126 



THE SIGNS OF LIFE 



[LECT 



regard the tissues as represented by a sponge of such NaCl 

 solution ; if you pass the current into the body by porous 

 electrodes soaked in some other salt and for this purpose we 

 shall take permanganate of potash you will, after a few minutes, 

 observe a visible sign of the transfer of the anion from electrode 

 to body in the form of a discoloration of the skin at the spot 

 where the anions have travelled against the direction of current 

 from kathode to anode. I chose permanganate of potash 



K MnOa 



FIG. 53- Circular areas of skin of the forearm that have served as electrodes to a 

 constant current for a few minutes. In the upper pair of circles the two electrodes in 

 contact with the skin were a solution of permanganate of potash ; the coloured ion was 

 the anion MnO 4 , which travels up stream and enters the body at the kathode. In the 

 lower pair of circles, the two electrodes in contact with the skin were a solution of 

 copper sulphate ; the coloured ion was the kation Cu, which travels down stream and 

 enters the body at the anode. 



because it has a coloured ion, in this case the anion. If I had 

 taken copper sulphate, where it is the kation copper that is 

 coloured, I should have made the anodic spot the more apparent 

 since the metal travels with the current and is carried into the 

 body at the anode. 



Two electrodes one-inch glass tubes half full of perman- 

 ganate of potash are strapped to the front of my forearm, 



