#monsterbuilding

On the backside of the Monsterbuilding. 📍🗺️2 Quarry Bay St 香港, 香港島 Hong Kong - China.

So I wrote The Breath of Life Part 1 over a year ago and I THOUGHT I had written a part two but apparently, no, just no. :/ So after much dealy and with no particular reason for it other than that I noticed I didn’t do it: The Breath of Life Part 2.

A Centaur CAN’T breathe like a human or a horse and survive. It just can’t get enough O₂. 

But there are living (and extinct) animals that can get enough O₂ for the metabolic needs that a Centaur represents. 

For living animals, it’s avians, but there’s mounting evidence that dinosaurs and certain modern reptiles and amphibians breathed in similar ways to cause the same effect, so this kind of power does scale. 

The Way bird lungs work is a bit more complex than human lungs. 

A human (and a horse as well) takes in a breath, filling its Aveolar sacs with fresh oxygen. The Aveolar sacs sit next to the blood flow, O₂ permeates across the thin membrane into the red blood cells in a gas exchange for the CO₂ in the blood cells. The human then exhales the CO₂. That’s a two Cycle Pattern. Inhale O₂, Exhale CO₂. 

Avians have a four cycle pattern. So they take two breaths to our one for a complete cycle. 

They inhale fresh O₂ which goes primarily into their Posterior Air Sacs but also a little into their lungs. On the exhale, that breath of O₂ is pumped from the Posterior Sacs into the Lungs. 

While a second breath repeats the above with a second breath of fresh air, the first breath continues to move through the second half of the pattern. 

On the 2nd inhale, that original breath is pumped across the Lungs toward the Anterior Air Sacs. On the second exhale, the air, now essentially empty of O₂, is pumped out of the Anterior Air Sacs (and just a little from the lungs) and back out the trachea to be exhaled. 

Like in mammals, the exhaled air does mix a little with the inhaled air inside the dead space of the trachea, but that also performs a function of warming and moisturing the incoming air in exchange for cooling and drying the outgoing air. This prevents some heat and moisture loss and makes the system run more efficiently. 

There is no gas exchange in the Air Sacs. They simply pump air. Birds tend to have between 7 and 9 air sacs in order to make this all work. 

All gas exchange happens in the lungs. And because of the air sac arrangement, the flow of oxygen is unidirectional. This is what allows it to be so much more efficient than humans (and horses). While we place O₂ next to blood in a sac and let blood flow across it for the exchange. Avians have two currents. The air flows one way, losing Oxygen as it goes. The blood flows the other way, gaining Oxygen as it goes. Because of the longer track of exchange, more O₂ can be removed, if the first red blood cell it touches doesn’t make the exchange, the thousandth one will. By the end of the route, nearly every bit of O₂ has been extracted, so the exchange gets darn close to perfect. 

The result of all of this is that avians tends to have a proportionally smaller lung than mammals but actually much more space devoted to the respiratory system. Those sacs take up a lot of room. For the overall system, a bird will devote about a 5th of its internal organ space to lungs while a mammal will only devote about a 20th, 4 times less. So if we give Centaurs this system, their lungs are a much more prominent feature than in a human or a horse and other efficiencies are going to have to be worked out elsewhere. 

Besides for the fact that I simply can’t stomach two spines...

What is that?? Just no. I can’t. That’s a structure designed to fail, and there are just too many of those already in this system. 

One of my reasons for scaling up Centaurs is that I don’t think they’re going to be barrel sprinters. 

They can go fast. They can have a lot of power. But I think no matter what you do, they’re going to be a bit on the cooler side of what they can do. In the end, they have a lot of needs for the space they have. A normal equine with the same dimensions of a Centaur’s horse part is going to be smaller, faster, better balanced. 

Cooler blooded simply seems implied to me. So I’m scaling them more like a draft. 

Or in the particular case of the Centaurs I’m thinking of for “The Coward Gloria Foxfoot” (assuming I pick it up again) more like a Pygmy Giraffe for the sake of that spine but it comes to the same thing. So bigger, slower, calmer. Which will also mean they require a bit less in the oxygen needs department anyway. With more room to stuff all that internal organ mass they’re going to need. 

They’ve got room for all that lung and their mass is going to be something to behold.

Not really, I just wanted to say something dramatic and I’m looking at breathing systems now.

Humans breathe like so:

You breathe in through the nose, mouth, or both into the trachea. At more or less the same time they contract the diaphragm, a dome-ish shaped muscle that divides your stomach from your chest. By contracting the diaphragm it flattens and so both lowers its top and pushes out its sides, opening the thoracic cage (the ribs) wider, which creates negative pressure on the lungs, causing them to expand. That in turn causes negative pressure inside the lungs which pulls the air from the trachea into the lungs to balance out the pressure. Inside the lungs the 48 million or so Alveolar Sacs bulge with the air and shunt oxygen (and some other stuff) into the blood vessels they’re woven together with, while taking back the Carbon Dioxide (and some other stuff) from them in return. The diaphragm relaxes, squeezing the lungs like they’re bellows, shooting the air back into the trachea which you breathe out through the nose, mouth, or both.

