. The anatomy of the central nervous system of man and of vertebrates in general. Neuroanatomy; Central Nervous System. 102 ANATOMY OF THE CENTRAL NERVOUS SYSTEM. appear on either side of the median portion^—the Hemisphceria cerebelli. In mammals they are developed synchronously with the appearance of the Pons to proportions which greatly exceed those of the middle part,—which latter is now called the Vermis. But the median segment of the cerebellum retains even in man the characteristic worm-like transverse folding acquired by the cerebellar plate in' the selachians. Immediately posterior to
. The anatomy of the central nervous system of man and of vertebrates in general. Neuroanatomy; Central Nervous System. 102 ANATOMY OF THE CENTRAL NERVOUS SYSTEM. appear on either side of the median portion^—the Hemisphceria cerebelli. In mammals they are developed synchronously with the appearance of the Pons to proportions which greatly exceed those of the middle part,—which latter is now called the Vermis. But the median segment of the cerebellum retains even in man the characteristic worm-like transverse folding acquired by the cerebellar plate in' the selachians. Immediately posterior to the cerebellum we meet in the roof of the medulla ganglionic masses which send out fibers of the Trigeminus and Acusticus. Usually fused with the cerebellum these form, in the higher vertebrates, unimportant nuclei; in fishes, however, well-marked lobes (see Fig. 55 ^4 and C). Nowhere else in the animal kingdom does the Vermis cerebelli reach. rig. 55.—Semidiagrammatic sagittal sections through the vertebrate brain. The cerebellum appears in blacky to show its relative size. A, Brain of Ray; B, of an Amphibian; C, of a Trout-embryo; D, of a Bird. such enormous development as in the great swimmers and the birds. This circumstance, together with the fact that in the same animals there are especially large connections with the tonus nerves of the labyrinth and with the Trigeminus, makes it most probable that in some way or other the cere- bellum must be involved in the maintenance of equilibrium. This is, in fact, indicated in its general development. The results of physiological ex- periments indicate the same thing. Phylogenetically the cerebellum is one of the oldest portions of the brain. Experiments upon the supra-CBSophageal ganglion in arthropoda indicate that it fulfills functions equivalent or similar to those of the cere- bellum in higher Please note that these images are extracted from scanned page images that may have been digitally enhanced for readabi
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