Part 1. Assessment of the method of contrast laryngography.
Discussing problems in the technique of contrast laryngography, the author presented the method that he used successfully. Urokolin Oily Suspension 60% and Dionosil Aqueous were used as the contrast agent. An usual X-ray apparatus was available. It was emphasized that patient's cooperation was essential to obtain a good laryngogram.
Part 2. Laryngographical study of pathological larynges.
In order to evaluate the contrast laryngography in clinical diagnosis, seventy-nine subjects with a pathological larynx were examined. The results obtained were as follows:
1) In the majority of the patients with recurrent laryngeal nerve palsy, the vocal cord on the affected side was thinner and situated lower than the non-affected cord, and the ventricle was often larger on the affected side.
2) In cases of recurrent laryngeal nerve palsy and so-called internus-palsy, median edges of the vocal cords were not so blown upwards during phonation as in the normal.
3) According to the contrast laryngography, the tumor of the larynx was accurately defined as to its location, size and extent.
Contrast laryngography was especially valuable to diagnose the pathological involvement of the ventricles or the subglottis which was often undetectable by mirror examination. The contour of benign tumor was more clear-cut than that of cancer.
4) Laryngograms were also useful to show the morphological and functional changes after the partial laryngectomy or the irradiation for carcinoma.
5) In cases of the vocal cord polyp a “double contour” was the most remarkable finding.
6) In cases with laryngeal injury, laryngogram was useful to elucidate the extent of the injury and to decide the procedure of treatment.
Part 3. Laryngographical investigation of the influence of the head position upon the larynx.
The influence of the head position upon the larynx was radiographically studied from the standpoint of the mechanism of phonation. Twenty-five patients with unilateral recurrent laryngeal nerve palsy as well as ten normal subjects were investigated. The following results were obtained:
1) When the head was tilted to the right or left, the vocal cord on the tilted side was often situated higher than the other in normal cases.
2) When the head was tilted to the affected side in the cases of recurrent laryngeal nerve palsy, both vocal cords were brought in the same level and the voice disturbance was improved.
3) In many cases, the length of the vocal cords was reduced and the hypopharyngeal and the supraglottic space became narrower when the head was tilted back.

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In spite of numerous investigations of the laryngeal nerves, there is no complete agreement as to the innervation of the laryngeal nerves. This study was carried out to elucidate the problems of the larynx innervation, especially to illustrate the motor nerve supply to the laryngeal muscles of mammals. Three methods were chosen for this study.
a) Dissection of excised larynges under a binocular microscope without staining. Twenty-five human larynges, ten larynges of the dog, cat, rabbit, goat, sheep, horse, cow and pig respectively were employed in this investigation.
b) Dissection of larynges, in which the nerves were supravitaly stained with methylen blue. Five dogs, five cats and ten rabbits were employed in this observation.
c) Histological examination of the Galen's anastomosis after the superior or inferior laryngeal nerve was resected. This experiment was planned in order to illustrate whether the Glen's anastomosis is composed of superior laryngeal nerve or inferior nerve. Four dogs, the superior or inferior laryngeal nerve of which had been disscted before one month, were studied.
The results were summarized as follows:
1) In all cases of man, dog, horse, sheep, goat and pig, the internal branch of the superior laryngeal nerve entered into the larynx penetrating the thyrohyoid membrane except one human case in which the nerve penetrated the thyroid cartilage at the thyroid foramen such as observed in all cases of cat, rabbit and cow.
2) The internal branch of the superior laryngeal nerve was divided into three main branches after penetrating the thyrohyoid membrane: Ramus anterior, media et posterior. In man and dog the site of division showed individual difference. In man the type of the intralaryngeal division was most frequently found, on the contrary the extralaryngeal division was most frequent in dog. In the other mammals the internal branch was divided after it entered into the larynx except one case of rabbit.
3) The epiglottis was innervated mainly by Ramus anterior in mammals: however, in horse and cow, whose epiglottis was comparatively large, it was observed that Ramus media as well as Ramus anterior supplied the sensory nerve to the mucosa of epiglottis.
4) The aryepiglottic fold and laryngeal vestibule were innervated by R. media: however, the subglottic space was never.
5) The arytenoid region was innervated chiefly by Ramus posterior: i. e., some twigs of Ramus posterior pierced the arytenoid muscle and supplied the sensory nerve to the inner surface of the arytenoid cartilage, and some of the others anastomosed with twigs of the inferior laryngeal nerve in the arytenoid muscle. These twigs of the inferior laryngeal nerve have been considered to innervate the arytenoid muscle, however it was not illustrated in this study whether the superior laryngeal nerve supplies a motor nerve to the arytenoid muscle or not.
6) Galen's anastomosis consisted of R. posterior of the internal branch of the superior laryngeal nerve and R. posterior of the inferior laryngeal nerve. Galen's anastomosis was very small in all cases of pig and was not occasionally found in some specimens of horse.
7) The external branch of the superior laryngeal nerve innervated the cricothyroid muscle in every mammal.
8) The inferior laryngeal nerve was fouud to be divided into two main branches before it entered into the larynx in many cases of mammals, except pig and few cases of man, cat and dog.
9) R. anterior of the inferior laryngeal nerve innervated the homolateral posterior cricoarytenoid, arytenoid, lateral cricoarytenoid and thyroarytenoid muscles in every mammal, however, in man and cat, the arytenoid muscle was double innervated by bilateral inferior laryngeal nerves. Ramus posterior composed Galen's amastomosis with a branch of the superior laryngeal nerve.

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