The literature of medicine contains numerous references to the mental disturbances due to opium and morphine. Krafft-Ebing[224] says of the habitual user that "Intelligence, it is true, is practically spared, but the highest mental functions—character, ethic feeling, self-control, mental energy, and force—always suffer.... In severe cases we find, in addition, weakness of memory, especially defect in the power of exact reproduction, difficulty of intellectual activity that may reach the degree of torpor, occasionally psychic depression reaching even marked dysthymia and taedium vitae, great emotionality, and, in general, profound deficiency of resistive power to affects; and besides, there may be episodically nervous restlessness, excitement, even attacks of fear due to vasomotor causes, and occasionally visual hallucinations." He also describes hallucinatory delirious conditions due to abstinence which strongly suggest alcoholism. In addition to clouded states of the same kind, Paton[225] speaks of the early occurrence, in chronic cases, of marked symptoms of hysteria. Apprehension and anxiety develop with mild suspicions and a moral deterioration very similar to that induced by alcohol. There may be considerable irritability and egotism, with a suggestion of flight of ideas and motor restlessness. Hallucinations and delusions are sometimes present, particularly if alcoholism is a complicating factor. Hyperesthesias, paresthesias and anesthesias are common. Barker[226] also speaks of a degeneration of character evidenced by ethical defects, lying, egotism and loss of memory. Under abstinence symptoms he includes restlessness, anxiety, despair, vomiting and delirium. White[227] regards the neuropathic diathesis as the most important cause of the morphine or opium habit. In habitual users he has noted hallucinated states with a paranoid coloring or a definite delirium. He has also observed delusions of persecution and poisoning, but emphasizes the importance of the gradual mental deterioration.