LECT. X. PHENOMENA OF THE SHOCK. 197 



from one to the other ; but we can readily understand, that 

 the phenomenon is one which is difficult to be seen ; and 

 that to succeed in its production, it is necessary to have, at 

 the moment of the discharge, the two gold leaves at the 

 proper distance for the spark to pass. 



We succeed more easily if we substitute for the gold 

 leaves a steel file, which is connected with one of the discs, 

 and on which we rub a metallic wire which communicates 

 with the other disc. 



All the phenomena of the shock of the torpedo must, 

 therefore, be attributed to an electrical current. The appa- 

 ratus which produces it, consists of two peculiar organs, 

 called the electrical organs of the torpedo. Each of the sur- 

 faces of these organs possesses an opposite electrical condi- 

 tion ; the dorsal surface is positive, the abdominal surface 

 negative. The discharge of the animal is voluntary, and 

 all external irritation acts upon the electric organ by the 

 intervention of the will only. In fact, as the discharge 

 would traverse the animal's own body if there did not exist 

 exterior circuits or conductors to receive it, it follows, either 

 that the animal will no more produce it, or would immedi- 

 ately cease to do so, if it were out of water, or if it were 

 either not touched or touched by insulated bodies. It is, 

 then, not without reason that nature has placed the animals 

 endowed with this property in a liquid conductor. 



The properties of the current of the torpedo resemble those 

 of the electric current, properly so called, more than those 

 of the discharge of the Leyden phial. 



Let us now examine the discharge of the torpedo as a 

 physiological function, and consequently study the influence 

 exercised on it by the different parts of the organ itself; 

 and by those parts which surround it or which have some 

 connexion with it, as well as by the circumstances which 

 affect the state of life of the animal. 



