a) The rabbits under those conditions such as non-treated, R.E.S. stimulated, R.E.S. blocked, splenectomized, liver protected, and cachectic, were given human cancer extract intravenously for seven days, determining the protein waves of the blood serum. It was found that the wave height of F. decreased and of D. increased, A/G and α and γ globulins increased, when the cancer extract was injected into them. In the liver protected and in the R.E.S. blocked cases the decreasing rate of F. wave height was less, and in the liver protected and in the splenectomized cases the increasing rate of D. wave height was also less. b) The filtrate protein waves were determined polarographically in the saline extract of the gastric cancer tissue, the mucosae of gastric cancer and of gastric ulcer. In the cancer extract the fluctuation in wave height did not appear even after alkali denaturation. c) In the paper-chromatograph completely similar nine spots were observed in the cancer tissue, the mucosae of gastric cancer and the ulcer. d) Filtrate protein wave was determined, after keeping the cancer tissue extract and the serum at various temperatures for 30 minutes and in the several concentrations mixed in vitro, and was compared with the result obtained in the non-mixed after the same procedure. In the temperature of 20℃ and the protein concentration of 1.1 gm. % , the mixed one showed higher wave than the non-mixed. As a control, same experiment was performed in the extract of mucosa of gastric ulcer, but it showed no differences between the mixed and the non-mixed. In short, the cancer extract which elevated the protein wave of rabbti serum filtrate is more denaturated than the extract of normal gastric mucosa, and the cancer extract has a direct action to the serum protein and to elevate the filtrate protein wave even in vitro.