In "Albatross", Spock breaks McCoy out of prison to find a cure for a disease which is killing the Enterprise crew. The Vulcan reminds him that if he goes and fails, he will also die. Bones' response? "I'm a doctor, Spock. A doctor. Get us beamed aboard!" Not since "The Empath" has one of McCoy's reminders about his profession been so heart-meltingly awesome.
In "The Pirates of Orion", McCoy's attitude around the terminally ill Spock.
Thelin: True. A warrior race has few sympathies, but one we do possess is for family. In your time plane, you will live and so will your mother. That is valuable. [Gives Spock the Vulcan salute] Live long and prosper in your world, Commander Spock.
Spock: [Returning the gesture] And you in yours, Commander Thelin.