The list of ways dogs have helped humans throughout history is almost endless.

They've guarded livestock, herded sheep, driven cattle and protected human dwellings from castles to condos. Dogs assist people with disabilities, sniff out illegal drugs and find food from birds to truffles. From detecting heart attacks and seizures before they happen to dragging drowning people to safety, it's hard to imagine any form of technology that could surpass the uncountable number of ways in which dogs lend us a helping paw.

In selectively breeding dogs for the skills that helped them help us, human beings have changed the dog both inside and out. Today, there are hundreds of dog breeds so different from each other in type that it's hard to believe they're members of the same species -- and yet, each of these dogs' forms grew out of a specific function.

"If people hadn't changed the dog to do certain tasks, he'd look very much like the dingo," said Heather Russell-Revesz, co-author of the "World Atlas of Dog Breeds". "Whether it was making a dog shorter-legged or faster, so he could catch a specific kind of prey, or making him tiny enough to sit on your lap, human intervention has brought an incredible diversity of type to the dog."

Not all the changes were about function. For example, when it became clear how easily the dog's physical appearance could be changed by human breeding choices, dog breeders in Victorian England became interested in seeing just how extreme those changes could be.

"Look at the bulldog, He's about as different from a 'natural breed' like the dingo as a dog can be. His face is flat; his legs are short and bowed. Another example is the field spaniel. The Victorians took a functional hunting dog and started breeding him smaller and smaller, until his legs were so short he could hardly walk, let alone hunt. He very nearly became extinct, until fanciers in the 1930s began to select for a less extreme dog."

Basics such as breathing and walking aside, even dogs originally developed to help humans in hunting, farm chores or family protection are increasingly out of a job in modern times. World War II threatened the existence of many dog breeds, because it was impossible to continue breeding or even feeding dogs during the war, and afterward, because human lifestyles changed profoundly in the post-war era.

Many dog breeds were wiped out, and others were on the brink of extinction. Their traditional work was largely obsolete, and it was only the extraordinary dedication of a few individuals that preserved the amazing legacy of traditional dog breeds.

Of course, not all canine work is obsolete. Dogs today are being bred for many of their traditional tasks, as well as new ones. And some dogs, once rendered unemployed by new technology, are being rehired. "When snowmobiles were introduced, the Greenland dog was out of favor as a reindeer herder," she said. "But it turns out that reindeer don't respond well to being herded by snowmobiles. It turns out the dogs are more useful than the machines -- and more environmentally friendly."

A Greyhound's long legs and great lung capacity or the insatiable urge to dig shared by the terriers may be a case of form following function. But there are 420 different breeds in the World Atlas, and the authors acknowledge they didn't list every breed. And yet it includes 30 French scent hounds, from the familiar basset hound to the now-extinct levesque. Does any nation need 30 different types of scent hounds?

But then, of course, the French celebrate the regional differences in their cheese and wine, so why not the ones in their dogs?

Depending on the prey, the terrain and the climate, they may have needed different-length legs or more or less coat. But the truth is that each region took great pride in its local hounds and wanted to have their own.

No matter how thoroughly your pet licks clean the food dish, it's not clean enough to use again without washing. That goes for water dishes, too, some of which always seem to have the beginnings of algae colonies forming on the sides and the bottom. Who'd want to drink from that?

Pick up your pet's food dish after every meal, scrub and wash in hot water and soap. The water dish should get the same treatment, on a daily basis. You may find it easier with the water dishes to have extras, so your pet will have access to one clean bowl while the other's being washed.

Stainless steel or heavy plastic "crock-style" dishes are best for frequent cleaning. They last through generations of pets and stand up well to the abuse a pet can dish out. And they can even be run through the hottest cycle of the dishwasher