a differential agglutination method for estimating erythrocyte lifespan; compatible blood possessing a group factor that the recipient lacks is transferred to the recipient; after the transfusion, sera with potent agglutinins for the recipient's red blood cells are added to samples of the recipient's blood, and the unagglutinated red blood cells are counted; with this technique, the red cell lifespan in normal persons is found to be 110-120 days.
