From the Vault: Thirst, Part 1

your Mind? My name is Robert Lamb and I'm Joe McCormick, And today I wanted to start off with a short reading of a few lines from the Odyssey that will introduce the subject we're getting into for the next few episodes. So this is from the Odyssey book eleven. I'm gonna

be reading from the m. Lee Wilson translation. But this is a section of the story where Odysseus is describing the horrors that he witnessed in Hades, and and there are different kinds of horrors, Like some of the horror of Hades is just a kind of profound, depressing disappointment with when he's confronted with the reality of how crappy it is to be dead, you know that, Like he he tries to talk to Ajax, and Ajax can't even

really say anything. But then there's this other section where he starts seeing more Dante in Inferno, kind of horrors of actual tortures, and so he sees King Minos, he sees a Ryan, he sees Sisyphus famously, you know, in the futile labor of pushing the boulder up a hill, longing to see it rolled down again. But eventually he comes to a figure called Tantalus. And then here's what Odysseus says about Tantalus. I saw the pain of Tantalus in water to his chin so parched, no way to drink.

When that old man bent down towards the water, it was gone. Some god had dried it up. And at his feet dark earth appeared, tall leafy trees hung fruit above his head, sweet figs and pomegranates, and brightly shining apples and ripe olives. But when he grasped them with his hands, the wind hurled them away towards the shadowy clouds now. When I look at the contraposition. Of the

two tortures of Tantalus, You've got the one. You know, he always wants to reach up to get the delicious fruit from the tree, but the wind kicks up, it pulls it out from his hands, and he can't ever get the food. That's a that's a a torture in Tartarus by starvation, which is not good. Obviously, starvation is

very bad. And it's probably more expressively phrase the second half of this, uh, the situation, but it's actually the first half that fills me with more horror when it talks about how he's he's standing in water, so it's like, you know, he feels it lapping around on his skin, but every time he tries to kneel down to put his face to it to get a drink, the water just is pulled away, as if by a tide. The gods dry it up away from his mouth, and he can't ever have a drink. To me, that's the more

terrifying half of this situation. Yeah, yeah, I love the image of Tantalus. Is this um this being that is uh, It's he's like he's suspended between his desires, between his needs needs or desires, depending on how you want to frame it here, right, Well, I guess this raises questions about the the biology of your shade in hades or tartarus, Like does it actually need to eat and drink and he can't get it? Or is this just some kind of I don't know, psychological need his soul has that's

not really biological. I guess yeah, given what we we we believe about the underworld the other myth cycles, I guess it's the idea that he doesn't actually need the fruit or the water to live, if you call this living. He's forever suspended in the state of of on death and on life. Um, but but wants to have the water, wants to have the fruit. Maybe that's the kind of question you're not actually supposed to bother thinking about this,

like the annoying pedantic question that Plato would bring up. Yeah, I mean well, Speaking of of philosophy, there is the concept of Burden's ass named for fourteenth century French philosopher gen Burden. This one. This is a basic idea that also pops up in the works of Aristotle and uh al Gazali various other writers. The more common thirst related version is if you have a donkey that is both hungry and thirsty and placed equal distance from both food

and water, it will remain immobile and die. Now, this may be apart from the lesson that the the thought experiment is trying to produce, but I think that's not necessarily true. I think there might very well be biological priorities that would place access to water above access to food. Yeah, it's it's one of the paradoxes that maybe doesn't You can't exactly recreate it in reality and expect it to be quite as a captivating but uh, abstractly it's it's

kind of fascinating. So as Aristotle put it, quote, a man being just as hungry as thirsty and placed in between food and drink must necessarily remain where he is and starve to death. So obviously that's not going to be the case. If you're hungry and thirsty and the waiter brings you your sandwich and your your cola at the same time, you're not gonna die. You don't have to give the waiter special instructions. You will. You worked

in restaurant industry, Joe. This is not like they don't tell you this, right, They don't say look, don't put the drink in the food in front of the customer at the same time, or they will they will just remain immobile and die. It is actually broadly considered very important in restaurants to get people their drinks before you get them their food. If you bring them food before

they get their drinks, people will get very confused and upset. Well, and uh, I know, I I often hear you know, when you're a lot of times when you're hungry, you're actually thirsty, and therefore, to avoid and prevent overeating, you want to make sure you have plenty of liquids as well.

