64 STUDIES IN ELECTRO-PHYSIOLOGY: 



same hand, and equally in opposition to each 

 other, and that they appear to form terminals of 

 a circuit with the fingers of the same hand, as 

 when the thumb is brought into contact a current 

 at once passes. 



" (/) That the approach of the thumb to the electrode, 

 even without contact, produces a slight deflection 

 which is probably not static, as the deflection 

 remains after all movement, so far as it can be 

 controlled, has ceased." 



The main points touched upon by Dr. Martin, i.e. 



(1) That unless both hands are used the contact of 



skin and metal will not exhibit electrical action, 

 and 



(2) That the thumbs are of different sign to the 



fingers 



may be very simply and conclusively proved in the follow- 

 ing manner : 



Take two electrodes, of the same size, of copper, silver, 

 or German silver, and connect them by two wires of equal 

 gauge and length to the terminals of the galvanometer. 

 Insert one of these electrodes between the first and second 

 and the other between the third and fourth fingers of the 

 left hand, and do not allow them to touch. No deflection 

 will be observed unless the hand is wet. In that case there 

 may be a slight leakage from the thumb. Then bring the 

 left thumb into contact with one of the electrodes and a 

 deflection will at once ensue. Repeat the experiment 

 with the right hand and the result will be the same, only 

 that the deflection ultimately obtained will be of opposite 

 sign. 



This experiment as conducted by Dr. Martin is thus 

 described by him 



" (a) One electrode was placed between the third and 

 fourth fingers, the other electrode between the 

 first and second fingers of the left hand ; not 

 allowed to touch each other. Key closed, i.e. 9 



