202 SECONDARY ELECTROMOTIVE PHENOMENA IN 



this experiment, which was moreover first suggested by me 1 , though 

 on account of theoretical difficulties it was not carried out, as an 

 experimentum crucis against the molecular theory of electrotonus 2 . 



To Hermann's estimate of the electromotive force acting in a 

 nerve whose dipolar molecules collectively turn their similar poles 

 to the same side, I am the less able to object in principle that 

 I explain the functions of the electrical organs by similar esti- 

 mates 3 . That no force comparable with the calculated one appears 

 in nerves has been vindicated by the assumption made by me 

 already in the ' Untersuchungen,' that when the molecules are 

 thrown out of the true direction in relation to the polarising 

 current their rotation amounts only to a small angle, and not 

 to i8o. 4 



The difficulty which Hermann's experiment offers disappears 

 before the known facts of nerve polarisation. With a long time of 

 closure, negative polarisation exceeds positive, and as boiling heat 

 destroys both, the living nerve ought apparently to conduct worse 

 than the dead one, not better, as Hermann expected. In order to 

 find the living nerve a better conductor than the dead one the 

 experiment must be made with a very short time of closure. Even 

 then positive polarisation predominates over the negative only when 

 the strength of the primary current is so considerable, that there 

 is little hope of observing the slight excess of positive over negative 

 polarisation when this is added to the primary force. There is, 

 however, one experiment which might be explained in this sense. 

 If a nerve closes the secondary circuit of an inductorium, the alter- 

 nating currents of which would otherwise, according to well-known 

 rules, compensate one another in the galvanometer, the quicker and 

 shorter opening currents predominate, according to Fleischl. A 

 single opening shock also passed through the nerve causes a 

 stronger deflection than a closing shock 5 . Inasmuch as the opening 

 shock is more exciting than the closing one, Hermann sees in this 

 nothing more than a special case of his 'theory of polarisation 



1 Untersucliungen uber thierische Elektricitat, vol. ii. part i. p. 328. 



2 Untersuchungen zur Physiologic der Muskeln u. Nerven, part iii, 1868, p. 67 ; 

 Pfluger's Archiv, 1872, vol. vi. p. 328; Die Ergebnisse neuerer Untersuchungen auf 

 dem Gebiete der thierischen Elektricitat, Sep. Abdr. aus der Vierteljahrschrift der 

 naturforschenden Gesellschaft in Zurich, 1878, part i. p. 17; Handbuch der Phy- 

 siologic, vol. ii. 1878, p. 172. 



3 Untersuchungen am Zitteraal, p. 275. 



* Untersuchungen Uber thierische Elektricitat, vol. ii. part i. p. 325. 

 5 Sitzungsberichte der Wiener Akademie der Wissenschaften, 1878, part iii. 

 vol. Ixxvii. p. 159. 



