EFFECT OF IRRITATION OF A POLARIZED NERVE. 367 



waste of " printer's iuk/' but wlien it is recollected that the Pfliiger laws 

 of electrotonns are universally adopted by electro-therapeutists, it will 

 be seen that such an innovation as I propose to make in this branch of 

 physiology must be substantiated by solid facts. As will be shown 

 either in this work or in a paper to appear later, the facts here pre- 

 sented are not only of importance in this connection, but really derive 

 their greatest importance from their affording us a long-sought-for means 

 of explaining the symptoms produced by certain previously occult 

 changes in the central nervous system. 



THE EXPERIMENTS OF THE AUTHOR. 



The mefJiod and apparatus employed. — The irritations were made by 

 means of 1-4 small Daniel elements, the strength of which was reduced so 

 as to produce a minimal contraction, by means of a rheochord compris- 

 ing 3,199 centimetres of silver wire. A Valentin hammer or " key," in- 

 troduced to make the connection of the current, was so placed as to 

 always fall from the same height. This is absolutely necessary in all 

 these experiments, as the height from which the hammer falls greatly 

 influences the height or strength of the contractions by affecting the 

 strength of the passing current. 



The polarising current was derived from 1-2 Daniel elements, and was 

 also in connection with a smaller rheochord, 58 centimetres in length. 



The electrodes employed for both i^olarization and irritation were 

 Du Bois Eeymond's " Zinc-clay non-i3olarizable electrodes," which, as 

 Pfliiger will no doubt concede, are less objectionable than the albumen 

 electrodes which he employed. 



The frog preparations and the electrodes were brought into a moist- 

 chamber, where all the irritations were made. 



The use of a myographion — especially with a weight attached, as it 

 seems Pfliiger used it — had to be dispensed witli in the first series of ex- 

 periments, as my object was to obtain minimal contractions, which can- 

 not be obtained with a myographion as these contractions are too feeble 

 to raise or move the lever of this instrument. 



The distance between the two irritating electrodes was 4—6"'"', which was 

 also the distance between the polarizing poles. The distance between 

 the two currents varied from 5-11™'". 



Tho, frogs employed had been in captivity but a short time and were 

 largely of the temporaria variety. 



These experiments were especially guarded against the errors arising 

 from the occurrence of " secondary polarisation,^^ and from umpolar excita- 

 tions. 



A descending polarizing current applied to a nerve above a descending 



irritating current. 



N. 



/ \ / \ 



I. c. p. c. 



