. The chordates. Chordata. : Comparative Morphology of Chordates fissure of Sylvius on the external side of the hemisphere, separating the frontal lobe from the temporal lobe, which is below and behind the fissure (Fig. 524). In the human brain parietal and occipital lobes also are recognized. These lobes are merely topographic, but are not functionally distinct. The question arises as to why a given volume of cortical substance should be disposed in this elaborately folded manner rather than in the form of a thicker layer lying smoothly over a smooth surface of "white ; It
. The chordates. Chordata. : Comparative Morphology of Chordates fissure of Sylvius on the external side of the hemisphere, separating the frontal lobe from the temporal lobe, which is below and behind the fissure (Fig. 524). In the human brain parietal and occipital lobes also are recognized. These lobes are merely topographic, but are not functionally distinct. The question arises as to why a given volume of cortical substance should be disposed in this elaborately folded manner rather than in the form of a thicker layer lying smoothly over a smooth surface of "white ; It is as if the cortex had been unable to increase in thick- ness as it increased in volume and accordingly was compelled to develop wrinkles. Certain advantages of the convoluted arrangement can be recognized. The innermost investing membrane of the brain, the pia mater, thin but richly vascular, is folded deeply into all the fissures. ANGULAR GYRUS FRONTAL POLE ORBITAL GYR FISSURE OF S SUPERIOR TEMPORAL GYRUS MIDDLE TEMPORAL GYRUS TEMPORAL TEMPORAL POLE' INFERIOR TEMPORAL GYRUS c OCCIPITAL LOBE OCCIPITAL POLE Fig. 524. Lateral views of brains of (A) rabbit, (B) dog, and (C) man. {) Olfactory lobe; (////) cerebellum; (Hyp) hypophysis; (Med) spinal cord; (NH) medulla oblongata; (Po) pons Varolii; (VH) cerebral hemispheres; (Wu) median vermis of cerebellum; (II-XII) cranial nerves. (A and B, courtesy, Wiedersheim: "Grundriss der vergleichenden Anatomie der Wirbeltiere," Jena, Gustav Fischer. C, after Sobotta. Courtesy, Neal and Band: "Comparative Anatomy," Phila- delphia, The Blakiston Company.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Rand, Herbert W. (Herbert Wilbur), 1872-1960. Philadelphia : Blakiston
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