MEMOIKS OF TUE XATIOXAL ACADEMY OF SCIENCES. 



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current was closed, aiul there was a tlasli dt' light oii lueaking. "When tiie nef/afive pole was 

 applied to the dry lip there was a very slight shock and flash ot light and no perceptible taste, 

 but sensations of piercing quickly followed, wliirh were unendurably painfnl. Wheu the electrodes 

 were taken ."> mtn. apart and applied on the arm or lip, there was a slight shock on closing, 

 followed by prickling sensations, not very ])uiufiil and without tetanus. The i)ain was at the 

 negative pole. We wish especially to call attention to the fai't that the current from the negative 

 pole was more intense and from the positive pole more diffused (extending with considerable 

 energy from the lip to the visual apparatus), which indicates that the current passes through the 

 body from negative to positive pole, confirming certain physical observations. 



We are not here further concerned with the galvanic current, having used a momentary 

 induced current in our experiments. The breaking of the pi'imarj- circuit causes a steeper wave 

 and greater physiological shock than the making. Unless we are mistaken in the direction of the 

 winding of the coils (we had proposed determining the direction of the induced current directly, 

 but tailed to do so), the breaking shock was strongest from the positive pole, ami we used this pole 

 to give the stimulus, the negative pole being conducted to the foot, where little or no sensation 

 occurred. When, however, the shock was weak there was Init little difference between tlie poles, 

 and the negative pole might even give the stronger shock.' 



The intensity and nature of the sensation varies according to the size of the electrode and 

 the part of the body stimulated. The sensation is more piercing from a pointed or small electrode 

 or when applied close to the nerve; it is more massive (as from a blow) when ai)plied by a larger 

 electrode or when there is muscle intervening. The sensation of a shock from eight cells on the 

 upper arm might be equal to that from twenty-eight cells on the wrist. The shock from the same 

 current also varied with the pressure of the electrode and especially with the moisture of the skin. 

 Further, as the experiments proceeded, the part of the skin to which the shock was applied 

 became continually more sensitive. These were the most perplexing factors in our exi)erimeuts, 

 as the diftereuce in the time of the reaction might be due to differences in the cerebral reflex 

 rather than to the distance traveled by the imjiulse. We tried to elinunate these complications 

 by adjusting the intensity and area and by choosing points on the skin where the sensations 

 were alike, and shall subjoin the results of our experiments. It was, however, this difticulty 

 which led us to substitute a touch or l)low for an electric shock, and we believe our experiments 

 on touch are the more satisfactory, as we couid measure the force of the blow, whereas we could 

 not measure the physiological effect of an electric shock. 



In our first experiments we chose four points on the skin for the application of the stimulus. 

 These were permanently fixed by pricking the skin and introducing nitrate of silver. Two of the 

 points were on the arm over the median nerve and two on the leg over the posterior tibial nerve. 

 The points on the arm 7> aiul D are shown in the lut: they were 30 cm. apart, and the length of 



i'lG. li. 



. the intervening nerve would be nearly the same. The corresponding points on the leg .1/ and ^V 

 were .")<» cm. ai)art. The same objective current did not call up the same sensation on the several 

 Ijoints. The shock was more massive and stronger at the upper points, and was followed by 

 contractions of the muscles. It was rather stronger on the arm than on the leg. Five hundred 

 reactions with the hand to stimulation of each of these points and five hundred reactions with 



' We are not in this place especially concerned with the muscular contraction directly following on electrical 

 gtiiuiilation of the skin. Motor points have been mapped out on the skin, the stimulation of which is followed 

 by thf contraction oj" special muscles. These are considered in work on the appliciitinn of electricity to medicine. 

 We have made some observations on this matter, especially on the eft'ects of successive stimuli, but they are not • 

 sufficiently systematic for publication. 



