295 



Of the Measure of the Limits of the Electric Nervo-muscular Sensi- 

 bility in Man, compared with his Mechanical Force. 



ExPERIMEiVTS OF ZaNTEDESCHI. 



The measure of the limits of tlie electric nervo-muscular sensibility 

 m man has a close relation to Physiology and Therapeutics. The 

 first obtains the means of ascertaining in a positive manner the vari- 

 ous degrees of sensibility of the human organism; as it has obtained 

 proof of the sensibility of the acoustic nerve from the extension of the 

 scale of perceptible sounds, and has determined the number of the vi- 

 brations which is necessary for the perception of a grave sound, and 

 of an acute one. Therapeutics procures a guiding rule for the pru- 

 dent application of electricity to different persons. I call to mind an 

 individual whose nervo-muscular sensibility was such that he could 

 not bear the electric motor force of a single combination of copper and 

 zinc with salt water. The electrodes were applied to the eyebrow of 

 an eye affected with paralysis. 



For investigating the subject of the limits of nervo-muscular sensi- 

 bility in the human subject. May 27, 1857, I caused to be constructed 

 the apparatus of Dubois Raymond, with an ordinary element in the 

 fashion of Bunsen, consisting of sulphuric acid of 40° B. and of water 

 acidulated with sulphuric acid of 10° B. and thoroughly amalgamated 

 zinc. The inducting spiral was of copper wire of the following di- 

 mensions : 



Length of the spiral, - - - 0.0800 metres. 



Internal diameter of the spiral, - 0.0250 „ 



Diameter of the copper wire, - - 0.0010 „ 



Length of the copper wire, - - 26.0000 

 Dimensions of the inducted spiral : 



Length of the spiral, - - - 0.0700 metres. 



Internal diameter of the spiral, - 0.0600 „ 



Diameter of the copper wire, - - 0.0033 ,, 



Length of the copper wire, - - 1187.4400 



In the interior of the inducting spiral there was a soft iron wire 

 with a diameter of 0.0015, and the length of 0.10 of a metre, and the 

 number 190. 



Twelve individuals were subjected to this experiment. There was 

 no positive rule of decrease of sensibility that would imply a minimum 

 degree in those advanced in life. I myself, 60 years of age, felt the 

 inducting volto-electric action at a distance at which it was quite in- 



