154 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
_D. Physiological experiments have shown that a small 
but distinct electrical change of exceedingly short duration 
is invariably produced in every nerve of a living tissue 
when a nervous impulse traverses the nerve; such an 
electrical effect is present when a nervous impulse reaches 
the motorial nerve ending in the muscle, and its presence 
is the physical signal of the establishment there of the 
unknown processes which are associated with such im- 
pulses. Its character is such that the nerve fibres always 
become galvanometrically negative to the nerve ends. 
EK. The arrival of a nervous impulse at a plate must 
therefore produce an electrical change due to the fact that 
the nerve fibres entering the surface will become galvan- 
ometrically negative to the more deeply situated ends and 
hence in each plate an effect must be produced of the kind 
indicated in C. The enormous number of nerve twigs in 
each plate, the enormous number of plates, their arrange- 
ment in pile, and finally the structural device through 
which the impulses reach all the plates at the same instant 
of time, are the factors by which the comparatively insignifi- 
cant change in an ordinary nerve has become magnified 
into the formidable shock of such an animal as the 
Gymnotus. 
