The size of cetacean brains has been used to support the argument that dolphins and other cetaceans have unusually great intelligence which may approach or surpass human intellect. Quantitative data from the literature by Donald Tower (1953) suggest an inverse relationship between mammalian cortical neurone density and body weight. The regression line slope has a coefficient of -.3.  Quantitative examination of Tursiops optic nerve axon size and numbers indicates that the total axon count is approximately equal to that found in dogs and cats while optic nerve cross-sectional area is very large.  An estimate of packing density calculated from these numbers suggests that dolphin places last on a distribution packing densities found in several terrestrial mammals including primates.

Supported in part by NSF grant BNS 79-14129.