An electron microscope study of the unmyelinated nerve fibres in normal baboon median nerves: negative effect of vitamin-B12 depletion.

The unmyelinated nerve fibres in the distal part of the median nerve of normal baboons (Group 1) and of baboons kept on diets deficient in vitamin B12, and supplemented with potassium cyanide and potassium thioxyanate injections (Groups 2-5), have been examined under the electron microscope. Qualitative and quantitative observations on the distribution, size and Schwann cell relationships of the unmyelinated fibres were made. There were no significant differences between the nerves of the normal and experimental groups. New data about normal baboon peripheral nerve are presented and discussed.