For the evaluation of calcium determinations on serum, plasma or whole blood it is necessary to know, first, whether the concentration of calcium is nearly constant and second, what factors influence this concentration. As the result of several thousand determinations in this laboratory, we believe that the calcium concentration of the serum of children is singularly constant and that the concentration is strikingly altered in only two conditions that we have met (a) tetany, (b) kidney insufficiency with or without nephritis.
In the last three years, several papers have appeared that would seem to show that the calcium concentration of the serum is not constant, that high values may be obtained even in frank tetany and that very low values may be found in the serum of children who present no evidences of tetany. This is entirely at variance with our experience. For this reason we wish to record some