A strain of Eperythrozoon coccoides was maintained in a pure state for 16 months in unsplenectomized Princeton mice by the intraperitoneal injection of parasitized blood, at intervals of 1 to 3 weeks. In the 39th passage three out of five mice developed marked ascites with innumerable neoplastic cells in the peritoneal fluid. By passage of this fluid the tumor cells and the eperythrozoon were transferred together, with the rapid development of ascites and early death of the animals. On continued passage of ascitic fluid and blood from the mice of the 39th successive group both the tumor and the eperythrozoon were ultimately obtained in a pure state. Development of the passaged tumor was uninfluenced by the eperythrozoon but growth of the latter appeared enhanced in the presence of the neoplastic cells. Throughout 50 passages in mice the ascites tumor has not altered in character.

The intraperitoneal injection of ascitic fluid was irregularly followed by the appearance of tumor cells in the blood, the rate of the carriage being 26 per cent in sixty-five animals. The subcutaneous and intramuscular injection of the fluid resulted in solid, highly invasive, local growths which did not metastasize. The solid growths proved transferable in series yet after 20 passages still produced the ascites tumor on intraperitoneal injection of their cells.

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