. Elements of physiological psychology; a treatise of the activities and nature of the mind, from the physical and experimental points of view . e middle peduncleconsists of the pontine fibres, which arise from the pontine nuclei,and are connected with fibres descending from the cerebrum. Thisis the path of communication from the cerebrum to the pontine fibres, then, are afferent to the cerebellum; they passto the cortex of the cerebellar hemispheres; whereas the rest of theafferent fibres go to the vermis. The development of the cere- TRACING AND NAMING OF NERVE-TRACTS 87 bella
. Elements of physiological psychology; a treatise of the activities and nature of the mind, from the physical and experimental points of view . e middle peduncleconsists of the pontine fibres, which arise from the pontine nuclei,and are connected with fibres descending from the cerebrum. Thisis the path of communication from the cerebrum to the pontine fibres, then, are afferent to the cerebellum; they passto the cortex of the cerebellar hemispheres; whereas the rest of theafferent fibres go to the vermis. The development of the cere- TRACING AND NAMING OF NERVE-TRACTS 87 bellar hemisphere varies with that of the cerebrum, being largestin man. (Further study of the inner structure of the cortices and othernuclei of the brain is deferred to a chapter on the nerve-cell and itsconnections; and, in case of the cerebral cortex, to a special chapteron that cortex.) § 23. As can readily be imagined from the large number of tractsand nuclei which have been mentioned even in the above hastyreview, the internal structure of the brain presents a bewilderingcomplexity of collections of nerve-cells and of bundles of fibres. Fig. 41.—Lower Surface of Cerebellum. ^. (After Sappey.) 1, vermis; 3, pons, bulb, and various pairs of nerves are also seen, thus; 12, 13, the fifth nerve;14, the abducens; 15, the facial; 16, the intermediate; 17, the auditory; 18, theglosso-pharyngeal; 19, the vagus; 20, the accessory; 21, the hypoglossal. coursing in various directions. In attempting to unravel this com-plexity, the most important task is that of tracing fibres from thecells which give them off to the cells which receive them. If weknew the fibres which connect the various centres or collectionsof cells, we should have taken a long step toward discovering thefunctions of the centres thus connected. Many ingenious methods for tracing the nerve-tracts have beenemployed, the chief of which are the embryological and the patho-logical or degeneration method. T
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