Statement of Purpose: Commercially available absorbable surgical hemostats swell in use (20-200%) because they absorb fluids and can compress the neighboring tissues leading to complications. This is especially a problem in cranial and spine surgery because the swollen hemostats cause neural compression leading to pain, paresis, and paralysis . Such hemostats are also slow acting and can take up to 10 minutes to achieve hemostasis, and these are often used several times per case. In this study, we present a patented system of two natural polysaccharides that form a hydrogel device in situ without the use of an external crosslinking agent. Even though one of the starting materials in our system, chitosan, has been shown to be hemostatic in in vitro tests, more appropriate testing using in vivo critical defect models demonstrated it to be not hemostatic . We have chemically modified the chitosan to be water-soluble so that it interacts with oxidized dextran via Schiff base formation to form a unique hydrogel structure that: 1) produces hemostasis in a short time, 2) leads to stable clot formation and 3) gently shrinks with time.