LARGE-SPOKED RINGWORM 



537 



(Fig. 163), and a number of allied species have been isolated in 

 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. velveticitm, M. vmibonatum, and M. tardum, pre- 

 senting cultural differences, have 

 been observed in man. 



Trichophyton. — These fungi, 

 which constitute the large-spored. 

 ringworms, are associated with 

 ringworm of the scaip, with the 

 various manifestations found in 

 the beard, and with the con- 

 ditions 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. 166). These in the 

 largest forms are from 5-8 fx in 

 diameter, but smaller forms ap- 

 proaching the size of the spores 

 in microspora also exist. There 

 is thus not the same differentia- 

 tion between mycelium and spore 

 formation seen in the microspora, 

 nor does the irregular mosaic ap- 

 pearance of the spores in the 

 latter come into evidence. There 

 is, however, the same primary 

 affection of the superficial epi- 

 thelium, 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 

 invade 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. 



Fig. 164. — Mierosporon audoui'ni 

 on Sabouraud's maltose agar. 



