

ON NERVE-EXCITATION BY THE NERVE-CURRENT. 131 



Czermak found 1 'that a current-testing- frog's limb gives a 

 closing contraction, if its nerve is raised on a glass rod and suddenly 

 dropped upon the natural longitudinal section of a rabbit's or 

 pigeon's muscle, which happens to be in partial idio-muscular con- 

 traction, so that it is simultaneously in contact with a contracted 

 and a non-contracted portion of such muscle.' He remarks also 

 that 'very excitable frog's limbs' likewise contract if their nerves 

 fall upon an unaltered natural longitudinal section of the muscle, 

 and he explains this by the assumption that there are weak currents 

 between different points of such a surface. But Czermak found also 

 that frogs' legs of the highest degree of excitability gave distinct 

 and even very strong contractions if he let their nerves fall upon a 

 quiescent portion of a rabbit's intestine, or upon the kidney or liver 

 of the same animal. To infer from such contractions that there is 

 current from these tissues is not admissible, until it has been shown 

 by adequate control experiments that the nerve does not react, to 

 the closure of its own current. 



Kiihne 2 has already called attention to the fact that Donders was 

 mistaken in regarding, as an effect of currents from the cardiac 

 muscle, the contractions of the frog's leg which may be obtained by 

 dropping its nerve on the pericardium during the cardiac pause, 

 and he has shown that similar contractions may be obtained when 

 the nerve is dropped on to the pericardium after the heart has been 

 removed. 



Interference between a nerve-current and a battery-current. 



The effects of electrical excitation of a nerve in the vicinity of its 

 transverse section depend so much upon the nerve-current which is 

 present as to be quite unintelligible if this current is not taken into 

 account. 



According to the report of the fifty-fourth meeting of German 

 savants at Salzburg, Griitzner has recently called attention to the 

 paramount importance of the nerve-current to the excitability of 

 the nerve, or of any other nerve lying in contact with it a con- 

 sideration which is already, to some extent, suggested by Pfliiger's 

 ' Researches on Electrotonus 3 .' 



He says 4 , 'As conducing to the effect of excitation with constant 



1 Uber secundare Zuckung von theilweise gereizten Muskeln aus Sitzungsberichte 

 dieser Akad. 1857, un d Gresammelte Schriften, i. p. 429, Leipzig, 1879. 



2 Loc. cit. p. 85. 3 p. 151. * Loc. cit. p. 119. 



K Z 



