“And the olfactory part of a dog’s brain is forty times larger than a human’s; depending on the breed, a dog can have up to 300 million olfactory receptors in his nose, compared to about 6 million in ours. Even with that extreme superiority in equipment, dogs don’t merely smell a superstrong version of what we smell (or don’t smell); instead, they can perceive multiple layers of smell, which gives dogs a far greater range of information.”