Although chitosan has virtually the same chemical structure as cellulose, it is a polysaccharide with a positive charge. When paired with the negative charge of red blood cells' outer membranes, opposites attract, Dr. Gregory said. As a result, a clot is formed independent of the body's normal clotting procedure.

Colonel Pusateri of the Army research institute believes that the key to the chitosan bandage is its adhesive quality, but Dr. Gregory is adamant that the bandage literally has the power to create its own clot, even among those with hemophilia.

Regardless of how it is done, the chitosan has held up to more bleeding than it was intended to take. In its own testing, the Army successfully stopped vast internal bleeding and reported that its subjects (pigs with lacerated livers) survived at least the hour specified, even though the dressing was originally intended for external hemorrhaging. That durability gives patients more time to reach treatment centers.

Chitosan has long been known for its clotting abilities, but it had never been made into a reliable product. ''You could use chitosan to control minimal bleeding, but no one ever built a durable bandage that could control the type of hemorrhage that we're talking about,'' said Dr. Bill Wiesmann, a developer of the bandage and the former head of combat casualty care for the Army.

Dr. Gregory said that his team's task was to create a bandage that would ''work at minus-50, equivalent to the Arctic, plus 140, the Sahara'' and, he added, ''I decided you have to be able to drive a Humvee over it.''

The technology could also have ramifications far beyond the armed forces.

Bleeding is a leading cause of death in trauma cases among civilians as well, and it accounts for an overwhelming majority of operating-room deaths in trauma patients. One neurosurgeon, for example, has requested advanced access to the bandage for an operation to remove tangled blood vessels in the brain, a procedure that carries a high risk of death from bleeding.

Dr. Gregory and his colleagues have formed a company called HemCon to produce the bandage for the Army, and they expect commercial production geared toward civilian hospitals to begin by summer or fall.

For now, the Army has ordered 20,000 of the bandages. ''There's something like 70 million E.R. visits a year for bleeding.'' Colonel Pusateri said. ''It's a huge problem. After all, everybody bleeds.''