SummaryThe author found that a muscle which shows electrical silence at rest did not do so immediately after relaxation, but showed chiefly fibrillation voltage for various period of time. This new wave form was named “follower potential” by Prof. Maekawa, and the author observed dynamically its genesis by electromyography. Materials selected were both inpatient and outpatient in Maekawa clinic and other clinics of Kyoto University Hospital. 225 cases with various diseases were examined in a total of 360 times and 1500 needle insertions. In this paper, the author described this special wave form chiefly in N. C. A. and allied diseases. Electromyograms were observed and photograFhed on a cathode‐ray oscilloscope and a simultaneously synchronized loud‐speaker, using a concentric needle electrode of my own design (bipolar and monopolar) and chiefly in continuous sweep. Spinal root segments from cervical to sacral were examined.Results obtained were as follows:1With regard to the wave form and sound in loud‐speaker, the “follower potential” was the same as fibrillation voltage such as is obtained by denervation. That is, its amplitude and duration were 10‐100μV. and 1‐2 msec., respectively; and it appeared at random.2“Follower potentials” showed segmental distributions. And their duration varied between 1/2 second and 6 min. 10 sec. The areas of such segmental distributions coincided with the areas of stiffness and tenderness on pressure and grasping of muscles. Aim, these segmental distributions were correlated with appearance of various symptoms, such as dizziness, dyspnea, abdominal discomfort and trigonum anomaly.3Appearance of “follower potentials” corresponded highly with occurrexe of arachnoid adhesion as found in myelography. And more, “follower potential” was intensified by stopping the flow of the contrast medium in cerebrospinal space.4“Follower potential” appeared chiefly in association with complex NMU voltage and synchronization voltage, especially with the latter.5In such segments where there is a left and right difference in subjective complaints, there also occurred a left and right difference in the firing of “follower potential” both in its appearance and duration. “Follower potentials” of short duration showed time‐to‐time variations in duration, but those of longer duration had almost fixed duration, this suggests reversibility and irreversibility of the conditions in respective cases.6Electric stimulations gave rise to the “follower potentials” when generally high electric currents were used. With low electric currents, they were induced in such muscles which have showed “follower potential” already before such stimulation.7“Follower potential” was affected by various agents; i.e., they were markedly increased by adrenalin, strophe and acetylcholine, increased by noradrenalin, vagostigmin and strychnine, markedly suppressed by myanesin, moderately decreased by imidalin and TEAB., and slightly decreased by pilocarpine and histamine.From various findings here recorded, it is concluded that the existence of “follower potential” indicates lower motor neuron lesions, especially the irritable lesion of the root. Moreover, it appears that various lower motor neuron lesions, especi