Corrected entry: In the scene immediately after Gena Davis receives a wound, she drinks some whiskey, or rum, and then pours some of the drink on her wound as an antiseptic. The understanding of germs and infection didn't occur until Pasteur's discoveries in the mid 1800's, well after the time period of this film.
Correction: True however they did understand keeping a wound clean. It was well known that the wadding from a pistol shot many times carried with the ball into the wound especially if done at close range. Festering would occur and that is why they later wished to cauterize it.