For the less culturally enriched, it is referring to the practice of the Brit milah. It is the Jewish tradition of swallowing the blood directly from the wound of a circumcised infant - complete with transmission of infectious diseases. Yum!
Not surprisingly, in recent times the practice has fallen out of favor with doctors in Europe. However, when legislation arose to ban this infant vampirism, the Jewish community was quick to claim it was anti-semetic.