The muscular contraction that deviates the head may be either clonic or tonic, bringing it to one side by a series of convulsions and allowing it to resume its original position in the intervals, or forcing it to maintain a vicious attitude for hours. Innumerable variants may occur, indeed are the rule, even in the same patient. In short, though mental torticollis may generally be classed as a tic of attitude, it matters but little whether the adoption of the attitude or the attitude adopted constitutes the tic. They are simply two successive phases in the same abnormal muscular act. The most elementary movement is rotation of the head; it may equally well be inclined on one shoulder, or be both inclined and rotated to one side, or it may be inclined in one direction and rotated in the other. There may be accompanying elevation of the shoulder, or the act may become a much more complex one, involving neck, shoulder, and arm. Each and all of the neck muscles may take a share in the torticollic movement, but some are more commonly affected than others, in particular the sternomastoid, whose contraction may either be isolated,[94] or modified by trapezius, splenius, levator anguli scapulæ, etc., of the same or the contralateral side. It is frequent to find the head inclined to one side and rotated to the other by the action of the sternomastoid, or displaced backwards and slightly turned to the side of the contraction by means of the splenius. If the sternomastoid and homolateral trapezius are acting together, torsion of the neck is very pronounced and the skin over that area is deeply lined.[95] It may happen that the head is rotated and inclined to the same side, as in Grasset's case, where the curious combination occurred of clonic convulsion of left trapezius and pectoralis major with right pectoralis major and sternomastoid. In the same patient the left arm was pressed against the trunk and the right extended posteriorly. There are other instances where it would be more accurate to speak of _retrocollis_, as in a case recorded by Brissaud, or _procollis_, the two sternomastoids contracting synchronously, as in another case due to Duchenne of Boulogne. The extreme degree of flexion induced in this way was neutralised immediately by supporting the head; the adoption by the patient of a reclining position sufficed to inhibit the tic's manifestation.