The reversible loss of excitability in isolated amphibian voluntary muscle

IN a previous paper [Duliere and Horton, 1929] it was shown that when a frog's sartorius muscle is dissected without the use of Ringer's solution and is suspended in a moist inert gas or in mercury or liquid paraffin, a condition of reversible inexcitability sets in. Dryness is not a factor, and chemical changes in lactic acid or phosphagen are not involved, but alterations in the time relations of excitability occur. Recovery of excitability follows immersion in certain solutions, notably sodium chloride, while a muscle which has been soaked in Ringer's solution for about an hour will not thereafter become spontaneously inexcitable. It was suggested that diffusion of potassium from the fibres into the interspaces of the muscle is the secondary cause of the phenomenon, and that the removal of this "free" potassium by Ringer's solution results in excitability being regained. The object of the present paper is to give quantitative evidence in support of this hypothesis, to show that inexcitability produced by different methods can be due to liberation of potassium from the fibres into the interspaces, and to consider the general question of diffusion in muscle tissue.