The reduction of calcium in the blood in infantile tetany and in tetany due to parathyroid deficiency has been well recognized since the classic work of McCallum and Voegtlin.1 On the other hand, no significant alteration in the total amount of calcium in the serum has been found in tetany induced by hyperventilation or by an overdosage of bicarbonate.2 The differences in the analytic observations of the chemical composition of the blood in tetany of diverse origin3 led Grant and Goldman to conclude: "Tetany occurs under so many circumstances that it probably cannot be attributed to a single etiological factor." This, however, has not deterred many from attempting to establish a common disturbing factor as the cause of all forms of tetany. Two hypotheses have been proposed with respect to the etiologic factors responsible for tetany: 1. All forms of tetany are due to an alkaline shift in the acid-base