354 FIRST FORMS OF VEGETATION. 
disease called Plica polonica, which occurs in Poland 
and the adjoining countries, said to be of Asiatic 
origin, and to have first appeared in Europe in 
the thirteenth century, in which the hairs get 
swollen, matted together, and become endowed 
individually with the most exquisitely painful sensi- 
bility. This fearful disease is caused by the growth 
of a fungus upon the head; the compact mass 
of hair being sprinkled over, as with flour, with 
its germs. The allied disease, known by the name 
of chin-welk or mentagra, affecting the beard of 
men ; the sordes on the teeth, occurring in persons 
affected with low typhoid fever ; the aphthe or 
thrush, as the white spots like curdled milk which 
cover the mucous membrane of the mouth and 
palate of infants are called; the disease called 
scald-head and ring-worm, so frequent on the 
heads of children, and so highly infectious; the 
pityriasis, or dandriff, which produces pale-brown 
circular spots on the neck and breast, accompanied 
by abundant desquamation of dry branny scales, 
constantly renewed ; the yaws, so prevalent in the 
West Indies, and in some parts of Africa; the 
elephantiasis, which so horribly disfigures the 
Egyptians ; the ichthyosis or fish-skin of the 
East ; the pellagra of the plains of Lombardy and 
Northern Italy ; the formidable disease known as 
the fungus-foot of India, which is very common 