So yeah, like, if I'm going into a restaurant situation, I definitely want my water first because I feel like I'm gonna I'm gonna have a more balanced experience eating lunch or dinner there, you'll certainly have a more pleasant experience. Though actually sorry, I'm just introducing exceptions to every single thing we say so far. But this does come up in a paper that I want to look at later.

There is a concept that's been documented widely in animal biology known as dehydration and do standardrexia, which is essentially the idea that many animals species. Certainly humans and rodents will naturally restrict their own food intake in response to dehydration. Again, there are some exceptions, some animals like get their water

entirely from food and so forth. But but but typically, like if you get rodents and and they're thirsty, they will eat less at each meal you give them, not saying that's a way to live your life, though, I mean better to be hydrated. Well, you know, coming back to mythology a bit, I thought we might mention just a few other you know, bits of myth and folklore

and legend and so forth concerning thirst. Uh, because I feel like, you know, we we have the sort of mythological echoes of the basic biological reality, and maybe these can help and inform and shape our conversation as we move forward. So there's one particular story I was taken with from from from ancient China. It's an ancient story dating back at least as far as the shan Haijing.

This is the the Fabulous Book of Monsters that we we did an episode, did a couple episodes on I think last year, and have recently or will be rerunning those episodes very soon. I think the title is sometimes translated as the Classic of the Mountains and Seas. Yeah. So there's a lot of a lot of mythological beings and places mentioned in the book Um and Uh, and

there's there is this account of Kuafu. It's a it's a it's a story that continues to be told today in modern China, and there have been many versions of it. According to Yang and and Turner. In Chinese mythology, basically, what you have in Kuofu is this primordial giant with two yellow snakes circling his ears and two more yellow

snakes in his hands. And he's powerful, very powerful, certainly, but he overestimates his own power, and depending on the story and the exact telling, he either challenges the Sun to a race, or he just wants to chase the Sun's shadow and catch the Sun. I've also read a version where he wants to prolong the day by catching the sun, Like if I can just get my hands on the Sun and then it can't move away, it can't set, the day will never end. Oh that's a

good plan. Yeah, Well, either way it works out. This giant runs after the Sun, intending to catch it um, but the Sun stays just ever out of his grasp, and what happens, well, he grows ever thirstier. So eventually he just has to stop for a second and he drinks the Yellow river. Um. Then he stops and he drinks drinks another river. But he's still so thirsty that he heads for the Great Marsh to the north. But on the way there he collapses. He dies of thirst.

And this is one of those stories that is often used to explain geography. So they are different, all these different details about what happens to his body once he falls, what happens to his walking stick um or his club once it falls, what happens to the dirt from his sandals, you know, they become foothills, that kind of thing. But

it's also a tale about just overreaching. And so the idea of of this giant chasing the sun is the idea that yeah, he's powerful, but he thinks he's more powerful than he is, and it's going to get him

into trouble. Oh that's interesting because to bring it back to Tantalus, I mean, it's somewhat different, but both stories have the The problem with the character is that they're in some way brazen or over audacious in their challenging of celestial figures or gods because the While there are multiple stories of what Tantalus did in order to deserve this punishment in tartarus Um, but one of the most

commonly received stories is that Tantalus well. So it's often said that Tantalus, like uh, shared a table with the gods, so he was a king, but he'd be invited up to Olympus to to dine with Zeus. And apparently at some point Tantalus was serving a banquet to the gods and as the main course, for some reason, he decided to kill and serve his own son. So he liked, yeah, that's that's that's a bad choice. So he yeah, he

boils his own son, serves his meat to the gods. Uh. It's like this horrible samelier competition, like can you tell this is my son you're eating? And the gods can tell they are good semeliers, so they figure it out

and uh. And apparently cannibalism and the kill of ken were considered among the worst taboos in ancient Greece, So it's like a story of the guy doing like the worst, most awful thing you can imagine in order to embarrass or humiliate the gods, and the gods catch him doing it, so they send him to this horrible punishment in the afterlife.

