Is it necessary to insist on the presence or absence of anatomical lesions which one tries to ascertain at the post-mortem examination? Shall we say with Sandras, Axenfeld, Huchard, Hack, Tuke, that neuroses are diseases without lesions? One finds lesions in general paralysis which is ranged with insanity and we find some also in epilepsies which are considered as neuroses; one no more finds lesions in melancholic conditions than in conditions of obsessions. Besides, as I have often repeated, this absence of lesions is of no importance; it is quite in keeping with our ignorance. Every one admits that organic alterations more or less momentary, but actually not suspected, must exist in neuroses as in other diseases. Neuroses as well as psychoses are much more likely to be diseases with unknown lesions than diseases without lesions, and it is impossible to take this characteristic into account to distinguish the ones from the others. In reality, the notion of lunatic has lost its former superstitious signification and it has taken no precise medical signification. That word is now the term of the police language. It indicates only an embarrassment felt by the police before certain persons' conduct. When an individual shows himself to be dangerous for others, the public administration has the habit of defending us against him by the system of threats and punishments. As a rule, in fact, when a normal mind is in question, threats can stop him before the execution of crime, and punishments, when crime has been committed, can prevent him from beginning again; that is the psychological fact which has given birth to the idea of responsibility. But in certain disorders it becomes evident that neither threats nor punishments have a favorable effect, for the individual seems to have lost the phenomenon of responsibility. When an individual shows himself to be dangerous for others or for himself, and that he has lost his responsibility, we can no longer employ the ordinary means of defense; we are obliged to defend ourselves against him, and defend him against himself by special means which it is useless to apply to other men; we are obliged to modify legal conduct toward him. All disorders of the mind oblige us to modify our social conduct toward the patient, but only in a few cases are we obliged to modify at the same time our legal conduct; and these are the sort of cases that constitute lunacy.