The Dog Breathes Out Sideways
a read-aloud about a nose that does not blow the smell away — with something you can try, and every source kept on the page for the grown-up
Somewhere, a dog is smelling something
You can smell things too. Bread. Rain. A person you know.
So it is easy to think a dog has a nose like yours, only better.
It does not.
A dog’s nose is a different machine. It even breathes out in a different direction.
Almost everything on the next seven spreads comes from one paper: B. A. Craven, E. G. Paterson & G. S. Settles, “The fluid dynamics of canine olfaction: unique nasal airflow patterns as an explanation of macrosmia,” Journal of the Royal Society Interface 7, 933–943 (2010), doi:10.1098/rsif.2009.0490. It is open access and we read it at full text.
Macrosmia is the word for having a very good sense of smell. The paper's argument is that the usual explanations — a bigger smelling organ, more smell genes — leave out the part that happens first: how the air actually gets there.
Count to one. That is four sniffs
Some scientists asked seven dogs to come and sniff things.
A very small fluffy one. A beagle. A big Labrador so heavy you could not pick it up.
Every single one of them sniffed four to seven times every second.
Say “one” out loud. That was about four sniffs. Try to do four sniffs yourself in that time.
The big dog and the little dog did it at the same speed.
J. R. Soc. Interface 7, 2010
The seven dogs, by weight: a Pomeranian (6.8 kg), a beagle (13.6 kg), a sheltie–husky mix (14.5 kg), a border collie–Labrador retriever mix (16.8 kg), a German shepherd (34.5 kg), a Labrador retriever (37.0 kg) and a Labrador retriever (52.9 kg). The paper gives breeds and masses; it does not give their names, so neither do we. They “were conditioned to sniff odour stimuli” while wearing a mask that measured the airflow.
Verbatim: “The frequency of sniffing was rather uniform for all seven animals, regardless of odour source. For all trials, each of the dogs sniffed within a frequency band ranging from 4 to 7 Hz.” Hertz means times per second.
One careful thing. The paper also reports that sniff frequency scales with body mass — so the big dog and the small dog are not exactly identical, they simply all land inside the same four-to-seven band. The read-aloud says “the same speed”, which is true at the resolution a five-year-old is being offered, and this is the sentence that makes it precise.
Blow at a feather
You will need something very light. A feather. A scrap of tissue. A dandelion seed.
Put it on the table in front of you.
Now breathe out at it, the way you always do. Straight ahead.
It went away, didn’t it.
That is what your breath does. It pushes things away from your face.
Now imagine the thing you blew away was a smell.
This is the demonstration the zine is built around, and it is doing real work rather than being an activity: the child needs to feel that exhaling is a problem for a smeller before the next spread can be a solution. Do part one and part two together, back to back, with the same feather.
If you have no feather, a torn corner of tissue on a smooth table works, or a dandelion clock outdoors. It needs to be light enough to move and light enough to stay when the air goes past rather than at it.
Now blow past it
Put the feather back.
This time do not blow at it. Turn your head a little and blow past it, so the air goes by the side.
Watch what happens. It wobbles. It spins. It stays.
That is what a dog does every single time it breathes out.
The air does not come out of the front of a dog’s nose. It comes out of the sides, in two little puffs, one each way.
So the smell does not get blown away. It gets stirred up — and then the dog sniffs it in.
J. R. Soc. Interface 7, 2010
Verbatim: “On expiration, owing to the internal shape of the nasal vestibule, a ventral-laterally directed air jet is ejected from the nose. When sniffing a surface, such as the ground, the direction of the vectored expired airstream is such that it promotes disturbance and mixing of ambient odorants that may be subsequently inspired, while minimizing sample ‘blow-off’ directly ahead of the nostril.”
Ventral-laterally means downwards and out to the sides. The comma-shaped slits along the outside of a dog's nostrils are where it goes — look at a dog's nose and you can see them.
Two jobs in one breath, and this is the elegant part: the outgoing puff is not merely avoiding harm. It actively stirs the air the dog is about to sniff, so the next sniff gets more to work with. Blowing sideways is better than not blowing at all.
Each hole smells a different bit of air
You have two ears. That is how you can tell which way a sound came from — one ear hears it a tiny bit before the other one.
