How we cite our quotes: (Chapter.Paragraph)
Quote #1
It seemed to them that their looks were penetrating each other's flesh and driving in sharp, clear statements. At times, they thought they could hear one another speaking aloud; their senses were distorted and sight became a kind of hearing, strange and fine; so clearly could they read their thoughts on the other's face, that these thoughts acquired a strange, resonant sound that shook their whole bodies. (21. 18)
After Camille's murder, Thérèse and Laurent develop a strange ability to read each other's silent thoughts. All they can think about is Camille's death, and they find it terrifying that they can see and hear each other's minds.
Quote #2
Mme Raquin was gradually being overtaken by paralysis [...]. The poor old woman was starting to mutter phrases that were not connected to one another, her voice was growing weaker and her limbs were failing one by one. She was turning into a thing. (24.11)
As Mme Raquin slowly loses her ability to speak, she gradually turns into an inanimate object. This seems to suggest that language and communication is an essential part of our human identity, and without it, we're reduced to being mere objects.
Quote #3
The stroke that had been threatening Mme Raquin's health arrived. Suddenly the paralysis, which for several months had been creeping along her limbs [...], seized her by the throat and immobilized her body. [...] Her tongue had been turned to stone, her hands and feet had stiffened. (26.1)
Mme Raquin's stroke results in both paralysis and muteness. The image of her tongue turning to stone also suggests that Mme Raquin has been reduced to a thing, an immobile statue.