This contribution tries to delimit the aesthetic course of a medical influence by taking as a revealing example the use by Huysmans of Great Hysteria defined by Charcot. Far from being limited to a theoretical corpus, the clinical knowledge of La Salpêtrière is in fact and before all associated, for the fin de siècle novelists, with a “savoir-représenter” – a capacity to represent –, an eminently aesthetic quality which Charcot himself attributes to Rubens’s demoniac painting so as to convert it into a perfect clinical description of Great Hysteria. Whereas naturalistic literature transposes this analogy between possession and hysteria by serving it with the anticlerical argument popularized by La Salpêtrière, Huysmans, for ideological reasons, chooses a divergent way which, however, does not deprive the pathological type of hysteria of its relevance, while making it the evidence of a mystery signifying the failure of the clinical perspective. The interest of the author of Là-bas in the knowledge of La Salpêtrière thus seems to be only its aesthetic aura, and he seemingly takes Charcot literally as regards the “power” that the clinician recognizes in “a well made description”.