ELECTRICAL ORGANS IN FISHES. 303 



are thrown into an opposite electrical condition, and a current 

 is the consequence. 



Pacini refers the structure of the battery in Gymnotus to 

 a ternary type ; consisting of a negative element the fibrous 

 layer on which the nerves ramify, together with the fluid 

 which it bounds below ; a positive element the ridged 

 vasculo-cellular layer ; and a conducting element, the inter- 

 diaphragmatic fluid. The vasculo-cellular layer predominat- 

 ing in this ternary type over the nervous, Pacini conceives 

 the electricity to be evolved in the organic actions of the 

 vasculo-cellular layer under the influence of the nerves. In 

 other words, the will of the Gymnotus, or the reflex action of 

 its electrical nervous centre, directs an influence along the 

 nerves of its batteries over the fibro-nervous layer ; which 

 suddenly exciting the nutritive or other organic actions of the 

 highly-developed vasculo-cellular layer, an electrical disturb- 

 ance is produced ; with an opposite electrical condition of 

 the fibro-nervous and vasculo-cellular layers of the diaphragms, 

 and consequently a current through the series. Pacini com- 

 pares the wide-meshed fibrous layer, on the under surface of 

 which the nerves ramify to the hollow cylinder of porous clay, 

 which in a Bunsen's or Grove's galvanic arrangement separates 

 the negative from the positive elements. 



As to the manner in which the animal avails itself of the 

 electrical currents which it has the power of exciting, without 

 alluding to the numerous experiments which have been made 

 on the Torpedo in air, I shall confine myself to the mode in 

 which the Torpedo and Gymnotus use their currents as means 

 of offence and defence in their proper aqueous medium. In 

 the first place, it is evident that in water, the currents between 

 the opposite surfaces of Torpedo, or between the ends of Gym- 

 notus, instead of being confined to a transverse area of limited 

 extent, as when they pass along a wire during a discharge in 

 the air, must be diffused through a considerable extent of 



