The 19th century enables the development of the clinic: the doctor learns to read the signs of illness in the body. This visual investigation is reinforced by the dialogue the doctor sets up with his patient : even as the questioning to which he submits him or her enables him to build up the illness’ story, what he says is supposed to give meaning to his patient’s symptoms. Although they are felt to be and to need to be the locus par excellence of the representation of this investigative dialogue, realist and naturalist novels in the second part of the 19th century, despite their desire to trasnsmit these new medical discourses and to participate in the construction of the knowledge of their times, seem always to be avoiding it or deviating from its meaning. This paper purposes to study the modalities by which medical discourse is transformed and thus highlight the functions it takes on within the narrative world.