Animals are such agreeable friends -they ask no questions and they pass no criticisms,” wrote the novelist George Eliot, and few pet-owners would disagree with her. For a great many people, a home is not a home without a four-legged friend.

Happily, science has now proved what animal lovers have known all along - that pets are good for you. Stroking an animal, according to recent research projects at veterinary schools in Pretoria and Melbourne, reduces stress by lowering the heart rate and increasing the production of endorphins, the so-called “pleasure” hormones (in human and animal alike). And the effects are even more marked when the animal is your own.

The Australian project also found that having a pet to go home to cut death rates among patients with heart disease and stress-related conditions.

“The emotional, physical and psychological benefits are real,” says psychologist Dr Roger Mugford, who runs the Animal Behaviour Centre in Chertsey, Surrey. “People may complain about dog mess on the streets and argue that the money spent on pet food should go to the Third World, but when you consider what pets offer, we get a good bargain.”

It’s missing the point, he says to scoff at doting pet-owners who maintain their animals understand every word they say. “What may appear a fantasy relationship to outsiders is actually very real and important, possibly the only important one in their lives. Animal companions are especially beneficial to the elderly, the lonely and those who are physically or intellectually impaired because, to an animal, we are all just as beautiful and loveable as the next person. And pets give people an opportunity to exercise social skills that might otherwise deteriorate.”

They are also, according to Dr Mugford, ideal for people in stressful occupations such as teaching because they allow you to let off emotional steam.

Diana Hillsdon, deputy head of Boston Spa C of E primary school in Yorkshire, considers her four dogs - Cinders, Meg, Luke and Rosie - central to her personal and professional life. She often takes one or two into school to help with RE, drawing, science, writing or assemblies. From time to time, parents (and younger brothers and sisters) are invited to come in and meet the dogs, so they can feel confident that they’re safe and childproof.

“It’s important children learn to respect dogs,” explains Ms Hillsdon. “With the reception class, I bring in a soft toy dog first so we can talk about the dos and don’ts. Then they meet my most steady dog, Luke, and talk to him, pat him and draw him.”

As the dogs are also regular “volunteer” visitors to the elderly residents of a Harrogate nursing home, all four have been registered with the charity PAT (Pets as Therapy), which means they’ve passed health and personality tests and are insured to visit institutions.

“They have quite a fan club there,” says Ms Hillsdon. “It’s amazing the response and recognition they get, even from people who are otherwise in a world of their own. Luke, my saluki, is just wheelchair height, so they can pat him and stroke him, and the ones who can remember and talk will tell me about pets they used to have.”

Although all Diana Hillsdon’s dogs had what she calls “a bad start in life”, coming from rescue organisations, they are now happy and well adjusted. “But they wouldn’t have their good temperaments if I hadn’t trained them,” she says. “It’s vital to socialise rescued dogs and make them people-proof from the minute you get them.” Each dog gets 10 minutes’ quality time with her every evening, when they do “play training”.

Ms Hillsdon says her devotion to animals (she and her husband also have four cats and two rabbits) springs from not being allowed any as a child. “As soon as I left home, I rebelled by having as many pets as possible.” Her car has been adapted as a dogmobile, and four base units have been removed from her kitchen to create kennel spaces. “The dogs are my soul mates,” she says. “Without them a whole dimension of my life would be missing.”

For Kathleen and Pat Moran (she’s head of St James’s C of E primary in Wigan, he teaches at Wigan’s Mornington High School) it’s pigs - a rare pedigree breed called middle whites, with squashed noses and large, butterfly ears.

“They look quite ugly,” admits Mrs Moran, “but we’re very fond of them.” Although the pigs don’t exactly return the Morans’ affection, they do jump up at the gate in a lively fashion when being fed.

According to Kathleen, about the only time middle whites look adorable is when they’re born, because they are all silky and soft. The boars, she explains, have to be treated with respect. “You use a board and a stick to move them around. They stand more than three feet high and have long teeth at the side of their mouths which can do serious damage.”

Although the appeal of these creatures might seem limited, the Morans have a lifelong devotion to them - though they try not to get too attached to the ones that will end up as (very superior) pork. “Pigs stop you getting stressed,” insists Kathleen Moran, “and the routine of looking after them is very satisfying.”

Eric Medway, a deputy head of Leeds Grammer School, is just as attached to his herd of Hebridean sheep, an ancient breed of black, horned, native sheep, descended from Viking stock. Because they are hardier than commercial sheep and can lamb more easily, they need less attention - on average about four or five hours a week.

But what Mr Medway really likes about them is that they’re less docile and more intelligent than your everyday sheep. “Every summer I take them to a lowland heath to do some environmental grazing for the Yorkshire Wildlife Trust, and the ones that have been there before always remember where to go. With ordinary sheep it would be a new learning experience every year.”

They also know when he’s annoyed with them. All he has to do, on the frequent occasions that they get on to the road, is find them and give them a piece of his mind. “The minute they see me they’re off back home and usually get there before I do.”

He finds teaching and sheep farming go well together. “You could say I’m making more work for myself, but I find being outside with the animals relaxing, and a change is as good as a rest.” The hobby attracts some friendly ridicule from colleagues and sixth-form students, but as another member of staff also keeps sheep, he’s not alone.

Woolly monkeys are the passion of Susan Pybus, who teaches Years 2, 3 and 4 at St Nicholas pimary in Downderry, Cornwall. Before doing her PGCE, Ms Pybus was education co-ordinator at Looe Monkey Sanctuary, of which she’s now a trustee. But she doesn’t keep a monkey at home because she believes they should live among their own kind.

In fact, the reason the sanctuary was founded, in the Sixties, was to rescue monkeys from the pet trade. All the 15 inmates are ex-pets or the offspring of pets and the conditions there enable them to live in their own society, largely uncontrolled by humans.

“They’re very affectionate to each other, and they can be to humans,” explains Ms Pybus, “but as it’s their territory, we don’t pick them up and cuddle them, we wait for them to come to us.” Each monkey knows its name, and she has the same policy with monkeys as with pupils - no favourites. But she doessee similarities between the species. “Young children use exactly the same instinctive body language until they learn to cover it up.”

Since taking up her post as headmistress of St Martha’s Convent in Hertfordshire, Constance Burke has undergone a conversion to cats. “When I came here last spring I wasn’t a cat person, in fact I thought I was allergic to them,” she admits. But St Martha’s had two resident cats, Moll and Meg, who quickly won her over. Now, when prospective parents and pupils come to be interviewed, they find Moll in Miss Burke’s in-tray. Meg, being more reflective, prefers the library.

“They’re part of our daily life here, and Moll, who’s very outgoing, is happy to be a resource in PHSE lessons on pets. They’re such charming cats that you’d have to be very anti-animal not to be affected by them. Having a cat in my in-tray is a wonderful ice-breaker, particularly if a little one is anxious or upset. And when first years arrive, the thing they remember about their interview is that there was a cat on my desk. I wouldn’t want people to think they’re a ‘feature’ of the school, but they’re good for the girls and we’re very committed to them.”

Next week: Pony tales from Lancashire. Pets as Therapy can be contacted at 6 New Road, Ditton, Maidstone, Kent ME20 6AD. Tel: 01732 872222.