The Oritjin of the, Electric Oryanx in Axlroxcojmx (iiiWitnx. 103 



DISCUSSION. 



Bernstein and Tschennak (is) have suggested that the electrical dis- 

 charges may be produced by different concentrations of sodium chloride 

 in the electroplaxes and in the intervening connective tissue, a theory 

 which necessitates the presence of a membrane between the two solu- 

 tions which is permeable to one kind of ions and not to the other. Such 

 a membrane is not known to be present, but neither is there any evi- 

 dence against its existence, and without it the bio-electric current 

 would appear to be arising without the ionization of anything. The 

 principle of the bio-electric current is that normal sodium chloride and 

 concentrated sodium-chloride solutions coming in contact diffuse their 

 ions at different rates, causing currents in small amounts, just as they 

 do in a muscle where such a membrane is known to exist. 



Engelmann (39) has compared the thin, dark areas (electric) of the 

 electric organs with the isotropic portion of the muscle-tissue, and the 

 thick, light area (nutritive) with the anisotropic portion. The action 

 current of an electric organ is the same as that of an ordinary striated 

 muscle, except that the arrangement of the electroplaxes in a column 

 makes appreciable an otherwise insignificant current. The action cur- 

 rent of muscle can only be detected by the galvanometer, while that of 

 an electric organ can be felt by the hand. Muscle, however, can be 

 stimulated to give off electricity by mechanical, thermal, and chemical 

 means as well as by the stimulation of the nerve. It can also be effec- 

 tively paralyzed by small doses of curare and atropin, so that the nerves 

 themselves are not affected, whereas electric organs can not be par- 

 alyzed unless the nerves are rendered powerless. 



The strength of the shock in fishes is made possible by the arrange- 

 ment of the electroplaxes in a column. In a battery, when the cells are 

 arranged so that all the positive poles are connected together and all 

 the negative poles together, they are said to be arranged in parallel, 

 and when each positive pole is connected with a negative one, they are 



E 



said to be arranged in series. According to Ohm's law, =-5. where 



K 



C= the strength of the current measured in amperes, E= the electro- 

 motive force measured in volts, and R= the resistance measured in 

 ohms. Now, when the cells are arranged in series the electromotive 

 force of the combination is the sum of the electromotive forces of the 

 several cells, and the resistance of the cells is the sum of the resist- 

 ances of the separate cells, providing high voltage and therefore high 

 shocking power, but little current. When the cells are arranged in 

 parallel the electromotive force is the same as that of one cell, while the 

 resistance is less, being inversely proportional to the number of cells, 

 thus providing a large current but low shocking power. By combining 

 these two arrangements- -that is, by putting the cells of one group in 

 series and then joining several such groups in parallel various 



