It hardly seems possible that it was only 35 years ago that Hevesy first introduced radioactive isotopes into medical and biological research. Particular application for these isotopes has been found in the field of hematology. In fact, the speciality could not have grown as it has, had it not been for these most useful tools. The measuring of red blood cell volume can now be accomplished through the use of radioactive phosphorus, chromium, and iron. Plasma volumes and hematocrit values can be determined through similar techniques. The survival of the red cell, once a tedious and at best inaccurate guess, can now be measured by Cr51- and sometimes by Fe55-, Fe59-,P32-, and C14-labeled glycine.
Tests for pernicious anemia and its differentiation from other macrocytic anemias have been developed through the use of radioactive cobalt. Iron metabolism has been clarified in regard to