The brain is divided in the mid-sagittal plane to expose the medial surface of the cerebral hemisphere and midline structures of the brain stem and cerebellum. The third ventricle, cerebral aqueduct, fourth ventricle and central canal are exposed. In the telencephalon the actual, cut surfaces include the corpus callosum, rostral lamina, lamina terminalis, septum pellucidum, fornix and anterior commissure. In the diencephalon the structures divided are the optic chiasma, infundibulum and floor of the third ventricle, massa intermedia, tela chorioidea of the roof of the third ventricle, pineal body and the habenular and posterior commissures. The hypophysis has been removed. The basilar artery is intact, but its branches to the left are all divided. The distribution of the anterior cerebral artery to the hemisphere is shown.