1 86 ELECTBOTONUS. [OH. xvi. 



current is as quick as that produced by an induction shock, is 

 ground for believing that in health the constant, like the in- 

 duced current, causes the muscle to contract chiefly by exciting 

 the motor-nerves within it. 



When the motor-nerve is degenerated, and will not respond to 

 any form of electrical stimulation, the muscle also loses all its 

 power of response to induction shocks. The nerve-degeneration 

 is accompanied by changes in the nutrition of the muscular fibres 

 as is evidenced by their rapid wasting, and any power of response 

 to faradism they possessed in the normal state is lost. But the 

 response to the constant current remains, and is indeed more ready 

 than in health, doubtless in consequence of nutritive changes 

 which develop what the older pathologists called, truly enough, 

 " irritable weakness." There is, moreover, a qualitative as well 

 as a quantitative change. In health the first contraction to occur 

 on gradually increasing the strength of the current is at the 

 negative pole, when the circuit is closed (see Pfliiger's law), and a 

 stronger current is required before closure-contraction occurs at 

 the positive pole. But in the morbid state we are discussing, 

 closure-contraction may occur at the positive pole as readily as or 

 even more readily than at the negative pole. This condition, the 

 reasons for which we do not know, is called the " Reaction of 

 Degeneration" 



Suppose a patient comes before one with muscular paralysis. 

 This may be due to disease of the nerves, of the cells of the 

 spinal cord, or of the brain. If the paralysis is due to brain 

 disease, the muscles will be slightly wasted owing to disuse, but 

 the electrical irritability of the muscles and nerves will be normal, 

 as they are still in connection with the nerve-cells of the spinal 

 cord that control their nutrition. But if the paralysis is due to 

 disease either of the spinal cord or of the nerves, this nutritive 

 influence can no longer be exercised over the nerves or muscles. 

 The nerves will degenerate; the muscles waste rapidly >; the 

 irritability of the nerves to both forms of electrical stimulation 

 will be lost ; the muscles will not respond to the faradic current, 

 but in relation to the constant current they will exhibit what we 

 have called the " reaction of degeneration." 



This illustrates the value of the electrical method as a means 

 of diagnosis, that is, of finding out what is the matter with a 

 patient. It is also a valuable means of treatment ; by making 

 the muscles contract artificially, their nutrition is kept up until 

 restoration of the nerves or nerve-centres is brought about. 

 Another illustration will indicate that the facts regarding 

 electrotonic variation of excitability are true for sensory as well 



