ANIMAL AND VEGETABLE 89 



at once can see that by using electrodes of a similar size 

 we should frequently obtain change of sign, which is avoided 

 by adopting Bailies' method. 



" Mr. Baines has pointed out that, in testing, a slow 

 excursion, say to 200 mm., is met with which may be 

 mistaken for a leakage from the nervous system. Anyone 

 using the galvanometer will soon learn to judge this 

 condition ; quantity as evidenced by the rapidity of 

 excursion being the test of a nerve flaw. 



" If the theory advanced of the source and distribution 

 of energy is correct, this false reading can be explained. 

 A local vaso-motor disturbance would result in increased 

 blood supply. For this read conveyance of energy, and 

 at once you have a local increase of potential, and the skin 

 insulating for a normal potential only, will allow of the 

 larger escape and give an excursion, but without the 

 quantity of a leakage from the insulated nervous tracts 

 where the potential is probably higher. 



" It will be understandable that the readings from this 

 cellular source of energy are comparatively unimportant, 

 and that the larger electrode may be used to govern the 

 direction of the flow without in any way interfering with 

 the usefulness of the readings. 



" An escape through a flaw in the insulation of a nerve 

 would result in diffusion, through moist substance, of a 

 current of much greater quantity, and give the rapid deflec- 

 tion of larger extent which one has learned to associate 

 with a genuine alteration in tissue metabolism." 



Unfortunately, as I have said in another chapter, our 

 knowledge of condenser action in the body is limited by the 

 absence of information regarding the specific inductive 

 capacities of natural dielectrics. With special reference to 

 the velocity of the nerve impulse the experiments of Dr. 

 Le Bon are of importance. He came to the conclusion 

 that electricity is able to propagate itself in insulators 43 



