Myofibrous organization of M. trapezius of crab-eating monkey

Abstract

In order to clarify the functional characteristics of M. trapezius of monkey, the myofibrous organization of the 10 right muscles of adult crab-eating monkeys (4 males and 6 females) were examined, noting the number and the size of red and white muscle fibers, which were differentiated by Sudan-Black B staining method.The following results were obtained.1. The number of muscle fibers per sg. mm. was the largest in intermediate part of M. trapezius, and was larger in females than in males.2. The number of white muscle fibers was about 30-45% of the total number of muscle fibers, and which was larger in caudal part than in cranial part of M. trapezius and larger in males than in females.3. Concerning the size of muscle fibers, it was general to be larger in males than in females, and the size of white muscle fibers was always larger than the red muscle fibers. And the size of muscle fibers was the largest in caudal part, and was correlated with the muscle weight positively.4. The muscle fiber density was about 70% in each of 3 parts, and was the lowest in cranial part of muscle. The density of white muscle fibers occupied half or more of the total muscle fibers.5. From these results, it was considered that the myofibrous organization of M. trapezius was most developed in caudal part, and this tendency was predominant in males than in females and also in white muscle fibers than in red muscle fibers. These findings suggest that the characteristics of myofibrous organization of M. trapezius concur with the characteristics of locomotion of monkey.