Further observations on the rôle of the blood fluids in connection with phagocytosis.

In a previous communication we showed that the phagocytosis which occurs when cultures of the Staphylococcus pyogenes are added to human blood, is directly dependent upon the presence of certain substances in the blood which exert a specific effect upon the bacteria. We suggested that the bacteriotropic substances here in question might appropriately be denoted by the term “opsonins.”