HELMHOLTZ IN KONIGSBERG 



of great importance that no contact or galvanic 

 electricity should be generated by bringing the 

 electrodes against the living tissue. The desideratum 

 was what is now called a system of non-polarizable 

 electrodes. Helmholtz tried unsuccessfully to make 

 such electrodes of pure silver immersed in a solution 

 of a salt of silver. Later it was found that pure 

 zinc amalgamated on the surface, and immersed in 

 a saturated solution of sulphate of zinc practically 

 fulfilled the conditions, a result that could not have 

 been theoretically anticipated, and was discovered by a 

 lucky hit. With pads of blotting paper immersed 

 in zinc troughs containing the solution of sulphate 

 of zinc, and with pads of sculptor's clay moistened 

 with saliva laid on the paper pads to protect the 

 muscle from the irritant action of the sulphate of 

 zinc, perfect non-polarizable electrodes were obtained. 

 It was then demonstrated that if a living muscle, 

 say the gastrocnemius of a frog, is cut in transverse 

 section, and if one clay point is applied to the middle 

 of the longitudinal surface and the other to the middle 

 of the transverse section, a current will flow through 

 the galvanometer in such a direction as to indicate 

 that the surface is positive to the transverse section. 

 To explain these phenomena, Du Bois Reymond 

 advanced a physical theory which may thus be 

 shortly described. If we take a cylinder of zinc, 

 having a bit of copper soldered on each side, and 

 plunge it into dilute sulphuric acid, or even water, 

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