A broad, thin muscle extending from the scapula to the elbow, on the inner aspect of the arm.

Origin. - By a broad, thin aponeurotic tendon from the posterior border of the scapula.

Insertion. - Into the superior and posterior part of the olecranon or elbow and into the fascia of the arm.

Action. - To extend the lower on the upper arm, and to tighten the fascia of the fore-arm to give the muscles support.