992 ASCOMYCETES AND BASIDIOMYCETES 



Saprophytic Life — Cultures. — Microsporum audouini grows well 

 on Sabouraud's maltose agar and other media. The rate of growing 

 is slow. In maltose agar the growth becomes evident about a 

 week after inoculation under the appearance of a plaque of a so- 

 called ' satiny aspect/ beneath the surface. In a few days more, 

 aerial hyphae develop, extending above the surface. When the 

 development is complete — generally this takes about six to eight 

 weeks — the growth is roundish, covered with short greyish duvet, 

 and presents often a central knob, and some concentric rings of 

 a whitish-greyish colour. The cultural characters, however, are 

 variable, and pleomorphism occurs. The cultural characters have 

 been thoroughly investigated by Sabouraud, Fox and Blaxall, Bodin, 

 and others. The fungus very slowly liquefies gelatine; on potatoes 

 it produces a brownish discoloration compared by Sabouraud to 

 the colour of dried blood. 



Reproduction. — ^This takes place — 



1. By sprouts from the mycelial tubes. 



2. By small terminal and lateral conidia, there being spore- 

 bearing hyphae of type Acladium (see Fig. 494). 



3. By large unilocular or multilocular spindle conidia. These 

 spindles are large structures 30 to 60 (jL in length, and 15 to 18 in 

 breadth. They may be septate or non-septate. 



4. By formation of chlamydospores. 



Pathogenicity.- — Microsporum audouini causes the most obstinate 

 form of tinea capitis. The patches affected are often large, scaly, 

 and present stumps, provided with an opaque whitish sheath. It 

 seldom attacks glabrous parts of the body. M. audouini is ex- 

 tremely common in England; but rare in the South of Europe 

 (Italy), and extremely rare in the tropics. We have never seen 

 cases of ringworm due to M. audouini in Equatorial Africa or 

 Ceylon, but a few cases have been described in Brazil, in Mada- 

 gascar, and in Senegal. 



M. audouini seems to live only on the human subject, but closely 

 allied species have been found by Fox in cats, by Bodin in dogs, 

 and by Bodin, Fox, and others, in horses. 



Microsporum velveticum Sabouraud, 1907. 



Resembles closely M. audouini, but the cultures are more velvety, 

 the duvet being white instead of greyish, and of closer growth. 

 Not inoculable into guinea-pigs. This species seems to be fairly 

 common in North America. 



Microsporum umbonatum Sabouraud, 1907. 



Found by Sabouraud in two cases of microsporosis of the scalp 

 contracted in Russia. The appearance of the growth when it has 

 reached complete development (about twenty-five to thirty days 

 after inoculation) has been compared by Sabouraud to the appear- 

 ance of an ancient round shield, with a central conical formation 

 representing the umbo of the shield. Not inoculable into guinea- 

 pigs. 



