The inorganic constituents of cardiac muscle and their bearing on cardiac activity have been receiving more and more attention in recent years. The work of Norn1 on potassium, especially his investigations on the excretion of this element, seems to indicate that the potassium content of the tissues of the normal individual, at least, is constant, and that the body responds promptly to excessive intake by establishing an equilibrium.
At the time of his experiment, Norn had not been able to raise the value of the blood potassium appreciably or for any length of time by administrations of relatively large doses of potassium chloride. Furthermore, to judge from this work, the normal diet furnishes far more potassium than the body can retain and, like sodium salts, that portion not utilized is excreted, principally no doubt, in the urine. The conditions under which the investigations of Norn were carried out were virtually