THE CEREBRUM, AND ITS FUNCTIONS. 753 



them, these fully bear out the conclusion that the Cerebrum is the organ of In- 

 telligence ;; since the animals which have suffered this mutilation appear to be 

 constantly plunged in a profound sleep, from which no irritation ever seems 

 able to arouse them into full activity, although they give manifestations of con- 

 sciousness. It would be wrong hence to infer, however, as some have done, 

 that such would be the natural condition of an animal without a Cerebrum ; 

 since it is obvious that much of the disturbance of the sensorial powers which is 

 occasioned by this operation, is fairly attributable to the laying-open of the 

 cranial cavity, to the disturbance of the normal vascular pressure, and to the 

 injury necessarily done to the parts which are left, by their severance from the 

 Cerebrum. Hence the persistence of consciousness, after the entire removal of 

 the Cerebrum which proves that the Cerebrum is not its seat, or at least not 

 its exclusive seat is a far more important fact than the positive destruction of 

 psychical power which is consequent upon the operation. So far as they can be 

 trusted, however, the results of such mutilations bear out the views already put 

 forth as to the superadded and non-essential character of the Cerebrum ; and 

 justify us in applying to the higher animals the inferences to which we should 

 be led by the contemplation of those forms of the nervous system in which no 

 Cerebrum exists. There is nothing, therefore, to oppose the conclusion, that 

 whilst sensations may be felt, and sensori-motor actions excited, independently 

 of the Cerebrum, the presence of this organ is essential to the formation of 

 ideas or notions respecting the objects of sense, and to the performance of those 

 psychical operations to which ideas furnish at once the material and the stimu- 

 lus to activity. 1 



785. The information afforded by Pathological phenomena is equally far from 

 being definite. Many instances are on record, in which extensive disease 

 has occurred in one Hemisphere, so as almost entirely to destroy it, without 

 either any obvious injury to the mental powers, or any interruption of the in- 

 fluence of the mind upon the body. But there is no case on record, of any 

 such severe lesions of both hemispheres, in which morbid phenomena were not 

 evident during life. It is true that, in Chronic Hydrocephalus, a very remark- 

 able alteration in the condition of the Brain sometimes presents itself, which 

 might a priori have been supposed destructive to its power of activity ; the 

 ventricles being so enormously distended with fluid, that the cerebral matter has 

 seemed like a thin lamina, spread over the interior of the enlarged cranium. 

 But there is no proof that absolute destruction of any part was thus occasioned ; 

 and it would seem that the very gradual nature of the change gives to the 

 structure time for accommodating itself to it. This, in fact, is to be noticed in 

 all diseases of the Encephalon. A sudden lesion, that may be so trifling as to 

 escape observation, unless this be very carefully conducted, will occasion very 

 severe symptoms ; whilst a chronic disease may gradually extend itself, without 

 any external manifestation. It will usually be found that sudden paralysis, of 

 which the seat is in the Brain, results from some slight effusion of blood in the 

 substance or in the neighborhood of the Corpora Striata ; whilst, if it follow 

 disorder of long standing, a much greater amount of lesion will usually present 

 itself. In either case, the paralysis occurs in the opposite side of the body, as 

 we should expect from the decussation of the Pyramids ; but it may occur either 

 on the same, or on the opposite side of the face the cause of which is not very 

 apparent. If convulsions accompany the paralysis, we may infer that the Cor- 

 pora Quadrigemina, or the parts below, are involved in the injury; and in this 



1 It is worthy of remark, that M. Flourens, who in the first instance maintained that 

 sensation is altogether destroyed by the removal of the Cerebrum, has substituted, in the 

 Second Edition of his Researches, the word perception for sensation; apparently implying 

 exactly what is maintained above. 

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