ELECTROTONTTS. 119 



lability of the nerve is only manifested at the closing or 

 opening of the circuit ? ' 



Anelectrotonus and Catelectrotonus. It is interesting to 

 note that when a portion of a nerve is subjected to a moder 

 ately powerful constant current, the conditions of the extra 

 polar portions corresponding to the two poles of the battery 

 are entirely different. ]N"ear the positive pole, or anode, the 

 excitability of the nerve and the rate of nervous conduction 

 are diminished. If, however, we have a galvanometer ap- 

 plied to this portion of the nerve, its electromotive power, 

 measured by the deflection of the galvanometric needle, is 

 increased. On the other hand, near the negative pole, or 

 cathode, the excitability of the nerve is increased as well as 

 the rate of nervous conduction ; but the electromotive power 

 is diminished. The above is laid down by Rutherford, as 

 the law of electrotonus. 8 These facts, at least so far as they 

 relate to the increase of the excitability of the nerve near 

 the cathode and its diminution near the anode, are partial- 

 ly explained by Matteucci upon purely physical principles, 

 depending upon - the electrolytic action of the current, as is 

 shown by the following experiment : 



Two cups are filled, the one with a very feeble alkaline 

 solution, and the other with an equally weak acid fluid. A 

 number of galvanoscopic frogs' legs are then rapidly pre- 

 pared, of which one-half the number is plunged in the alka- 

 line and one-half in the acid fluid, for from thirty seconds 

 to one or two minutes. The parts are then removed from 

 the liquids, and are carefully washed and dried in bibulous 

 paper. By touching the nerves with a strong solution of 



1 It is necessary to note, in this connection, that Matteucci (Joe. cit.) found 

 that the electrotonic condition in the platinum wire covered with moistened 

 cotton was affected by a strong ligature in nearly the same way as a living nerve, 

 when, of course, " the alteration consists principally in the solution of continu- 

 ity thus produced in the moist covering of the metallic thread." 



2 RUTHERFORD, Electrotonus. Journal of Anatomy and Physiology, Cambridge 

 and London, 1868, vol. ii., p. 98. 



