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THOMPSON YATES LABORATORIES REPORT 
The physical structure of the nerve fibre is therefore a 'core model' structure, and 
necessarily comprises — 
(1) an outer solution of electrolytes. 
(2) a partially permeable membrane. 
(3) an inner solution of electrolytes. 
Having come to a definite conclusion, that the three conditions of conductivity 
inferred as existing concentrically in the nerve fibre must be the outcome of a con- 
centric arrangement of at least three different structures, we are in a position to ask 
whether the statement is still justified that the most internal structure has a specific 
conductivity of great comparative importance. 
Is conduction of an electric current by a nerve trunk a phenomenon mainly 
occurring in the axis cylinders of the nerve fibres ? If so, is this to be explained by 
the presence of a relatively greater volume of an uninterrupted (by membranes, etc.) 
solution of electrolytes here than elsewhere in the nerve, or is it to be explained by 
the presence of a solution of small volume but great concentration and conductivity ? 
The question seemed answered in the affirmative by a reference to the metallic 
core of the metallic core model. Such a core model does not, as has been stated, 
however, adequately represent the distribution of structures in the nerve fibres. 
Core models, however, such as Grlnhagen's, have been frequently used, which 
attempted more completely to imitate the distribution of structures in the nerve, 
being entirely composed of moist conductors. It is of great practical interest, that in 
such models it has always been found necessary to make the internal solution of 
relatively great specific conductivity before a resemblance was experimentally found 
between the nature of the electrical conductivity of the model and the known nature 
of the conductivity of the nerve, which it was designed to imitate. 
The characteristic feature of electrical conductivity in nerve is provided by the 
electrotonic currents and by their distribution. The electrotonic currents can be 
imitated by the core model, the distribution of such currents in the nerve can only 
be imitated by a core model in which the internal solution is of high specific 
conductivity. 
This experimental fact is at least an indication which cannot be neglected, and is 
universally recognized as such. It is taken to mean that the axis cylinder of the nerve 
fibre is a better conductor than the tissues which ensheath the fibre, and, therefore, 
that more electricity is conveyed along the axis cylinders than is simultaneously 
carried by the other tissues of the nerve, when both are carrying an electrical 
current. 
It has been taken, however, by Hermann to mean that more conducting 
material is present in the axis cylinder and not that the conducting material present is 
of a better kind. 
