By using Ehrlich tumor ascites of ddN mice, the phagocytosis of ascites macrophage and the tumor cell has been observed in vitro in the medium containing chondroitin sulfric acidiron colloid.
Observations revealed that macrophage phagocytizes the colloid particles but the tumor cell does not in spite of its marked pinocytotic activity. Macrophage adsorbed the colloid particles on its surface but the tumor cell did not, indicating that the adhesion of the colloid particles induces phagocytosis. At the area where the colloid particles were adsorbed small rhopheocytotic vesicles developed and then phagocytotic vesicles were formed, suggesting that rhopheocytosis is the initial step of phagocytosis. The adsorption of the colloid particles occured on the cell surface with a certain distance but not covering whole the surface of the cell. This fact indicates that specific groups having the affinity to the colloid particle should exist on the cell surface of macrophage, by which macrophage can phagocytize the particles. The particles were found to be accumulated in the phagocytotic vesicles. This should be obtained by the membrane flow toward the inside of the cell. Generally the vesicle is connected to the cell surface by narrow tubule. The number of colloid particles in vesicle will increase with the reduction of vesicular volume by dispersing water and the small molecules into cytoplasm.