Distraction suspends the activity of tic; physical fatigue and emotion are calculated to arouse it.
Tics always disappear in sleep.
They are unaccompanied by any alteration in sensation, in the reflexes, or in the trophic functions.
They are not associated with pain.
In this general way we have indicated the distinctive features of tic, and we may take the opportunity to remind ourselves of their extreme variability.
In discussing the question of diagnosis, we shall have occasion to emphasise the importance of fruste, atypical, and transitional cases, not because we think they can be systematised as yet, but because they may be capable of new pathogenic interpretations which we cannot afford a priori to set aside.
We venture to believe that tic has a clinical individuality of its own which we have tried to portray, and we go so far as to say that an appreciation of the points we have touched on will prove of service in matters of diagnosis.
CHAPTER XVI
DIAGNOSIS
TICS AND STEREOTYPED ACTS
WE have already, on more than one occasion, drawn attention to the phenomena known as stereotyped acts, demonstrating their intimate kinship with the tics and the frequent difficulty of establishing a differential diagnosis. To ensure precision of ideas and of terminology, we must restrict the expression to motor disturbances in which the characters of the muscular contraction are identical with those of normal acts. On this view many motor reactions are really classifiable as stereotyped acts, and among them are those denominated by Letulle "habit tics."