Further Observations on Dorsal Root Components. ∗

Abstract

Additional evidence, both anatomical and physiological, has been introduced by Barron and Matthews 1 , 2 to support the presence of efferent components in the dorsal roots. These investigators believe that their histological evidence in the cat, suggests that collaterals of fibers in the posterior funiculi pass to the periphery through the spinal ganglia without cell stations. Such collaterals are said to constitute about 32% of the fibers in the lumbosacral dorsal roots and are of the myelinated variety. The literature bearing upon this subject was reviewed by Hinsey 3 , 4 and, since that time, additional work has been presented by Okelberry, 5 Kahr and Sheehan, 6 and Lugaro. 7

If approximately one-third of the myelinated fibers in the lumbosacral roots are collaterals of posterior funiculus fibers, it should be possible to demonstrate their degeneration in the distal stumps after section of the dorsal roots, appropriate degeneration times, and staining with the Marchi technic. Hinsey 4 reported that there was no evidence of degeneration of such fibers in serially sectioned Marchi preparations of the distal stumps, ganglia, and peripheral nerves following section of the 6–7 L and 1–2 S dorsal roots in the cat and appropriate degeneration times. He found traumatic degeneration near the point of section but none that passed through the ganglion. This experimental procedure should certainly have shown collaterals of the size which Barron and Matthews illustrate. 2

We have performed 6 additional experiments bearing on this problem. In young adult cats we sectioned the right 7 L (4 animals), the 6 L and 7 L (1 animal), and the 7 L and 1 S (1 animal) dorsal roots proximal to the ganglia near the spinal cord.