* * * * * _Age._--Tics may occur at any period, except in infancy. "Nervous movements" appearing previous to the age of three or four cannot be tics, as has been made plain in the chapter on pathogeny. It is only with the development of psychical function--about the age of seven or eight--that revelation of its imperfection, if such exist, becomes possible. Initiation or exacerbation of a tic is very frequent about the time of puberty, when both physical and mental evolution is peculiarly apt to suffer interruption. _Sex._--Sex is without influence on the disease. _Race._--In spite of the absence of precise statistics on the subject, the opinion that the tendency to tic increases with the advance of civilisation is not, we think, premature. We have had the curiosity to interrogate several travellers familiar with different savage tribes of Central Africa, who, although notified beforehand to be on the look-out, declare they have practically never met with tic in negroes. These observations require to be confirmed. It may be questioned if the level of mental attainment of such primitive peoples is sufficiently high to allow of the establishment of tics. Their occurrence in the lower animals has been recorded, it is true; but with our ignorance of what constitutes an animal tic, and until further information is forthcoming, it is prudent not to speculate on these matters. We must be content with the remark that savages and animals are less exposed than the civilised to circumstances facilitating the development of mental instability. _Trauma_ and _infectious disease_ may provide the occasion for either the appearance or the disappearance of a tic, but of themselves they are incapable of originating the affection. One of Noir's patients had a brother similarly afflicted, and a sister in whom an attack of bronchitis at the age of five was accompanied by tics of arm and head, which recurred subsequently in an exaggerated form during smallpox. On each of two occasions on which J. suffered from influenza his tics increased in violence and extent; while in the case of G. aggravation heralded the approach of measles. Young M., on the other hand, remained free of all his face and head movements during the immobilisation of a fractured leg, with the cure of which his tics returned. To disturbance of the reproductive organs, in particular to uterine disorders and even pregnancy (Gowers, Bernhardt), has been ascribed the onset of tic. Of the possible influence of climate, season, and atmospheric change in general, precise information is lacking. Stormy weather or a falling barometer frequently exercises a depressing effect on the subjects of tic, but this is habitual in all neuropathic individuals. Oppenheim declares he has seen severe cases of convulsive tic follow an earthquake.