Abstract
As part of a series of studies on the function and morphology of skeletal muscles, I compared the localization and distribution of red muscle fibers, intermediate muscle fibers and white muscle fibers in the m. biceps brachii of the white-handed gibbon and crab-eating monkey. While the white-handed gibbon possesses a specific suspensory locomotor system and lives in trees, the crab-eating monkey is active both on the ground and in trees and moves about mainly by quadrupedal walking. Morphologically polar specimens were obtained from a cross-section of the belly of the m. biceps brachii. In the white-handed gibbon, red muscle fibers, which show slow, long-term contraction were observed to be most frequent. In contrast, white muscle fibers, which are used for bursts of fast activity, were found to be most frequent in the crab-eating monkey. It appears that differences in the proportion of muscle fiber types between these two species depend on functional differences in locomotion: brachiation in the white-handed gibbon and quadrupedal walking in the crab-eating monkey.
