Ancient biblical Judaism ascribed magical and supernatural properties to blood. Both Rabbinic Judaism and Christianity inherited this attitude toward blood, and adopted, each in its own way, symbolic and spiritualized rituals connected with blood. Throughout the centuries, Judaism and Christianity borrowed beliefs and rituals from one another. Argues that the blood libel emerged as a negative by-product of an increase in popular eucharistic piety. Encouragement for this accusation was provided by the Fourth Lateran Council of 1215, which approved the doctrine of transubstantiation and heightened popular interest in blood, especially Christian blood. The alleged Jewish consumption of Christian blood seemed to prove the dogma of transubstantiation in popular consciousness. In the 19th century the blood libel emerged again in Europe, devoid of its theological underpinning but supplemented with a belief in blood as the bearer of heredity, and hence of the ethnic and racial traits of the person. Academic authorities, from August Rohling to the Nazi Erich Bischof, tried to prove the truth of the blood libel and created the theory of blood - i.e. racial pollution. It was in such a form that blood mysticism was picked up by the Nazis. The revival of the blood libel in the 19th century provoked a wave of literature refuting the accusation. Paradoxically, while Jews were vigorously rejecting the claim that human blood played a role in their rituals, some of them adopted the blood language of modern nationalism, a belief in the nation-making "Jewish blood".