This link takes you to the opening address that Dr. T. H Crozier gave to the new medical students of Royal Victoria Hospital in Belfast, in 1956. He addresses how medicine has changed, and the various folklore behind medicine, such as sacred wells, amulets and witch-doctors.
One of the parts I found really interesting is this:
Seventh sons are credited with magical healing powers. Seventh sons of seventh sons (no daughters intervening) are even more potent healers. A seventh son (not left-handed) could be called in to hasten tardy childbirth by giving the patient three shakes; if no seventh son available, any lucky man would do, provided he was not married to a red-haired wife. Babies born feet-first are reputed to become skilful manipulators of bones and joints. (50)