l(j-i Papers from the Department of Marine Biology. 



degrees of shocking power with much or little current may be obtained 

 (Kimball67). 



In the case of the electric fishes it would seem that the electric organ 

 itself forms the battery in which the different concentrations of sodium 

 chloride form the poles, and in which the electroplax takes the place of 

 the battery cell ; or if the organ be composed of columns, then each col- 

 umn is a complete battery in itself, in turn acting as a cell in the larger 

 battery, the electric organ. The surrounding medium, salt or fresh as 

 the case may be, forms the conductor, and the nerves form the key 

 which closes the circuit. When the nerve is stimulated the circuit is 

 closed and the organ gives a shock. The organ being self-excitatory, 

 is peculiarly adapted to give interrupted shocks after the manner of an 

 induction coil, for when the nerve has been restimulated by the first 

 shock it will go on opening and closing the key until the organ is worn 

 out by fatigue. Gotch has shown that it is as impossible to fatigue the 

 electric tissue as it is to paralyze it unless the nerve be fatigued (so). 



In nearly all the electric fishes the electric organs are divided into 

 columns. In Torpedo ocellata, for example, there are 450 columns in 

 each electric organ and 400 disks in each column (Gotch so) . The cur- 

 rent in this fish goes from ventral to dorsal, the ventral surface being 

 negative to the dorsal one. In each column the disk nearest the ven- 

 tral surface of the body will present its negative side to the surface, 

 while the disk nearest the dorsal end will present its positive side, so 

 that to complete the circuit between these two points it will be neces- 

 sary to connect a positive with a negative surface. Thus the electro- 

 plaxes of each column will be arranged in series, so that the voltage of a 

 column will be equal to that of all 400 disks combined, the amperage 

 that of one. The 450 columns of the electric organ, however, are 

 arranged in parallel, since all the surfaces facing the dorsal side of the 

 body will be positive and all those facing the ventral side will be nega- 

 tive. In Torpedo ocellata, therefore, the amperage will be 450 times that 

 of one column, the voltage 400 times that of one electroplax, a condi- 

 tion providing for a large amount of electricity and at the same time for 

 a comparatively strong shock. Salt water is a million times better 

 conductor than fresh water (DuBois-Reymond) , thus furnishing very 

 little resistance, so that Torpedo, although a fish of sluggish habits, has 

 everything in its favor for effectively shocking its enemies, high voltage, 

 high amperage, and low resistance. 



In Gymnotus there are four electric organs lying lengthwise in the 

 body and divided into a variable number of columns, each of which may 

 have as many as 10,000 electroplaxes. Here, as in Torpedo, the col- 

 umns as well as the four organs themselves are arranged in parallel and 

 the electroplaxes in series. The resistance of fresh water is very great, 

 but the arrangement of the columns in parallel provides for a larger 

 ;i mount of electricity and the extraordinary number of electroplaxes in 



