Dissection of the Interventricular Septum to Demonstrate the Third Ventricle. The body of the corpus callosum has been removed to provide this superior view of the lateral ventricles and third ventricle. The anterior poles of both thalami are retracted laterally to demonstrate the internal cerebral veins. The pineal gland is observed along the posterior aspect of the third ventricle. The floor of the third ventricle can be seen as far rostral as the mammillary bodies. (Image courtesy of AL Rhoton, Jr.)