Observations on the topographical relations of spinal nerve roots in the rat.

The spinal cord along with the ventral and dorsal roots (C1-S4) were dissected out in 10 male and 5 female CF rats. The vertebral levels of origin and exit of the spinal nerve roots and termination of the spinal cord were recorded. It was observed that from the mid-cervical to the sacral region, the roots arose increasingly at cranial levels compared to their levels of exit. This disparity was at its maximum in the lumbar and sacral segments. The spinal cord terminated between the third and fourth lumbar vertebrae. There was no sexual dimorphism either at the level of termination of the cord or at the levels of origin and exit of origin and exit of the various nerve roots.