But if the consciousness of the normal adult be, as it admittedly is, a most elusive conception to define, how infinitely more precarious is the task in the case of idiots or infants! Cruchet says it is impossible to be sure whether at any given moment a tic has been above the threshold of consciousness or not; and we do not think the question will be elucidated by the introduction of data so difficult to comprehend as the consciousness, unconsciousness, or subconsciousness of the tic patient. In any case, these conceptions are quite inadequate for the establishment of useful distinctions. All that we can say is that the participation of consciousness in the phenomena of tic varies in time and degree. To hazard farther would be to invite disaster. TIC AND POLYGON The proposal has been made by Grasset to apply his attractive hypothesis of the cortical polygon to the interpretation of the pathogenesis of tic. It is desirable, first of all, to recall briefly the significance of the word polygon in the sense adopted by that neurologist.[16] At the central end of the physiological ladder is the superior or cortical system of perception neurons whose cells form the grey matter of the convolutions. Physiological and clinical research necessitates the subdivision of this system into two groups--the neurons of psychical automatism, and the neurons of superior (_i.e._ voluntary or free) cerebration. The former function is not of the same level as the ordinary reflex arc, since it is in relation to co-ordinated, intelligent, and in a sense conscious acts; at the same time it is to be distinguished assiduously from the latter, in which we include our personality, moral consciousness, free will, and responsibility. Activity on the part of the inferior psychical neurons is seen: 1. In normal individuals--during sleep, dreams, and acts of distraction. 2. In the nervous--in nightmares, oniric states, table turning, thought reading, the use of the divining rod, automatic writing, cumberlandism, spiritualism. 3. In the diseased--in somnambulism, catalepsy, hysteria, certain phenomena of epilepsy, hypnotism, double personality; also in some cases of aphasia, and in such conditions as astasia-abasia. Every manifestation of this inferior psychism is characterised by spontaneity, herein differing from mere reflex acts, but not by freedom, which is the _propre_ of superior psychism. The various neurons subserving the former or inferior function are cortical, and form the cortical polygon. Situated at a higher physiological level are those for the latter function, united in what I designate the centre O. Grasset's general conception of tic is accordingly as follows: