One European Union country after another this week re-imposed border controls to prevent the spread of foot-and-mouth disease to their domestic herds.
Foot-and-mouth disease is one of the most infectious diseases known, although it rarely affects the health of human beings. But it can wipe out entire herds in a matter of weeks and leave the agricultural sector of any country where it strikes devastated for years.
At one level, these national precautions are no more than the product of good sense by EU member states that want to limit the spread of this disease.
And the EU itself continued to act as a unified group with respect to outsiders. For example, the European Commission said that it is considering retaliation against the United States and Canada, which have banned the import of EU livestock, fresh meat and dairy products.
But at a more fundamental level, each of the EU states acted almost completely on its own. The Belgians set up checkpoints to stop imports of French meat. The Germans set their own policies.
Few appeared to want to listen to Portugal's call for an EU-wide ban on the movement of livestock and meat products until the danger has passed.
One reason for this is some countries expect to gain from the situation. If people cannot buy meat from one source they will turn to another, and that second source will inevitably benefit.
Indeed, Canadian livestock operators very publicly said that they expect to reap a bonanza from customers who because of the epidemic have nowhere else to turn. Others are likely to be making similar calculations more quietly.
But beneath such prudential and economic calculations is the view that whatever the member states of supranational organizations like the European Union proclaim, their citizens look to their own governments to take care of them, and the individual governments inevitably do the same.
Much of the history of the formation of the European community has been the story of the tensions between those who want to form a united Europe in the future and those who still see their national attachments as more important.
But over the last decade, Europeans have projected a sense of optimism that they can in fact achieve monetary and eventually political unity.
Consequently, the responses to the foot-and-mouth disease outbreak are especially troubling to those who most consistently argue that a united Europe now exists.
These responses, which represent the modern equivalent of raising the drawbridge against an enemy, call that self-confident optimism into question. And they are already causing some on the continent to think that Europe may be far less united than has been advertised.
Over the past 40 years, there have been two visions behind the European project. One, long championed by former French President Charles de Gaulle, was a Europe of the fatherlands, a Europe based on the continuing importance of nation states.
A second, which has recently been the official version, is a federal Europe, one in which the nation states cede ever more of their powers to a new centralized administration.
The response of EU countries to foot-and-mouth disease suggests that the former may be a more accurate description, and for many a more desirable goal than the latter.
They suggest that in the most unified continent on earth, the powers of the nation and the nation state remain predominant in the calculations of both peoples and their governments.
Nearly a century ago, a politician at the edge of Europe observed that when things are going well, everyone is prepared to cooperate, "common interests first and foremost," but when things go wrong, he said, "everyone retires to his own national tent" Ð or in this case, to his own national customs post.