Light and electron microscopy studies of the ulnar, saphenous, and caudal cutaneous sural nerves of the dog

Transverse sections of the ulnar, saphenous, and sural nerves taken at specific levels in normal, young-adult beagle dogs were examined qualitatively and quantitatively at both the light and electron microscopic levels. The aim of this investigation was to provide baseline information for future studies of peripheral nerve disease in this species. A systematic sampling technique was used for the determination of nerve components (i.e., unmyelinated axons and Schwann cell and fibroblast nuclei). In all nerves sampled, the average size distribution for unmyelinated axons was unimodal, and most of the axons were 0.4-1.1 micron in diameter. Within this range, there were slight individual and nerve-to-nerve variations in the location of the largest diameter peak. The mean densities of Schwann cell nuclei (numbers/mm2) ranged from 841/mm2 in the palmar branch of the ulnar nerve, to 1,223/mm2 in the caudal cutaneous sural nerve, being nearly four times the average density or fibroblast nuclei. In every animal and in almost every nerve, a few abnormalities were found; and these should be kept in mind when assessing peripheral nerves in the dog.