80 



THE SIGNS OF LIFE 



[LECT. 



with the discharges of an electrical organ. I do not mean to say 

 that eyeball or skin are specifically " electrical organs," for there 

 are no structural features in common ; but I think that the 



voit 



QIO \ 



OO5 



o 



A 



o 



10 



15 



2.0 mins. 



FlG. 36. Normal (head to tail) discharges of a strip of the electrical organ of a 

 skate {Raia clavata) in response to tetanisation and to strong single break induction 

 shocks. 



comparison goes some way towards generalising our notion 

 of the electrical signs of life. It is at least remarkable that the 

 electro-motive values of the discharge in the cases of the eye- 

 ball and of the skin are of the same order of magnitude as that 

 calculated for a single plate of the electrical organ (0.03 to 0.05). 

 According to a recent estimate by Gotch,* the E.M.F. of nerve 

 in response to a single induction shock reaches a value not far 

 short of this -viz., 0.03 volt. And the very points where 

 the comparison is defective should serve to instigate further 

 study. Thus the organs of Torpedo, Gymnotus and Raia are 



Gotch and Burch, Proc. Roy. Sac., vol. 63, p. 300, 1898. 



