

1905. | The Structure and Function of Nerve Fibres. 349 
conceivably be accomplished in two different ways. In the one case a nerve- 
fibre excited itself by a negative charge, and transmitting a negative charge to 
successive portions of its length, might possess a small terminal portion, a 
membrane, which reversed the condition prevalent in the remainder of the 
fibre by permitting the more rapid migration of the positive ion, and checking 
the movement of the naturally more rapid negative ion. In this case there 
would be a condition as a corollary to this. The terminal portion of the fibre 
abutting upon the membrane would be left in a state of continuous excitation 
involving a prolonged communication of positive charges to the innervated 
tissue, and a prevalence in it of a condition of inhibition. 
The other case conceivable is one in which the colloid solution of the 
nerve-fibre was excited by a positive charge, and contained an electrolyte the 
positive ion of which was the more rapid in its migration. Such a nerve-fibre 
would be excited at the anode of a polarising current, in the manner in which 
there is some evidence that certain afferent fibres are excited. It should be 
pointed out that, in such a case, there would be no reason to expect the 
“action current” to differ in kind from the action current of an ordinary 
nerve-fibre, the direction of the action current being primarily determined by 
the impermeability of the sheath of the fibre to the positive ion. The 
negative variation of the injury current, and the injury current itself, might 
differ, notwithstanding the predominant influence of this sheath, in their 
production also, but the degree to which this difference might rise could not 
be anticipated without at first exactly determining the nature of the 
permeability of the sheath. 
In conclusion, I would like to offer a few words in explanation of the attitude, 
which I have now for some time adopted, in a series of investigations undertaken 
in the hope of throwing some light upon nerve-function. ‘The nature of the 
conditions conducive to an exhibition of increased nerve excitability, as, for 
instance, the increased excitability to mechanical stimuli shown during cooling 
of the nerve, has long convinced me of the improbability of the attempt made to 
explain nerve-function in terms of chemical reactions. I have therefore con- 
tinuously sought for a possible physical explanation of this process. The most 
probable explanation, in terms of physical conditions, was an electrical one. 
From this point of view, the main characteristic of nerve was the number, 
character, and arrangement of the electrolytes contained within it. These things 
being unknown, remained to be discovered, but the chances of their discovery 
were being continually diminished by the tendency to explain all the physical 
phenomena of nerve in terms of functional ability and activity. To me the 
ability to function was equivalent to the retention of some favourable disposition 
of electrolytes, the act of function the motion of electrolytes. 
I have therefore strongly resisted the introduction of terms conveying other 
than a purely physical meaning, and, most of all, have resisted the mention of the 
