Jim has given up that sport himself and confines himself to a little harmless duck- or snipe-shooting, or a little quiet trifling with the rats during the Christmas holidays, after which he will return to the University and try and not be plucked, once more. He has already eschewed green coats, red neckcloths, and other worldly ornaments, and is preparing himself for a change in his condition. 
Jim had given up green coats, red neckcloths, and hunting, to prepare himself for the change in his condition. 