THE DEMONSTRATION OF A TUMOR GROWTH-INHIBITING FACTOR FROM NORMAL HUMAN CONNECTIVE TISSUE.

Extracts from fresh normal human connective tissue (rectus sheath) exhibited a decided inhibiting action on grafts of Rat Tumor 256 transplanted into test animals. There was complete inhibition of tumor growth in 66 per cent of the animals; there was a marked retardation in the rate of growth in another 15 per cent, the tumors in these instances being much smaller than the controls transplanted at the same time. In only one experiment was there failure to obtain a lasting growth-inhibitory effect. The tumors in these animals (19 per cent) although showing an initial retardation in growth, apparently overcame the restraint and at the end of 5 weeks were larger than the control series. Extracts from fresh normal human muscle tissue, on the other hand, showed no such inhibiting action on grafts of Rat Tumor 256.