

 cultures of the microspora. The cultures, however, vary so greatly 

 among themselves in appearance that no description can be given 

 which would apply to the genus as a whole. 



Classification. Sabouraud lists thirty species. His classification is based 

 primarily on the appearance of the parasite in the infected hairs. Such 

 a scheme has the disadvantage that it groups together forms which have 

 diverse cultural characteristics and separates others which culturally are 

 similar. He divides them first into three divisions : 



I. The Trichophyton endothrix in which the fungus is found only within 



the medulla of the hair. 



II. The Trichophyton neo-endothrix in which some infected hairs show 



also a few filaments on their surface. 



III. The Trichophyton ectothrix in which besides invading the substance 



of the hair the fungus proliferates actively on its surface. 

 Of this third division there are two groups : 



A. The microid endothrices, of which the spore-like elements about the 

 infected hairs are from 3 to 4 microns in diameter. They are again divided 

 into two sub-groups, differing culturally: (a) The Gypseum Group and (b) 

 The Niveum Group. 



B. The megalospora, of which the rounded elements are from 6 to 8 

 microns in diameter. These Sabouraud again divides into: (a) A group 

 forming downy cultures, and (b) A group in which the cultures are faviform. 



The typical members of the Endothrix Group (Tr. crateriforme and 

 Tr. acuminatum) form small raised colonies less than 4 cm. in diameter. 

 They are white or slightly yellowish and are covered from the first with 

 a short powdery or velvety duvet but show little tendency to pleomorphic 

 change. They produce numerous conidia in thyrses or small clusters but 

 show no other characteristic structures. Sabouraud describes many variants 

 of these species which differ in the contour of their colonies or in pigment 

 production. They are frequently found in mild ringworm of the scalp in 

 France but so far we have not found them in New York. 



Trichophyton violaceum, which is also an endothrix, is a very different 

 organism. It develops slowly, forming small wrinkled colonies with a hard 

 glistening surface, which slowly develop a black-violet color. The mycelium 

 is made up of short crooked elements and no conidia are formed. It is 

 found with relative frequency in tinea of the scalp, body and nails. A 

 variant (Tr. glabrum) differs only in the absence of pigment. 



Trichophyton cerebriforme, the type of the Neo-Endothrix, Group, re- 

 sembles in culture the Tr. crateriforme. 



