54. MICROBES, FERMENTS, AND MOULDS. 



infected hairs, surrounded by spores; but, wbile the 

 centre is in process of healing, the fungus extends to 

 the periphery and continues to spread. The raised 

 surface of the patch is formed by this parasitic growth, 

 which forms a circular excrescence, always increasing 

 in size, while raising and thickening the epidermis. 

 The parts affected by the mycelium are characterized 

 by a slight suppuration throughout the patch ; the 

 indurated tissue is gradually absorbed, leaving deep 

 scars which persist after a cure has been effected. 



The mycelium is found on infected hairs between 

 the coats of their bulbous roots, while the numerous 

 spores are only found between the epidermic layers of 

 the hair. 



This fungus may be inoculated in all parts of the 

 skin, but its favourite site is the head, where it pro- 

 duces the disease long known as ringworm, or favus. 



It has been already said that fungi prey upon each 

 other. Thus Achorion has for a parasite Pucciniafavi, 

 a minute fungus of a reddish-brown colour, which is 

 often developed on the whitish epidermic scales which 

 cover the mycelium on fresh spots of ringworm. The 

 same parasite has also been observed on Pityriasis. 



Trichophyton tonsurans. — This fungus, allied to 

 the preceding, subsists likewise on skin covered with 

 hair, and produces tinea tonsurans. 



It is formed of a mycelium with two sorts of 

 hyphse, some simply nutritive, others with short 

 articulations, separating into chaplets of rounded 



