Retraction of Fornix to Demonstrate Internal Cerebral Veins. The right fornix and interventricular septum have been retracted to demonstrate the floor of the lateral ventricle and foramen of Monro.  The internal cerebral veins, visible bilaterally, receive drainage from he thalamostriate and anterior septal veins. The proximal segment of the right basal vein of Rosenthal is observed along the posterior aspect of the retracted fornix. (Image courtesy of AL Rhoton, Jr.)