Innervation of the levator scapulae, the serratus anterior, the rhomboideus and the scapular muscles in the gray kangaroo (Macropus giganteus). Comparisons are drawn to the crab-eating macaque and man.

The origin, course and distribution of the nerves to the levator scapulae, rhomboideus, serratus anterior, supraspinatus, infraspinatus, subscapularis, teres minor, deltoid, teres major and latissimus dorsi muscles were examined in 7 kangaroo body-halves. The levator scapulae and the serratus anterior formed a continuous muscle sheet arising from the transverse processes of the lower 5 cervical vertebrae and the upper 6 ribs. The rhomboideus arose from the occipital bone in addition to the cervical dorsal median raphe. Six segmental nerves from C3 to C8 innervated these 3 muscles. Each segmental nerve originated from the dorsal surface of the corresponding root of the cervicobrachial plexus. All these nerves innervated the levator-serratus muscle sheet and 4 segmental nerves from C3 to C6 innervated the rhomboideus. Of the remaining scapular muscles, the supraspinatus was well developed, and the teres minor was a small muscle. The nerves supplying the scapular muscles originated from the area between the upper trunk and the posterior cord of the brachial plexus. Four segmental nerves from C5 to C8 usually innervated these 7 muscles. Judging from the relationships between nerves and muscles, all of these muscles are thought to have originally belonged to the same 2 groups of the dorsal musculature extending between the trunk, the shoulder girdle, and the limb. Muscle type and modes of nerve supply to the muscles in the grey kangaroo are similar to those found in the crab-eating macaque.