Rhomboid major - Musculus rhomboideus major
Origin: Spinous processes of the T2 to T5 vertebrae
Insertion: Medial border of the scapula, inferior to the insertion of rhomboid minor muscle
Artery: Dorsal scapular artery
Nerve: Dorsal scapular nerve (C4 andC5)
Action: Retracts the scapula and rotates it to depress the glenoid cavity. It also fixes the scapula to the thoracic wall.
Antagonist: Serratus anterior muscle
The Rhomboideus major arises by tendinous fibers from the spinous processes of the second, third, fourth, and fifth thoracic vertebrae and the supraspinal ligament, and is inserted into a narrow tendinous arch, attached above to the lower part of the triangular surface at the root of the spine of the scapula; below to the inferior angle, the arch being connected to the vertebral border by a thin membrane. When the arch extends, as it occasionally does, only a short distance, the muscular fibers are inserted directly into the scapula.
This definition incorporates text from a public domain edition of Gray's Anatomy (20th U.S. edition of Gray's Anatomy of the Human Body, published in 1918 – from http://www.bartleby.com/107/).