In several earlier communications 1 it was stated that completely parathyroidectomized animals could be cured of all symptoms of parathyroid tetany by the intravenous injection of Ringer's solution. It was furthermore shown that this treatment could be stopped after from forty to sixty days without the appearance of tetany except under special conditions described in the papers referred to. In the course of this work it was found that calcium-free Ringer's solution or Locke's solution from which the calcium was partly precipitated possessed some efficacy in conserving the life of parathyroidectomized animals, but that ordinary Ringer's solution was incomparably better, especially early after operation. These results strongly suggested that the calcium contained in the Ringer's solution was in some way responsible for the beneficial results seen following its intravenous administration in parathyroidectomized animals. When, however, calcium chlorid was administered orally in quantities from 2.6 to 3.6 times as great each