Estimate of the number of myelinated axons in the cat's optic nerve

Abstract

The number of myelinated axons in the cat's optic nerve has been estimated from a partial count of sections of the nerve examined by electron microscopy. The average count obtained from four nerves was 128,600 (range 112,800‐147,200). This figure is within 10% of a previous estimate of the number of ganglion cells in the cat's retina, but is 33% lower than the only previous estimate of the number of these axons based directly on electron microscopy. Possible sources of the discrepancy are discussed. The functional implication of this total, in the context of earlier work on ganglion cell topography, are also discussed.