248 ELECTRIC CURRENT. L.ECT. XII. XIII. 



The excitability of the nerves of a frog, thus tetanized 

 by the passage of the electric current, is very feeble when 

 compared with that of another frog upon which a continued 

 current has been made to act. I have often repeated this 

 comparative experiment by submitting two frogs, prepared 

 alike, the one to the action of the continued current pro- 

 duced by forty-five elements, and the other to that of a 

 pile of the same force, but in which the current was inter- 

 rupted and re-established at short intervals. 



In each of these cases the experiment lasts ten or fif- 

 teen minutes. By submitting afterwards, the lumbar nerves 

 of these frogs to the passage of the direct current, I ob- 

 served that a greater number of elements was required to 

 cause contraction in the animal which had been previously 

 submitted to the interrupted current, than in that which 

 had been subjected to the direct one. I also satisfied my- 

 self of the difference of the excitability of these two frogs, 

 by causing a continued current to act upon them at the 

 same time ; the diminution was constantly greater in the 

 one which had been submitted to the influence of the inter- 

 rupted current. 



Marianini, also, found, that by comparing two frogs, one 

 of which had been traversed by a continued current al- 

 ways in the same direction, and the other by a current 

 transmitted sometimes in one and sometimes in the other 

 direction, that the excitability of the nerves, was less ex- 

 hausted in the first animal, than in the second one. 



This great diminution of excitability in the nerves, or to 

 speak more precisely, in the nervous force, induced by the 

 passage of the current renewed at very short intervals, has 

 been clearly demonstrated by the experiments of Masson. 

 The apparatus by which this philosopher succeeded in trans- 

 mitting the electric current a great number of times through 

 an animal, and interrupting it for very short intervals, con- 



