v.] DIRECT RESPONSE 81 



modifications of muscle.* The organ of Malapterurus (which 

 does not follow Pacini's law) is a modification of cutaneous 

 gland ; we therefore want to examine that organ by the light of 

 what we have learned of skin. Does the electrical case of 

 Malapterurus give an outgoing current ? Perhaps one of these 

 days we shall have an opportunity of finding out. 



Meanwhile let me warn you that our knowledge of even 

 the most carefully studied of electrical organs that of Torpedo, 

 namely is by no means exhaustive. Its discharge is of very 

 short duration ; one may feel an intense thrill from a discharge 

 giving by no means an excessive effect upon a galvanometer ; 

 the organ itself while reacting perfectly well to indirect excita- 

 tion, is peculiarly refractory to direct electrical excitation. This 

 same peculiarity is exhibited by the excised organ or by strips 

 of organ from even the most lively fish, and I have failed to 

 obtain from such strips any well-marked response to single 

 induction shocks ; I had to use tetanising currents to bring out 

 any regular venter-to-dorsum response ; the organ was easily 

 exhausted, and easily injured, by e.g., removal of the skin, 

 which is closely attached to it ; obviously an effect obtained 

 only in the presence of skin, and not obtained after its removal, 

 might not straightway be set down as "organ-response"; I 

 have indeed seen similar responses, of a value of +0.005 volt, 

 with strips of fish that contained no electrical organ at all, but 

 only muscle between two layers of skin. 



So that on the whole the case of the electrical organ is a 

 good deal less satisfactory than that of the skin, and in com- 

 paring the skin and the eyeball with an " electrical organ," we 

 use the expression in a general rather than in a special sense. As 

 regards blaze-currents, the skin of a frog is a far more efficient 

 electrical organ than is the electrical organ of a Torpedo. And 

 perhaps this is not so very unfortunate ; you may easily control 

 statements concerning the frog's skin, you would have to take 



* Developmental!)', inasmuch as muscle and electrical organ come from 

 the same muscle plates ; and, in the skate, muscle shades into organ by 

 gradual transition. Gotch considers the electrical organ to be a nerve- 

 ending. But, in a sense, muscle itself is a nerve-ending. 



F 



