The control of beating and of micro-fibrillation by means of potassium, calcium and sodium in the chick embryo heart potassium fibrillation

In a previous paper (Murray 1938) it was shown that fibrillation by excess of calcium in the medium depended upon an abnormally high ratio between calcium at the cell surfaces and potassium in the cell interiors. In the present paper further experiments are described, from which it will be concluded that fibrillation by excess potassium in the medium depends upon a similar relation, but in this case between potassium at the cell surfaces and potassium, and perhaps also sodium, in the cell interiors. The methods used were the same as in the experiments described earlier (Murray 1938). The media were pure salines, or saline-glucose, in watch glasses. Table I gives the compositions of the various solutions. In the text, an arrow between the names of two solutions means that hearts were first treated in the solution on the left of the arrow and then transferred to the solution on the right. For further details, refer to the earlier paper.