in the 18th century, there were three primary professions in medicine: physicians, surgeons, and apothecaries, although the barriers among them were starting to become blurred. william cullen practiced as all three. because medical practitioners were not as established as they are now, patients generally took advice from a myriad of sources, including personal experience, books, and several consultations. furthermore, because the diagnostic tools were not as advanced, patient history was the primary and most important information for the physicians to diagnose their patients. there were no strict government regulations in place for physicians, surgeons, and apothecaries. as a result, to become successful in the medical marketplace depended more on social skills than on medical expertise, similar to other forms of businesses. cullen was one of the more successful physicians because of his shrewdness in handling difficult patients. teaching at the university and seeing patients at the edinburgh infirmary as charity also helped cullen become more famous.