And so I do think it's kind of telling that this is a guy who does like the worst thing you could possibly imagine doing in in ancient Greek ideas like that, he commits the worst violent taboos, killing his own son and trying to get the gods to commit cannibalism. And what what is the punishment for that? It's eternal unsatiable hunger and thirst. Yeah, yeah, there's this. There's something about thirst, especially that it's just so it's so primal and it's uh, and it's this thing that can just

crescendo towards madness and of course death. Um. So we we we find numerous accounts where the gods become involved with human thirst. Um. There's an interesting story in Hindu traditions. This one appears in the Mahaparata. It's about a desert dwelling sage by the name of utanka Uh and Utankah is Uh. There are various accounts of you know, of what he got up to, but there's basically one of the key ideas here is that he was witnessed to

Krishno's universal form. So this is the same universal form that shown to Argina during the famous uh you know, now I am become death encounter. Oh yeah, okay. But with Utanka, he's given a special divine boone. Uh. So he's told whenever he feels thirst, his thirst will be quenched. Um So. You also there's this idea that he's followed by by rain clouds even in the desert, and so sometimes uh you'll see these clouds in real life referred to as Utanka's clouds. Um So, the clouds sent by

the gods to follow him around ound. And there's another story to that involves him him thirsting and the thirst being quenched uh and but water being sent to him via a member of a lesser cast, a lower cast, and and then he refuses. As it turns out the water in question was going to be uh the potion of immortality, but he was not ready to receive it spiritually because he was not willing to accept it from

this individual. M hmm. Coming back to the earlier detail in this where Utanka has given the boon that whenever he is thirsty, his thirst will be quenched. I wonder what is the what is the more specific imagination of that scenario, like that that water will appear somehow for him to drink, or that there's a kind of quinching without water, in which case it kind of makes you think, what is quinching? Because that when I think of the feeling of quenching thirst, it is specifically the feeling of

like water filling your mouth and going down your throat. Yeah, yeah, the it's not just the idea that we're going to suddenly feel magically, I'll go across. How would that happen? Right? You can't just turn it off with a switch. Our our one our primary means of alleviating thirst is to drink water. And therefore, you know, it's hard to disconnect

the too well. Actually, one of the some of the studies I want to talk about as we go on in this series have to do with the what is the relationship between the feeling of thirst quenching and the hydration of the body. It's not as direct as you might think. Now, another example of supernatural thirst, and in

this case also hunger um. Of course, you have in verious Eastern traditions, you have hungry ghosts and the the gaki are a type of hungry ghost in the tradition of Japan, also described as as always hungry and always thirsty, just monsters of torments, so that have huge bellies, be steel heads, talents, and so forth. And their home is the barren wasteland realm of Gakito, and they sometimes dragged the dying to hell, but they can be driven out

through ceremonies. I think that they also are often illustrated as having very narrow necks, so it's like their hunger there is great, their belly is great, their neck is narrow, like their their throat is narrow. Their ability to quench uh, their their bodily hunger and thirst is entirely insufficient. Of course, how hungry ghosts are, you know, widespread again in Eastern traditions.

But but I ran across an interesting tradition from pre Islamic Arab culture that I'd never heard of before that

I thought was really interesting, and it concerns owls. I was reading Echoes of a Thirsty Owl by T. M. L. Hammer and published in the Journal of Near Eastern Studies from so The author here writes that there was an idea you know again in the pre Islamic Arab cultures that the soul of a bird was quote unquote spread out through the body of a human being, and when the human died, um, the resulting birds are called the body and cried out over the grave of the deceased.

