Conduction of nervous impulses in NaCl-deficient media.

Since Overton's finding on muscle (1), examination on the effect of Na deficient media upon the nervous function has been a centre of interest (27). The blocking concentration, or the minimal concentration required for conduction, has been said to be 10-15% of that of the normal Ringer for nonmyelinated fibres of the Crustacean (4) and 0.011 M for myelinated fibres of the frog (5), which are almost coincident with that obtained for muscle by Overton (about 10%). However, no precise determination has been made with respect to fibres of different types or sizes, although it seems certain that different fibres react in different manners to NaCl-deficiency (6, 7). According to Crescitelli, B-fibres are most sensitive to lack of sodium; they are blocked earlier than A-fibres and many of C-fibres in one and the same NaCl-deficient fluid; further, there are some differences among fibres belonging to A-group itself. These facts suggest that not only fibre types but also individual fibres of each type resist to NaCl-deficiency in different grades. The present study aims to clarify this point and, at the same time, to carry out observations on some phenomena of conduction NaCl-deficient solutions.