Muscles of the back, historical artwork. The skin, fascia (connective tissue), and first three layers of muscles have been removed to expose the fourth muscle layer (red) of the back. At top is the base of the skull, from which complexus muscles descend to the base of the neck. The rib cage (centre left & right) forms a protective cage for the internal organs (not seen). A mass of tendons (blue/white) attach to the spinus processes of the vertebral column (backbone), at the base of which is the pelvis. On either side of the backbone are the longissimus dorsi and the sacro-lumbalis muscles. Published in The Muscles of the Human Body... by Jones Quain in 1836.