Electric Organs. 531 



being positive to silver. Hie top of each of the plates becomes positive, 

 and the bottom negative. The top of the pile is therefore positive, and 

 a wire connecting it with the bottom will conduct, a current from the top 

 to the bottom. The woolen cloths must have been saturated with dilute 

 sulphuric acid (or a solution of sal-ammoniac in water ). 

 The creation of the current is due to the chemical ac- 

 tion of the acid upon the metals. It has been proved 

 that all chemical action develops electricity. 



Any irritating agent outside of the body coming into 

 ' w contact with the skin, sends, by way of the sensory 

 \ w nerve to the central ganglion either in the brain or 

 spinal cord, a stimulation, which, deflected from the 

 ganglia, returns to the electric organ along the motor 

 nerves. If these nerves be cut in two and their cut ends 

 B be irritated, an electrical discharge takes place, the 



254 ~ Voltaic electrical organ, in this case, performing its function, as 

 -sner^Tcloth tlj e musc 'l e does under similar conditions. As before 

 W.-Moist wool en mention^ these nerves are looped in their terminations 

 the same as the nerves serving the muscles. The continued or repeated 

 action of the organs soon exhausts them. The first shock of the Gym- 

 notus is very formidable, and will easily kill any small animal, as a fish 

 such as they use for food. Humboldt relates that horses are often killed 

 by them, these animals being used by the South American Indians in 

 fishing for the G}Tnnoti ; the process being to compel the horses to re- 

 ceive the shocks of the fishes till they are exhausted, when they can be 

 safely taken by the Indians. Rest and nourishment recuperate their 

 functions, as in the case of muscles. The effect of strychnine is to 

 cause involuntary discharges from the electric organs; at the same time 

 it produces tetanus or violent involuntary contractions in the muscles. 



The aponeurotic lamina and partitions which intersect the electric or- 

 gans, appear to have the quasi insulating properties possessed by the 

 neurilemma and sarcolemma sheaths of the nerve and muscle fibres ; 

 because each nerve fibre in the electric organ ministers to a definite 

 tract, and when such nerve fibre is irritated ( at its cut end ), the electric 

 discharge takes place only in so much of the organ as it reaches. If 

 part of the motor nerves suppl} r ing the organ be cut, and a stimulus be 

 applied to the skin of the animal, he is able to discharge the electricity 

 of the part still in connection with the central ganglia, the brain or 

 spinal cord, but not the part to which the severed nerves belong. 



The shock or discharge from an electric fish is greater when two 

 points are touched at once, and the farther apart the points are, the 

 greater the shock. The most powerful shocks from the G3 r mnotus are 

 when the head is grasped by one hand and the tail by the other. But 



