DISSOCIATION OF COMPLEX SENSATION 6/1 



In experimenting on the effect of mechanical stimulation, 

 the intensity and frequency were so adjusted as to bring 

 about a neutral and imperfect fusion. In a particular 

 experiment, for example, the frequency of stimulus was four 

 times in a second. The receptive point for this experiment 

 was the very sensitive back of the end joint of the human 

 fore-finger that is to say, the space immediately adjacent to 

 the quick of the nail. In order to study the electrotonic 

 effect, one electrode was applied by means of a piece of 

 cotton, moistened in normal saline, and placed on the 

 receptive area, the second being on a different finger. After 

 so adjusting the intensity and frequency of stimulus as to 

 give the required semi-continuous and indifferent sensation, 

 the receptive point was made kathode, the E.M.F. employed 

 being moderate that is to say, of 1*5 volt. The resulting 

 sensation was distinctly painful and continuous. By now 

 reversing the electrotonic current, the receptive point was 

 made anode, and the resulting sensation was not only 

 positive or soothing, but also strikingly discontinuous. In 

 order to exhibit the reversal of these effects under feeble 

 E.M.F., I employed an E.M.F. of '2 volt. The initial 

 indifferent sensation was now found to be converted under 

 anode, to negative and continuous, the kathode inducing a 

 soothing and discontinuous sensation. The effect under 

 a feeble E.M.F. is thus found to be in every way the opposite 

 of that under strong. When frequent experiments are 

 carried out on the same finger, the result is apt to be blurred 

 in consequence of fatigue. It is therefore advisable to carry 

 out the preliminary adjustment with one, and to repeat the 

 experiment on another finger. The normal opposite effects 

 of anode and kathode may in general be easily demonstrated 

 by an E.M.F. of 1-5 volt. But the value of the feeble 

 E.M.F. which induces the reversal of these, varies with 

 different individuals and with different modes of stimulation. 

 It is, therefore, advisable to start with the Jowest possible 

 E.M.F. of the order of about -01 volt, and increase it 

 gradually, till the reversal of effects is most pronounced. On 



