EFFECT OF IRRITATION OF A POLARIZED NERVE. 365 



found that when a sohition of salt, just strong enough to produce mus- 

 cular twitchings, was aj^plied above either a descending or ascending 

 polarizing current, augmented contractions always occurred during the 

 passage of the latter current. When, however, the salt solution was 

 strong enough to i)roduce tetanus, a polarizing current in either direction 

 caused this to cease. 



In another series of experiments the irritation was made by the clos- 

 ing of a constant current. When this irritating current was taken so 

 weak as to produce only a trace of contraction in the muscle, the polar- 

 izing current on the contrary being very strong, the augmented excita- 

 bility was only produced by a descend ng irritating current, and the con- 

 trary effect was produced by an ascending irritating current. When the 

 polarizing current was of less strength and the irritating current stronger 

 Pfliiger's results were obtained. 



Fick * used the induced current as an irritant. His results are as fol- 

 lows : 



1. A descending irritating current applied to the nerve above an as- 

 cending polarizing current caused marked augmentation in the muscu- 

 lar contractions during the x)assage of the polarizing current. 



2. An ascending irritating current applied to the nerve above an as- 

 cending polarizing current jiroduced an unimportant augmentation in 

 the muscular contractions during the passage of the latter current. 



3. A descending irritating current applied to a nerve above a descend- 

 ing i)olarizing current produced marked diminution in the muscular con- 

 tractions during the passage of the latter current. 



4. An ascending irritating current applied to the nerve above a de- 

 scending polarizing current produced not very marked diminution in 

 the muscular contractions during the passage of the latter current. 



From these results Fick concludes, against Piliiger, that, with mod- 

 erately strong induced currents, the exciting impulse does originate in 

 the region of the negative electrode, and that, with a very strong polar- 

 izing current the wiiole intrapolar portion of the nerve is put into a 

 state of anelectrotonus. 



In descending katelectrotonus Munkt found the excitability of the 

 nerve increased for the descending and diminished for the ascending 

 irritating current, but immediately after electronizing the nerve the re- 

 verse effect was obtained. In weak ascending anelectrotonus the mus- 

 cular-contraction-excitiug properties of the descending irritating cur- 

 rent were increased, diminished for the ascending, while the opposite 

 effect was obtained when the polarizing current was stronger. In weak 

 ascending kate- and anelectrotonus the excitability was increased for 

 currents traveling in the same direction. By polarization with stronger 

 currents the excitability was increased for irritating currents traveling 



*Beitrage zur Phys. des Elektrotouus, Vierteljahrsclir. der Ziiricher Naturforsch. 

 Gesellschaft, 1866, p. 48. 



tUnters. zu alJgem. Nervenphys. Arch, fiir Aiiat. uud Pbys., 1866, p. 369. 



