The human spine is a complex piece of machinery, and should be studied and treated with respect at all times.

The only subcutaneous parts of the vertebral column are the apices of the spinous processes, and are palpable through the skin, most prominently at the nape of the neck. In order to identify any particular spinous process it is necessary to count from the spinous process of the seventh cervical (vertebra prominens), and the first thoracic; of these the later is the more prominent. But from this region downwards they are sunk into the median furrow which extends from the external occipital protuberance to the sacrum. On each side of which the deep longitudinal muscles form a rounded projection, of the thoracic the first is the most prominent: the third should be noted as it is on a level with the root of the spine of the scapula, that of the seventh with the inferior angle of scapula; that of the twelfth with the lowest attachment of trapezius and head of twelfth rib, of the lumbar the second is the most important as it corresponds to the termination of the spinal cord; the fourth marks the highest point of the iliac crest and the bifurcation of the abdominal aorta. The lumbar spines `project horizontally, and correspond with the vertebral bodies. Owing to the obliquity, of the thoracic spines most of them do not tally with the heads of the corresponding ribs, thus the spine of the second corresponds with the head of the third, the spine of the third with the head of the fourth rib; and so on down to the eleventh and twelfth vertebrae, which do tally with their corresponding ribs. The posterior superior iliac spine is on a level with the second sacral vertebrae. At birth the spinal cord ends at the level of the third lumbar spinous process. The subdural and subarachnoid cavities end opposite the third sacral vertebra, which is at the level of the dimple marking the position of the posterior inferior iliac spine.

The area of the back is isolated laterally by a vertical line drawn from the posterior axillary fold to the iliac crest, and is divided into nine regions, one median, the interscapular, and four on each side; superior scapular above the spine. inferior scapular below the spine, and above the plane of the inferior angle; infrascapular between the last and the level of the eleventh rib; posterior lumbar between the last and the iliac crest.