We used to have the world's dumbest cat, name of Al. He would crouch all night in the bathtub, waiting for a mouse to come out of the drain. Eventually one did.

Al chased cars, too, until one day he caught a Plymouth sedan. But this story is not about Al. This story is about Sam, who may be even dumber than Al.

Actually it's about the baby cottontail rabbit Sam caught the other night, but first you need to know a little about Sam.

Sam turned up some weeks after Al caught the car, and showed, by running into walls and falling down steps, that he was a worthy successor. He's an organge tiger cat, as big and nearly as round, but not quite so witty, as a medicine ball.

Instinct makes him jump on any little thing that moves, but Sam is even nicer than he is dumb, so he never knows what to do after that. Not for him the long cruel sport of your average house cat; Sam is so tendermouthed and has such a brief attention span that his victims usually get away no worse for wear. Sometimes they don't, and then Sam, like big simple Lennie in John Steinbeck's Of Mice and Men , is inconsolable. Until dinnertime.

But about the bunny rabbit. I was sneaking a cigarette on the back porch when a cat barked in the yard below. Cats don't bark, but try to tell that to the dogeared tabby that drops by daily to torment Sam. I turned on the floodlight and saw Sam crouched over what looked like a young rat, with Tough Tabby trying to take it away. We like to think Sam really was just protecting his playmate, which proved to be a bunny perhaps a week old -- unweaned, eyes barely opened, tiny enough to curl up in a young child's hand.

The creature was stiff with cold and fright, but unmarked. I thought his right hind leg was hanging at an unnatural angle, but was hushed by three optimists named Karen, 14, Laura, 12, and Mark 7, whose record with orphan wildlings then was 2 for 2.

The gray squirrel that lives in our big maple tree was not much bigger than the bunny when it fell off a limb into Sam's mouth. And then there was the tattered fledgling starling, ugly as homemade sin, that was coaxed back to life so that it could further nature's plan by bullying songbirds. That's like saving Attila the Hun a seat in the lifeboat, but a baby bird is a baby bird.

Handwarming relaxed the rabbit's tiny brown-and-white body, and after a dropper of warm sugar water he was tucked away in a shoebox on a heating pad. Mother and I tried to discourage discussion of a name for him, because we didn't expect the little guy to last the night. Nameless dread is better.

He was not only alive but livelier in the morning and received, along with his first meal of baby formula from the drugstore, the name Hopalong Cassidy, Hoppy for short. He seemed to grow stronger through the day, so that even the old folks began to believe in him. But Doctor Grandmother, although she was as upbeat as medical discipline allowed, diagnosed spinal and possibly other internal injuries. The chances for any baby rabbit are slim at best, she said, try not get too attached to Hoppy.

Ah, yes. But the way he wiggled his nose; and why did he have to be so (SECTION) mall ? After feeding he would snuggle into the crook of an arm, or a sleeve or pocket, until he was reluctantly put back in his box on the principle that too much handling was harmful. A cage project was started, and the question was broached of permanent residence vs. a release program (it took weeks to get Risky the squirrel rewildered).

It being Sunday, the library didn't open until 1 p.m. It might have been better if the librarians had stayed home, because we came away with a book that said all baby mammals need tender loving care; that in the wild their mothers cuddle and nuzzle them and that, if left too long alone, an orphan may literally starve for affection. That certainly is true of human babies, and probably was good advice, but it was, I think, overstated, and it led, I think, to disaster.

Tender loving care Hoppy got. Gentle care, patient and subdued handling with a featherlight touch. But between the time Karen put him down to rest at bath time and when she went to feed him at bedtime, Hoppy's candle flickered out.

Perhaps it was the delayed effect of internal injuries and maybe nothing better could have been done, but I dunno. We had seemed to be doing pretty well until we got expert advice.

There was some dificulty deciding on where in the yard to bury Hoppy, because many a small corpse picked up from the street has been laid away under our lawn. An opening was found between two elderberry bushes, a hole was dug, and filled, and nobody could think what to say.