The rôle of the calcium ion in the metabolism of rickets has for a good many years formed the keystone of the arch in the study of this disease. The conception, recently advanced by Howland and his associates, of the existence of two forms of rickets, the low calcium and the low phosphorus types, is based chiefly on the chemical study of the blood.
Experimentally, the feeding of low phosphorus diets to animals leads to the production of true rickets, whereas low calcium diets lead not to true rickets, but to osteoporosis. It is a fact that in all forms of rickets the body as a whole shows a marked lowering of its calcium content.
Recently, one of us1 has shown that in the breast milk on which babies develop rickets there was no reduction in the inorganic phosphate constituents, and it seemed worth while to study also the