• The splenium of the corpus callosum of a primate (Macaca mulatta), examined with the electron microscope, was found to contain both myelinated and nonmyelinated axons. The majority of nonmyelinated axons had diameters of less than 0.25 μ. On the basis of this diameter distribution, it is expected that many callosal axons conduct impulses at velocities of less than 1 m/s and that interhemispheric conduction times for some callosal axons are at least 30 ms and possibly much longer.
Swadlow HA, Waxman SG, Geschwind N. Small-Diameter Nonmyelinated Axons in the Primate Corpus Callosum. Arch Neurol. 1980;37(2):114–115. doi:10.1001/archneur.1980.00500510072016
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