54 MICROBES, FERMENTS, AND MOULDS. 
infected hairs, surrounded by spores; but, while 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 
sears 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. 
Tt has been already said that fungi prey upon each 
other. Thus Achorion has fora parasite Puccinia favi, 
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 
hyphe, some simply nutritive, others with short 
articulations, separating into chaplets of rounded 