This is called exchange tidal flow. Because it works like the tide of the ocean. Air comes in, air goes out, you make the gas exchange at the peak, where the air is all the way in but hasn’t gone out yet.

Like the tide though, there are inefficiencies in the system. Two of interest. If you’ve ever looked at the tide you’ll have noticed that as one wave comes in, the dregs of the previous wave are still trickling out. There’s an overlap. This happens in breathing as well. Which is why breathing exercises are all about exaggerating the points in the cycle. Breathe in more than you do naturally, hold longer than you do naturally, exhale longer than you do naturally. You are, in essence, controlling the tide to decrease overlap. It’s also part of the reason that when you do all that you breathe in through the nose, the narrower aperture, and out through the mouth, the wider aperture. Because you’re trying to flush as much of the outbreath tide out as possible.

Most bodies are fairly well adapted at getting as much oxygen as they need. And they have a natural enforcement limit. If you can’t get enough, you just can’t keep going. You get tired and you fall over. So the inward tide full of Oxygen is absolutely necessary but it is the tide of lesser concern.

The old truism of death by fire is that the fire’s smoke, the waste product of its chemical reaction, is more likely to kill you than the fire’s flames. Carbon Dioxide is the smoke in this simile. CO2 is one of our bodies’ fundamental waste products and the one we can tolerate the least of. Too much in our system at a given time and it makes it so we can’t get enough oxygen because there isn’t room for the exchange and it poisons us.

CO2 eventually leads to panting for more oxygen that you can’t get, a racing heart rate, arrhythmia so your heart can no longer steadily pump your blood, and “impaired consciousness” like difficulty thinking and being able to move. Concentrations of greater than 10% may cause any or all of convulsions, coma and the big D.

So as important as it is to get Oxygen in, it’s extra important to get that CO2 out. That’s also a part of why long term meditators and conscious breathers tend to feel healthier. They literally do have less toxic material in their bodies.

The second feature of interest for me is dead space.

Not that dead space.

This dead space

Dead space is the amount of space given over to breathing where no gas exchange takes place. Which for us is the trachea, oral cavity, and nasal cavity. If you snorkel, you add in the snorkel because the length of the tube is always used to move the air while having no role in making the breath pay off. It just helps you get the air where it is going. It’s easier to understand with the snorkel because without it, you don’t breathe at all. Necessary, not wasted.

And our natural dead space is much the same. It performs vital functions besides gas exchange. Mostly adjusting the temperature of the air toward our internal body temperature so it’s easier to deal with and the amount of moisture toward where it is easiest to perform a gas exchange.

And another benefit of exaggerating the tide of breath is in there as well. By dividing the air ways, breathe in through the nose and out through the mouth, you can dedicate a short portion of dead space to a particular part of the exchange, allowing for less overlap of the tides and less mixing of CO2 and O2.

But depending on where you put lungs or whatever breathing apparatus they have in a Centaur, there’s the issue of either having a LOT of dead space, too small lungs, or too far to carry the oxygen, or etc. etc. etc.

If there is only one set of lungs. The human lungs are small and there is a lot of body to cover that is very far away from the lungs. So picking that set has issues. The ungulate lungs have a giant dead space though. Way too large. So that’s not great either.

So, is it two sets of lungs that each work that way. I’m not sure that isn’t worse instead of better. Because you would still have the dead space of both. The anterior humanish lungs would have what all mammals do. The posterior ungulate lungs would have what more extreme mammals like giraffe’s have WITH THE ADDITIONAL DIFFICULTY or sharing part of that space with the other lung set. And they’re both using the same set of apertures designed essentially to feed just one set. Unless you do a full redesign and add a second set of intakes for the second lung set. There is apparently a book somewhere out there that has a nose in place of where the humanoid naval would be. Which just doesn’t sit right with me for no particularly good reason. Other than it adds to the pressure problem.

If the lungs aren’t synced right, then you might have the pressures from one set of lungs interfering with the other set. If you modulate the anterior lungs to talk because Centaurs talk like people, then you’re altering the airflow without there necessarily being regard for the posterior lung set, which would up the pressure, forcing an exhale instead of speech. You might get little snippets of talking but unless you exactly sync the lungs will interfere with each other. Worse, if the larger anterior lungs purposely hold their breath because they don’t want to smell some stupid scented perfumery, with it deflated and held, you’ve got a low pressure force pulling on the anterior lungs, keeping them expanded, which is going to make it darn hard to breathe, even once the posterior lungs give up, because the anterior lungs have formed a high pressure block in response, and somehow they would have to force that to deflate before you can rebalance the system. So, all in all, mammalian style lungs just aren’t sounding great to me for Centaurs.

But, thankfully, while mammals are all pretty much the same as people, that’s not the only type of pulmonary system that there is. And some pulmonary systems work much better than ours. So that’s part 2.