A dog has two nostrils. And when it sniffs, each one takes air from a different little patch of the world.
Not the same air twice. Two separate helpings, at the same moment.
Left nostril: this. Right nostril: that.
than the gap between them
Verbatim: “the reach of a nostril is smaller than the internostril separation, indicating that each nostril samples air from spatially separate regions.” That is the geometry Figure 3 draws: the reach is shorter than the gap, so the two intake zones cannot overlap.
The ear comparison in the read-aloud is ours, and it is an analogy rather than a finding. Binaural hearing works on timing and intensity differences; this is two spatially separate samples of a chemical. They are alike in the useful way — two receivers, two readings, one moment — and unalike in mechanism.
Not just what. Maybe which way
If the left nostril gets a strong smell and the right one gets a faint smell, then the smell is probably over on the left.
So a dog might not only know what is there. It might know which way to go.
We put “might” in that sentence on purpose.
The scientists measured the two helpings of air. They did not prove the dog uses them to find the way. They said it looks likely, and somebody still has to check.
That is allowed. That is how it works.
This spread exists because of the gap between two verbs. The spatially separate sampling is a result — computed from an anatomically accurate model and stated flatly. What it is for is a proposal: the authors write that it “may be used for bilateral stimulus intensity comparison and odour source localization”, and elsewhere that it “may be exploited”. Modal verbs, and they mean them.
Telling a five-year-old the difference between we measured this and we think this is why is not a dilution of the science. It is the science. It is also the same distinction No. 98 marks as a leap joint on its own spreads, for adults, about the same species.
One nose, two roads
Here is the surprising bit. Most of the air a dog sniffs in is not for smelling.
Just inside the nose the air comes to a fork, with a little shelf of bone in the middle of it.
Most of the air goes down one road, to the lungs. That road is for breathing.
About twelve bits out of every hundred turn off down the other road, into a special room at the back. That room is for smelling. The air goes in and stays a while.
Breathing and smelling are two different jobs, and a dog’s nose does them down two different roads.
Verbatim: “For the case described here of a relaxed, undilated nostril, the splitting of olfactory and respiratory airflow is such that approximately 12–13% of inspired air reaches the chemosensory region.” The paper immediately hedges its own number upward — nostril motion during real sniffing “may increase this percentage” and “has yet to be fully defined for the canine” — so treat 12–13% as a floor from one modelled case, not a constant.
The “special room” is the olfactory recess, set at the back of the nasal cavity and walled off from the main breathing path by a bony shelf called the lamina transversa. Air that reaches it is not simply passed through. The paper quotes Negus (1958): the recess “is seen at its height of perfection in the dog” — and notes it is largely absent in primates. Including us.
Your nose cannot do any of that
You do not have the special room at the back. You breathe out of the front. Your two nostrils are close together, so they get the same air.
And here is a funny thing the scientists found: in a person, the left side of the nose and the right side often do completely different things from each other, in the very same sniff.
For smelling carefully, that is not very handy.
Your nose is not a broken dog nose. It was never trying to be one.
It is a nose for a different job. It tells you the bread is ready. It tells you to stop eating that. It does those jobs well.
Verbatim: “human sniffing can yield dramatically different intranasal airflow patterns in the right and left nasal cavities of the same subject, or even separated airflow within the olfactory region, a fluid dynamic phenomenon that is undesirable for consistent odorant deposition.” That judgement is the paper's, not ours.
This is the spread the whole zine is for. The comparison runs in the direction a reader will not expect — the dog is not a better version of us, and we are not a worse version of the dog. Two noses, built to different specifications, each doing its own job properly. The zine stops there deliberately: it makes no claim at all about people, or about children. That is a house rule for this collection, and the argument a reader may be reaching for is made elsewhere, on human evidence, at Developmental Pace.
Kevin, Delfi and Charlie
A dog’s nose-tip is bare and wet and cold. Colder than the rest of it. Nobody was sure why.
Some scientists had an idea: maybe a cold thing is good at feeling warmth a long way off.
So they asked three dogs. Their names were Kevin, Delfi and Charlie.
Two things to choose from, both too far away to touch. One a little bit warm. Could they tell?
