TRICHOPHYTONEAE 461 



Returning- again to the main line of Ectotrichophyton at the stage reached 

 in E. felineum, we find an easy transition to Megatrichophyton. This genus is 

 very small and has lost all spore forms except chlamydospores and aleurospores. 

 In M. roseum we find chlamydospores suggestive of very degenerate clostero- 

 spores, in M. caninum these have disappeared although the chlamydospores are 

 still well formed, while in M. equinum the latter are not numerous and are be- 

 ginning to degenerate. The lesions seem to be confined to the follicles and 

 epidermis, although a sheath of large spores is formed about the hair. There 

 is no inflammation. 31. roseum may also be found on animals, at least it is 

 inoculable to guinea pig. M. caninum has been found only once on dog. M. 

 equinum, nonnall}^ adapted to and not uncommon on the horse, is inoculable to 

 man and the guinea pig, producing only evanescent lesions in the latter. 



For the main group of Trichophyton which still bears the name, let us 

 retura in the main line of Ectotrichophyton to the transitional species, E. multi- 

 color. Nodular organs and spirals have disappeared. The transition to Tricho- 

 phyton flavum is easy, although here the closterospore has disappeared. The 

 species has not been found on domestic animals but is inoculable to the guinea 

 pig. In this group (neoendothrix of Sabouraud), the juvenile condition of 

 the lesion with the spores borne both without and within the hair persists for a 

 long time. 



The wholly endothrix species of Trichophyton form two groups: (1) those 

 in which the craterif orm type of colony is retained, where the hairs do not break 

 quite so readily, and the basal portion is folded in the scale, (2) the more 

 advanced group in which the colony has become umbonate and the hair breaks 

 at the mouth of the follicle. There is some degeneration of chlamydospore 

 and aleurospore traceable in this group. The end members no longer bear 

 aleurospores in compound thyrses. 



Returning to the main line in Ectotrichophyton we find E. scorteum as a 

 transitional species to the Microsporum group, where the hair is invaded by 

 mycelium and surrounded by a sheath of spores. In the Neomicrosporum group, 

 the lesion has retained some of the suppurative character found in Ectotricho- 

 phyton. Usually the same organism is capable of attacking several host species. 

 The closterospore is highly developed and characteristic. The chlamydospore is 

 rare but functions as a cell of a closterospore, when present. Aleurospores are 

 present and normal. In Eumicrosporum, the closterospore has become rare and 

 reduced in number of cells until it is hardly more than a chlamydospore with a 

 specialized shape but normal functions. Parasitism has become more specialized, 

 until it is limited to prepubertal individuals in man and is very difficult to 

 inoculate into any experimental animal. A still more specialized group is the 

 subgenus Kamhayashia in which some species have completely lost the clostero- 

 spore and aleurospore. This subgenus seems confined to the yellow race of man 

 as a host (see p. 545). 



A somewhat similar line of degeneration may be traced in Achorion. 

 Achorion gypseum (reported by Nannizzi to produce ascospores and conse- 

 quently to belong in Gymnoascus) is very close to Neomicrosporum in the type 

 of lesion produced (cf. Biltris 1929), but more suppurative, producing kerion 



