However preposterous such reasoning on her part may appear to us and however vaguely and subconsciously the mental process may have been carried on, it offers the only theory adequate to explain all the facts and to account for the almost incredible union of contradictory traits in her character. The enthusiasm of the experimenter overbore in her the native sympathy of the woman. She observed the writhings of her poisoned victims with as “much delight” as Professor Mantegazza confesses he felt in studying the physiology of pain in the dumb animals “shrieking and groaning” on his tormentatore. “The physiologist,” says Claude Bernard, “is no ordinary man. He is a savant, seized and possessed by a scientific idea. He does not hear the cries of suffering wrung from racked and lacerated creatures, nor see the blood which flows. He has nothing before his eyes but his idea and the organisms, which are hiding the secrets he means to discover.” Marie Jeanneret was a fanatic of this kind. She, too, was a woman possessed with ideas as witches were once supposed to be possessed with devils. Had she prudently confined her experiments to the torture of helpless animals, she might perhaps have taken rank in the scientific world with Brachet, Magendie and other celebrated vivisectors, and been admitted with honour to the Academy, instead of being thrust ignominiously into a penitentiary. The assertion as regards any supposed case of madness, that “there’s method in it,” is popularly assumed to be equivalent to a denial of the existence of the madness altogether. But psycho-pathology affords no warrant for such an assumption. An individual, who commits murder under the impulse of morbid jealousy, pecuniary distress, social rancour, political or scientific fanaticism, or any other form of monomania, is not the less the victim of a mind diseased because he shows rational forethought in planning and executing the deed. His mental faculties may be perfectly healthy and normal in their operation up to the point of derangement, from which the fatal act proceeds. No chain is stronger than its weakest link; and this is equally true of physical and psychical concatenations. Under such circumstances the sane powers of the mind are all at the mercy of the one fault and are made to minister to this single infirmity.