They put frogs on the boils and waited until the frogs had sucked out all of the liquid then they would explode. This is only one of the ways that they tried to cure the Black Death.
There are cures for the plague but back when it was thriving there was only old wives tales (like putting a toad/frog on the boils/buboes or like shaving a chicken and placing it's butt on the boil)...
In the medieval times; they didn't. We have antibiotics now that can fight it, but in the middle ages all kinds of ridiculous methods were used that did not work. Some as crazy as drilling a hole in...