The relation between axon diameter and axonal conduction velocity of Y, X and W cells in the cat retina.

Axon diameters of ganglion cells were measured electronmicroscopically from the cross-sections of the optic nerve fiber layer in the cat retina. The diameter distribution revealed 3 well-separated groups which correspond to axons of Y, X and W cells. Mean intraretinal axonal conduction velocities were estimated physiologically for the 3 classes. Between the means of axon diameter (D, micron) and conduction velocity (V, m/s) the following positive correlations were obtained: V = 3.85 square root D-2.3 when short axes of cross-sections were measured, and V = 3.33 square root D-2.3 when long axes were measured.