A NOSE WITH ATTITUDE

摘要

A dog's sensitivity to odours is staggering. Dogs can detect n-amyl acetate, which smells like apples and bananas, at just 1.1 to 1.9 parts per trillion. That is the equivalent of a pinch of sugar in a billion cups of tea. They are 100,000 times more sensitive to scents than we are. No wonder. The olfactory surface within a dog's nose can measure more than 150 square centimetres and contain up to 300 million olfactory receptors. Breeds vary (see diagram, below) but all canine noses are impressive compared with the measly 5-square-centimetre surface area and 6 million receptors in human noses. What's more, the olfactory area of a dog's brain is proportionately about 40 times as big as ours, accounting for about an eighth of its total brain mass, compared with less than one-hundredth for us.