They could. Kevin got it right 32 times out of 40.
But nobody has finished working this out.
Three dogs is only three dogs. The scientists wrote that they still do not know how it works. Somebody will find out. It might be somebody who is little right now.
Source: A. Bálint, A. Andics et al., “Dogs can sense weak thermal radiation,” Scientific Reports 10:3736 (2020), doi:10.1038/s41598-020-60439-y. Open access, read at full text. Two-alternative forced choice; the stimulus was 11–13 °C above ambient, a circular patch 102 mm across, detected from at least 1.6 m. All three dogs beat chance: Kevin 32/40 (80%), Charlie 68/89 (76%), Delfi 44/65 (68%). A second experiment scanned thirteen more awake dogs and found the warm stimulus raised activity in the left somatosensory association cortex.
Why this is on a spread rather than in a fact: two independent methods agreeing is a strong design, and n = 3 on the behavioural half is a small sample. Both are true at once. The authors' own words: “It is unclear how thermal radiation is transduced in the dog rhinarium” and “The limits and mechanisms of this ability remain to be elucidated.” The read-aloud layer says exactly that, in shorter words, and does not round it up into a fact.
Not:
A dog breathes out through the sides of its nose, so the smell is stirred up instead of blown away. Your nose cannot do it. Your nose was never trying to.
Did the feather stay the second time? What did it do?
What is your nose for? What has it told you today?
The scientists said they do not know how the cold nose works. How do you think somebody could find out?
What is something you can do that a dog cannot do at all?
Where all of this comes from
The nose, spreads three to nine. B. A. Craven, E. G. Paterson & G. S. Settles, “The fluid dynamics of canine olfaction: unique nasal airflow patterns as an explanation of macrosmia,” Journal of the Royal Society Interface 7(47), 933–943 (2010), doi:10.1098/rsif.2009.0490. Open access, read at full text. Source of the seven dogs and their masses, the 4–7 Hz sniff band, the ventral-lateral expiratory jet, the nostril-reach geometry, the 12–13% airflow split, the lamina transversa, the olfactory recess, and the human comparison. Every phrase in quotation marks in the grown-up boxes is verbatim from it.
The cold nose, spread ten. A. Bálint, A. Andics et al., “Dogs can sense weak thermal radiation,” Scientific Reports 10:3736 (2020), doi:10.1038/s41598-020-60439-y. Open access, read at full text. Kevin, Delfi and Charlie are the dogs' real names and their scores are the real scores, from the paper's own Table 1.
How this one is built
Two layers on every spread. Large plain type for the child, first in the document, so a screen reader meets it first — then a bordered box for the adult, holding the measurements, the exact words, and every place the evidence runs out. Pictures sit between the two, where a child following the large type will actually reach them. The refusals on spread eleven are addressed to you, not to the child.
This one adds something the other five do not have: a thing to do. Spreads four and five are a single demonstration split in half, and they are the reason the zine works — a child who has watched a feather blow away and then watched it stay has felt the problem and the solution in their own breath before either is explained. Do them together, with the same feather, back to back.
What we left out, and what is still open
A number we did not use. While this was being built, a paper arrived on the domestic dog's body-size range — Shearin & Ostrander, PLOS Biology 8(3), e1000310 (2010). It is an Essay rather than a research report, its central claim is hedged in its own text (“arguably the most morphologically variable land mammal”), and the figure it actually states is over 30-fold between a Cane Corso and a Yorkshire terrier — not the hundred-fold Chihuahua-to-mastiff range that circulates widely and is attributed to the literature. Nothing in this zine rests on any of it, and the discrepancy is recorded because it is the kind of thing that gets repeated.
Open, and said on the page. Whether a dog actually uses its two nostril samples to work out direction — measured as two samples, proposed as a direction-finder. How the cold nose-tip senses warmth at all. And what the 12–13% figure becomes once real nostril motion is modelled, which the paper itself says has “yet to be fully defined.”
For grown-ups who want the rest of it. No. 97 follows a different finding about the same animal — four dogs telling thirty-six strangers' stress apart by smell alone — and No. 98 is thirteen linked steps on where dogs came from, which nobody can answer. Neither is written for a child, and this zine borrows nothing from either into its read-aloud layer.