(_f_) Localized spasms, not monoplegic, are observed. For example, the orbicularis palpebrarum may be the seat of clonic spasm, or the masseters of tonic spasm for long periods of time; the œsophagus or urethra may be temporarily closed by constriction; chorea may affect a small muscular {47} group. A rhythmic spasm limited to a single muscle is termed myoclonus; the use of this term should not lead one to forget the nervous origin of the spasm. A localized tonic arterial spasm may be so severe and prolonged as to produce great ischæmia, even gangrene of the affected part. (_g_) Fibrillary contractions, non-rhythmic contractions of fasciculi in muscles, spontaneous or provoked by direct mechanical excitation, may be considered as hyperkinesis. Subjectively, fibrillary contractions are felt as a quivering or as if a worm moved under the skin; objectively, they appear not unlike the rising and falling of a cord under the cutaneous covering. They unquestionably occur frequently in muscles which are undergoing degenerative or atrophic changes (progressive muscular atrophy), but they are also met with in cases of lead paralysis, neurasthenia, etc. INCO-ORDINATION, or DYSKINESIS, is the condition in which volitional movements are not performed with normal precision and steadiness. Several varieties are recognized. (_a_) Ataxic tremor is distinguished from common or spasmodic tremor by the fact that it is developed during the performance of a volitional act in parts which are quiet when not used. Thus, tremor appears in speaking, putting out the fingers, using the hands, etc. in the muscles actively employed, and occasionally also in others at the same time. This form of tremor is well seen in dementia paralytica, where in certain cases the patient's muscles are still until we induce him to make voluntary movements or provoke expression movements. In cases of disseminated sclerosis the same phenomenon is a characteristic symptom, a coarse tremulous ataxia or oscillatory trembling appearing whenever volitional acts are attempted. In looking, there appears nystagmus, a rhythmic ataxic tremor of some of the ocular muscles; in speaking, an irregular, jerky, slow, or syllabic speech is heard; and when the hand is carried to a given object or pointed the extremity exhibits oscillatory trembling. Common and ataxic tremors may coincide, as in some cases of dementia paralytica and in alcoholism.