Fig. 43-16. Median sections. A shows important features of the brain stem and a cross section of the midbrain. The interthalamic adhesion is indicated by an asterisk. B emphasizes the meninges, subarachnoid space, and cisterns. Aq., aqueduct; Ep., epiphysis (pineal body); 1, fissura prima; 2, fissura secunda; 3 and 4, third and fourth ventricles. The interrupted line indicates the orbitomeatal plane, which has been used for orientation, thereby rendering the brain stem almost vertical. Click for high resolution image.