Hypertrophy of the osseous structure of the spinal column never occurs to an extent at all to be compared with what is observed in the skull: sometimes only, in opening a vertebral canal, we may meet with some difliculty, in consequence, apparently, of the bony tissue being more dense than usual. Exostosis, too, is rarely found: when it does occur, its texture is generally cellular. If it spring from the back of the bodies of the vertebrae, and encroach upon the spinal canal, it may lead to serious consequences. The bridge-like osteophyte situated at the margins of the vertebral bodies, and that more abundant one which seems poured out upon them, are both commonly confounded with exostosis.

Atrophy of the vertebrae takes place, for the most part, only when there is general wasting of the whole skeleton. When it is a local affection, it is produced by aneurisms of the thoracic and abdominal aorta, and goes on to an extreme degree: the front and sides of the bodies of the vertebrae have, in some few cases, been completely eroded, and the spinal canal opened.