Fig. 13.Basal view of the brain showing the external surface of the floor of the hypothalamus and its arterial vessels. The infundibulum (I) lies posteriorly to the optic tracts and chiasm (ot) and anterior to the mammillary bodies (m). The arterial circle of Willis surrounds the hypothalamic floor and provides the arterial supply to the hypothalamic nuclei and fiber tracts. ac = anterior cerebral artery, aco = anterior communicating artery, b = basilar artery, ic = internal carotid artery, P = pons, pc = posterior cerebral artery, pco = posterior communicating artery. (From the XIX century wax collection of human brains at the Museum of the Department of Human Anatomy of the University of Bologna, Italy.)