SWIMMING around and around an aquarium tank is more wearing than it might look. It's not the actual exertion that takes the toll, but the nervous strain. If you were doing it, hour after hour, seven days a week, you, too, would probably have ulcers like the three dolphins at the National Aquarium in Baltimore. They have been taking Maalox, like many of the people who come to see them, and it hasn't done much good. The dolphins' doctors are now sending them off to Florida for a long rest.

A shark can swim in circles forever without getting ulcers, or anything else but hungry. A shark is not a sensitive intelligence. The amiable carp does not swim in circles because it has trouble remembering the traffic pattern; it is not greatly susceptible to psychosomatic illness. But dolphins think about things. They fret, and that affects their stomachs.

Perhaps, as you stand there watching them move through that cool green water, it seems to you that nothing could be more pleasant than being a dolphin. But to a dolphin with cultivated sensibilities, aquarium life leaves a good deal to be desired. It's the awful lack of privacy, for one thing. There is the constant press of the crowds. It's noisy. The neighborhood has gotten terribly commercial and not all the neighbors are those whom one would have chosen. Life in the tank in Baltimore, as the dolphins tell it, begins to sound like life outside the tank in any big city.

The crowds don't much bother the turtles. The eels need no Maalox. But turtles and eels are simple souls, who read nothing and rarely engage in any cultural activity more elevated than watching television. Dolphins, in contrast, are full of humor and spirit. They watch the world, and reflect on its shortcomings. Having brains, unfortunately, is not always good for the digestion.