One day as I was moving my head about I felt a "crack" in my neck, and forthwith concluded I had dislocated something. It was my concern, thereafter, to twist my head in a thousand different ways, and with ever-increasing violence, until at length the rediscovery of the sensation afforded me a genuine sense of satisfaction, speedily clouded by the fear of having done myself some harm. The painlessness of the "crack" induced me to go through the same performance many and many a time, and on each occasion my feeling of contentment was tinged with regret: even to-day, notwithstanding that I ought to be persuaded of the harmlessness of the occurrence and the inanity of the manœuvre, I cannot withstand the allurement or banish the sentiment of unrest. One could not desire a more lucid exposition of the pathogeny of so many of these head-tossing tics. The fundamental importance of the psychical element that precedes the motor reaction, with the secondary psychical reaction in its turn, the impulse to seek a familiar sensation, and the illogical interpretation of it under the influence of a tendency to nosophobia, are all admirably illustrated in O.'s description. In addition to such "cracks" as are perceptible to others, O. is conscious of various bizarre subjective sensations that he refers to the same region--"bruised," "dragging," "crackling" feelings, not at all dolorous, to which he devotes an inordinate share of his attention. There is nothing abnormal about these, of course; not only may we notice them in ourselves, but, with a little effort, we may even reproduce them. Our indifference to their presence is the exact opposite of the interest they arouse in the patient's mind; his fickle will is, for no adequate motive, concentrated on a commonplace event, and on this slender basis delusions are fostered and tics are shaped. The insight into the close association between the state of the mind and the development of tic yielded by a study of the foregoing narrative will enable us to appreciate the perspicacity of what follows: I suppose that we who tic make a great number of voluntary movements with the deliberate purpose of withdrawing attention from the tics we already exhibit; but step by step they become so habitual that they are nothing less than fresh tics appended to the old. To dissemble one tic we fashion another. Certain objects become for us what might be called _para-tics_. Such, for an instance, is my hat. I used to imagine I could mask all my oddities by tilting it on my head. I used to carry it in my hand, and play with it in every conceivable manner--to the advantage of the hatter solely, for it did not last me more than six weeks.... We are our own physicians at first: the discomfort of a tic is an urgent reason for our seeking to compass its overthrow.