534 



PATHOGENIC FUNGI 



the dog, the cat, and the horse, and these are of importance from 

 the frequent infection of man from such animal sources. Other 

 species, e.g., M. velveticum, M. umbonatum, and M. tardum, pre- 

 senting cultural differences, have been observed in man. 



Trichophyta. These fungi, 

 which constitute the large-spored 

 ringworms, are associated with 

 ringworm of the scalp, with the 

 various manifestations found in 

 the beard, and with the conditions 

 occurring on the smooth parts of 

 the body and in the nails. They 

 are characterised by the fact that 

 the mycelium, wherever observed, 

 whether in epithelial squames, in 

 pus, or within a hair consists of 

 chains of oval or rectangular spore- 

 like bodies (Fig. 165). These in the 

 largest forms are from 5-8 /JL in 

 diameter, but smaller forms ap- 

 proaching the size of the spores in 

 microspora also exist. There is 

 thus not the same differentiation 

 between mycelium and spore for- 

 mation seen in the microspora, nor 

 does the irregular mosaic appear- 

 ance of the spores in the latter 

 come into evidence. There is, 

 however, the same primary affec- 

 tion of the superficial epithelium, 

 and in hairy parts the invasion of 

 the hair where it emerges from its 

 sheath. 



In certain species there is a 

 tendency for the parasite to in- 

 vade the follicle by growing down 

 between the hair and its sheath 

 for a considerable period before 

 the hair itself is invaded, the so-called Trichophyton ectothrix. 

 A great number of trichophyta presenting different cultural 

 characteristics have been isolated. These are associated with 

 difference in site of election and in method of spread in different 

 parts of the body. There is evidence that certain varieties are 

 more common in some countries thanjn others ; for instance, r jn 



FIG. 163. Microsporon Audouini 

 on Sabouraud's maltose agar. 



