486 LIVING TOEPEDOS IN BERLIN. 



in order to determine the values of a?, 8 d , 8 r , we have the three 

 equations, 



0-002 1 6 d + x = o-ooi 2, 



+ 0-0067+5,, # = +0-0057, 



. = -<. 



whence we have 



8 d = 0-00024, 5 = 0-00131, 



and according- as x is calculated from the first or the second of the 

 equations containing it, and which do not agree exactly with each 

 other on account of errors of observation, 



x = 0-000924 or = 0-000869, mean = 0-000896. 



It would have been scarcely practicable to give more exact values 

 of the ratio of the lengths of the positively and negatively acting 

 segments of the columns ; at any rate, the attainment of better 

 numbers, if it is worth the trouble, must be reserved for the future. 

 In the mean time, it seems as though the electromotive force of the 

 skin is considerably less in the winter fish (about four times) than 

 in the summer fish ; this is very possible. 



Thus the skin of the torpedo behaves electromotively like that of 

 the gymnotus, in regard to the direction as well as to the magni- 

 tude of the action, and certainly like that of malapterurus in regard 

 to direction ; the force is probably here much the same in amount 

 as in the two other fishes (see above, p. 482). Three modes of 

 explaining this action offer themselves. 



The first question to occur is, whether it does not denote a differ- 

 ence of potential between the longitudinal and transverse section of 

 the columns, for perhaps the skin may play the part of an inactive 

 conducting covering over the natural transverse section of the 

 columns, like the tendinous expansions over natural transverse 

 section of muscle. This idea is negatived, because no action is 

 perceived between the lateral surfaces of the columns and an 

 artificial transverse section, and there is no perceptible change in 

 the organ current, on moving a clay point which is near a transverse 

 section, to the transverse section itself. 



The second hypothesis is, that in the case of the gymnotus, the 

 skin forms with the material for leading-off and the organ, a liquid 

 battery in the following way 1 , 



Physiological Clay | Organ + Organ | Skin + Skin wetted with river water | Clay ; 



Gesammelte Abhandlungen, etc., vol. ii. p. 265. 



