Abstract
In considering the changes in the maternal organism during pregnancy many observers from the time of Rokitansky have noted alterations in the teeth and skeletal tissues. 1 In this connection, Seitz 2 has pointed out that “of all the mineral substances, calcium passes in the greatest amount from the mother to the foetus” during gestation. It has been found also that about the time of very active development of bone in the foetus, which probably necessitates the mobilization of a considerable supply of calcium in the foetal body, the parathyroid glands of the embryo are already differentiated morphologically. 3 Of immediate interest, however, are the recent investigations of Collip, 4 as a result of which there is available an extract of the parathyroid glands which exerts a powerful influence on the mobilization of calcium in the blood. By means of this highly concentrated parathyroid substance, the old problem of the mechanism which is involved in the exchange of calcium from mother to foetus is reopened to experimental inquiry from a new angle. The possibility of the escape of active parathyroid substance from the foetus to the mother across the placental boundary, can be tested by direct observation.
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