A dog's nose is a many-splendored thing

We don't think of books and magazines as having a smell, but they do. When you smell them deeply, you'll get a small glimpse of what it's like to be a dog.

Dogs live in a world of smell, not sight, writes Alexandra Horowitz, a professor of animal behavior, in her new book "Inside a Dog's Mind: What Dogs See, Smell, and Know."

We humans depend mostly on our eyes to perceive the world around us. We notice shapes, colors, textures, light and shadow.

Our noses don't tell us much. We have a poor sense of smell compared to dogs.

We only have about six millions sensory receptor sites in our noses. The nose of a sheepdog has more than 200 million of these sensory receptor sites. Beagle noses have more than 300 million!

Many dogs also have long, projecting snouts and big noses, the better to sniff the world with.

A dog's world is alive with smells. Think about walking a dog. The dog stops at an informational smell, takes a few sniffs, then buries its head in the ground and smells and smells, inhaling in long, satisfying breaths.

My own dog stays planted with her nose in the smell even when I am tugging at her leash -- hard.

Dogs can smell differences in roses of the very same type, says Horowitz, because the different roses have been visited by different insects. Dogs can identify plants in the process of decaying and aging.

Dogs also recognize us by our scent, by our cocktail of smells, even though we humans think they are recognizing us just by looking at our bodies.

Even if you take a shower at the gym and come home wearing freshly washed clothes, dogs will recognize your distinctive scent.

"Humans stink," points out Horowitz. "The human armpit is one of the most profound sources of odor produced by any animal.

"Our breath is a confusing medley of smells. Our skin is covered in sweat, fluid, and oils which communicate our particular brand of scent.

"When we touch objects, we leave a bit of ourselves on them. We leave behind a trail of skin cells. We smell like what we've eaten today, whom we've kissed, what we've brushed across."

When a strange, menacing dog approaches us, we know we should not show fear. But dogs can figure out when we are afraid of them.

"Fear smells," says Horowitz. When we are stressed, we sweat, and our perspiration is full of odor that communicates our fear even if we are trying to hide it.

Dogs' brilliance at smelling is being put to good use. Dogs are trained to rescue lost people, track criminals and sniff for drugs and other contraband in packages and luggage at the airport.

But dogs are also being trained to detect disease, such as the chemical smells that come with cancer. This research is in its infancy but the results are startling.

In one study, dogs trained to sniff out cancer missed the cancer in just 14 of 1,272 attempts, reports Horowitz.

"The latest studies show trained dogs can detect cancers of the skin, breast, bladder, and lungs at high rates."

But don't think your dog can sniff out a developing cancer in you. First the dog has to be trained -- rewarded when he identifies the smell of cancer and not rewarded when he makes a mistake.

You also would have to be trained to recognize when your dog is giving you the signal for cancer. And the change in you might be too gradual for your dog to notice.

Still, maybe the day will come when you go to visit the doctor and find you also have an appointment with a new medical assistant --a dog trained to smell out disease.

Judith Kleinfeld is a professor of psychology at the University of Alaska Fairbanks.