Degeneration time for optimal staining by Nauta technique. A study on transected vagal fibers of the cat

Cervical and abdominal vagus nerves taken at various survival times, (1–16 days following transections) have been stained with the Nauta technique and a modification of this technique, as well as with other stains commonly used to demonstrate Wallerian degeneration in peripheral nerve. Counts of the myelinated fibers were made on transverse sections of the osmium‐stained cervical vagus to furnish a measure of the rate of disappearance of the fibers. Approximately half of the myelinated fibers had disappeared in seven days and all were gone at 14 days. Fragmented axons in the cervical and abdominal vagi were demonstrated as early as three days and remained observable at seven days with the Nauta stain. In the abdominal vagus evidence of degeneration had disappeared by 11 days. In the cervical vagus, however, although only occasional axonal fragmentation was evident at 16‐days survival time large globules of myelin debris still persisted in the larger fibers. Unlike the CNS, fragmented axons persist for relatively short periods in the PNS and particularly in the small and unmyelinated fibers the survival time which allows demonstration of axonal fragmentation is critical.