MICROSPORUM AUDOUINI 



689 



M. audouini var. equinum is the cause of the contagious herpes of colts. In 

 cultures it is highly pleomorphic. It is infective for horses, guinea-pigs and dogs. 

 The parasite may develop on man and produce small, transient, erythematous 

 lesions. 



[Microsporum felineum is parasitic on the cat and may be transmitted to both 

 children and adults. It grows with great rapidity in artificial culture, and is charac- 

 terized by the flat disc-like appearance of its culture with a small central raised 

 button marking the site of inoculation of the medium. Cats, dogs, and guinea-pigs 

 are easily infected experimentally.] 



1. Microscopical appearance. An infected hair after being treated with 

 potash (p. 690) will be seen to be covered with a mosaic of " mycelial 

 spores " : these spores measure 1-3/z in diameter, are round or polyhedral 

 from mutual pressure, irregularly agglomerated, never arranged in chains, 

 and possess a clear transparent envelope (fig. 327). The " spores " never 

 penetrate into the interior of the hair. 



FIG. 327. Microsporum audouini. Photograph of an hair showing spores forming 

 a sheath around the shaft. (Kindly lent by Dr. H. G. Adamson.) 



Microsporum audouini grows on the hair from above downwards : the 

 older the lesion the more deeply does the parasite sink into the part around 

 the root of the hair. 



2. Cultural characteristics. Lay an hair on a sterile slide, cut it into 

 very short lengths, and sow each piece on a separate tube of one of the 

 media used for the cultivation of the Tricophytons. In the majority of cases 

 a pure culture will be obtained in the primary growths. 



Potato. On potato the growth of M. audouini is characteristic. After 

 7-8 days a grey streak is visible which tends to change its colour to reddish- 

 brown as time elapses and about the tenth to the twelfth day small bouquets 

 of a scanty short down appear here and there. The fungus retains its vitality 

 on potato for several months ; under similar conditions the tricophyton dies 

 in 18 days. 



Bee.r-wort-agar. After 3-4 days tufts of the mycelium strike out and 

 grow into the substance of the medium, taking the silky appearance of 



2x 



