The demonstration of the preventive and curative action of radiant energy and of the organic factor contained in cod liver oil in rickets has made studies of the action of these therapeutic agents of fundamental importance. At the present time, investigations indicate that the salts chiefly concerned in the disturbance in mineral metabolism which constitutes rickets are those of calcium and phosphorus. The experiments reported in this paper, begun in January, 1922, were planned to demonstrate whether or not cod liver oil exerts a regulatory influence on the calcium and phosphorus metabolism of rats.
Before describing the experiments, it seems advisable to point out certain facts recently discovered concerning the calcium and inorganic phosphorus content of the blood.
The concentration of calcium in the blood serum is apparently never above a value believed in normal children to be between 10.0 and 11.0 mg. per hundred cubic centimeters of serum, and