428 LIVING TORPEDOS IN BERLIN. 



silence the course of the current curves in the animal itself, nor 

 could he form any distinct conception of them, for it was not until 

 seventy years later that I showed that the assumption of the exist- 

 ence of insulating sheaths in 1 electrical fishes was both superfluous 

 and anatomically inadmissible 1 . We are now able to correct and 

 complete Cavendish's diagram in both directions. 



In 1831 Daniel Colladon of Geneva, by his investigations at La 

 Rochelle, arrived at the three following propositions as to the distri- 

 bution of electricity on the surface of the Torpedo when giving a shock. 



1. All points on the back are positive to any point on the belly. 

 The strength of the current diminishes in proportion to the distance of 

 these points from the organ, and almost entirely disappears at the tail. 



2. Any two unsymmetrical points of the back, or any two of the 

 belly, almost always yield a current in the galvanometer. The one 

 nearest to the organ is positive in the back, negative in the belly. 



3. When contact is made with two symmetrical points either 

 of the back or belly, there is no deflection in the galvanometer. 



As Colladon was the first to determine the electrical condition of 

 the dorsal and ventral surfaces of the Torpedo, I have given the 

 name of Colladon's currents to the currents between points on 

 either of these surfaces. 



Colladon's observations were published in 1836. A year later 

 Matteucci, who had previously denied the existence of such cur- 

 rents, asserted (without mentioning Colladon) that the points of 

 the organ corresponding to the entrance of the nerves were positive 

 on the back, negative on the belly ; a statement which is connected 

 with the erroneous opinion he then held as to the origin of the elec- 

 tricity in the brain of the Torpedo 2 . 



As I had already foreshadowed to myself the electrical plates 

 since made known by Bilharz, I preferred another explanation 3 . 

 The greater the length of a Torpedo column, provided that the 

 number of plates in a unit of length is the same, so much the 

 greater must be its electromotive force. The columns diminish in 

 height from the inner to the outer edge of the organ by about 0*6 



1 Gesammelte Abhandlungen, vol. ii. p. 678. 



2 The literature, both old and new, of the subject is to be found in the Gesammelte 

 Abhandlungen, vol. ii. pp. 684 if. I may remark that the concluding sentence of 

 par. vi. p. 690, is not quite exact as to Matteucci's frequently changing expressions, 

 but the correction of it would require a lengthy setting forth and is no longer of 

 interest to any one. 



3 Preliminary sketch of an investigation of the so-called frog-current and of 

 electromotive fishes. PoggendorfFs Annalen, 1843, vol. Iviii. p. 25, par. 64, 65. 

 Gesammelte Abhandlungen, vol. ii. pp. 668, 670. Untersuchungen, pp. 284, 285. 



