MUSCLES, NEKVES, AND ELECTRICAL ORGANS. 169 



and wearisome course of experiments 1 . I understand by this a 

 resistance which is created by the current itself; which on ces- 

 sation of the current gradually decreases ; and which on its 

 reversal gradually disappears. The secondary resistance which is 

 developed in coagulated albumen between zinc pads is capable of 

 weakening the current from a Grove's battery of twenty elements 

 to such an extent, that only a tenth of the original strength 

 remains. Consequently, the secondary resistance may greatly 

 surpass the increase of conducting power consequent on the warm- 

 ing of a moist porous body by the passage of the current through 

 it. Reversal of the current in moist porous bodies in which 

 secondary resistance prevails, does not, like reversal in polarised 

 conductors, give rise to a sudden positive increase in the strength 

 of the current, but it presents the remarkable phenomenon of a 

 gradual increase, which goes on for some minutes, until the current 

 almost reaches its original height. From this point the decrease 

 begins, to be again exchanged for slow increase if the current is 

 once more reversed. 



There are two kinds of secondary resistance, i.e. an external and 

 an internal secondary resistance, corresponding to the external 

 and internal polarisation of moist porous bodies. The seat of the 

 first is the point where the current enters, and although much 

 remains obscure, it may be explained by the cataphoric action of 

 the current driving the fluid in the circuit onwards from the 

 anode to the kathode. Where a zinc pad conducts the current 

 to animal tissues a very strong external secondary resistance is 

 developed, but it is easy to prevent it from coming into existence 

 by the methods which I give. The internal secondary resistance 

 which has its seat everywhere in moist porous bodies has up to this 

 time only been observed in any great degree in the tissues of living 

 plants, and therefore comes less into consideration in the experi- 

 ments of which we are treating 2 . 



The investigation of external and internal polarisation, of external 

 and internal secondary resistance of moist porous bodies which 

 engaged me for many years, was only one link in the series of 



1 Gesammelte Abhandlungen, vol. i. pp. 80-130: ' tJber den secundaren Wider- 

 stand, ein durch den Strom bewirktes Widerstandsphanomen an feuchten porosen 

 Korpern' (Dec. 20, 1860). 



2 For further information on Secondary Resistance, see H. Munk, Uber die 

 kataphorischen Veranderungen der feuchten porosen Kb'rper. Archiv fur Anatomie, 

 Physiologic, &c., 1873, pp. 241 if. 



