1. In this investigation one was impressed by the close relationship that exists between the constituent parts of the intervertebral discs and the surrounding supporting structures. The part that is responsible for the maintenance of a co-ordinated balance between these structures, and hence for the effective mechanism of the spine, is the nucleus pulposus.

2. The cruciate arrangement of the annulus fibrosus is related to spinal function, and the angle of intersection of consecutive laminae of the annulus fibrosus is more or less constant.

3. In the Bantu it was found that the interspinous and supraspinous ligaments differ from the classical descriptions given in anatomical text-books.

4. The movements taking place between two vertebrae are comparable to those of a rocking-horse.

5. Narrowing of a disc is a progressive process which is the result of the disturbances in the balance between the components of the force to which a disc is subjected. The process is initiated by the loss of nucleus pulposus content.

6. With the approximation of two adjacent vertebrae a disturbance of the relations of the structures in the intervertebral foramen was noted. On anatomical grounds, when a disc is narrowed it appears that the most likely structures to cause pressure on the nerve root are not the disc itself, but the superior articular processes with their overlying ligamentum flavum.