Locomotor Ataxia, Tabes Dorsalis, is a term applied to a disease one of the most characteristic symptoms of which is an ataxia or disorder of locomotion. The patient's gait somewhat resembles that of a drunken man; he raises his feet unduly high and brings them down to the ground with peculiar suddenness. He is unsteady, and sometimes is unable to maintain the standing posture when his eyes are closed. The legs are especially involved in this disease, but the arms may be affected, and sensation as well as movement may be implicated. Peculiar darting pains in the limbs are of frequent occurrence, and to them the term lightning pains has been applied. Pain in the region of the stomach with gastric symptoms (gastric crises) constitute another characteristic group of phenomena. Other symptoms are loss of "knee-jerk," affection of the joints, and a peculiar condition of the pupil of the eye, the aperture of the pupil becoming smaller when the stimulus of exposure to light is applied, but the normal contraction when the vision is accommodated for near objects not being observed (Argyll Robertson phenomenon). In some instances there is atrophy of the optic nerve with loss of sight. The disease begins in middle life, and runs a very protracted course. It is more common in men than in women. It is caused by a process of degeneration or sclerosis affecting the posterior columns of the spinal cord. In some instances it occurs in persons who have previously been the subjects of syphilis, and in them treatment by appropriate remedies may be productive of considerable benefit.