Anomalous head of the brachial muscle penetrates the deltoid muscle.

We report here, for the first time a specimen in which the insertion of the deltoid muscle is divided into two parts, composing a canal. The brachial muscle was composed of medial, lateral, and anomalous heads. The anomalous head arose as a thin tendon from the surgical neck of humerus, passed through the canal, and then became confluent with the lateral head. The musculocutaneous nerve innervated the brachial muscle. The lateral head, but not the anomalous head, received a thin branch from the radial nerve.