1906.] The Structure of Nerve-fibres. 17 



teased nerve-fibres stained with the same dye. Now I have already produced 

 evidence in favour of the view that teased nerve-fibres are traversed by an 

 electrical current — their own injury current. Bethe's observations enable me 

 therefore to identify this distribution of staining capacity in teased nerve- 

 fibres as due to polarisation caused by this current. The pallid stretch of 

 homogeneous intramyelin material is the anodal region of the self-polarised 

 nerve. The deeply-stained region, in which coagulative changes are observ- 

 able, is the kathodal region where the injury current leaves the nerve-fibre 

 to traverse the external circuit of the salt solution. We can now return to 

 the evidence obtained as to the distribution of potassium. 



Injury suddenly elicits the appearance of strong solution of potassium at 

 the injured point. Given time, this solution diffuses into the neighbouring 

 stretch of the nerve-fibre. This phenomenon is accompanied by an electrical 

 phenomenon, the injury current. The traverse of the injury current polarises 

 the fibre and gives rise to the appearance of a new mass of potassium 

 solution, accompanied by appearances characteristic of coagulation at the 

 kathodal region. 



Macallum has more recently published an account of the distribution of 

 the inorganic chlorides present in nerve-fibres. With the assistance of 

 Miss Menten he has penetrated the false character, which the vagaries of the 

 slowly -diffusing silver nitrate confer upon their apparent distribution, and 

 has discovered the fact that the inorganic chlorides are everywhere present 

 in great quantity in the intramyelin material. The drawings accompanying 

 this paper also reveal a very remarkable addition to this statement of 

 chloride distribution. In most of these illustrations it is easy to observe 

 indications of effects produced by the nature of the reagents made use of. 

 The proportion existing between the diameters of the myelin sheath, the 

 intramyelin material, and the whole fibre, are alone sufficient basis upon 

 which to make this statement. The intramyelin material does not occupy 

 one-half of its usual relative cross-section. Where this is not the case, and 

 the right proportions are maintained, the authors describe the fibres as 

 swollen. Wherever, in the illustrations, this swollen, but normal, appearance 

 of the fibre is present, the distribution of the chloride coincides exactly with 

 the appearance of teased nerve-fibres stained with basic dyes, and also with 

 appearances obtained by the use of Macallum's reagent for potassium. 

 I have no hesitation whatever in urging, upon this basis of evidence, the 

 necessity of conjugating these facts. The salt present is potassium chloride. 

 It is present in extraordinary quantity. It is present in some masked 

 position in the structure of the intramyelin material. From this position 

 there is direct evidence that it is enticed by injury, and by the kathodal state. 

 vol. lxxix. — b. c 



