464 



NA TURE 



{^March 17, 1887 



CEREBRAL LOCALISATION "^ 

 II. 



WE have considered the main positions first taken up 

 by Dr. Ferrier with regard to functional locaHsa- 

 tions, and it will be convenient to examine in the same 

 order the criticisms and statements of other observers 

 regarding those positions. 



(i) The Rolandic region. — The effects of excitation and 

 ablation in this region, so far as relates to the production, 

 or the paralysis, of the movements of voluntary muscles, 

 are almost universally admitted, and to this extent the 

 researches of Dr. Ferrier have received brilliant corro- 

 boration. But the inference that this region is therefore 

 of necessity motor has not been so generally acceded to. 

 The attacks to which it has been subjected are based, 

 almost without exception, upon a denial of the statement 

 that lesions of this region do not involve the loss or im- 

 pairment of sensation in the paralysed parts. It is alleged 

 that, on the contrary, the motor paralyses are invariably 

 accompanied by loss or impairment of sensation, either 

 of the so-called muscular sense (Hitzig, Nothnagel ; " sense 

 of movement," Bastian), or of tactile sensibility (Schiff, 

 Tripier), or of sensibility in general, muscular and 

 cutaneous (H. Munk) ; and it has been supposed that the 

 paralyses of motion which result from these cortical lesions 

 arc not true motor paralyses, such as would be caused by 

 destruction of a motor centre, but are rather due to the 

 loss of the sensations which guide the volitional move- 

 ments, or the ideas of such sensations, of which the part 

 of the cerebral cortex removed is assumed to be the 

 seat. 



The question seems, on the face of it, one which is 

 easily determinable. Do animals, and especially monkeys, 

 in which a lesion in the Rolandic region has been esta- 

 blished, exhibit loss of tactile (or any other form of) sensi- 

 bility.-' Are cases of motor hemiplegia in man which are 

 produced by injury or disease of this region accompanied 

 by loss of cutaneous or muscular sensibility, or are they 

 not.' As regards animals, many, indeed most, observers 

 answer this question emphatically in the positive sense. 

 As regards man, the evidence is more conflicting. We 

 have, it is true, the advantage of being able to obtain a 

 direct answer regarding the existence, or absence, of sensi- 

 bility in any particular case ; but on the other hand there 

 is not necessarily the same restriction of the lesion to the 

 cortical gray matter, and the exact localisation is much 

 more difficult of determination. Accordingly we find that 

 cases of motor paralysis from cortical lesions in man have 

 been put in as evidence upon both sides, according as 

 they have been accompanied or not by impairment of 

 sensibility. Dr. Ferrier is, however, very positive upon 

 this point, relying upon the accuracy of his own observa- 

 tions in animals, as well as upon evidence derived from 

 pathological observations in man, and the allegations to 

 the contrary are disposed of by him in the following 

 manner : — 



"The conclusion that tactile sensibility is lost or 

 diminished after destruction of the cortical motor area is 

 based on defective methods of investigation and erroneous 

 interpretation of the reactions of the lower animals to 

 sensory stimulation. Though an animal does not react 

 so readily to sensory stimulation of the paralysed side, it 

 does not follow that this is due to diminished or absent 

 perception of the stimulus. An animal may not react, or 

 react less energetically, to a sensory stimulus, not because 

 it does not feel it the less, but because it is unable, or less 

 able, to do so from motor defect. . . . All that the experi- 

 ments of Schiff and Tripier demonstrate is that motor 

 reactions are less readily evoked on the side opposite the 

 cortical lesion. But the same thing occurs in cases of 

 purely motor hemiplegia in man " (pp. 374-75). 



' "The Funclionsof theBrain." By David Ferrier. M.D., LL.D., F.R.S. 

 Second Edition, re-written and enlarged. (London : Smith, Elder, and Co., 

 1S86.) Continued from p. 441. 



" Strictly cortical lesions of the motor area do not cause 

 anaesthesia in any form, and it may be laid down as a rule 

 to which there are no exceptions that if anaesthesia is 

 found along with motor paralysis the lesion is not limited 

 to the motor zone" (p. 378). 



" The total abolition of the muscular sense (as in loco- 

 motor ataxy) does not paralyse the power of effecting 

 movements. Even though the impressions ordinarily 

 generated by muscular contraction are not perceived, yet 

 the person can walk or move his limbs with perfect 

 freedom under the guiding sense of vision. Even with 

 the eyes shut the patient can intend his movements with 

 correctness " (p. 3S0). 



" Loss of the muscular sense never occurs without 

 general anaesthesia of the limb. . . . The statements 

 to the contrary, sometimes met with, rest only on the 

 foundation of a demonstrably false hypothesis as to the 

 nature of the ataxy which it is invoked to explain " 

 (p. 3S0). 



" The idea of a movement may be perfect when the 

 motor centres are entirely destroyed. A dog with his 

 motor centres destroyed has a clear idea of the movement 

 required when asked to give a paw, and exhibits its grief 

 at being unable to do so in an unmistakable manner ; and 

 the patient suffeiing from cortical motor lesion, after 

 making futile eftbrts to carry out his ideally realised 

 movement, not uncommonly bursts into tears at his failure. 

 There is no defect in the ideation, but only in the realisa- 

 tion, of the movement" (p. 383). 



" The cortical centres are motor in precisely the same 

 sense as other motor centres, and are differentiated anato- 

 mically from the centres of sensation, general as well as 

 special " (p. 393). 



Certainly, if it can be shown that a distinct part of the 

 cortex is concerned with the perception of impressions of 

 general sensibility, this would afford strong prima facie 

 evidence against the Rolandic region being endowed with 

 sensory functions. And we shall presently see that such 

 evidence is forthcoming. 



(2) The evidence for the second proposition (that the 

 visual centre is situated exclusively in the angular gyrus) 

 has not found confirmation, and is virtually surrendered 

 by the author. That the angular gyrus is at all concerned 

 in the visual process is entirely denied by H. Munk, who 

 has shown that complete blindness is produced by re- 

 moval of the occipital lobes alone, without the implication of 

 the angular gyri, and that removal of one occipital lobe 

 produces blindness of the corresponding half of both 

 retina" (hemianopsia). According to Munk, this blindness 

 is permanent ; but Luciani and Tamburini, who have 

 obtained the same immediate result, affirm that it may 

 after a time disappear. Dr. Ferrier, however, denies that 

 the mere removal of the occipital lobes is followed by any 

 perceptible deficiency of vision ; and in support of this 

 statement, which was already made in the former edition, 

 he quotes the results of his own more recent experiments, 

 which were performed in conjunction with Prof Yeo, and 

 also certain unpublished results which have been obtained 

 by Mr. Horsley and myself Dr. Ferrier has, however, 

 been mistaken in supposing that our observations bear 

 out his statement, for we invariably found, when an exten- 

 sive removal was efi'ected in the occipital region, that 

 hemianopsia resulted therefrom, as described by IVIunk. 

 But in the few experiments which we performed the blind- 

 ness was not permanent, only persisting, so far as we 

 could judge, for some days, or, at the utmost, weeks ; and 

 in one of these cases, in which we af/erwards destroyed 

 the angular gyrus, hemianopsia which appeared to be 

 permanent was produced. This is confirmatory of the 

 statements of Drs. Ferrier and Yeo. I am myself, how- 

 ever, not at all sure that the permanence of the result 

 was due to the destruction of the angular gyrus, and may 

 not rather have been produced by the more complete 

 removal of the occipital lobe which that destruction 



