MUSCLES, NERVES, AND ELECTRICAL ORGANS. 167 



that the soaking fluid should not belong- to the class of better con- 

 ductors. Only a weak action is obtained with solution of common 

 salt and of sulphate of copper. The best liquid to use is distilled 

 water. I studied on prisms of wood the effect of the length and 

 sectional size of bodies susceptible of internal polarisation, upon the 

 strength of the polarisation-current under circumstances in other 

 respects the same. In the first place, it is apparent that in internal 

 polarisation it is not the strength but the density of the current 

 which comes into consideration. In accordance herewith it became 

 further apparent that the strength of the internal polarisation is a 

 function of the resistance of the moist porous body, in so far as this 

 resistance is determined by the dimensions. This function possesses 

 a maximum, which, in a given circuit, the length of the internally 

 polarisable body remaining constant while the transverse section 

 increases, is arrived at the later, the more imperfectly the soaking 

 fluid conducts l . 



4. Continuation of Preliminary Studies. On Polarisation at 

 the surface of contact of dissimilar Electrolytes. 



While studying internal polarisation I met with facts showing a 

 second kind of polarisation in moist conductors, i.e. the polarisation 

 at the surface of contact of dissimilar electrolytes. In contrast with 

 internal polarisation it possesses the peculiarity that it can also be 

 positive. If there is at the same time in the circuit an internally 

 polarisable body, action in opposite directions (doppelsinnige Wir- 

 kung) is often obtained, i.e. a deflection first in one direction and 

 then in the other 2 . If, for instance, a pad of blotting-paper soaked 

 with water placed between two pads of the same sort soaked with 

 a solution of common salt has a current passed through it, there 

 follows on the opening of the polarising circuit and the closing of 

 the galvanometer-circuit, first a negative preliminary deflection 

 (Vorschlag), which is immediately followed by a positive deflection 

 of longer duration. The preliminary negative deflection arises from 

 internal polarisation of the water-pad, the positive from the sum of 

 the positive polarisations at the contact of salt solution with water, 



1 Gesammelte Abhandlungen, vol. i. pp. 29-41 : 'Uber den Einfluss welchen die 

 Dimensionen innerlich polarisirbarer Korper auf die Grosse der secundar Elektro- 

 motorischen Wirkung tiben ' (January 31, 1859).. 



2 Op. cit. vol. ii. Leipzig, 1877, p. 407. 



