ANIMAL AND VEGETABLE 179 



" When the nerves are completely degenerated (as, for 

 instance, when they are cut off from the spinal cord, or 

 when the cells in the cord from which they originate are 

 themselves degenerated, as in infantile paralysis), no 

 muscular contraction can be obtained on stimulating the 

 nerves, even with the strongest currents." 



Obviously, there is a complete loss of conductivity. 

 In the old days the cables laid in South American waters 

 were insulated with india-rubber. The sulphur in the 

 rubber caused rapid degeneration of the conductors, and 

 the application of 1,000,000 volts at A would not cause a 

 receiving instrument at B to contract, by reason of a break 

 or breaks of continuity. 



" The changes in the excitability of the muscles are less 

 simple, because in them there are two excitable structures, 

 the terminations of the nerves (end-organs) and the mus- 

 cular fibres themselves." 



It is open to question whether the end-organs are not 

 inducing bodies. Nowhere do they appear to make actual 

 contact ; that is to say, they do not connect as wires are 

 connected so that a direct current flows through them, but 

 appear to act inductively upon the organs they influence. 



" Its excitability " (that of muscle) " corresponds in 

 degree to that of the nerve supplying it." 



In accordance with Ohm's law the degree of excitability 

 of the muscle would be governed by the resistance of the 

 motor nerve supplying it. 



" The fact that, under normal circumstances, the con- 

 traction which is caused by the constant current is as quick 

 as that produced by an induction shock, is ground for 

 believing that in health the constant, like the induced 

 current, causes the muscle to contract chiefly by exciting 

 the motor nerves within it." 



Tensions being equal, the effect of an induction shock 

 is not, cannot be, the same as the effect produced upon 



