Take a big breath in your mouth and out your nose. Take a big breath in your nose....and out again. What did you smell? Likely, nothing at all unless you had a strong, new or offensive odour nearby. When you exhaled you pushed all the air out in one direction so if a new scent appeared in that moment, you wouldn't have detected it until the next time you inhaled. We have around 5 million sensors in our comparatively boring human noses. Dogs can have up to 60x that, with 300 million sensors allowing for a much more acute sense of smell. Think of a chocolate cake fresh out of the oven vs being able to detect each separate ingredient and who touched it, on what appears to us to be an empty plate.
The ability to smell is made possible by moist surfaces in the nose which capture the molecules floating around. Even if a dogs nose is dry on the outside, it will be damp inside so scent particles can “stick” to the nasal tissue. From there, the olfactory organs then send signals to the brain allowing for the perception of smell. One part of a dogs nose, if laid out flat would give 150cm2 – that's a huge surface area! And it's packed in to their cute little faces purely for trapping odorants.
While people (usually) have larger brains compared to dogs, the part of the brain that's to do with scent is 40x ours – think of a raisin vs a plum. This is one of the reasons why they can detect compounds of 1 part per trillion. And it gets even cooler...
The breathing exercise we did at the beginning – air in and out? Dogs can inhale and exhale....at the same time! Look at your dog - air goes in the round part of the nostril and out the slits at the sides. This allows them to continuously sample, concentrate and process odorants giving them the most up to date info as as well as processing what's happened there in the past, at the same time. And smell IS information. Being able to smell means they can detect hazards, find food and know it's safe to eat.
The left nostril is predominantly for familiar odours and goes to the left side of the brain. The right nostril is mostly for novel odours and goes to the right side of the brain. To run this incredible machine takes a lot of life force – or blood. Google "blood vessels in a dogs nose" and check out the images. Thanks for reading part one - I hope you can start to appreciate how amazing the nose is and are hanging out for part two, coming soon :)
