Karetot 22: Blood Loss at the Time of Death

How do we know which blood is forbidden to consume when we are only told that it is the blood that comes out at the time of death?  Rabbi Yochanan describes it as "the blood that spurts forcefully" while Reish Lakish says "from the last black drop onward".

Rashi gives further detail. He says that when the arteries are cut, the blood that escapes is first dark and then is red.  In the second stage, it is more forceful in its second stage, and then eventually the force weakens and the blood leaves the body gently.  Rabbi Yochanan believes that only the blood that leaves the body forcefully is the "life blood", while Reish Lakish says that the blood that leaves the body after that last black drop is the "life blood" and thus forbidden.

 Rabbi Zeira offers another argument: even though the Mishna is clear that inner organs do not hold blood that makes one who consumes it liable to receive karet, blood in the animal's heart "absorbs" the forbidden blood and thus it is off limits.

Steinsaltz goes on to describe the scientific process of sudden blood loss, including the state of hypovolemic shock followed by contracting blood vessels (to lead blood to the heart).  The heart's right ventricle then creates a vacuum to draw blood from the veins so that as little blood is lost as possible.  This would be a physical explanation of Rabbi Zeira's commentary about the blood held in an animal's heart.