First, the myths. Cats have nine lives and they suck out the breath of babies. Or, Doberman pinschers are vicious.Or, feeding a dog gunpowder will make it mean.

Now, the facts: Cats are not reincarnated all those times -- they're just very agile -- and they like to lie next to babies because of their affinity for sleeping on, or next to warm things. Dobermans are gentle; they acquired their vicious reputation when they were trained as guard dogs during World War II. Gunpowder won't make a dog mean -- only sick.

It is myths like these, along with others (such as the one about garlic as a cure for worms) that Sheldon Gerstenfeld, V.M.D., wants to debunk. "Conscientious pet owners are like conscientious parents," he says. "Both want to provide the best in medical care."

Two years ago, in the midst of a very heavy snowstrom, Gerstenfeld received an emergency call from a frantic pet owner who thought her dog was severely ill. Gerstenfeld, who operates the Chestnut Hill Veterinary Hospital in Philadelphia, trudged -- "It was the only way I could get there" -- the several miles to the woman's home. He treated the animal for what was actually a mild illness, returned home and told his wife that if the owner had a book to consult quickly she would have known what to do.

A year and a half later, Gerstenfeld's books -- "Taking Care of Your Cat" and "Taking Care of Your Dog" (Addison-Wesley, $6.95 each) -- were ready. The precise, down-to-earth, animal health books include decision charts to help diagnose the severity of an animal's illness, advice on home remedies, and information on how to give emergency treatment until you can see a vet.

Gerstenfeld also explains how and what to look for when deciding to get a dog or cat. He talks about the pros and cons of purebreds and suggests that a good pet -- young or not -- can come from many sources. "There are a lot of adult animals in the humane shelters begging for homes."

There's a pet for everyone and for every age, he maintains, be it a gerbil, guinea pig or a bird. Rabbits can be litter-box trained and fish require minimum care. His first pet, he says, was Joe, the Turtle, who died of a stroke and was given a ceremonial burial.

A pet, says Gerstenfeld, is a way of making a young child responsible for something. At an early age -- 3 or 4 -- a child can help feed and groom the pet, give it water and play gently with it. "The child needs something that's responsive, loving and a pet is a perfect way to satisfy those needs. Especially, if there aren't too many neighborhood friends. And, in return, the child will get back a lot of affection and love from a pet that's treated well."

So far as picking a pet's veterinarian, Gerstenfeld says, "Look at the office, the way the doctor handles the animal, and the way the doctor responds to the owner. It's a three-way deal -- the pet, the owner and the doctor. There's got to be communication.

"There's a pet owner I'm working with right now. He's a mailman, terrified of dogs, and he decided to conquer the fear. So, he got himself a German shepherd-type stray from the humane society, named it Hitler, and tried to make friends with it. Right away, I realized that everything wasn't right. The dog and its owner were off to a bad start."

Gerstenfeld started working with the mailman and the dog, complimenting both on giving and receiving commands. He taught the owner how to care for the dog, and now, "they're good friends and companions." He adds, shaking his head, that he hasn't gotten the owner to change the dog's name yet.

As testimony to Gerstenfeld's and his wife Traudi's affection for animals they have one dog and four cats.

"You know," says the vet, "animals are really very good citizens of the earth. They have a better sense of right and wrong; they don't take hostages . . . they don't pollute the earth. Maybe we have to wonder if we humans are on an animal's level."