js5972, the mask were worn by doctors during the time of the plague. these "doctors" were hired by towns to treat plague victims only and were more often than not not very skilled. the plague doctors wore the mask filled with aromatic herbs and items because of the foul smell of the ill and it was believed that the foul oder carried the plague. needless to say these plague doctors did not last very long. i think italy has a festival in which the plague doctor mask is one of the popular ones to ware. hope this answers at least part of your question.
Panther