The structure and function of nerve fibres.―Preliminary communication

Abstract

The electrical phenomena characteristic of nervous function have always served to attract attention to the distribution of electrolytes within nerve-fibres. The complexity of this distribution has been realised since the early observations of Du Bois Reymond, who first clearly defined the necessity of making all available information of this kind the basis from which to discuss the electrical phenomena elicited from nerves. An important hindrance to the acquisition of the necessary detail is offered by the extreme minuteness of the individual nerve-fibre. Most of the information already acquired has therefore of necessity been indirectly obtained, and can in general be described as a series of deductions drawn from a detailed observation of peculiarities in the conductivity of the nerve-trunk-a structure containing some thousands of nerve-fibres arranged in a complex of ensheathing tissues. It has been found that the conductivity of the nerve-trunk cannot be expressed as that of a simple homogeneous conductor, and can only be imitated by an arrangement of at least three kinds of conducting material in a definite pattern-an external medium of poor conductivity material in a definite pattern-an external medium of poor conductivity, a dividing membrane, and an internal solution of a conductivity of a higher order than that of the external solution. With good reason the properties of these three hypothetical tissues have usually been transferred to the structures of the individual nerve-fibre. For example, it has been frequently supposed that its axis-cylinder represented the internal solution of more than usual conductivity. Within recent years evidence has been gradually collected pointing to the fact that the major part of the conductivity of the tissues of the body, nerve included, is due to the inorganic salts they contain. It is therefore a fair assumption that here, where the internal solution of the nerve has been credited with an unusually concentration of inorganic salts within the nerve-fibre. Unfortunately, this statement cannot be adequately tested by an appeal to the "ash" of the nerve-trunk, since the axis-cylinders of the nerve-fibres form only a small proportion of the total bulk thus examined. The only fact gleaned from such as examination is that the salts present are very largely salts of potassium. Summing up all this indirectly-obtained evidence, it might therefore be said that there was reason to believe that a solution of potassium salts of more than usual concentration was present in the interior of individual nerve-fibres.