Just a footnote...
I have read the entire 20 1/2 book 'Master and Commander' series which describes Medical Practice at about this time. My recollection is that Arsenic was frequently used as a 'curative' medicine.
Arsenic was used as chemotherapy until surprisingly recently. Instead of arsenic, radioactive stuff is used, which can hardly be touted as an improvement. :') The concept is to poison the tumor so it dies, but not give the patient so much poison that they die.