The Use of Ruthenium Red in an Electron Microscope Study of Cytophagocytosis

In a recent study of the cytophagocytosis of Sarcoma I (SaI) cells by alloimmune macrophages', the problem arose as to whether a SaI cell, that was surrounded by a macrophage within the plane of section, was in fact completely phagocytized or whether a portion of the cell surface was free in another plane . Certain observations, such as the absence of clear areas between the plasma membrane of the SaI cell and the membrane of the macrophage and the presence of electron-opaque material within the