Sentence:  they impressed my youthful mind with a sincere aversion to the northern inhabitants of Britain, as a people bloodthirsty in time of war, treacherous during truce, <WSD>interested</WSD>, selfish, avaricious, and tricky in the business of peaceful life, and having few good qualities [...]. 
Meaning of the word marked with <WSD> tags:  Motivated by considerations of self-interest; self-serving.