Abstract
The muscle fibers of anterior serratus muscles, trapezius muscles, rhomboideus muscles and atlantoscapular muscles from ten adult crab-eating monkeys (six females and four males) were studied for elucidating the functional characteristics of upper extremities muscles in the anthropoids. The muscle fibers were differentiated by Sudan Black B staining method into two types, termed white and red fibers in respect of fiber staining density, and measured each fiber size and counted each fiber number in certain area of muscles.
Results were following ;
1) The white fiber ratio (the number of white fiber to red fiber per unit area) was more than 1 in cranial and intermediate parts of anterior serratus muscles, and caudal parts of rhomboideus muscles in males, and anterior and posterior atlantoscapular muscles in both sex. In other parts of above muscles and trapezius muscles, the white fiber ratio was less than 1 in males and females.
2) A great number of larger size of white fiber was apparently seen in caudal parts than other parts of anterior serratus as well as rhomboideus muscles, in males and females. In atlantoscapular, anterior parts had many thicker white fibers than posterior parts in males and females. In trapezius, great number of larger white fiber was visible in caudal parts than other parts in appearance. The size of white fiber was mostly larger in males than females, in all parts of all muscles except in the caudal parts of anterior serratus muscles. However, in all cases, the size of red fibers was smaller than that of white fibers.
3) The distribution in the size frequency of muscle fibers was tend to broader in white fiber than red fibers and in thick fiber parts than thin fiber parts. Respect to the body weight and sex, the size of muscle fiber was distributed to widespread in heavy monkey and so in males.
4) In consideration of concerning to movement of scapula, the thickness of muscle layer, the number of muscle fiber per sq, mm. and the size of muscle fiber were the most developed in the parts of muscle which participated in abduction of scapula, second most in the part of which took parts in the motion in cranial-cauda direction of the bone, and small in the parts of which fixed the bone to the body. Those of tendency might be derived from the characteristics of body movement of crab-eating monkey.
