"They're waiting for the blood to congeal"
Blood Tofu
Creative Commons AttributionBlood Tofu - Credit: Takeaway

It is common in many cultures to consume the blood of slaughtered animals in some form, either by cooking it, drinking or eating it raw, or letting it coagulate and then consuming it. Usually strength, courage or intelligence is associated with the ingestion of blood.

A popular Chinese dish, "Blood Tofu", is normally made of coagulated duck or pig's blood. In this case, coagulated buffalo blood is cut into rectangles and eaten.

You can see blood tofu on the right side of the dish pictured. It looks a bit like a square beet (tastes different though).