1895.] Influence of Sensory Nerves upon Movement, $c. 483 



paratively slight at the hip, it is successively greater at knee and 

 ankle, and greatest (amounting as regards volition to absolute loss) 

 in the digits. 



In this respect it curiously closely simulates the impairment of 

 motility ensuing upon ablation of the limb region of the cortex 

 cerebri ; but it is, in the monkey, somewhat more severe than the 

 impairment following cortical ablation. 



We find, however, that forcible and rapid movements, even of the 

 fine joints at the end of the limb, can be induced in the animals by 

 causing them to " struggle " ; for instance, while recovering from 

 ether inhalation, or while trying to free themselves on being held 

 awkwardly, the whole limb at all its joints may exhibit movements ; 

 but even under these circumstances it is only once or twice that we 

 have seen "grasping" movements of the digits, although sharp exten- 

 sion of the digits is not nearly so infrequent. 



We are led from these and other considerations, which will be 

 detailed in a fuller paper, to conclude that associated movements in the 

 limb (" Mitbewegungen ") are comparatively little impaired by loss of 

 the sensation from the limb in which they occur ; but that the inde- 

 pendent and more delicately-adjusted movements which employ pre- 

 ponderantly the smaller and more individualised muscular masses 

 of the hand and foot, and serve to move the digits, especially the 

 hallux and the thumb in fact, just those movements which are repre- 

 sented most liberally in the limb area of the cortex, are extremely severely 

 impaired, and, in some instances, are abolished. We say ' abolished ' 

 advisedly, because we are persuaded from our observations that, in 

 the case of certain movements, e.g., grasping movements of the hand 

 and foot, opposition of pollex and hallux, the animal is rendered 

 absolutely powerless to perform them, even under the strongest 

 possible inducements. This conclusion has been gradually forced 

 upon us. Although we are aware of the danger of introducing terms 

 relating to consciousness into descriptions based almost solely on 

 motor reactions, we believe that we cannot more lucidly state the 

 condition of the animals than by saying that the volitional power for 

 grasping with the hand, &c., had been absolutely abolished by the 

 local loss of all forms of sensibility experimentally produced. Further, 

 that this yolitional power was lost immediately from the time of 

 operation, and that there was not the slightest evidence of any 

 recovery of it during the longest periods to which our observations 

 extended (about four months). 



This being so, it is natural to inquire what influence, if any, is 

 exerted by the section of the posterior spinal nerve-roots of the limbs 

 upon the reactions obtainable from the limb area of the cortex ? 

 That no diminution, but rather a slight increase of the excitability of 

 the cortex, is the immediate result has been shown by one of us 



