Spatial fibre architecture of Mm. pectorales in macaques: their morphological, phylogenetical, and functional...

The pectoral muscles of the 2 monkeys, Macaca fuscata and M. fascicularis, were described particularly in the light of 3 dimensional fibre architecture. There existed throughout the muscles the rotation in the same direction and radiation of fibre bundles as well as the consecutive and multi-stratified structure; This architectural design suggested that the deep pectoral masses of the mammals were derived from the caudal portion of the primitive pectoral plane through fibre migration caused by the whole muscle rotation, probably in response to the functional necessity peculiar to the mammalian locomotion.