So the and then in time this bird grows and it becomes a savage and shrieking owl, and the owl, of course haunts the places of death. Well that almost makes me wonder. I mean, I think about the spooky movie trope of having an owl hooting in the darkness in the graveyard. But I don't know. The more I think about that, that's probably a coincidence. Well, I mean, owls are are are are associated with with death and and the supernatural throughout various cultures. You know, because they're

they're creatures of the night. They fly so silently that it's almost like they're not even there. Um, you know, they have those large eyes, their their their head appears to have various kind of humanoid qualities. Uh So, you know, I think there is some connection there, maybe not not a direct connection, about a connection via the the the widespread associations and various cultures between the owl and the

and the dead, and also the various omens. You know, sometimes in different cultures the owl is a is a dire omen to behold. Well, I guess this would depend on the owl species, but also their vocalizations have to play a role in in spooky associations. Yeah, yeah, and I think and also I mean, sometimes owls don't make a sound at all. Again, either they're flying silently or they're just sitting there silently, just kind of watching, and

so uh may be connected to that. That that that it's also said that these owls may also just sort of check in on sons and grandsons to see what happens after they have died. Other traditions say that the owl returned to the grave once every century. And then there's this idea that in the event that the deceased might seek vengeance for something or another, the grave of the dead should be watered to quote slake the thirst of the dead. Oh wow, yeah, now, of course, and

this we're probably getting into that. You know something we we hinted out already, the idea that that thirst takes on so many different forms, and the water quenches the thirst, or the liquid the quenches that thirst takes on so many different forms in our traditions. Like is thirst. Uh, thirst is of course something we all feel. It's a

you know, we all need water. But depending on how it's written up, you could you can describe thirst as a as a as a need, or as a desire, as something that your will has the ability to overcome or not overcome. Uh. You know, thirst can be uh portrayed as something positive, like the thirst for knowledge, the thirst for for for for God. But also thirst can be seen as like the thirst for for wine, or

for blood or for vengeance. Well, yeah, exactly. So I was also thinking about the abstract metaphors of thirst that we use um and what it means to to choose that word, in particular, to to say that you want something by saying that you thirst for it. So, in the example of someone who has a thirst for vengeance, how is that different from just wanting vengeance? To me?

At least in that case, thirst as a metaphor, as a metaphor for want, implies a kind of irrational desperation in the in the acquisition behavior, something that will be sought without hindrance and without reason. Now, obviously that wouldn't exactly apply to other metaphorical uses of thirst, like you said the thirst for knowledge. But again that that word choice seems to me to imply something different than somebody just saying somebody likes knowledge or seeks knowledge. It suggests

a kind of primal need. I guess, yeah, And I guess you also have to factor in that. You know, for a lot of us, we live in in very water rich environments and water rich cultures and uh socioeconomic places. So you know, we we we don't feel true thirst for the most part. You know, we don't. We don't feel the thirst that is approaching madness and death, um and the and and then again it comes down to,

like what is the person thirsting for? If you're talking about somebody feeling a mighty thirst, but you're alluding to their desire to have an alcoholic beverage, like that's that's a slightly different thing that just talking about Oh well, this is this is thirsty work that they're doing, and you know, implying that they're just they're just building up a natural uh need for a big draft of water to satisfy their thirst. It seems when people use thirst

to talk about alcohol. I always detect an air of of irony, and that just like it's supposed to be a little bit funny that you're using it that way, right because if you're truly thirsty, alcohol is not what you should be using right now. Just to come back to the the idea of these owls briefly, apparently some writings say that the blood and the brain in the in the deceased fused together after death to form the owl.

Others would say that it was born of one's bones and that the owl would then erupt from the head, which I think is a wonderful and horrifying supernatural uh picture. But it was a reference in a number of different poems um by a lot of pre Islamic Arab poets. The Arabic poet Alan Bari wrote, quote and it is said that man, when he has killed and his revenge is not taken, an owl comes out of his grave and then continues screeching, quench me, quench me, continuing so

until his killer is killed. Anyway, that that article is titled Echoes of a thirsty owl um. If anyone's interested, I recommend reading that. He also compared, you know, compares it to various other traditions concerning the owl as some sort of a supernatural being. He talks a little bit about about the role of the owl and Greek mythology

and so forth. Now we we can't very well cover a complete cultural history if him and thirst here, but it is worth thro having him that thirst is an important aspect of history and civilization UM, in in obvious

ways and maybe sometimes in less obvious ways. I was reading a article in the Journal of European Archaeology by uh Slavamil Vehicle titled the Archaeology of Thirst, and in it the author points out that naturally, the human satisfaction of thirst is an essential part of the human experience, and it's a it's of course of great interest in archaeology, but a number of obstacles have to be overcome. So first of all, you just have the volatile nature of liquids.

