If Snape made Sectumsepra and he knew the counter-course (vulnera sanentur), and Snape accidentally hit George Weasley with the curse, why didn't Snape heal him?
If Snape made Sectumsepra and he knew the counter-course (vulnera sanentur), and Snape accidentally hit George Weasley with the curse, why didn't Snape heal him?