VII 



.] TARCHANOFF'S EXPERIMENT 123 



to the first. The spot is " pulled by the ingoing capillary 

 soakage." 



Here, now, is a counter experiment : 



Both fingers are resting against the bottom of the vessels, as 

 indeed was recommended by du Bois-Reymond in order to 

 avoid the fallacy that I have just mentioned, and when the spot 

 is at rest I squeeze one of my fingers, say, of the left hand, 

 against the bottom of the vessel. The current through the 

 galvanometer is now from the compressed skin. The spot is 

 " pushed." In case you should object to the possible muscular 

 or secretory origin of the current by reason of the voluntary 

 action on that side used to effect the compression, I will remain 

 perfectly passive, and have the compression effected by a second 

 person without any act of mine. The effect follows as 

 before. 



While I am on this subject, let me show you one more 

 surface experiment. You have seen that contraction pulls the 

 spot, that soaking skin pulls the spot, that squeezed skin pushes. 

 I want to dry a wet finger in order to dip it in dry, I naturally 

 rub it, and then proceed to show that on soaking it again the 

 spot is pulled. But now, as you see, the effect is reversed, the 

 spot is pushed ; dry rubbed skin pushes the spot. 



And so we may use for our memorandum, that if zinc 



pulls the spot, last-dipped and therefore soaking skin pulls, 



that squeezed skin pushes, and that recently rubbed skin 



pushes. Neither du Bois-Reymond's contraction current, nor 



Hermann's secretion current are above suspicion in presence 



of those unavoidable capillary currents. And for my part I 



find it quite impossible to contract the muscles of my forearm 



without moving a finger or pressing it against something. 



73. TarcJianoff's experiment. Over ten years ago, Tar- 

 chanoff published an account of observations on the skin- 

 currents of the human subject, in which he considered that he 

 had obtained evidence of their reflex causation by all kinds 

 of peripheral stimuli by tickling, by induction shocks, by 

 pricking with a pin, by hot and cold water, by sudden sound, 

 sight, taste, and smell. He assures us, further, that imaginary 