You also have the scant chemical signatures to be found inside ancient drinking vessels UM, also scarce paleo botanical analysis of those residues. UM. They also mentioned quote the functionally unspecific nature of most vessels, which I thought was interesting, reminding me of our our holiday discussion of leg shaped vessels. Yeah, it's a hard. A lot of times people are like,

I don't know what people would put in this leg. Yeah, like we can assume they would put oil in it, you know, but it depending on what the vessel is and what the culture is, and how much additional information we have. We might just have to guess and be like, Okay, it seems like you might drink out of this, or you might just or maybe this is just for storing some sort of oil. On top of that, we often

have scant iconographical information. Also, this is a big one, and this is this applies to far more than just drinking vessels. But if the vessel is organic in nature, we may not have any uh, surviving examples of what it was. And on top of that, by and large, we tend to focus on exceptional examples of drinking and storage vessels, which of course limits study to a very

slim part of a given culture. You know. So it's like a highly ornate decorative piece that you know, maybe is of the same shape and basic function is what people would have in general been using to drink water or store water, etcetera. But maybe not like maybe it is um it's it's more about looking interesting as opposed to anything else. But the archaeology of thirst ends up

encompassing some very ancient examples UM, including things like neolithic wells. Um. Water is the most basic means of meeting human thirst, and it's taken on mundane and fantastic connotations at times. But on top of this, of course humans have come to drink SAPs blood, of course, various concoctions such as meat and wine and beer and more. But but I guess water, you know, water remains the big one. Obviously.

Another idea worth mentioning in all of this that I was reading about UM is the idea that, okay, so human thirst is of course ubiquitous. Everybody is going to thirst, everyone needs water UM. And so if you look back um to to Jewish and Islamic traditions, you you find in both legal traditions this idea of the right of thirst UM. The the idea of being that like every every every human government by this law, has this right of thirst UH to this right to water via their

own thirst. And in Islamic law, apparently this extended to animals as well. Animals had the right of thirst, which gave them meant that they had a right to access water based on their thirst. But but it's also it's interesting how you know this sort of this this foreshadows a lot of our our modern relationship with water, the idea that that the right to water is classified as

a basic human right by the United Nations. UM. But of course, at the same time, uh, not everyone has equal access to to water and uh, and this is going to continue to be a problem moving forward, and of course you can't help. But then take all of that and relate it back to our metaphorical treatment of thirst.

You know, how does the how does that change? You know, if you're if you're if you're talking about thirst in reference to spiritual needs and um, and you know, a thirst for knowledge, Like, how is that different if you're if you're expressing that, uh within a you know, in a place where there where water is plentiful, where a drinking water is plentiful, or a place where access is

more limited. But I guess before we can answer any of these questions, we need to back up quite a bit and just talk about thirst as a biological reality. What is it and how does it work? Yeah, And so this was actually rather interesting to me because it turns out I knew less about thirst than I realized. And uh, and what we do know about thirst and what we don't know about thirst are both pretty interesting.

So I was reading an article called just called Thirst that was published in Current Biology in sixteen by David E. Leeb, Christopher A. Zimmerman, and Zachary A. Night. And this article is essentially a summary of all the existing research on thirst. It is, as of the year twenty sixteen, a sort of perfect primmer catching everybody up on what do we know about Thurston? What do we not know? Now? Before

we get into the meat of that discussion? I guess, uh, to to just cover the very basics, Uh, the first fact before we get into anything else. You are a water bag. That that is what we are. That is what all of us are. We we are not just simple water bags, but our bodies are essentially water bags over any other material description. All the animal life that currently lives on land evolved from creatures that used to live in the ocean, where you're surrounded by water all

