In the book it says somthing akin to "The hands of a healer are the hands of a king" which is the begining of a poem. It bascially means that kings should not just beable to make war and should beable to heal...all in the numenorain timeline can heal now...but only with kingsfoil...Aragorn has mega ultra leet beat ass whicked (or in other words really good) healing powers beacuse hes got some Maiar and Elven blood in him, as most numenorains do.