When Emilie is Writing out and signing his confession , you can clearly see that he is using a marker with a thin tip on it .
Charon is shot and Porthos prepares to cut it out by holding a knife over a flame. But in the 17th Century, no one knew about microbes so no one preparing for surgery would have known of the need to sterilize surgical instruments. In actuality, through the American Civil War, surgeons went from patient to patient without ever washing their hands or instruments.