Electromyographic examinations were performed on the crycothyroid muscle, the vocal muscle, the arytenoid muscle and the posterior cricoarytenoid muscle of the normal and paralyzed human larynx. A suitable concentric needle electrode was designed for the purpose of intralaryngeal examinations under observation with laryngeal mirror. The action current of a single neuromuscular unit of the vocal muscle was 100*V, and the maximal frequency of spike discharges was 20 per second. The electrical activity of the vocal muscle increased in higher pitch of the voice, while no differnce of the activity was observed in higher intensity. In whispering, contraction of the adductor muscles was much weaker than in ordinary phonation. Respiratory fluctuations in the activity of the laryngeal muscles were observed; activation of the abductor muscles occurred at inspiration, that of the adductor muscles at expiration. The electromyogram, recorded on unilateral and bilateral paralysis of the recurrent laryngeal nerves, revealed that the arytenoid muscle received motor fibers from bilateral recurrent nerves, though none from the superior laryngeal nerve. Various figures of the paralyzed vocal cords, from midline to cadaveric position, were observed on the patients with recurrent laryngeal nerve paralysis. In recovery stage of a patient, true figures of the abductor paralysis were investigated by means of laryngoscopic and electromyographic examination. On clinical examination of the laryngeal paralysis, electromyogram also presented important and reliable findings in diagnosis, suggesting the grade of the lesion, its localization and the prognosis of the condition.
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