RALPH:  This is odd, Davina. Macduff and Malcolm are in England, soliciting King Edward's help in overthrowing Macbeth. Then a doctor enters, and Malcolm launches into this long explanation of how King Edward possesses this miraculous power to cure a particular disease. 

DAVINA:  The disease they’re referring to is scrofula, a tuberculosis infection that causes the lymph nodes to become hideously enlarged, a not uncommon disease in Shakespeare’s England. During King Edward's reign, a superstition arose that the king had the power to cure it. This practice, called “touching", would be performed by subsequent English monarchs for the next 700 years. 

RALPH:  That's interesting, Davina, but it doesn't explain why Shakespeare included this in the play.

DAVINA:  Supposedly, the cure consisted of a prayer that was passed down by each monarch to his or her successor. Perhaps Shakespeare is flattering King James, the king at the time the play was written and performed, by referring to his newly acquired power.

RALPH:  Interesting… though James is from Scotland, so maybe he’s playing to the English nobles in the audience who are thinking,  "Well, James, you may have ruled some second rate country like Scotland, but now that you’re king of England, you’re in the big leagues. English kings can work miracles.” 

DAVINA:  According to scholars, actually, King James thought this practice of “touching” was nonsense. His advisors had to push him to do it. But his grandson, Charles the Second, was the opposite. He probably didn’t believe in miracles either, but he understood public relations. During the 19 years of his reign, he "touched" over 100,000 victims of the disease.