Quotes
Moreover, this Trento crime was not an exception: Toaff discovered many cases of such bloody sacrifices connected with the mutilation of children, outpouring of blood and its baking in Matzo (unleavened bread) spanning five hundred years of European history. Blood, this magic drink, was a popular medicine of the time, and of any time: Herod tried to keep young bathing in blood of babies, alchemists used blood to turn lead into gold. Jewish wizards meddled in magic and used it as much as anybody. There was a thriving market in such delicacies as blood, powder made of blood and bloody matzo. Jewish vendors sold it accompanied with rabbinic letters of authorization; the highest value was blood of a goy katan, a gentile child, much more usual was blood of circumcision. Such blood sacrifices were "instinctive, visceral, virulent actions and reactions, in which innocent and unknowing children became victims of the love of God and of vengeance," Toaff wrote in the book's preface. "Their blood bathed the altars of a God who, it was believed, needed to be guided, sometimes impatiently pushed to protect and to punish."
    Toaff explains that there was widespread fear of the Jews in Europe in the middle ages, and that this fear sprung from their known reputation for kidnaping children for the slave trade. What is implicit in Toaff’s research, is that the orthodox Jews had an established insular group, that was practiced and expert in abducting children, whether it be for purposes of slavery or ritual murder:

During this period, Jewish merchants, from the cities in the valley of the Rhône, Verdun, Lione, Arles and Narbonne, in addition to Aquisgrana, the capital of the empire in the times of Louis the Pious (Louis I); and in Germany from the centres of the valley of the Rhine, from Worms, Magonza and Magdeburg; in Bavaria and Bohemia, from Regensburg and Prague - were active in the principal markets in which slaves (women, men, eunuchs) were offered for sale, by Jews, sometimes after abducting them from their houses. From Christian Europe the human merchandise was exported to the Islamic lands of Spain, in which there was a lively market. The castration of these slaves, particularly children, raised their prices, and was no doubt a lucrative and profitable practice.
    The first testimony relating to the abduction of children by Jewish merchants active in the trade flowing into Arab Spain, comes down to us in a letter from Agobard, archbishop of Lyon in the years 816-840. The French prelate describes the appearance at Lyons of a Christian slave, having escaped from Córdoba, who had been abducted from Leonese Jewish merchant twenty four years before, when he was a child, to be sold to the Moslems of Spain. His companion in flight was another Christian slave having suffered a similar fate after being abducted six years before by Jewish merchants at Arles. The inhabitants of Lyons confirmed these claims, adding that yet another Christian boy had been abducted by Jews to be sold into slavery that same year. Agobard concludes his report with a comment of a general nature; that these were not considered isolated cases, because, in every day practice, the Jews continued to procure Christian slaves for themselves and furthermore subjecting them to “infamies such that it would be vile in itself to describe them.”
    Precisely what kind of abominable “infamies” Agobard is referring to is not clear; but it is possible that he was referring to castration more than to circumcision.743 Liutprando, bishop of Cremona, in his Antapodosis, said to have been written in approximately 958-962, referred to the city of Verdun as the principal market in which Jews castrated young slaves intended for sale to the Moslems of Spain. During this same period, two Arab sources, Ibn Haukal and Ibrahim al Qarawi, also stressed that the majority of their eunuchs originated from France and were sold to the Iberian peninsula by Jewish merchants. Other Arabic writers
mentioned Lucerna, a city with a Jewish majority, halfway between Córdoba and Málaga in southern Spain, as another major market, in which the castration of Christian children after reducing them to slavery was practiced on a large scale by the very same people.
    Contemporary rabbinical responses provide further confirmation of the role played by Jews in the trade in children and young people as well as in the profitable transformation of boys into eunuchs. These texts reveal that anyone who engaged in such trade was aware of the risks involved, because any person caught and arrested in possession of castrated slaves in Christian territories was decapitated by order of the local authorities.744 (744.Ariel Toaff  provides the following authority in an endnote: “On the rabbinical responses relating to the trade in castrated young slaves and on the role of Lucena (outside Córdoba) as a center for the castrations, see A. Assaf, Slavery and the Slave-Trade among the Jews during the Middle Ages (from the Jewish Sources), in "Zion", IV (1939), pp. 91-125 (in Hebrew); E. Ashtor, A History of the Jews in Moslem Spain, Jerusalem, 1977, vol. I, pp. 186-189 (in Hebrew).”)  Even the famous Natronai, Gaon of the rabbinical college of Sura in the mid-9th century was aware of the problems linked to the dangerous trade in young eunuchs. “Jewish (merchants) entered (into a port or a city), bringing with them slaves and castrated children [Hebrew: serisim ketannim]. When the local authorities confiscated them, the Jews corrupted them with money, reducing them to more harmless advisors, and the merchandise was returned, at least in part.”745 But if one wishes to interpret the significance and scope of the Jewish presence in the slave trade and practice of castration, it is a fact that the fear that Christian children might be abducted and sold was rather widespread and deeply rooted in all Western European countries, particularly, France and Germany, from which these Jews originated and where the greater part of the slave merchants operated.
    Personalities in the clergy nourished that fear, conferring religious connotations upon it with an anti-Jewish slant, failing to account for the fact that slavery as a trade had not yet gone out of fashion morally and, as such, was broadly tolerated in the economic reality of the period. On the other hand, the abduction and castration of children, often inevitably confused with circumcision, which was no less feared and abhorred, could not fail to insinuate themselves in the collective unconscious mind of Christian Europe, especially the French and German territories, inciting anxiety and fear, which probably solidified over time, and, as a result, are believed to have concretized themselves in a variety of ways and in more or less in the same places, as ritual murder.746  [2011] Solving the Mystery of Babylon the Great by Edward Hendrie