726 THE CEREBRAL CORTEX. 



parts of the cortex, which throws all the other muscles on the same 

 side of the body into contraction. If the area, excitation of which 

 produces facial movements, be cut away, there is paralysis of the 

 cheek-pouch, but after recovery from the immediate effects of the 

 operation the monkey still shows consciousness of the presence of food 

 within the pouch, and occasionally empties it by pressure with the hand 

 from outside or of the cheek against the shoulder. 1 



When there is paralysis of sensation produced by a lesion of the 

 Eolandic region, it is not necessarily localised to the limb the muscles 

 of which are deprived of voluntary motion, nor is it ever so com- 

 plete as it would be if the paralysis of motion were due to sensory 

 paralysis. 2 Charles Bell obtained paralysis of the facial muscles on 

 cutting the trigeminal nerve ; Exner and Pineles, 3 paralysis of all the 

 muscles of the larynx of the horse on cutting the superior laryngeal 

 nerve ; and Mott and Sherrington, 4 paralysis of the upper limb of the 

 monkey, on cutting all the posterior roots of the nerves supplying the 

 limb. Mott and Sherrington found that if only one posterior root of 

 the nerves proceeding to the upper limb were left, all the other sensory 

 fibres being cut, the paralysis which they obtained from severance of all 

 the posterior roots did not occur. Bastian 5 has suggested that this effect 

 is probably due to a diminution of excitability of the cells of the spinal 

 cord, consequent on the absence of the advent of peripheral impressions ; 

 thus there would be a diminution of tonus of the muscles concerned. 

 These cells and muscles are still capable of being excited to action 

 by electrical excitation of the cortex cerebri, and are also brought 

 into action in violent voluntary movements. 6 Nor does sensory 

 paralysis ever occur, as asserted by Munk, if the cortex connected with 

 the movements of a limited part of the body, such as one limb, be alone 

 removed. I have found 7 that if in successive operations even the whole of 

 the motor cortex be removed in the monkey, there may be no appreciable 

 effect upon the sensibility of the opposite side of the body, yet voluntary 

 paralysis is complete, v. Bechterew 8 makes a similar statement for 

 the motor cortex of the dog and monkey. Mott 9 came to the conclusion, 

 from his experiments upon monkeys, that there was sometimes, after an 

 extensive lesion in the Rolandic region, a certain amount of deficiency 

 in the sensibility of the paralysed limb. But the method of testing this 

 upon which he chiefly relied was one on which reliance cannot be placed. 

 He fixed a " bull-dog " clip alternately to the skin of the sound and 

 the paralysed limb, and found that it was usually at once removed from 

 the sound limb but was frequently left on the paralysed side; he 

 concluded that this showed a loss of tactile sensibility on the paralysed 

 side. That this conclusion is erroneous is shown by the fact that 



1 E. Flood, Brit. Med. Journ., London, 1894, vol. ii. p. 189. 



'-' It is an ascertained fact that voluntary movements are directed by sensations and 

 cannot be performed without the guidance of some sort of sensation. 



3 CentralU. f. Physiol., Leipzig u. Wien, Bd. iv. S. 741. See also Exner, Arch. f. d. 

 ges. Physiol., Bonn, 1891, Bd. xlviii. S. 592; and " Entwurf zu einer physiol. Erklarnng 

 der psych. Erscheinungen," Wien, 1894. 



* Proc. Roy. 8oc. London, 1895, vol. Ivii. p. 481. 5 Ibid., 1895, vol. Ivii. 



G Mott and Sherrington, loc. cit. ~ Schafer, loc. cit. 



8 Nein'ol. Ccntratbl., Leipzig, 1883, S. 409. This statement lias, however, been somewhat 

 modified by Bechterew, see ibid., 1898, S. 139. See also "Die Leitungsbahnen im Gehirn 

 u. Riickenmark," Leipzig, 1894, S. 146 ; and Ann 1 . 2, 1899, S. 429. Bechterew regards the 

 parietal lobe as being especially associated with all forms of cutaneous and muscular 

 sensibility. 



9 Journ. Physiol., Cambridge and London, 1894, vol. xv. p. 464. 