the time. And when we evolved to live on land, we had to create essentially bags that would contain water to take with us. Because all of the of the biological chemistry, the biochemistry of life takes place in water, in solutions of water, and so as water bags. You know,

we we are complex autonomous water bags. But most of those complex autonomous activities actually re wire that there be a fairly precise amount of water in the bag and a fairly precise concentration of various substances things like sodium for instance, that pretty precise amounts be dissolved in the water in the bag, and so various processes of life are constantly leading to water coming in and out of the bag. So there there are several common routes of

water to be added to the bag. Were familiar with the most common of those, which is drinking fluid, drinking water or or fluids that are mainly water, or eating food with water content. And that the second one, they're eating food with water content, is less prominent for humans because you know, we typically drink a glass of water with food or between meals or whatever. But there are some animals that that basically get almost all of their

water from their food. Yeah, this includes certain desert species such as the kangaroo rat and the kangaroo mouse, which, of course, on the planet Iracus becomes the the the the mouse. Deep. Um. We also have things like the sand cat, the sand gazelle. Um, and uh, I know, just in my household, it also seems to include my cat,

who does not seem to drink water at all anymore. Um. We we have to lean heavily on moist foods to get to get her her liquids, so feeding her wet food, adding a little bit of water like sneaking it into the wet food. And yet if we make the wet food too wet, she will say, no, it's too much like water. I will not have it, And then we put out water for We've tried the fountains, we've tried everything.

The only thing she ever actually drank out of was a fish tank when we had a fish tank, and then she would not stop drinking out of the fish tank. But any other thing we've tried, she hasn't gone for. And so when she's had some issues before, it's like, you know, she's clearly dehydrated. In the past, we even had to I had to use an ivy to give her the water. So we we still have a whole bunch of bags of fluid around in case she has any any flare ups. Of her issues, but in terms

of just like drinking straight water, she's not interested at all. Wow. Well, simultaneously that is kind of fascinating, But also I feel for her and I feel for you guys that that's very frustrating. Now we're weird. I mean, everybody seems to be at a comfortable level right now. She's she seems to be getting all the liquid she needs through her

her meat paste. But but it's it's weird with cats because yeah, I think some people have this experience with with cats where they really have to be tricked into drinking water, but others will just drink it on the fly out of toilets or dripping faucets and so forth. Right, So all of that is direct water acquisitions. Of course, you get water from drinking water. You get some smaller

amount of water from eating food that contains water. But then apparently there's there's a secondary route for water acquisition by eating food through what's known as metabolic water, which is in your metabolism oxidizes various energy containing substances that you eat and produces water in the process. So some water is created at the molecular level by your metabolism, and there are some organisms that get a large amount of their their water content from metabolic water. Humans only

get a very small amount from it. But yeah, I mean I think like some desert dwelling organisms and some birds and stuff get get all or almost all of their water by by chemical reactions that happen inside their body after they eat food and turn parts of that food into water molecules. Now, one of the interesting things I was reading about some of these desert species um

and at least with some of them. You know, if they're in a captivity and they are offered water, well, then when they they theirst builds up, they will drink the water. So it's not it's not like everything. I don't want to imply that anything out there that gets most of its water through its meat is going to be like my cat and just refused to drink water. You know, she has her own issues going on. Yeah,

I'm sure that varies by organism. Okay, but those are the routes in you've got directly through drinking and eating and then secondarily through metabolism. But then you've got a number of routes for water to be to be eliminated, So you've got urination of course, and then you've got

lost through defecation. You've got evaporation through the lungs of people sometimes don't think about this, but you lose water when you exhale water, vapor comes out of your mouth or out of your nose, and then there is also evaporative loss of water through the skins just through sweating, so uh, and then other other more minor things. I mean, obviously some extremely tiny amount of water evaporates off of the liquid on the surface of your eyes and so forth,

