Vertebral column, 18th-century illustration. Shown in sagittal (side view) section, the upper part of the vertebral column (spine) is at left, and the lower part at right. It runs from the skull to the pelvis, and is a flexible column of small compact bones called vertebrae, that enclose and protect the spinal cord. In adults, there are 26 vertebrae: seven cervical, twelve thoracic, 5 lumbar and the fused vertebrae of the sacrum and coccyx. This illustration is from 'Osteographia, or the Anatomy of the bones' (London, 1733) by English surgeon and anatomist William Cheselden (1688-1752). It was the first full and accurate description of the anatomy of the human skeletal system.