Abstract
In order to clarify functional development of primates' upper extremity muscles, their muscles were studied on relative muscle weight and muscle fiber organization. The muscles from one adult pig-tailed macaque (P) and one infant chimpanzee (C) and seventeen adult humans (H) were weighted, and thin sections of muscle samples (P) were examined. Resulte were as follows : 1) The results of comparisons of the relative ratios of muscle weights for all upper extremity muscles were H>P (17%) >C in Triceps br., P (13%) >H>C in Biceps br., C>P (11.5%) >H in Flex. digit. prof., H>C>P (6%) in Brachialis, C>P (6%) > H in Flex. digit, superf. and P (6%) ≥C>H in Brachioradial. 2) On the comparison of total muscle fiber numbers in upper extremity muscles of the pig-tailed macaque, the following results were obtained : Triceps br. >Biceps br. >Brachialis ≥Flex. digit. prof.> Flex. digit. sup. >Brachioradial. 3) On the cross-sectional area of muscle fiber in pigtailed macaque, the mean sizes were relatively larger in Triceps br, and flexor muscle group in ante-brachii and larger in the flexor muscle group in the brachii, and so on, and smaller in extensor muscle group in antebrachii. 4) Consequently, the upper extremity muscles of the pig-tailed macaque could be assumed functionally close to those of humans, although morphologically, they are at a stage of development between that of chimpanzee and human.
