. PHENOMENA OF THE SHOCK. 193 



discharge or current. Frogs, prepared after Galvani's 

 method, and arranged upon the body of the torpedo, suffer 

 contractions at each shock which this animal gives, on being 

 excited. The same effect takes place even when the frogs 

 are put at some metres [yards] distant from the torpedo, 

 provided that they, as well as the torpedo, are placed on a 

 wet cloth. If the frog, prepared in the way stated, be held 

 in the hand, and brought, by means of the extremity of its 

 nerves, in contact with a point of the body of the torpedo, 

 it suffers contractions at each shock from the fish ; but they 

 cease when the torpedo is insulated, or when the frog is 

 suspended by means of an insulating thread. Notwith- 

 standing this precaution, contractions take place when a 

 long portion of its nervous filament is spread over the body 

 of the torpedo. This fact is analogous to that of receiving 

 the shock in the fingers when the torpedo is insulated. 



When we distribute several frogs over many points of 

 the surface of the torpedo, at first all of them contract at 

 each discharge of the fish ; but, in proportion as its vigour 

 lessens, we perceive that those frogs which suffer contrac- 

 tions for the longest time are those placed upon the sides of 

 the animal near the head: in other words, the points which 

 preserved the faculty of making the frogs contract for the 

 longest period, are those which correspond to two peculiar 

 organs, situated laterally and symmetrically towards the 

 cephalic extremity of the fish. When the two extremities 

 of the platinum wires of a moderately sensible galvanometer 

 are placed in contact with the back and belly of the torpedo, 

 and the animal is irritated in order to obtain the discharge 

 we observe, that at the moment when the frogs contract, the 

 needle of the galvanometer deviates suddenly, then im- 

 mediately returns back, oscillates, and stands at 0, even 

 though we continue to keep the circuit closed. When 

 a fresh discharge from the fish occurs, the same phenome- 

 13 



