Coughing tics also are of remarkably common occurrence. Many individuals ceaselessly interrupt the thread of their conversation to make more or less audible explosive expirations, for which there is neither reason nor necessity, since the respiratory paths are free from all irritation or obstruction. These useless little coughs do not always deserve the appellation of tics; in many instances they are mannerisms comparable to the gestures of conversation or reflection, although in some people their insistence, abruptness, and irresistibility might justify their incorporation in the other category. Their co-existence with tics of face and limbs has been noted, as in a case published by Tissié[116] of an eight-year-old child, with ocular and facial tic and spasmodic cough. Clonic contraction of the diaphragm gives rise to conditions imitated or caricatured by the tics, in particular sobbing and hiccoughing. It must not, of course, be forgotten that these are apt to occur in hysteria, as well as in organic disease of the nervous system, and in grave infectious states. Careful and searching inquiry must therefore precede any expression of diagnosis. Tonic diaphragmatic contraction is of very much greater rarity. In such cases abdominal respiration comes to a momentary standstill, whereas thoracic respiration is accelerated. The patient is in imminent danger of being asphyxiated, and the insertions of the diaphragm sometimes become painful. What is known as acute pulmonary eructation is occasionally the sequel to this convulsive affection. Tonic contraction of the diaphragm is nearly always of an hysterical nature, and is doubtless akin to the aerophagic type. CHAPTER X TICS OF SPEECH In movements of inspiration or of expiration the passage of air through a more or less contracted glottis gives rise to all sorts of sounds, some of which, under certain conditions, must be included in the category of tics. The most elementary of these, and at the same time the most common (says Guinon), is the involuntary exclamation. In the midst of his tics and grimaces, a cry--ah!--escapes the patient's lips at intervals, a shrill, sudden, and momentary cry which interrupts his talk, or breaks in on a period of silence, and which he repeats only once or perhaps several times in succession. The thread of his conversation, nevertheless, is seldom if ever discontinuous, and his audience is witness of its rationality and accuracy of expression. Rather more complicated is the ejaculation "ouah!" Sometimes one meets with noises that are faithful reproductions of the sounds emitted by various animals.