How we cite our quotes: (Chapter.Paragraph)
Quote #1
Camille's blood had been impoverished by illness and he felt none of the urgent desires of adolescence. With his cousin, he remained a little boy, kissing her as he would kiss his mother [...]. When he played with her or held her in his arms, he felt as though he were holding a boy; not a shudder passed through him. And it never occurred to him on such occasions to kiss Thérèse's hot lips as she struggled free. (2.16)
Who wouldn't want to be married to a guy who kisses you like he kisses his mother? Yuck. In Zola's study of temperaments, Camille's weak ("lymphatic") temperament impairs his sexual virility. He feels no lust at all for Thérèse. Which makes him a really poor match for his insatiable wife.
Quote #2
She had never before seen a real man. Laurent amazed her: he was tall, strong and fresh-faced. [...] Laurent came from true peasant stock, with a somewhat heavy manner, rounded back, slow, studied movements and a calm, stubborn look about him. You could sense the swelling, well-developed muscles beneath his clothes, and the whole body, with its thick, firm flesh. Thérèse examined him curiously from his hands to his face, feeling a little shudder pass through her when she reached his bull's neck. (5.10)
When Thérèse first lays eyes on Laurent, she is immediately overcome by lust. His manly-man self is a perfect match for her passionate yearnings.
Quote #3
This world of animal pleasures had left him with urgent lusts. (5.24)
After indulging his sexual appetite with Thérèse, Laurent finds that he cannot stop thinking about her. He becomes consumed by the need to be with her. Constantly. This is the same need that later drives him to murder Camille.