The sectioned corpus callosum has the appearance of a broad-arched band and forms the most distinguishing portions on the surface of the cerebrum. If the two hemispheres could be observed when they are still interconnected, the corpus callosum is on the floor of the longitudinal cerebral fissure. It consists of three divisions: (1) a curved front end called the genu, which tapers down gradually intomycontentbreak a thinner portion called the rostrum. The rostrum continues down and back to join the lamina terminalis; (2) a thick, rounded, back end called the splenium; (3) a middle portion or trunk arches over the back, between the front and back extremities. Central to the curvature of the front half of the corpus callosum can be seen the laminae of the septum pellucidum. These are two thin plates of gray and white matter that extend on each side between the corpus callosum and another curved, flattened bundle of white matter fibers, called the fornix. The function of the corpus callosum is to link the two cerebral hemispheres and allow the two sides of the brain to intercommunicate.