Bones McCoy was the chief medical officer on the Enterprise and frequently argues with Spock.  He is Kirks other main advisor and he and Spock often had very different viewpoints on how to handle the situations the crew found themselves in. Bones was a compassionate scientist and the glue that bonded the relationship of the three.  He also had a catchphrase - 'He's Dead Jim' but I don't know if he ever really said 'Its life Jim, but not as we know it'