Sentence:  Favus is a chronic inflammation of the hair-follicles, associated with the production of a peculiar yellowish substance which surrounds the cylinder of the hair, and is seen through the epidermis as a minute circular spot, not raised above the level of the skin. The yellow substance, after a short period, escapes from the follicles upon the surface of the epidermis, and <WSD>desiccates</WSD> into yellowish friable crusts, forming a distinct cup with an inverted border, around the base of each hair. 
Meaning of the word marked with <WSD> tags:  To become dry; to dry up.