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.The only difference is, that they aremore clearly separated by small inexcitable areas.In all cases, the regions lying beyond the parts specified,i.e., in particular, the anterior portion of the frontal brain and the temporal and occipital lobes, proved to beinexcitable on the motor side.These results of stimulation are, on the whole, borne out by the results of extirpation of various regions of thecortex, if we allow for the greater margin of uncertainty which the abrogation method always leaves (p.191).It is noteworthy, also, that the disturbances are apparently less quickly compensated in the more highlyorganised brain of the monkey than they are in the dog, so that the symptoms of abrogation and stimulationare here more nearly in accord.Nevertheless, according to the observations of HORSLEY and SCHÄFER, itis impossible to induce an approximately complete paralysis upon the opposite side of the body, even in theinterval immediately following the operation, unless the whole centromotor zone is extirpated.If the area ofinjury is more limited, the muscles involved show only a weakening, not a total abrogation of movement.The determination of the centrosensory centres is, again, far less certain; the interpretation of the symptomspresents very much greater difficulties.Hence for the brain of the monkey, as for that of the dog, the resultsmay he regarded as reliable and assured only in so far as they refer to the general delimitation of the varioussense departments.With this proviso, we may conclude from the experiments of HERMANN MUNK, withwhich those of other observers agree on these essential points, that the cortical surface of the occipital brainconstitutes the visual centre, and that of the temporal lobe the auditory centre.The area for touch, taken asinclusive of all the organic sensations, coincides in position with the centromotor regions for the same partsof the body, i.e.is situated in the neighbourhood of the two central gyres and of the superfrontal gyre.[ 40]We have, in the above discussion, left the question of the nature of the cortical functions untouched, save inCHAPTER V.Course of the Paths of Nervous Conduction 110 Principles of Physiological Psychologyso far as it is connected with the problem of the termination of the paths of conduction in the cerebral cortex.The question cannot come up for consideration in its own right until the following Chapter, when we reviewthe central functions in their entirety.Even with this limitation, however, the experiments upon theterminations of the conduction paths still leave room for differences of interpretation.At the same time,physiologists are on the road to an agreement: it cannot be disputed that the ideas of the moderate party, ideaswhich compromise between the hypothesis of a strictly circumscribed localisation, on the one hand, and thedenial of any local differences whatsoever, on the other, have gradually gained the upper hand.It is thismiddle course that we have followed on the whole, in the preceding paragraphs.It may be that the lines of thevarious motor areas will, in the future, be drawn somewhat more closely or somewhat more widely; but thefundamental assumption that the functional areas extend from definite and narrowly circumscribed centres,and that at the same time they frequently overlap one another, has established itself more and more firmly, asthe most probable view, in the minds of impartial observers.GOLTZ has protested with great energy againstthe hypothesis of sharply defined localisations.His work has done a great deal, both by its positive contentsand by the stimulus it has given to other investigators, to clear up our ideas upon the subject.[41] But theresults which GOLTZ has obtained in his later papers do not differ in any essential respect from those of mostother observers; and he himself has now come to accept a certain dissimilarity of central representation,which in its general features resembles the account given above.Cf.also Ch
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