The regiment, the mother, the mare

Vronsky's inner life is wholly taken up by his passion while his outer life runs on its old rails. The regiment is fond of him and proud that a man of his wealth and abilities has put its interests nearest his heart, and he feels bound to justify that view. He never speaks of his love and silences anyone who hints at it, yet the whole town knows; young men envy him precisely for Karenin's rank, and the young women who have long been weary of hearing Anna's virtues praised are already preparing lumps of mud to throw once opinion turns. His mother was pleased at first, thinking an intrigue in the best Society the finishing touch on a brilliant young man, until she heard he had refused an important post to stay near Anna and that this was a Werther-like passion rather than a graceful liaison. His brother, who keeps a ballet girl, objects only because it displeases those who must be pleased. Vronsky's other passion is horses, and he has entered the officers' steeplechase.

Tolstoy sets out the whole machinery of the coming ruin in one dispassionate chapter: what Society will forgive, who is holding the mud, and on what timetable. The brother's ballet girl establishes that the offence is never adultery. Introducing the mare in the last lines, beside a passion he must find rest from, is the structural joke the race will complete.