The existence of psychical abnormalities in the subjects of tics is no new observation. Charcot[18] used to say that tic was a psychical disease in a physical guise, the direct offspring of mental imperfection--an aspect of the question which has been emphasised by Brissaud and by ourselves on more than one occasion.[19] How is the involuntary and irrational repetition of a voluntary and rational act to be explained? Why is inhibition of a confirmed tic so laborious? It is precisely because its victim cannot obviate the results of his own mental insufficiency. Exercise of the will can check the convulsive movement, but it is unfortunately in will power that the patient is lacking. He shows a peculiar turn of mind and a certain eccentricity of behaviour, indicative of a greater or less degree of instability (Brissaud). Noir writes in much the same strain, that careful examination will readily demonstrate the secondary nature of the motor trouble; behind it a mental defect lurks, which may pass for singularity of character merely, or childish caprice, but which none the less may be the earliest manifestation of fixed ideas and of mania. It is a matter of some difficulty to describe adequately the features of this mental condition; their extreme variability has its counterpart in the diversity of the motor phenomena. In this polymorphism of psychical defect is justification for the numbering of the tic patient with the vast crowd of degenerates, and indeed Magnan[20] is content to consider tic one of the multitudinous signs of mental degeneration. As a matter of fact, one does find numerous physical and mental stigmata in those who tic, just as one finds them in those who do not. It therefore becomes desirable to specify in greater detail the mental peculiarities of patients who, by reason of their motor anomalies, form a distinct clinical group both from the neuropathological and from the psychiatrical point of view. The pathogeny of these motor troubles will thus be elucidated and valuable indications for treatment obtained. Whatever be our theory of tic, whatever be the shape the individual tic assumes, it is in essence always a perturbation of motility, corresponding to a psychical defect. No doubt appearances are deceptive, and the brilliance of the subject's natural gifts may mask his failings. His intelligence may be high, his imagination fertile, his mind apt, alert, and original, and it may require painstaking investigation to reveal shortcomings none the less real. This practice we have scrupulously observed in all the cases that have come under our notice, and we believe that the information gleaned in this way, coupled with the results of previous workers, warrants the attempt at a systematic description of the mental state common to all who tic.