104 BACTERIOLOGY. 



licles, especially of the scalp, and forms yellow crusts 

 about the base of the hairs. If the crusts are re- 

 moved and examined under the microscope, the para- 

 sites can be found in them. The disease is very 

 resistant to treatment. 



RINGWORM. 



This is a very common affection among children, 

 and is caused by the Tinea trichophyton. There are 

 three types of the parasite: the Tinea tonsurans, 

 which attacks the hairs of the scalp ; the Tinea sycosis, 

 which attacks the hairs of the bearded part of the 

 face, and the Tinea circinata, which attacks the skin. 

 It starts as a slightly elevated, scaly spot, which 

 gradually widens, forming a red, scaly patch, with 

 raised edges. The hairs invaded by the parasites 

 break off and leave the center devoid of hair. The 

 disease spreads from one person to another by direct 

 contact. 



