|Henry Gray (18251861). Anatomy of the Human Body. 1918.|
|interval, together with the lower portions of the choroidal fissures, is sometimes spoken of as the transverse fissure of the brain. At its base the two layers of the velum separate from each other, and are continuous with the pia mater investing the brain in this region. Its lateral margins are modified to form the highly vascular choroid plexuses of the lateral ventricles. It is supplied by the anterior and posterior choroidal arteries already described, The veins of the tela chorioidea are named the internal cerebral veins (venæ Galeni); they are two in number, and run backward between its layers, each being formed at the interventricular foramen by the union of the terminal vein with the choroidal vein. The internal cerebral veins unite posteriorly in a single trunk, the great cerebral vein (vena magna Galeni), which passes backward beneath the splenium and ends in the straight sinus.|
FIG. 750 Tela chorioidea of the third ventricle, and the choroid plexus of the left lateral ventricle, exposed from above. (See enlarged image)
Structure of the Cerebral Hemispheres.The cerebral hemispheres are composed of gray and white substance: the former covers their surface, and is termed the cortex; the latter occupies the interior of the hemispheres.
| The white substance consists of medullated fibers, varying in size, and arranged in bundles separated by neuroglia. They may be divided, according to their course and connections, into three distinct systems. (1) Projection fibers connect the hemisphere with the lower parts of the brain and with the medulla spinalis. (2) Transverse or commissural fibers unite the two hemispheres. (3) Association fibers connect different structures in the same hemisphere; these are, in many