494 MEDICAL MYCOLOGY 



& Milochevitch has shown spirals to occur on other media for the greater por- 

 tion of the natural group separated hy Sabouraud as the Trichophyton microide 

 group. 



This genus is here conceived as the primitive group from which all the 

 other dermatophytes were derived by degeneration. I have attempted to in- 

 clude all those species which have retained the closterospore or a nodular or- 

 gan derived from it, where these organs are quite regularly produced in the 

 fresh isolation. Very rarely a single author has remarked that in a single 

 culture he found spirals or closterospores or nodular organs very degenerate, 

 and that his organism was isolated from a relatively mild lesion. Such scat- 

 tered species, which seem to have much closer affinities to the members of some 

 other group, have been left with them. There remains a small residue of inade- 

 quately described organisms treated in the following key and descriptions, 

 which have been referred here on the basis of lesion or colony character, but 

 which might also be referred elsewhere and in most cases were not originally 

 placed here by their author. It is to be hoped that some one will again find 

 these organisms and give us further data on their morphology. T. persicolor 

 Sabouraud has been referred to Epidermophyton, since it has not been found 

 to penetrate the hair follicle and the type of lesion it causes seems rather 

 closer to the usual lesion of Epidermophyton. Sabouraud (1910) remarked that 

 in his microide group the species was anomalous in several respects. The related 

 group of pink and reddish species of Epidermophyton has been too poorly de- 

 scribed to make clear the resemblance at that time. 



The genus includes most of the kerion-producing organisms and many of 

 those producing sycosis. The failure of hyphae to penetrate the hair or to form 

 favic scutula easily distinguishes the lesions produced by Ectotrichophyton from 

 suppurating lesions produced by Microsporum or Achorion, while the sheath of 

 small spores and mycelium about the hair distinguishes the genus from Epi- 

 dermophyton. 



Key to Species 



Clostospores absent, at least on Sabouraud sugar media, their functions apparently taken by 

 the enlarged cells of the nodular organs; spirals often present, if not on Sabouraud 

 media on other agars. 

 Nodular organs present, formed of curved chains of chlamydospores usually a crateriform 

 colony with radial folds. 

 Powdery yellowish white disc with larger granules, center small, spirals on other 

 media but not on Sabouraud; usually on horses, easily inoculable into 

 guinea pig. -E. granulosum. 



Smooth, light yellow green ; light gray cerebrif orm on Sabouraud conservation agar ; 

 spirals not reported on any medium; on man; only slightly pathogenic for 

 guinea pigs. ^- eriotrephon. 



Dirty yellow becoming pale rose, center darker, powdery, acuminate, no radial fur- 

 rows; tinea cruris. Ateleothylax Viannal (p. 431). 

 Nodular organs not found on Sabouraud agar. 



Closterospores and spirals on various media but absent on Sabouraud, center long 

 velvety, more or less crateriform, spirals and coremia abundant on cereal media. 

 Margin with long slender rays. E. felineum. 



