990 



A SCOM YCETES A ND BA SIDIOM YCETES 



Genus Microsporum Gruby, 1843. 



Definition, — Gymnoascaceae with only Fungi Imperfecti forms 

 known; producing in the lesions mycelial filaments and mycelial 

 spores, which are small, roundish, and about 2-3 microns in diameter. 

 In cultures hyphag bearing sessile conidia may be seen and septate 

 or non-septate fusiform bodies. The lesions in man do not produce 

 yellow favic scutula. 



Type Species. — Microsporum audouini Gruby, 1843. 



Remarks. — The fungi belonging to this genus are generally para- 

 sitic in the hairs and hair follicles, but may attack glabrous parts. 

 When parasitic in the hairs, they are characterized by the mycelial 

 spores being roundish, small (2 to 3 /^), and irregularly arranged 

 in a mosaic-like manner. They are easily cultivated on Sabouraud's 

 and other sugar media (see Genus Trichophyton, p. 996) . In cultures 

 the microsporons proliferate by sprouting with branching of the 

 mycelium ; and also, often, by — 



1. Spore-Bearing HyphcB — of type Acladium, the conidia being 

 oval, 3 to 4 in length, and 2 to 3 in breadth. They are not 

 supported by short sterigmata, as is the case in the genus Tricho- 

 phyton. 



2. Terminal Septate or Non-Septate Spindles. — These structures 

 are found at the end of certain filaments, and may be considered 

 to be modified terminal conidia. They are large fusiform struc- 

 tures, 30 to 60 in length, and 15 to 18 in breadth. They have 

 granular contents, and may be septate or non-septate. The surface, 

 especially at the apex, presents some peculiar hair-like formations 

 which are not observed in the spindles of the fungi of the genus 

 Trichophyton. 



3. Chlamy do spores. — Certain mycelial articles become expanse, 

 ovoid, or ampuUiform, 22 to 18 ^ in length, and 6 to 8 in breadth. 

 Their protoplasm may be granular, and the membrane may become 

 much thicker and have a double contour. These elements are 

 chlamydospores. They are generally found when the fungi vege- 

 tate under unfavourable conditions. Another structure often 

 seen in fungi of the genus Microsporum are the so-called denticu- 

 late or pectinate bodies, which are mycelial segments, generally 

 curved, showing on one side^the convex side as a rule- — several 

 small protruding processes. Bodin has demonstrated these pro- 

 cesses to be mycelial tubes arrested in their development. 



Pleomorphism.— After a time, and often rapidly, the cultures of ' 

 microsporons lose their characteristics and become pleomorphic. 

 This phenomenon is not very prominent, however, in the most 

 important species — viz., Microsporum audouini — while it is very 

 accentuated in some microsporons of animal origin, especially 

 M. minimum, in which, according to the complete investigation 

 carried out by Bodin, two types may be met with: — 



1. The downy type [Acladium type). 



2. The glabrous type iEndoconidium type). 



