340 PRESENT STATE OF OEGANIC ELECTRICITY. 



affords no explanation of its progressive character ; the current 

 is not accounted for. 



The theory which most satisfactorily combines the anato- 

 mico-physiological as well as the electrical phenomena of the 

 apparatus, is that lately propounded by Professor Pacini of 

 Florence.* 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 nu- 

 cleated cellular texture occupy the other ; he finds in these 

 structural peculiarities the condition which is wanting in 

 Valentin's theory to explain the progression of the electricity. 

 Pacini refers the electrical batteries in the fish to two forms 

 of structure, and two modes of action ; of the first and 

 simplest form, the Torpedo affords the type, of the second and 

 more complicated, the Gymnotus. The batteries of Malap- 

 terurus are probably referable to the form in Torpedo, those 

 of Eaia certainly to that in Gymnotus. In the Torpedo, ac- 

 cording 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 peculiar dynamical difference in the condi- 

 tion of the two surfaces of each diaphragm of this binary type 

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

 of the electric diaphragm correspond to the bismuth and 

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

 tric 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,t 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, 



* Sulla struttura intima dell' (/rgaiio elettrico del gymnofo, e di altri pesci 

 elettrici, 1852. t Phil. Trans. 1773. 



