ELECTRIC FISH 



sands of them. A torpedo of average size has from 400 

 to 500 prisms, each with 300 to 400 disks, that is 

 120,000 to 200,000 elements. In this living electric 

 battery, so original in its complexity, are the termina- 

 tions of large nerves which come from the brain and 



Fig. 29. — The discoid body of a Torpedo, dissected so as to show the 

 two electric organs of areolar appearance. 



bring their branches to all parts of the apparatus. This 

 nervous inflow acts as a control, and when the discharge 

 of electricity takes place, the current is directed out- 

 wards from the back, which is positive in polarity, to the 

 under side of the body, which is negative. 



Our first impulse on becoming acquainted with a 

 structure and properties of this sort is to assume that 

 the animal makes use of them for attack or defence. 

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