5 88 THE PHYSIOLOGY OF ELECTRICAL ORGANS. 



vital electromotive changes, but they appear to the author to be far 

 more in harmony with the alteration theory than with any other ; and 

 if, as experiments seems to show, the change is that of nerve-endings 

 magnified by the peculiar symmetry of their arrangements, this theory 

 can embrace them as harmoniously as it does those of nerve itself. 



The reflex response of the organ. — The nerve fibres which 

 supply the electrical organs are in all cases the axis cylinder branches 

 of special nerve cells. In Gymnotus and Mormyrus, these cells form 

 a vesicular column on each side of the spinal cord, but in Torpedo 

 they are massed into special lobes of the medulla oblongata. In the 

 case of Malapterurus, there being only one nerve fibre for each lateral 

 organ, there is only one giant nerve cell in each half of the cord ; 

 this is situated between the exit of the first and second spinal nerves. 

 In all these fish the organ can be made to respond reflexly to special 

 sensory stimulation, the most efficient being electrical or mechanical 

 excitation of the skin. Mechanical pressure appears to be a particularly 

 efficacious means of evolving the reflex. Thus in the skate, a reflex 

 response of the organs in the tail is readily evoked by rubbing the rough 

 spines upon the dorsal surface. Torpedo and Malapterurus discharge 

 when the surface is pressed. The telephone forms a convenient mode 

 of ascertaining the presence of the response, the fish being placed in a 

 suitable tank and connected by means of either plates or an appropriate 

 net with the necessary metallic leads. The reflex responses are 

 enormously increased by the action of strychnia, the organ like the 

 muscles being thrown into a series of prolonged intermittent phases of 

 functional activity ; they are diminished by narcotisation and by pro- 

 longed cold. 



In the case of the active Malapterurus, discharges of the organ often 

 occur when it is swimming about, and the same appears to be true of 

 Torpedo. The Gymnotus, kept in a tank, will discharge when small live 

 fish are placed in the water. The discharge stuns a certain number of 

 the fish, and the sluggish eel is thus able to devour them at his leisure. 



These natural discharges present two points of interest. In the first 

 place, the discharge is a succession of organ-effects ; thus the electro- 

 magnetic signal vibrates, and a singing sound is heard in the telephone. 

 In the second place, both the rate of succession and the intensity of 

 the organ responses are extremely variable. The writer recorded with 

 an electro-magnetic signal a torpedo discharge of 110 successive electrical 

 changes in the second. At Naples, working with the recording telephone, 

 Schonlein found a maximum of 187 in the second. This rapid succession 

 cannot be kept up for any length of time, the longest period of rapid 

 discharges observed at Naples was only 0*896 sec, but in this time ninety- 

 two separate responses occurred. 1 It appears also that the responses of 

 both organs are evoked simultaneously, so that the numbers just given 

 must indicate the rate of discharge of each of the organs. 



A special interest attaches to the study of the reflex organ response, 

 in consequence of the light which it may throw upon the working of the 

 central nervous system. For if, as seems probable, the organ response 

 is due to the functional activity of nerve-endings, then the reflex dis- 

 charge should give a tolerably faithful picture of the character and rate 

 of the outflow from those nerve cells with which the nerve-endings are 

 structurally continuous. 



1 Schonlein, loc. cit. 



