on the basis of morphological investigations two areas were distinguished in the periaqueductal grey of the cat midbrain : medial , directly surrounding the sylvius aqueduct and containing small neurons with significant ( p less than 0.001 ) prevalence of fusiform cells and lateral with larger neurons , where triangular cells were significantly ( p less than 0.001 ) prevalent .
C0025462
midbrain
C0007769
sylvius aqueduct