The hemostatic activity of sodium alginate was studied by in vitro and in situ experiments and by a clinical application. 1. 5% solution of sodium alginate did not gelatinize when mixed with rat plasma in vitro, but easily gelatinized in the coexistence of rat plasma and rat gastric juice or artificial gastric juice. 2. 5% solution of sodium alginate did not gelatinize in the presence of calcium ion equivalent to the concentration of Ca2+ in plasma (10 mg/dl), and more than 70 mg/dl of calcium was required to cause an intense gel formation. 3. The sedimentation and diffusion velocities of the peripheral blood of rabbits in the sodium alginate solution were delayed as the concentration of sodium alginate increased. 4. Bleeding from the injury of rat gastric mucosa caused by a biopsy was significantly interrupted earlier than controls when 5% solution of sodium alginate was applied to the injury. 5. In a clinical application, 5% solution of sodium alginate also suppressed the bleeding from the injury of human gastric mucosa caused by a biopsy.
