Abstract
The myofibrous organization of the laryngeal muscles of the human and the macaques were investigated for the morphological analysis of the correlations between the vocalization and the laryngeal muscles. Materials and methods : The materials were obtained from the 4 adult human and 4 crab-eating macaques. The materials were embedded in gelatine and stained with Sudan Black B. On the transverse section of the muscle belly, the number, the size, the density and the type of the muscle fibers were investigated. Results : 1. On the number of muscle fibers of human laryngeal muscles, that of the arytenoideus muscle and the cricothyroideus muscle were the largest, and those of the epiglotticus muscles were the smal-lest. 2. On the fiber size of the human laryngeal muscles, that of the epiglotticus muscles were the largest and the thyreoarytenoideus muscle showed the secondmost size. Within the rest of laryngeal muscles, the arytenoideus muscle showed the smallest size of the fibers. 3. On the muscle fiber density of human laryngeal muscles, that of the epiglotticus muscles show-ed the remarkable low density. 4. Each laryngeal muscle in human contained about 40% white fibers, about 35% red fibers and about 25% intermediate fibers, respectively. 5. The macaques lacked the epiglotticus muscles. The number of the muscle fibers and the size of muscle fibers of each laryngeal muscle of the macaques were smaller than that of human. Above all, the differences observed in the arytenoideus muscle and the cricothyroideus muscle between the human and the macaques were remarkable. And the percentage of the white muscles fiber in the each laryngeal muscle of macaque were higher than that of human. 6. On compare to human, the muscles which participate the closing of the posterior part in the glottis and the extending, tensing and adducting of the vocal cord are undeveloped relatively in macaque. Consequently, the larynx of macaque is good for the short phonation accompanying the high sound and not good for the continuous and various tone phonation.
