Is a learned emotion that may someone from doing something they know is wrong.

Guilt would most likely be the answer. Guilt is an emotion we learn through socialization, so when we're growing up, and even after growing up. 

When we feel guilty about something, we know we have probably done something we shouldn't have done. What is interesting is that guilt is very culturallly specific. What might bring feelings of guilt to someone in a particular culture wouldn't do that in another one. 

Imma gonna say go with the very first answer (:

Blood transfusions were rarely done and often fatal; they were outlawed until the nineteenth century.