Certain convulsive affections--for instance, the _spasmus nutans_ of young children, the salaam tic, and what are known as "baboon movements"--are still rather obscure and in many cases seemingly not equivalent to tics. Their occasional association with strabismus or nystagmus constitutes a plea for their possible dependence on some encephalic lesion. In two cases under Oppenheim's observation the nodding spasm appeared solely in the hours of the night and during sleep. From want of more precise knowledge we must confine ourselves to the remark that conditions analogous to, though not identical with, the tics, in addition to others more specifically hysterical, have probably been incorporated with them. It is a task of peculiar difficulty to determine the share in the final product to be apportioned to individual muscles, of which the sternomastoids, as being the most superficial and the most obvious, are apparently comprised the oftenest, though the trapezius and the muscles of the underlying strata, such as the splenius, complexus, and other smaller ones, may also assist. According to Guinon, isolated contraction of one sternomastoid, whereby the head is rotated and inclined once or twice or several times consecutively, to the usual accompaniment of facial contortions, is very frequently to be noted. If there occur simultaneous contraction of the platysma, its fibres will be seen to line the cervical integuments longitudinally from the chin to the infraclavicular fossa. Synchronous involvement of the two sternomastoids will flex the head and approximate the chin almost to the sternum, but more commonly there is only a slight forward inclination of the head exactly similar to a gesture of assent. Extension and lateral deviation are less generally encountered. Extreme variability characterises the exciting causes of these tics. It has been remarked more than once that insecurity of the headgear the subject happens to be wearing ought to be blamed; instead of readjustment with the hand, a little toss of the head will make the hat sit properly, and one need not search further afield for the germ of the patient's tic. We have been able to trace this mode of inauguration quite as conspicuously in young men as in young women. Prohibition of unstable head coverings and resort to exercises of immobilisation suffice for the tic's correction in early cases.