. Comparative Zoology, structurelles et systématiques : pour une utilisation dans les écoles et collèges. Zoologie, anatomie, physiologie, comparatif, comparatif. 172 Comparative Zoology. Le bulbe rachidien est le lien entre le cerveau et le cervelet et la moelle épinière. Dans la structure, il ressemble à la moelle épinière, la substance blanche et grise étant à l'extérieur de l'intérieur. L'ancien se trouve sous ou derrière le cerveau, en passant par le trou occipital du crâne, et fusion imperceptiblement en le cordon. Ce dernier est un appareil continu de matière grise en- fermés dans les brins de fibres blanches. Il usuall

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. Comparative zoology, structural and systematic : for use in schools and colleges. Zoology; Anatomy, Comparative; Physiology, Comparative. 172 COMPARATIVE ZOOLOGY. The medulla oblongata is the connecting link between the cerebrum and cerebellum and the spinal cord. In structure, it resembles the spinal cord—the white matter being external and the gray internal. The former lies beneath or behind the brain, passing through the foramen magnum of the skull, and merging imperceptibly into the cord. The latter is a continuous tract of gray matter en- closed within strands of white fibres. It usually ends in the lumbar region of the vertebral column, but in Fishes it reaches to the end of the tail. In Fishes, Amphibians, and Reptiles, the cord outweighs the brain: in Birds and Mammals, the brain is heavier than the cord. In Man, it weighs about an ounce and a half. Besides these parts, there are also the olfactory and the optic lobes, which give rise respectively to the nerves of smell and sight. The parts of the brain are always in pairs; but in rela- tive development and po- sition they differ widely in the several classes of Ver- tebrates. In Fishes and Reptiles, they are arranged in a horizontal line; in Birds and Mammals, the axis of the spinal cord bends to nearly a right an- Fig. 139.—Brain of g]e jn passincr through the the Perch, upper o r o & view: a, cerebei- brain, so that the lobes no him; &, optic . lobes; c, cere- longer lie in a straight line. ryniobes.°f ml In Man, the fore-brain is Fw. MO.-Brain of the „, , , , ', m _ _ "FYnov nnnw vipw V A.* duiia oblongata. g0 developed that it cov. ers all the other lobes. In looking down upon the brain of a Perch, we see in front a pair of olfactory lobes (which send forth the nerves of smell), behind. 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 t

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• bookcentury1800
• bookdecade1880
• booksubjectzoology
• bookyear1883