. Elements of comparative zoology. Zoology. VERTEBRATES. 299 narrower portions. In the brain five divisions may be distinguished. Eeginning in front, these are:* (1) the cerebrum, composed of right and left halves or hemi- spheres, and containing in their interiors the first and second ventricles; (2) the smaller 'twixt-brain, with thin. FIG. 109.—Diagram of vertebrate brain, c, cerebrum; cb, cerebellum; h, in- fundibulum; TO, medulla; o, olfactory nerve; ol, optic lobes; s, spinal cord; 1-4, ventricles. walls and enclosing the third ventricle; (3) the thick- walled optic lobes; (4) the cerebe
. Elements of comparative zoology. Zoology. VERTEBRATES. 299 narrower portions. In the brain five divisions may be distinguished. Eeginning in front, these are:* (1) the cerebrum, composed of right and left halves or hemi- spheres, and containing in their interiors the first and second ventricles; (2) the smaller 'twixt-brain, with thin. FIG. 109.—Diagram of vertebrate brain, c, cerebrum; cb, cerebellum; h, in- fundibulum; TO, medulla; o, olfactory nerve; ol, optic lobes; s, spinal cord; 1-4, ventricles. walls and enclosing the third ventricle; (3) the thick- walled optic lobes; (4) the cerebellum; (5) the medulla oblon- gata, the fourth ventricle being contained in cerebellum and medulla. In the lower vertebrates these five regions are nearly equal in size, but the higher we go in the scale the larger proportionately do the cerebrum and the cerebel- lum become, until in man the cerebrum weighs about nine tenths of the whole brain. From the brain are given off, typically, twelve pairs of nerves, which are spoken of both by numbers and by their proper names. The majority of these are unlike the spinal nerves in that they have but a single root, and are correspondingly either sensory or motor. Thus the first or olfactory nerve, which goes to the nose; the second * Other names are frequently applied to these parts, as follows: Cerebrum, Prosencephalon, Parencephalon, Thalamencephalon, Diencephalon, Mesencephalon, Metencephalon, Myelencephalon, "Twixt-brain, Optic Lobes, Cerebellum, Medulla, Midbrain, Epencephalon, 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 Kingsley, J. S. (John Sterling), 1854-1929. New York, H. Holt and Company
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