458 MEDICAL MYCOLOGY 



The next group from which the other genera seem to be derived by spe- 

 cialization both as to the organ attacked and as to the host, with the usual 

 accompanying degeneration phenomena, is the genus Ectotrichophyton (Tricho- 

 phyton microide group). The lesion, starting in the horny layer of the epi- 

 dermis, invades the hair follicle where it develops a sheath of mycelium and 

 spores about the infected hair, suggesting the condition which we find more 

 highly specialized in Microsporum and Achorion. It is easily inoculable into 

 a wide range of experimental animals with little apparent specialization on any 

 one host. The lesion is usually of the kerion or sycosis type accompanied by 

 inflammation and suppuration. Closterospores and spiral ornamentation and 

 nodular organs characterize the genus as a whole although, as we shall see 

 later, the beginnings of specialization and consequent degeneration may be 

 seen within the genus since any one or two organs may be absent on some of 

 the usual media. 



Closterospores are abundant onlj' in the first few days of culture. Later 

 and in subcultures, the relative number diminishes and the chlamydospores as- 

 sume their functions. The nodular organs, which seem to have developed 

 from degenerating closterospores, resemble in some species coiled chains of 

 chlamydospores. Both closterospores and chlamydospores have 3-5 nuclei per 

 cell and germinate by several germ-tubes after a rapid multiplication of 

 nuclei. The cells of the closterospores are often subspheric and show forms 

 transitional to the chlamydospores. The number of nuclei in the secondary 

 mycelium is unknown but the aleurospores produced by it are uninucleate. 



The most primitive species seems to be Ectotrichophyton memtagrophytes 

 which produces practically all the organs characteristic of the dennatophytes, 

 and infects a large number of hosts with kerion formation. E. circuluscentricum 

 appears to be closely related but shows the beginnings of separation. From 

 these species we have at least three diverging lines : Achorion gypseum which, 

 by increasing development at the mouth of the hair follicle, paves the way for 

 the Achorion line; the E. farinulentum line which continues the main trend of 

 evolution but has left out the nodular organ; and the E. lacticolor line which 

 has retained and even developed the nodular organ further only to lose it in 

 Pavotrichophyton. 



In Ectotrichophyton farinulentum and in E. scortenm the spiral begins to 

 disappear, being found only on pleomorphic mycelium; the primitive umbilicate 

 colony gradually gives way to an umbo ; both species seem restricted in distribu- 

 tion and in case of E. scorteum, the lesion is milder. The Microsporum line 

 probably emerges at about this point. In the E. griseum and E. erioton group, 

 the spirals have completely disappeared, the central area is often elevated and 

 sometimes folded, and beginnings of the transition from the powdery or 

 chalky to the woolly colony are found. In E. multicolor which form a transi- 

 tion to the Trichophyton line, the colony has become cerebriform and the lesion 

 less inflammatory (see p. 500). The further development of this main line lies 

 in E. felineum which produces closterospores and spirals on some of the com- 

 plex carbohydrate media but has lost the power tO' produce them on Sabouraud 



