A case of muscle subclavius posticus with special reference to its innervation.

A subclavius posticus muscle was found in the left side of a Japanese male cadaver. This muscle arose from the first costal cartilage, inserted to the upper margin of the scapula, and was innervated by a branch from the nerve to the subclavius. This excess intermediary muscle between the subclavius and the inferior belly of the omohyoid appears to be more closely related to the subclavius, based on detailed examination of the innervation of this muscle. A possible schematic model of the origin of this muscle is proposed.