Cerebrum
The dissectors should begin by reviewing between the skull and brain with the assistance of a dried skull, and should note the relation of the parts of the brain to the folds of dura mater (the falx cerebri and the tentorium cerebelli) if a partially head is available. Reference should also be made to the short account of craniocerebral topography and to figs. The longitudinal fissure is the narrow cleft between the tow hemispheres. It is occupied by: (1) the falx cerebri; (2) the fold of arachnoid which follows the surface of the falx; (3) the mater covering the medial surfaces of the hemispheres; (4) the arteries and veins which lie in the subarachnoid space between the arachnoid and the pia. The falx was removed when the brain was taken from the skull, but the other structures are still.
Anterior cerebral artery
The beginning of this vessel has been examined already, but it can now be followed from the anterior communication artery on the surface of the corpus callosum, or in the sulcus cinguli. It supplies the medical surface and the adjacent margin of the superolateral surface as far posteriorly as the splenium of the corpus callosum.
Posterior cerebral artery
This vessel supplies the remainder of the medical surface of the hemisphere and the greater part of the tentorial surface. Its main branches on the medical surface run in the calcarine and parieto-occipital sulci. Follow the branches of these arteries, noting in particular the posterior choroidal branches of the posterior cerebral artery. These arise as if runs round the lateral aspect of the midbrain, close to the superior surface of the margin of the tentorium, and they pass deep to the cortical margin. Shortly after its origin the posterior cerebral artery lies on the parahippocampal gyrum which ends anteriorly in a rounded swelling, the uncus. This is normally grooved by the free edge of the tentorium, and tends to be thrust through the tentorial notch when the supratentorial pressure exceeds that in the infratentorial compartment.