The authors of this volume have been resolute in their reference of the pathogeny of tic to a mental process. It is true, recognition of the psychological aspect of the affection is ready enough where the tic corresponds or is superadded to other "episodic stigmata of degeneration"; but the task is infinitely more delicate should the sole indication of an abnormal psychical state be the tic itself. Even in these cases examination always reveals insufficiency of inhibition, to which are due the inception and the persistence of many "bad habits." We can thus appreciate the rôle of habit in the evolution of tics, and recognise the analogy they offer to all functional acts. A tic is frequently nought else than the ill-timed and inapposite execution of some function. We may even conceive a sort of functional tic centre, formed by nerve elements corresponding to the functional grouping of the muscles involved in the tic. In advanced cases we may imagine some sort of hypertrophy of this functional centre, which may be reduced by suppression of function--that is to say, by certain methods of immobilisation. This is the secret of the treatment of tics, and to ignore it would be disastrous. As a matter of fact, tic is not merely a neurosis, but a psycho-neurosis, or, to be more exact, a psychomotor encephalopathy. The degeneration whose first manifestation in a child is the development of a tic may reveal itself later by more disquieting signs. This word "degeneration" is employed either too indefinitely or too explicitly by those who are ignorant of its true meaning in medicine. To-day the physician's diagnosis is often anticipated by the parents, who are willing to own their child "nervous" because of his tic; but they are not so ready to admit he has a tic because he is nervous, as they would infer immediately that they have begotten a degenerate. The consolation of "superior degeneration" does not exclude a certain degree of humiliation. No doubt superficial study is content to characterise children thus afflicted by the simple epithet "nervous," on the ground that their tic does not constitute a menace to life. But a tic in itself can never be a negligible quantity. The more it is repeated the more inveterate it becomes, and the greater the likelihood of its becoming generalised; at the same time the influence of the neuropathic diathesis is intensified. An analogy might be drawn between the tics and chorea. Prognosis, even in a mild case of adult chorea, should always be guarded, inasmuch as once the ordinary limits of the duration of the disease are over-stepped, we find ourselves face to face with the dreaded chronic variety.