Note 28: capacities of cylindrical condensers 419 



The following table gives the charge as computed by Cavendish compared 

 with that given by the correct formula. 



NOTE 29, ART. 437. 

 Electrical Fishes. 



The fishes which are known to possess the power of giving electric shocks 

 belong to two genera of Teleostean Fishes and one of Elasmobranch Fishes, 

 and the position and relations of the electric organs are different in each. 



In every instance, however, the electric organ may be roughly described 

 as being divided in the first place into parallel prisms or columns by septa, 

 which we may call (with reference to the organ, not the fish) longitudinal septa, 

 and in the second place each column is divided transversely by diaphragms, 

 the structure of which is different in the different families, but in every case 

 the terminations of the nerves lie on that surface of each diaphragm which 

 during the discharge becomes its negative surface. 



In the large family of the Torpedos the electric organs are formed of a 

 large number of short columns, the columns running from the belly to the back 

 of the fish. The nerves terminate on the ventral surface of each diaphragm, 

 and the electric discharge is from belly to back through the organ, or in other 

 words, the back of the fish becomes positive with respect to the belly. 



There seems to be but one species of Gymnotus. It is a long eel-like fish. 

 Its electric organs consist of a smaller number of very long columns running 

 from the tail to the head of the fish. The nerves terminate on the posterior 

 surface of the diaphragms, and the electric discharge is from tail to head through 

 the organ, or the head of the fish becomes positive with respect to the tail. 



There are three species of Malapterurus which are known to be electrical. 

 In these the electric organs run longitudinally. Bilharz, observing that the 

 nerves appear to terminate in an expansion like the head of a nail on the posterior 

 surface of the diaphragms, concluded that the electric discharge must be from 

 tail to head through the organ, as in the Gymnotus. Ranzi* however, and 

 afterwards, independently of him, Du Bois Reymondf found that the discharge 



* Nuovo Cimento, Tomo II, Dicembre 1856, p. 447, quoted by Du Bois Raymond 

 "Zur Geschichte der Entdeckungen am Zitterwelse," Archiv fur Anatomie u. Physio- 

 logic, &c. Leipzig, 1859, p. 210. 



f Monatsbericht il. k. Akatl. Berlin, 1858. 



272 



