Abstract
The myofibrous organization of the biceps femoris muscle, which plays the greatest role in the driving force behind monkey quadripedalism, was examined and compared with other muscles of the same subjects. Muscle samples were obtained from 10 adult crab-eating monkeys (4 males and 6 females) and were sectioned and stained with Sudan Black B. The following results were obtained: 1) The muscle weights were greater in M. biceps femoris that in spinohumeral muscles, M. deltoideus and M. tibialis anterior, and were greater in males than females. 2) The number of muscle fibers per sq. mm, was the smallest in the muscles compared, and were smaller in males that in females. 3) The ratio of 3 types of muscle fibers was the highest in white fibers (48.1 %), the secondmost in intermediate fibers and the smallest in red fibers. 4) As to the size of muscle fibers, white were the greatest, intermediate fiber secondmost and red were the smallest, in addition, they were greater in size in males than in females. Compared to other muscles, M. biceps femoris had the largest diameter of muscle fiber among the muscles. 5) The muscle fiber density was 72.5 % on the average and was larger in males than females. They were equivalent to those of the M. rectus abdominis of sportsmen who were studied by INOKUCHI, et al.
