If you were ill one alternative was to visit a physician (17th century Doctor). Depending on the location, our garrison members will portray different levels of medicine. At one end of the spectrum, the empiricist (a person who has found cures by trial & error), and has been licensed to produce those cures, will sell his wares to the poor.
Further up the scale, the apothecary will make simples (made from a single ingredient) and compounds (several ingredients) from herbs and other materials. Originally produced to a physician's prescription only, these were sold to those who could afford the price of the medicine, but not the price of a consultation with the physician.
At the top comes the physician astrologer. He will diagnose a patient's illness and prescribe medicine to be bought from the apothecary. But physicians are in short supply and his prices are out of the reach of the common folk, except perhaps on a few days in each year when some charity work might be done.