302 ELECTRICAL OKGANS IN FISHES. 



the apparatus, is that lately propouudcd by Professor Pacini 

 of Florence {SuVa struttura intima dell organo elettrico del 

 Gijmnoto, e di altri pesci elettrici, 1852). Having discovered 

 the important anatomical fact, that the nerves are distributed 

 on one surface only of the electrical elements of the battery ; 

 while the vessels and nucleated cellular texture occupy the 

 other ; he finds in these structural peculiarities the condition 

 wanting in Valentin's theory — an explanation of the progres- 

 sion of the electricity — the current. Pacini refers tlie 

 electrical batteries in the fish to two forms of structure, and 

 two modes of action ; of the first and simplest form the Tor- 

 pedo affords the type, of the second and more complicated, 

 the Gymnotus. The batteries of Malapterurus are probably 

 referable to the Torpedinal type, those of Eaia certainly to 

 that of Gymnotus. In the Torpedinal type of battery, accord- 

 ing to Pacini, the action is analogous to that which takes 

 place in a thermo-electric pile, inasmuch as he conceives it to 

 depend upon a dynamical difference, a certain different con- 

 dition, in the two surfaces of each diaphragm of this binary 

 type of pile. The nerve-surface and the vasculo-cellular sur- 

 face of a Torpedinal diaphragm correspond to the bismuth 

 and copper, or bismuth and antimony elements of a thermo- 

 electric arrangement ; the nervous influence in the former 

 taking the place of the heat applied in the latter. There is 

 here assumed, what on other grounds is highly probable, that 

 the electrical and nervous forces are correlative ; and here it 

 must be admitted that in Torpedo, as pointed out by John 

 Hunter {Phil. Trans. 1773), the bulk of the nerves in relation 

 to the batteries is much greater than in Gymnotus, which 

 exemplifies Pacini's second or ternary type of animal battery. 

 When the Torpedo, therefore, wills a shock, or when, through 

 the reflex action of its electrical nervous centre, a shock is 

 induced, a sudden and copious nervous influx flowing over the 

 under surfaces of its electric diaphragms, the upper surfaces 



