In the eruptive malady called the white-sickness all the hairs get
grey; and instances have been known where the hair became grey while
the patients were ill of the malady, whereas the grey hairs shed off
and black ones replaced them on their recovery. (Hair is more apt to
turn grey when it is kept covered than when exposed to the action of
the outer air.) In men, the hair over the temples is the first to turn
grey, and the hair in the front grows grey sooner than the hair at the
back; and the hair on the pubes is the last to change colour.