TICS OF THE TRUNK
The rarity of isolated involvement of the thoracic muscles, and the frequency of their inclusion in tics of the neck and limbs, arise from the fact of their insertion into the bones of the extremities, and consequently conditions affecting them will be dealt with in another place. Omitting for the present all reference to the muscles of respiration, we have to consider only the vertebral and abdominal groups. These pass into activity in the rhythmical salutation and balancing movements so common among idiots, movements bearing the most intimate analogies to the tics, though their peculiarity of rhythm justifies their separate classification.
Tonic contractions that find expression in attitude tics of the body are generally associated with tonic tics of the neck and limbs, and in some cases of mental torticollis the deformation they produce is extensive.
The material part played by the abdominal muscles in the function of respiration explains their implication in respiratory tics. A curious case of this kind has been published by Pierre Janet[98]:
A woman thirty-two years old had been afflicted for three years with a respiratory tic that consisted in imitating with the lips the neighing of a horse, and with a still more extraordinary tic of the abdominal parietes. She appeared to "swallow her stomach"; in other words, her abdomen, prominent enough in its ordinary state, was flattened and retracted, and the skin so stretched and dragged upwards that the umbilicus approached the costal margin. Just as it seemed to be disappearing, to be "swallowed," relaxation of the abdomen slowly took place, and this procedure was repeated ten or twelve times a minute. Pressure on the epigastrium inhibited the abdominal movement, but was accompanied by immediate renewal of the neighing, whereas with the relief of the pressure the sequence of events was inverted.