These considerations determined my view of his trouble as a peculiar form of tic, which consisted in "muscular spasms systematically harmonised to produce the alternating deglutition and expulsion of a certain quantity of atmospheric air" (Pitres), which therefore might be denominated an _aerophagic tic_. Different varieties of this tic exist, according as the air swallowed is derived from the exterior or from the lung, and depending on its penetration into the stomach or simply into the pharyngo-œsophageal canal; and further, the physiological mechanism of the condition varies with them. Let us suppose that the swallowed air comes from the lung. In this case, a certain quantity of air is imprisoned at the beginning of expiration in the pharyngo-œsophageal cavity, whose orifices are firmly closed by simultaneous contraction of the muscles of the palate, glottis, and base of the tongue. At this moment a brisk contraction of the constrictors of the pharynx drives the accumulated air out by the mouth, setting the membranes surrounding the supero-anterior opening of the cavity into vibration in so doing, whereby the air escapes as a more or less noisy eructation. Should the mouth not open at this juncture, however, the air is compressed and crowded back into the lower part of the œsophagus, whence it passes through the easily dilatable cardiac ring into the stomach, to be expelled again by the mouth in the same noisy way once it has accumulated in sufficient quantity. The deglutition of external air is preceded by an aspiratory thoracic effort; closure of the glottis forces the œsophagus to open under the stress of increased negative intrathoracic pressure, and to suck air down. When aspiration ceases, this air is either driven out forthwith, or gathered in the stomach, as we have just seen. One may sometimes notice that the act of suction is succeeded by movements of swallowing, in which case the probability is that at the moment of aspiration the closure both of glottis and of pharynx prevents the penetration of atmospheric air into either the trachea or the gullet, in spite of the differences of pressure, and that these movements allow its passage through the œsophagus. Aerophagia is by no means, therefore, a simple involuntary movement, but a combination of systematised muscular actions. In fact, it is a tic, and as such has both a physical and a psychical side.