[In this connection reference may be made to certain conditions occasionally noted among those who tic--viz. a curious tendency to maintain abnormal positions of the limbs or trunks, and difficulty in or impossibility of relaxing various muscles (_catatonic aptitudes_). Patients are sometimes given to the exaggerated repetition of the ordinary movements of their members (_echokinesis_), as well as to imitation of the actions of others (_echomimia_). Such catatonic and echopraxic phenomena[51] are not confined to sufferers from tic, for they are encountered among psychopathic subjects generally, and indicate defect of cortical control--what is called by Brissaud "passive activity." These catatonic aptitudes may be discovered by resort to clinical tests, such as letting the arm fall from the horizontal position.[52]] INTENSITY OF THE MOTOR REACTION The muscular contraction varies considerably in intensity, in most cases exceeding that of the corresponding normal movement, and, especially in tonic tics, being often so powerful as to necessitate the exertion of great force to overcome it. Even though one's effort prove unavailing, however, it is only needful to distract the patient's attention to perform any and every passive movement with consummate ease. In the case of S., any attempt to budge the head from its torticollic position on the left evokes strong muscular resistance; but engage him in conversation or otherwise divert his mind, and the difficulty soon vanishes. By similar means, the resistance awakened by sudden change of the direction of passive rotation will rapidly die down. Occasionally the muscles brought into play surpass their fellows of the opposite side in size and power, this secondary hypertrophy being the natural sequel of repeated exercise. It was noted by Charcot that in rotatory tics the disused muscles atrophied, whereas the affected muscles hypertrophied, but they may do so only in appearance. The tonus of the muscles at the moment of examination may create differences inappreciable during relaxation. Sometimes one comes across such expressions as "paresis" or even "paralysis" of antagonistic muscles, and "contracture" of those in which the tic is localised. To draw a distinction between slight contracture of the latter and mild paresis of the former is a problem practically always insoluble. Opinion has been ever divided on this point; yet some, in their desire to harmonise the two, take up an eclectic position and do not hesitate to speak[53] of "paralytic contracture," or "mixed contracture, at once active and passive," a terminology by no means calculated to simplify the question, and one the discussion of which we do not care to pursue.