Abstract
The constitution of the muscles of the thigh were examined in 24 male and 26 female crab-eating monkeys (Macaca fascicularis). The boundary of the origin and the insertion of the muscles were defined. The composition of the spinal nerves was observed in two specimens. The n. femoralis, n. obturatorius and n. flexoris femoris arose from the lumbar plexus and ranged from the third to the fifth, the fourth to the sixth and the fifth to the seventh lumbar nerves, respectively. The segmental innervation of the muscles in the same specimens was studied. The muscles of the thigh were categorized into seven groups based on the innervation and their relative positions. More cranially arising muscle groups received a higher segmental nerve. They were inserted more medially because of rotation of the hip joint during embryogenesis. More distally and laterally inserting muscles within the same muscular group received a lower segmental nerve than the others. These findings suggest a uniform mechanism in the myotome arrangement of the lower limb during embryogenesis in man and the monkey. On this basis, the dual innervation and intermuscular septum in the thigh are well explained by the developmental process.
