It has been found that the addition of red cells to the CLG and S-F media inhibits the multiplication of the K-9 strain of Entamoeba histolytica. After about 5 days the amebae recover from the inhibitory action of the erythrocytes and grow in a normal fashion when optimum amounts of red cells and amebae are used. During the inhibitory period there is actual destruction of many of the trophozoites originally seeded, suggesting the presence of a toxic material in red cells. E. histolytica strains 103 and 200 showed resistance to the effect of red cells. It was observed that these strains readily hemolyze red cells. This, and their ability to migrate up the sides of the culture tubes, may explain their resistance to the red cells' effects which were observed with the K-9 strain.
Present address: The Lutheran General Hospital, 1775 Dempster Street, Park Ridge, Illinois.