A further mark of the motor reaction is the circumstance that it ceases for a longer or shorter interval, independently of the tic's localisation, intensity, or form, the result being an alternating series of "attacks" and periods of respite. In different patients, and in the same patient, the number and the length of these attacks are as variable as are the spaces of rest that separate them. We remember a girl with a tic consisting in a toss of the head repeated perhaps fifteen times a minute, three or four occurring together at intervals of one or two seconds, and being succeeded by a relatively long pause. The effect of treatment was to modify the sequence entirely, and to reduce the tic to an isolated jerk reappearing not oftener than once in a quarter of an hour, and in itself constituting the attack. In another case the patient's head used to turn to the left, remain so for a moment, then resume its ordinary place. After a time of repose the tic began again, and even when the movements followed each other more rapidly, the intervening period was always appreciable. On the other hand, we have seen a youth afflicted with multiple tics which continued without intermission the whole day long; the attack lasted, strictly speaking, from morning to night, and any break in its continuity was altogether exceptional. It might then be more exact, perhaps, to use the epithet paroxysmal in reference to the external manifestations of tics, but it signifies little what word we employ provided we are familiar with the clinical facts. The attacks vary with circumstances and environment. One of our patients remained quite free from them during a visit to the theatre. Tissié had a young patient who did not tic at all while on holiday, but the reopening of his classes was the signal for a fresh outbreak. Similarly, no rule whatever seems to govern the duration of the times of relief; they may never be longer than a few seconds, or they may run into months. In the face of these data we cannot supply further generalisations; it will be sufficient if we impress on ourselves the importance of one fundamental element in the constitution of tic--viz. its repetition. LOCALISATION OF THE MOTOR REACTION--VARIABLE TICS--FIXED TICS