We have studiously avoided the designation of a tic by the muscle or muscles that determine it. To specify the precise muscle involved is sometimes attended with no little difficulty, while if several, as is customary, are concerned, their association is rarely anatomical; indeed, this is one of the chief aids to diagnosis between tics and spasms. Should the convulsion chance to follow an anatomical distribution, neighbouring muscles are apt to participate as well. Hence it is advisable to name a tic after its morphological situation, or, better still, from the functional act of which it is, in Charcot's phrase, the caricature. This is the plan we shall pursue in our successive examination of the different parts of the body disposed to be the seat of tics. FACIAL TICS--TICS OF MIMICRY Of all tics, those of the face are the most frequent, and the most easy to see. No other part is as rich in muscles whose functions are so diversified--nictitation, mastication, suction, respiration, articulation, etc. Moreover, the face is the abode of the mimic expressions, each one of which is the revelation, by muscular play, of some sentiment, or passion, or emotion. Hence the idea has been entertained of adopting a physiological classification. In the smiling tic of Bechterew, for an instance, the muscular contractions are framed into a smile in the absence of any provocative to mirth; in a similar fashion, the sniffing tic brings to mind the inhaling performances of snuff-takers. Facial tic is frequently unilateral. It is rare to find the whole muscular distribution of one facial nerve involved, however, this being a property rather of spasm, as is also the restriction to a particular branch. A common event is the simultaneous abstention of some facial muscles and implication of others belonging to a different nerve supply. If the condition is bilateral, as a general rule only those muscles on each side co-operate that are wont to act in concert for the accomplishment of some function. In a case reported as bilateral facial spasm by Claus and Sano,[61] in which both sides of the face and neck were affected, the exaggeration of the convulsions by emotion, their curtailment daring rest and disappearance in sleep, coupled with the fact of their temporary arrest by recourse to subterfuge, suggest that the condition is really one of tic. The contractions of the facial muscles are usually associated to produce a more or less complex grimace. Movements of forehead, eye, nose, or mouth, may succeed each other or be superimposed one on the other without any preconceived order, or the tic may consist in the synchronous activity of two or more muscles. Of course any and every facial tic may occur by itself, but careful investigation will often reveal concomitant reactions of other muscular groups. The sniff that accompanies puckering of the nose indicates the engagement of the muscles of inspiration.