The functional specialization and the regulation of the contraction in Musculus deltoideus, Musculus biceps brachii and Musculus extensor digitorum communis was studied electromyographically. The fibers of the muscles are devided in two neuromuscular units (NMU) functionally; the kinetic NMU and tonic NMU. The former is concerned with the pyramidal tract and the latter with extrapyramidal tract. By these both, the contraction is regulated, and each muscle has its own and fixed ratio of the content of these both NMU. Before the excision of area 6 of cerebral cortex in the epileptics, the regulation of contraction was almost similar in the normal side, but in the focal side, it was myographically rather insufficient. But the ratio of content of these both NMU had no remarkable difference from those of the normal. After the operation, the regulation of contraction became more insufficient and the tonic NMU became less. As time elapsed, they approached to the state before the operation and about 21 days after the operation the majority of them became almost as same as before the operation. In the patients who had a lesion in the area 6 of cerebral cortex, almost similar results to the epilepties were obtained, while in those who were not affected in the area 6. almost similar results to the normal were seen. But in all cases there was found no change of the content ratio of both NMU.
Acetylcholine effected to disturb the regulation of contraction in normal skeletal muscles, but in abnormal muscles it did to correct the regulation of contraction, while it did not influence the content ratio of the both NMU. On the contrary, strychnine nitrate did not influence at all.