How we cite our quotes: (Chapter.Paragraph)
Quote #4
The young man's sanguine nature, his resonate voice, his hearty laughter and the sharp, strong smells that he emitted disturbed the young woman and plunged her into a kind of nervous anxiety. (5.41)
Laurent's temperament exerts a powerful force over Thérèse, who feels incomplete when she isn't with him. These two are truly crazy about each other. And by the end of the novel, they drive each other crazy too.
Quote #5
Laurent was amazed at finding his mistress beautiful. [...] The young woman, sinuous and twisting, possessed a strange beauty, an utter abandon. It was as though her face had been lit from inside and flames were leaping from her flesh. And around her, her burning blood and taut nerves released hot waves of passion, a penetrating, acrid fever in the air. (7.5)
Laurent's desire for Thérèse is unleashed when he sees her naked for the first time. Zola emphasizes here how heredity affects Thérèse's behavior: her "burning blood" (inherited from her mother) and her "taut nerves" are the two factors that determine her need to be with Laurent. This affair is destined to be, we guess.
Quote #6
For a fortnight, Laurent had not been able to go near Thérèse, and he realized how essential the woman had become to him. Indulging in his lusts had created new appetites for him, which urgently demanded satisfaction. [...] A raging of the blood had infected his flesh and now that his mistress was being taken away from him, his passion burst out with bind fury. [...] Everything in the blossoming of this animal being seemed unconscious: he was obeying his instincts, letting himself be driven by the will of his body. (9.5)
Zola presents Laurent's desire for Thérèse as an animalistic need—an uncontrollable "instinct." There is no mention here of love because Laurent supposedly has no soul. It'd be pretty hard to love anything or anyone if you didn't have a soul.