192 SECONDARY ELECTROMOTIVE PHENOMENA IN 



the current lasted those sensations of heat and cold were experienced 

 which J. W. Bitter made the subject of his speculations in the 

 beginning- of the century x . The friends of my youth, Wilhelm 

 Beetz, Ernst Briicke, Karl von Erlach, J. G. Halske, Gustav 

 Karsten, shared then with me the difficulties of these experi- 

 ments. I am happy to be able here, after nearly forty years, to 

 render them my thanks. The result was at first an irregular 

 confusion of positive and negative deflections, but it was soon 

 possible to control the phenomena. With a short closing of the 

 battery, there followed a positive polarisation, and with a long 

 one (15" was all that could be endured) a negative polarisation. 

 With a moderately long closure and rapid transference of the 

 fingers from the battery basins into the conducting vessels, 

 negative polarisation followed, and when the transference was slow, 

 positive polarisation. 



The actions were strong enough to try if they would not make 

 themselves apparent in a rheoscopic thigh. This was in reality the 

 case. According to Humboldt's method 2 , the nerve had two pieces 

 of beef laid on it as conductors ; if I touched these with my fingers 

 after I had polarised myself in the battery circuit, the leg con- 

 tracted most vigorously. As one cannot succeed in making the 

 frog's leg contract by means of voluntary tetanus it is rather 

 interesting that it can be done by secondary electromotive 

 action. Experiments in polarising the human body by means 

 of the shocks of a Leyden battery were without result. On 

 the whole these facts seem to be in complete accordance with 

 those in frog's muscles and in living frogs. Unfortunately so much 

 uncertainty attaches to them that it for the present deprives 

 them of value. I was not then aware of the polarisation at 

 the surface of contact of electrolytes. I only looked to see whether 

 the fingers, after the closure of the battery, had an acid or alkaline 

 reaction like the ends of a frog through which a current was passed, 

 and I found once after long closure, traces of acid reaction on one 

 finger, though they appeared to me to be too slight to lay further 

 stress upon them, more especially as intentional soiling of the fingers 

 with dilute nitric acid and liquor potassae produced no actions com- 

 parable to those which we have to explain. I cannot now, however, 

 understand why I did not alter the experiment so as, for instance, to 



1 TJntersuchungen, vol. i. pp. 356, 357. 



* Versuche iiber die gereizte Muskel und Nervenfaeer, Fosen und Berlin, 1797, 

 vol. i. pp. 35 ff. 



