We may devise a fluid containing practically all the inorganic diffusible constituents of the blood except
calcium, and use it to dialyze normal blood in such a way as to remove from it a large part of its
calcium. The dialyzed blood when perfused through an isolated extremity produces an extreme hyperexcitability of the nerves quite like that observed in
tetany. Since perfusion with blood dialyzed in precisely the same way against a fluid of the same composition, but containing
calcium in the proportion found in the normal blood, causes no hyperexcitability of the nerves, it is evident that the hyperexcitability is due to the lack of
calcium. This effect can be attained in only a slight degree by replacing the blood of a whole animal with the dialyzed blood, since under the conditions of the experiment the tissues cannot be sufficiently depleted of their
calcium. It seems probable that the parathyroid secretion is not removed by dialysis, but is returned to the body with the dialyzed blood. To bring this result into relation with the condition in
tetany following
parathyroidectomy, animals in
tetany were bled and the blood was replaced in one case with normal blood, in the other with dialyzed blood poor in
calcium. The normal blood immediately relieves the
tetany and lowers the excitability, while the dialyzed blood does not. We therefore believe that this is a further proof that in the
tetany of
parathyroidectomy also the twitching and hyperexcitability of the nerves is due to lack of
calcium in the blood and tissues.