LOCALISATION IN THE CORTEX CEREBRI 727 



animals display consciousness of and clearly localise a slight touch 

 or gentle stroking of the paralysed limb, upon which a fairly strong 

 clip will be left unnoticed. The reason why the pressure of the 

 spring clip is felt upon the non-paralysed side is probably to be 

 found in the fact that the muscles of that side are constantly in 

 slight activity, and the variations in tension which this produces 

 upon the skin converts the constant stimulus of the clip into a variable 

 stimulus which is at once appreciated. On the paralysed side this 

 of course does not occur. 1 



That the above is the correct explanation of the results with the 

 " clip " test, is probable also from the fact that as soon as the " associated 

 movements " of the paralysed limb return, the difference of behaviour of 

 the two limbs to the clip is no longer apparent. 2 Even where there 

 appears a slight defect in the localisation of sensory impressions 

 after removal of a localised portion of the Eolandic cortex, this by no 

 means shows that the region in question is sensory, any more than 

 defects of olfaction or vision after lesions of the trigeminal prove 

 that olfactory and visual impressions are conveyed by this nerve. 3 

 For after such lesions there invariably follows, as the result either of 

 inactivity of the muscles or of vasomotor changes, a general swelling of 

 the limb due to the accumulation of lymph ; there is usually also 

 dryness of the epidermis, and vaso-dilatation ; any of which conditions 

 would tend to affect its sensory functions. This will be further 

 discussed when the clinical evidence has been alluded to. 



The conclusion arrived at, therefore, so far as we can interpret 

 experiments upon animals, is that removal of the part of the cortex with 

 which the volitional movements of a limb are connected, either does not 

 at all affect the tactile sensibility of the limb, or if a slight effect is 

 produced it is in an indirect manner ; the paralysis of motion cannot be 

 the result of loss of tactile sensibility. 4 



It is difficult to determine in an animal questions which involve 

 differences in general sensibility, and quite impossible to determine 

 questions involving what has been called " muscular sensibility," or 

 appreciation of muscular contraction through the position of the limbs. 

 It is necessary, therefore, to turn to clinical experience to assist us in 

 determining whether a lesion of the Eolandic region of the cortex, which 

 in man as in monkey produces according to its extent paralysis of 

 voluntary motion, is accompanied by loss of sensibility in the paralysed 

 parts. The reply which clinical medicine has furnished to this question 

 is not uncertain. Very many cases have been recorded in which 

 sensibility has been most carefully tested, and in which not only has 



1 The same explanation holds good for the results obtained by Mott from hemisection of 

 the eord. He came to the conclusion that the paralysed limb in this case also was deficient 

 in sensibility, because there was as a rule no tendency to remove a clip from it. I have 

 found, however, in monkeys with hemisection of the cord, that although these animals may 

 not remove a clip from the paralysed side, they will react, by looking round or otherwise, 

 to a touch or stroking of the paralysed foot, so that Mott's conclusion, which was based 

 wholly upon the "clip" phenomenon, cannot be accepted without reservation in either case. 

 Mott himself, in his hemisection experiments, got evidence of reaction to touch {Phil. 

 Trail*., London, 1892, vol. clxxxiii. B, p. 1). 



'-' Mott, ibid. 



3 Gf. on this subject, v. Bechterew, Neurol. Ccntralbl., Leipzig, 1894, S. 2f>2, 297. 



4 Schafer, Journ. Physiol., Cambridge and London, 1898, vol. xxiii. p. 310. On the 

 other hand, the tactile and general sensibility of a part may be completely abolished by 

 cocain, but the action of the muscles in no way affected. This is stated to be the case 

 with the larynx by Beaunis (Bull. Soc. de psych, exp., Bordeaux, 1888, tome iii. p. 14). 



