Many investigators have studied the malignant tumor cells in vitro. Lambert and Hanes (1) have cultivated the rat sarcoma; Carrel and Burrows (2) cultivated the Rous chicken sarcoma, the rat sarcoma, human sarcomata, carcinomata from the dog, the Flexner-Jobling rat carcinoma and several human carcinomata. Losee and Ebeling (3) cultivated human sarcomata. Carrel and Burrows, Losee and Ebeling stated that sarcomatous tissue grew as well during a few days as normal fibroblasts, but afterwards the rate of growth became less rapid and the tissue could not be kept alive for more than about two months. The life of the cultures is short, which may be due to technical factors. Liquefaction of the plasma clot occurred generally and no further growth and increase of the mass of the tissue takes place. It is difficult to prevent the liquefaction of the coagulum. Recently Carrel (4) found that the addition of small amounts of serum and trace of sodium linoleate to a fibrinogen-tyrode medium partly prevented the liquefaction of this medium when normal fibroblasts were cultivated in it. This was tried also in our cultures of sarcomatous tissue cells, but showed not to prevent the extensive liquefaction of the medium. The best results of this kind were obtained by reducing the amount of embryonic tissue juice in the culture medium.