The Elements of Psychology

lobes and interlobar fissures; (3) the outside layer of cell-bodies and cell processes, i. e., the nerve cells of the cerebral cortex; (4) the white central mass of the hemispheres composed of nerve fibers which connect the different parts of the cortex, and the cortex with other parts of the central nervous system. These structural features will be considered in the order named. The Cerebral Convolutions and Fissures. ? Superficially viewed, the most conspicuous feature of the surface of each hemisphere is its division into numerous folds or elevations ? the cerebral convolutions, or gyri ? and fissures, or sulci, which separate the convolutions from one another. A number of the more prominent convolutions of the lateral aspect of the left hemisphere are indicated on Fig. 5, p. 25. The figure also shows the location of the Sylvian and the Rolandic fissures. The Cerebral Lobes and Interlobar Fissures.? For the purpose of description, brain anatomists divide the surface of each hemisphere into more or less definite areas known as lobes, the boundaries of the lobes being marked roughly by the more conspicuous cerebral fissures. The locations of the lobes and the interlobar fissures are indicated withsufficient exactness by the accompanying figures (3, 4, 5, 6), which give respectively the inferior and the superior aspects of the brain, and the lateral and mesial (inner) aspects of the left hemisphere. The interlobar fissures are: (1) The Sylvian fissure, seen ...