60 STUDIES IN ELECTRO-PHYSIOLOGY: 



occur are always ascribable to charge imparted by some 

 source or vehicle of energy to the article under examination. 



As I have before remarked, it is owing to this fact, and 

 to the further important truth that all fluids and moist 

 objects possess conductive and inductive capacity, that the 

 results obtained by various investigators have so materially 

 conflicted. 



But when under the same conditions we test anything 

 in which there is life, we have different factors to deal with. 

 In the section upon Electrical Structure and Function 

 in Plant Life I have given a summary of some ten thousand 

 tests of fruits and vegetables in which I used steel darning- 

 needles as the electrodes, but one or two of them may be 

 repeated here. 



First theory : Take two equal lengths of insulated 

 flexible copper wire and solder to each length a steel 

 darning-needle, connecting the other ends to the terminals 

 of the recording instrument. Call the needles R and L 

 respectively. 



Now select a sound onion and insert the R needle in 

 the root, and the L needle in the foliage end. Upon 

 depressing the galvanometer short-circuit key a constant 

 negative deflection will be observed. Theoretically, there- 

 fore, the L needle is electrically positive to the R needle, 

 and the juice of the onion being the exciting liquid galvanic 

 action is set up. If that is so, and if we do not reverse the 

 connections, the polarity of the needles is established, and 

 we must continue to get a negative deflection, no matter 

 where we insert the needles. If, however, the onion is 

 reversed, so that the R needle is in the foliage end and the 

 L needle in the root, there will be an equally constant 

 positive deflection, showing that the difference in polarity 

 is in the vegetable, and not in the needles. 



Again, take two suitable electrodes, say two silver rods 

 6 in. by f in., provided with terminals ; attach them to 



