484 Drs. F. W. Mott and C. S. Sherrington. [Mar. 21, 



previously.* But the question remained, what will be the result 

 when, for many weeks, the severance of the roots has led (as above 

 shown) to disappearance from the limb of those very movements 

 which the cortex, when experimentally excited, is especially able to 

 produce ? We Lave answered this, both by electrically exciting the 

 cortex and by giving absinthe intravenously to produce epilepsy 

 (Magnan). On exciting the cortex cerebri of the hemispheres in the 

 appropriate regions for eliciting movements of the thumb, hallux, or 

 digits, the responsive movements have been as easily elicited from the 

 apsesthete limb as from the normal limb, and it has several times 

 seemed to us rather more easily, that is to say, with a slightly less 

 intensity of faradic current (the rate of interruption always remain- 

 the same, -"). 



As to the absinthe epilepsy, it always affected the apaesthete 

 limb in a manner not distinguishably different from the normal 

 limb. Convulsions sometimes started in the normal and desensi- 

 tized limb simultaneously, sometimes a little earlier in one or the 

 other ; but no indubitable predominance or preference was shown by 

 either limb. In a very few of our experiments (three) no movement 

 was obtained in the apaesthete limb on excitation of the cortex; 

 this was found to be explained subsequently by naked-eye degenera- 

 tion of the pyramidal tract as revealed after hardening in Miiller's 

 fluid. This degeneration was due to injury accidentally inflicted 

 upon the lateral column of the cord by the operation. The spinal 

 tonus in the muscles of the apaesthete limb is undoubtedly much 

 diminished. 



These observations seem to us to point to the profound difference 

 existing between the production of the finer movements of the limb 

 in volition on the one hand, and by experimental stimulation of the 

 cortex on the other. The fundamental importance of sensation for 

 those finer movements of the limb, which are so especially well repre- 

 sented in the cortex of the ape, has by no authority been more 

 forcibly emphasized than by Dr. Bastian. We think these experi- 

 ments go even further than his arguments in pointing to the influence 

 of sensation upon voluntary movement, inasmuch as they indicate 

 that not only the cortex, but the whole sensory path from periphery 

 to cortex cerebri, is in action during voluntary movement. 



(2.) Effect of Section of a single Sensory Hoot. In striking con- 

 tradiction to the above-stated impairment of movement in the limb 

 ensuing upon section of the whole series of its sensory nerve roots 

 stands the effect of section of any one of the sensory nerve roots of 

 the series singly and alone. In the latter case no impairment of 

 movement at all results, or, at least, can with certainty be detected. 



This is the case even when the largest and most important sensory 

 * C. S. Sherrington, ' Phil. Tran-.,' vol. 184, B, pp, 690, 691. 



