instance, whereas human blood serum exhibits a con¬ tent of 9 or 10 mg. per hundred cubic centimeters, the serum of infants suffering from tetany may exhibit a decrease in calcium amounting to more than 50 per cent.2 A second problem concerns the possibility of alter¬ ing the calcium content of the blood. Considerable evidence might be cited to show that the feeding of diets rich or deficient, respectively, in calcium makes no appreciable difference in the amount of this element found in the blood, bones or other tissues.3 Confirma¬