1905. | The Structure and Function of Nerve Fibres. 333 
one time to be of different sizes and in different number in neighbouring 
portions of the axis-cylinder. There is, therefore, no temptation to consider 
them as permanent units of structure, and yet, after the admission of 
“‘ fixatives,’ these very granules are joined together in lines to form neuro- 
fibrils. The granules not being permanent units of structure, it is therefore 
logical to conclude that the fibrils thus formed by their agglutination also are 
not permanent units of structure. The fibrils then may be said to be 
observed under conditions suggestive of artificial formation. This fact also 
has to be taken with the complementary fact, that artefacts of just this kind 
might be expected to appear within the nerve-fibre. 
Let us in illustration of this statement consider the possibility mainly dealt 
with in this paper, that the process of coagulation is attended with a sudden 
liberation of inorganic molecules, and therefore with a new condition of 
activity—molecular motion—around every centre of coagulation. It seems 
not unlikely that, in the extremely minute tubule of the nerve-fibre, this new 
activity, and the conditions of pressure occasioned by it, might systematise the 
spatial arrangement of these centres of activity along lines parallel to the long 
axis of the fibre. This being the case, there seems an ample basis for the 
opinion, that we should expect a symmetrical arrangement of lines of 
coagulated material. In fact given the sudden appearance of a uniformly 
distributed agency determining coagulation, we should expect the formation 
of “ neuro-fibrils ” as a consequence of the energy changes accompanying this 
process. I shall continue then, in this paper, to speak of the axis-cylinder as 
a homogeneous colloid solution. This point defined, it is possible to turn more 
freely to a consideration of the disturbance of this homogeneity taking Dee 
at each site of injury. 
Evidence that the appearance of potassium salt at a site of 1 injury is due to 
physical and not to chemical change can partly be found in a consideration of 
the quantity of the change observed. I have found it impossible to secure a 
sudden precipitation of neutral-red, one of the dyes used for the detection of 
this change, by the addition of potassium salts, unless the salt is added in very 
considerable quantity. A small quantity of the salt, 0-1 per cent., will 
determine a considerable precipitation in a considerable time. The 
precipitation occurring in the nerve is however sudden, and can only be 
imitated by the use of concentrations of more than 5 per cent, The same 
point was brought out by my examination of the amount of potassium salt 
required to annul the injury-current. If it is admitted that the quantity is 
considerable, then it follows that if its appearance were really due to a 
chemical change, we should expect an appearance of other products of this 
change in similar considerable quantity. And yet the ingenuity of observers 
