I have been meaning to write about the resurgence of anti-Semitism in Europe, a topic to which I last devoted a column in April 2002. Jews, I wrote then, "are the canary in the coal mine of civilization. When they become the objects of savagery and hate, it means the air has been poisoned and an explosion is soon to come."

At the time, much of official Europe resented the attention being paid to the return of anti-Jewish hatred to the continent where 6 million Jews were murdered between 1938 and 1945. "Stop saying that there is anti-Semitism in France," the French president, Jacques Chirac, admonished a Jewish editor. "There is no anti-Semitism in France."

Official Europe takes the attacks on Jews, most of which are the work of Muslim immigrants from the Middle East, more seriously now. At a conference in Brussels last month, Romano Prodi, the European Commission president, acknowledged that there are "vestiges of the historical anti-Semitism" in Europe today. "Attacking a Jew," French Prime Minister Jean-Pierre Raffarin has said, "is tantamount to attacking the French republic." Chirac told the president of Israel during a state visit that he would be "uncompromising" in rooting out anti-Semitism.

And yet the hatred spreads.

At the University of Geneva, a Jewish researcher wearing a small Star of David necklace was attacked in a campus elevator by Arab students. When she reported the attack, she was told not to wear the necklace in public.

In Hasselt, Belgium, Muslim fans at a soccer match between the Israeli and Belgian national teams waved Hamas and Hezbollah banners, and chanted: "Jews to the gas chambers!" and "Strangle the Jews!"

The British Political Cartoon Society awarded first prize in its annual competition to a cartoon in depicting a gigantic, naked Ariel Sharon biting off the head of an Arab baby. "What's wrong," reads the caption, "you've never seen a politician kissing a baby?"

In Germany, scores of Jewish graves and Holocaust memorials have been defaced. At the cemetery in Beeskow, for example, "Heil Hitler" and "Crap on the six million lie" were painted on gravestones. At Langenstein-Zwieberge, a sub-camp of the notorious Buchenwald concentration camp, vandals plastered the walls with copies of anti-Semitic Third Reich newspapers.

According to a poll conducted by the European Union last fall, 59 percent of EU citizens identify Israel as the world's greatest threat to peace -- ahead of Iran, Iraq, and North Korea. In December, millions of Europeans with satellite TV reception were able to watch "Al-Shatat," a Syrian film that portrayed Jews as blood-drinking monsters who conspire to rule the world.

In a leading Greek newspaper, a journalist wrote that the Jews "have vindicated the persecutions of the Nazis. . . . They deserved such an executioner [as Hitler] since they proved to be murderers themselves." At a televised reception to mark the publication of his memoirs, Mikis Theodorakis, the composer of "Zorba the Greek," denounced Jews. "These little people are the root of evil," he told an audience that included two cabinet members -- neither of whom reacted to his antisemitic outburst.

The hatred has been most palpable in France. There have been so many attacks on Jews in recent months that the chief rabbi has urged religious boys and men to wear baseball caps instead of yarmulkes outside their homes. In November, a newly-built wing of the Merkaz Hatorah school outside Paris was gutted by arson. Last week, in a newspaper column headlined "Jewish children are in danger," six French scientists described recent episodes of anti-Semitic violence in Parisian schools. In one of them, a girl was thrown to the ground and beaten by 20 students, who were yelling, "Dirty Jew! Dirty Jew!"

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As this is written, it is Friday afternoon, about 36 hours since the massive bombing that tore apart Madrid's commuter-rail network. The death toll has reached 199. Another 1,500 victims have been wounded, many severely. The Arabic newspaper Al-Quds al-Arabi says it has received a statement of responsibility purportedly issued in the name of Al Qaeda. The statement describes the bombing as "part of settling old accounts with Spain, the crusader, and America's ally in its war against Islam." Spanish police have found a van with seven detonators and an Arabic tape of verses from the Koran.

Whether this massacre, like earlier massacres in Istanbul and Bali and at the Pentagon and the World Trade Center, was the work of radical Islamists, the world will know soon enough. What the world should already know but so often forgets is that Jews are the canary in the coal mine of civilization. Anti-Semitism is like cancer; unchecked, it can metastasize and sicken the entire body. When civilized nations fail to rise up against the Jew-haters in their midst, it is often just a matter of time before the Jew-haters in their midst rise up against them.