Sentence:  "I don't mean all of your friends&mdash;only a small proportion&mdash;which, however, connects your circle with that deadly, idle, <WSD>brainless</WSD> bunch&mdash;the insolent chatterers at the opera, the gorged dowagers, the worn-out, passionless men, the enervated matrons of the summer capital,nb...!" 
Meaning of the word marked with <WSD> tags:  Unintelligent, with little common sense.