78 VEGETABLE PARASITES 



and readily broken off, instead of pulled out. 

 There is, of course, considerable risk of conta- 

 gion, especially of the nails, for the operator. 

 Favus, fortunately, is not a common disease, and 

 is found naturally amongst the lowest classes, 

 where misery, and its accompaniment, dirt, give 

 a large planting field to these spores, floating in 

 the air and water, and on nearly every substance 

 with which the skin comes in contact. During 

 disease, this fungus, achorion 8ch'6nleini, does 

 not flourish well. 



Ringworm of the head and body is the next 

 parasitic disease we will describe. Its technical 

 name is herpes tonsurans, and it is due to the 

 presence of a fungus called trichophyton tonsurans, 

 showing under the microscope the spores and 

 sporular tubes we have above described, in the 

 root and shaft of the hair. The first symptoms 

 •of the growth of the parasite is itching, followed 

 by a generally vesicular eruption, taking a circular 

 form. The hairs, where the affection exists, be- 

 come dry and dull, losing their lustre, and gray- 

 ish or reddish, according to the color of the per- 

 son's hair; i. e., light or dark. They are also 

 twisted and very brittle, breaking off a little way 



