A further note on regeneration of the cut spinal cord in fish.

Abstract

In 1922 Koppányi and Weiss 1 reported in a preliminary note regeneration of the spinal cord in the fish (Carassius vulgaris, a small specimen 4-5 inches), and in the larvae of the salamander (Salamandra maculosa). Their method was complete section of the vertebra and cord in the high thoracic region. In one experiment three vertebrae were removed with their corresponding spinal cord. Regeneration occurred in both cases. Regeneration was evidenced by functional return in paralyzed regions and morphologically by histological examination. After the section, the animals were quiescent caudad to the section. Three weeks later the salamander larvae showed motility of the posterior portion. The motility slowly recovered until four or five weeks after the section when there was apparently complete functional recovery; their locomotion was coordinate and regular. During this period some of the salamanders metamorphosed. This confirms Loeb's statement that transection of the spinal cord in Axolotl does not prevent metamorphosis. Regeneration was less rapid in the fish, requiring six to eight weeks. There was apparent functional recovery, for swimming was coordinate, but the animals always lay upon the side and seldom swam in the normal position. Histologically, in conjunction with Kolmer, we traced the fibers across the section. These fibers were somewhat fewer in number than in the normal cord. They were mostly gathered in bundles although there was considerable interlacing.

In the salamander with the three vertebrae removed, the vertebrae and cord regenerated completely.

Our first experiments in the present series were done on the adult newts, Diemyctylus viridescens and Diemyctylus torosus. These animals were unsuitable for the experiments because the cord is so far dorsal that the body musculature is unable to hold the cut ends of the spinal cord in opposition when the vertebral column is transected. We used, therefore, the goldfish (Carassius auratus). These were large specimens fro'm 8 to 14 inches in length. A small transverse section was made through the skin and the muscles spread apart and the entire vertebral column cut in two with scissors. There was no bony continuity remaining between the regions above and below the section. A probe was passed fully from side to side in the section. The spinal cord must have been sectioned. The skin was sutured with silk. Wound healing was slow and was incomplete in about six weeks time.