364 EFFECT OF IRRITATION OF A POLARIZED NERVE. 



tions which He to the side of the negative pole (Imthode) of a polarizing cur- 

 rent is increased; while all irritations lying to the side of the positive pole 

 [anode) have their action diminished. 



When, however, this author used stronger currents he obtained the 

 Eckhard results. 



Pfluger repeated his irritations, alternately with and without polari- 

 zation, sixty or more times a minute. This is certainly too often to ob- 

 tain accurate results, as under these circumstances I have a number of 

 times observed that the effects of the removal of the previous irritation 

 overlap into the time of the succeeding irritation. His results were ob- 

 tained on frogs taken in winter, spring, and summer, and in both varie- 

 ties of the Buna esculenta, and m diseased as well as in healthy frogs. 



When this investigator nsed polarizing currents of greater strength 

 he obtained the results of Valentin and Eckhard. Both the irritations 

 and the polarization were made by means of the albumen electrodes 

 (/. e., uon-polarizable electrodes). To obtain the weakest possible cur- 

 rents which would produce muscular contractions, Pfliiger made use of 

 the rheochord. In some of his experiments the irritations were made 

 by an interrupted current. 



Schlflf,* though in a number of experiments he obtained results simi- 

 lar to those obtained by Pfliiger, Avas the first to experimentally criticise 

 the theory of this investigator. He states that an experiment which at 

 first corresponded in its results to those obtained by Pfliiger, after a 

 half hour gave the very opposite results. He also saw diminished ex- 

 citability of the nerve produced by the constant cuirent to the side of 

 negative pole (katelectrotonus), and increased excitability occur to the 

 side of the positive pole (anelectrotonus). In one experiment he saw 

 augmented excitability of the nerve both above and below a descending 

 polarizing current and diminished excitability above and below an 

 ascending polarizing current. 



Valentin, t in a later work on this subject, found, when very weak cur- 

 rents were employed, an increased excitability to occur to the side of 

 the negative and also to the side of the positive pole of the polarizing 

 current. These experiments were made with the nerve in sitti, and con- 

 sequently the non-polarizable electrodes had to be dispensed with. 



Nor was Budget more successful in his eflbrts to convince himself of 

 the constancy of Pfliiger's results. This experimenter's polarizing cur- 

 rent was derived from 1-2 Daniel cells. His electrodes in some experi- 

 ments were of amalgamated zinc, but in other experiments platinum and 

 copper electrodes were used, as with these Budge states he obtained the 

 same results as with the former. To test the excitability of the nerves 

 this author resorted to a solution of ordinary salt as an irritant. He 



* Lehrbuch der Nerven uud Muskelphysiologie, 1859, p. 94, 



t Valentin's paper I was never able to obtain, but was kindly informed of its con- 

 tents by Professor Schiff. 



1 Virchow's Archiv., Bd. 18, p. 457. ; Bd. 28, p. 398. 



