5. Notes more especially on the Bridging Convolutions in the Brain of the Chimpanzee

Abstract

The late Professor Gratiolet, in his elaborate and beautifully illustrated memoir, “Sur les Plis Cérébraux de l'Homme et des Primates,” attaches great weight in his differential diagnosis of their cerebral characters to the presence or absence of one or more members of a series of convolutions, which he designates as the plis de passage. When present, these convolutions bridge over the external perpendicular fissure of the hemisphere, and connect the parietal and temporal with the occipital lobes. By various anatomists in this country they are called bridging, connecting, or annectent convolutions. In the brain of the Chimpanzee M. Gratiolet states that the first bridging convolution is altogether wanting; that the second is present, but concealed under the operculum of the occipital lobe; that the third and fourth are superficial.