1. Experiments are described which show that active extracts of ovarian tissue minus corpus luteum can be obtained which significantly raise the lowered level of the serum calcium in ovariectomised toads; and also raise the serum calcium level in normal toads above the normal level.
2. Injection of adequate doses of antuitrin (Parke, Davis and Co.), raises the lowered level of serum calcium in hypophysectomised toads almost to normal; and of ovariectomised toads to the normal level. The effect is obtained more readily in the ovariectomised condition.
3. Injection of pituitrin (Parke, Davis and Co.), depresses the serum calcium level in normal, ovariectomised and completely hypophysectomised toads. The effect is more readily obtained in the normal intact animal than in the ovariectomised or the totally hypophysectomised state, when the ovaries have undergone involution.
4. It is suggested that there is evidence that the principles exerting a hormonelike action on calcium metabolism are not, in the case of the ovary, either oestrin or the luteal hormone, or in the case of the pituitary, the gonadotropic hormone.