He could not help his heart beating at each double knock of the postman in case there might be a letter from Mildred sent on by his landlady in London; but he knew that there would be none. Now that he could think it out more calmly he understood that in trying to force Mildred to love him he had been attempting the impossible. He did not know what it was that passed from a man to a woman, from a woman to a man, and made one of them a slave: it was convenient to call it the sexual instinct; but if it was no more than that, he did not understand why it should occasion so vehement an attraction to one person rather than another. It was irresistible: the mind could not battle with it; friendship, gratitude, interest, had no power beside it. Because he had not attracted Mildred sexually, nothing that he did had any effect upon her. The idea revolted him; it made human nature beastly; and he felt suddenly that the hearts of men were full of dark places. Because Mildred was indifferent to him he had thought her sexless; her anaemic appearance and thin lips, the body with its narrow hips and flat chest, the languor of her manner, carried out his supposition; and yet she was capable of sudden passions which made her willing to risk everything to gratify them. He had never understood her adventure with Emil Miller: it had seemed so unlike her, and she had never been able to explain it; but now that he had seen her with Griffiths he knew that just the same thing had happened then: she had been carried off her feet by an ungovernable desire. He tried to think out what those two men had which so strangely attracted her. They both had a vulgar facetiousness which tickled her simple sense of humour, and a certain coarseness of nature; but what took her perhaps was the blatant sexuality which was their most marked characteristic. She had a genteel refinement which shuddered at the facts of life, she looked upon the bodily functions as indecent, she had all sorts of euphemisms for common objects, she always chose an elaborate word as more becoming than a simple one: the brutality of these men was like a whip on her thin white shoulders, and she shuddered with voluptuous pain.