I was leafing through a Passover Haggadah yesterday, preparatory to last night’s Seder. It’s one of many in my possession, a text, with extensive commentaries in English and Hebrew, that was published in New York in 1950. Although it’s been used in many Seders, it’s not in bad shape. If you were a used book dealer, you would note in your description of it: “In good condition, except for several dark stains on pp. 56-61.”

Some of you may have already guessed what’s in these pages. They’re the section of the Haggadah dealing with the Ten Plagues of Egypt. In the course of reciting this section, which begins with the first plague, in which Moses is said by the Bible to have turned the Nile to blood, the practice is for the participants to dip a finger into their wine glass and flick a drop of wine onto their plates or on the tablecloth for each plague. Even with the best of aims, some drops will inevitably, over the years, land on the Haggadah.

It’s an old tradition. I have, for example, a facsimile edition of an illustrated French Haggadah printed in Bordeaux in 1813. Each of the Ten Plagues has its own black-andwhite woodcut, the one for the plague of blood depicts a river flowing past a town and under a bridge; a dead fish floats on its surface, a woman who has come with a large jug stands looking perplexedly at the foul water, and several men with shovels are hard at work digging wells for which they never had any need before. And there are wine stains all over the page.

Another facsimile edition that I own was published in Amsterdam in 1668. Here the illustrations are hand-painted and in color. Once again there is a city in the background and a river flowing under a bridge. This time it is red, and a Dutch burgher in 17th-century clothing is gesticulating at it in wonder. Wine stains are all around it.

But the tradition is at least several hundred years older than that, if not more so. In fact, it figures prominently in the now infamous book, “Pasque di Sangue” or “Bloody Passovers,” about a “blood libel” trial that took place in the northern Italian town of Trent in 1475. The book was published two months ago by the Italian-Israeli scholar, Ariel Toaff, who is the son of the chief rabbi of Rome. On the basis of confessions extracted from sixteen Jews under torture, they were convicted at this trial of murdering a two-year-old Christian boy before Passover and using his blood to bake matzos and to add to the wine they counted off the Ten Plagues with. One of the convicted men, Moses of Würzburg, declared in describing this ritual (the translation from Italian is my own):

“The head of the family takes some blood from a Christian child and puts it in a glass full of wine … then, putting his finger in it … he sprinkles it over the table and over the food that is on it, pronouncing the Hebrew formula that commemorates the Ten Plagues which God brought upon Egypt for refusing to liberate the Jewish people.

At the end of this passage, the same family head, referring to the Christians, proclaims the following: ‘So do we implore God to bring down these Ten Plagues on the Gentiles who are enemies of the Jewish faith.'”

Professor Toaff — who absurdly argues in “Sangue di Pasque” that the Trent trial confessions should probably be regarded as trustworthy, even though they were long ago dismissed by all reputable historians as fabrications whose sole purpose was to put an end to unbearable torments on the rack or the prospect of them — takes this account of Moses of Würzburg’s seriously too. In doing so, however, he is thinking more like a 15th-century Catholic inquisitor than like a 15th-century Jew.

Although there is no way of proving it, I strongly suspect that the “information” provided by the Trent defendants regarding the use of Christian blood at their Passover Seder was less designed to satisfy the lurid fantasies of their Christian interrogators than to let their fellow Jews know that their confessions were a pack of lies.

Although other Jews would have found it hard to believe that their co-religionists had killed a Christian child out of sheer vengefulness, this would perhaps not have been totally unimaginable. But that they should have actually swallowed this child’s blood and dowsed their food with it — surely no Jew of the times, hearing of the Trent trial, would have put the least credence in this.

After all, not only is the consumption of animal, let alone human, blood strictly forbidden by the Bible, the Jewish dietary laws demand that kosher meat be specially salted before being cooked and always be eaten well-done to make sure not a trace of blood remains in it.

Nothing could be more instinctively revolting to an observant Jew than to eat food with human blood. Nothing could more effectively have warned other Jews that an account was untrue.

Indeed, while charges of murdering Christian children were made against Jews in Europe throughout the late Middle Ages, starting with the mid-12th century, the accusation that Jews used Christian blood in their Passover food and rituals had never surfaced before the Trent trial and was obviously the invention of Moses of Würzburg and his co-defendants.

The art of cleverly inserting an outrageous lie into a confession made under duress as a way of informing the right people of the truth is a well-known one. Unfortunately, Ariel Toaff was not half as clever as were the Jews he has preposterously accused of being guilty of the blood libel.