Plague doctors (wicki) were special medical physicians who treated plague victims. Their skull-like mask had a long beak and looked truly freaky. The beak was filled with scented materials and straw. The straw was thought to filter out “miasmic bad air”. In case you were wondering the eyes were traditionally covered with glass.
The talented Chrisopher Lovell created this wonderful illustration, called ‘Plague Dr’. It depicts a skulled figure wearing one of these plague masks. Though as you can see, this fella requires no protection from the plague. Here is another link to a Tumblr dedicated to plague Doctors.