but but those are the big ones. The defication is worth mentioning, probably stressing again because I think most people are probably familiar with this. But obviously if one is in a UH, is suffering from a condition the results in you know, um um diarrhea or um, you knows, some sort of dysentery situation. You end up losing more and more water through defecation, and therefore you have to make sure you're drinking more and more water to make

up for that water loss. Also, just a reminder out anyone out there, a well fitted and well manufactured still suit will collect all of this as it leaves your body. UH. All the routes out will be covered and you'll lose no more than a thimble's worth of water per day. We've gotta stress well fitted though. You get the still suit on there, you're gonna have all kinds of gaps and things not working right. That's right. You don't know how to work the straps and you're not you don't

have that forehead piece on correctly. It's just not gonna work um at an optimal level than right. Well, anyway, I want to come back to some of the findings that are summarized in that current biology paper by leave at all that I mentioned earlier than again, this is from so there will be more research that we get into from after that adds to some of these findings. But this is where we were when this when this

good summary came out. So in the human body, the brain monitors the body's water content, and when certain thresholds are reached in the that information monitoring system, it motivates the body to drink fluids. Of course, it's not only the decrease of fluid volume in the body that makes us thirsty. One of the most important things to understand in the maintenance of the body's water content is the

importance of something known as OSMO reality. That's O s M O L A l I T Y. This is the concentration of various particles such as electrolytes like sodium, that are dissolved in the body's water content. And you'll you'll see this often described as blood OSMO reality. It's basically functionally the same thing. The liquid part of our blood plasma is roughly water, So when people talk about blood OSM reality, they're talking about OSM reality of the

body's water content. The brain is actually incredibly sensitive to changes in blood OSM reality. An increase in just one percent of of the blood osmality can cause an animal to feel thirst and the author's right quote. This sensation, in turn is sufficient to orient and energize all of

an animal's actions towards the goal of finding and consuming water. Thus, the study of thirst is the study of how the brain performs this remarkable transformation, such that small changes in the composition of the blood become a potent and specific

motivational drive. Uh And and the more I thought about that, the more interesting it became that essentially just sort of eating a small amount of salt, for example, is enough to to motivate my brain to change all of my behavior because my osmolality goes up, the salt dissolved in my body's water content increases. In order to balance that out, my body wants me to go get some more water to drink, and that I will interrupt whatever I'm doing to go do it. And we and we did not

even really think about this. We don't think, oh, now my body has need of water, I must go get it. It's just like, it's just what you do. Yeah. Like I mean, right here, as we're recording, and I have a big thermis of water and I just end up casually sipping on it the whole time. Yeah. Same here. I always get a nice big glass of water before

we start recording. But but the question would be, why are our bodies so sensitive to these tiny changes in osmolality in the amount of of osmolites dissolved in the blood. Why would like a one percent increase in salt concentration really cause that much of a problem. Well, the authors offer some explanations. They say, first of all, you've got this thing in your body known as the electrochemical gradient. The cells in our bodies are selectively permeable to specific ions.

Quote resulting in an electrochemical gradient across the plasma membrane that is exploited for numerous cellular functions. So this means that there's a difference in the electrical charge and the concentration of various chemicals on opposite sides of the membrane that surrounds each of our cells, and the difference or the gradient here, the fact that it's different on each side of the membrane is what permits the transportation of ions across the membrane so that cells can do things,

so that they can send and receive things. So if you change your blood osmolality, you say, increase the concentration of salt in the body's water content, You change this gradient, and you change the water contents inside cells, and you quote degrade normal cellular function. Now, I was trying to think of a rough analogy, and here's what I came up with. This may be very rough, but it's my

best attempt. So when you change your blood osmolality away from its ideal, I would say your body sort of becomes like a city that starts having system wide problems opening and closing doors. Now, is the problems opening and closing doors of all kinds throughout a city get worse. Eventually, this would just cause myriad diverse problems throughout the city. Uh, much like it would in your body. Well that did that just sounds like chaos. That just sounds like like

all order is falling out out the window, right. And you can actually see that the represent visual representation of that chaos in a chart that the authors include in their paper, where it shows what the typical symptoms are as the blood osmolality goes too far above or below what it's supposed to be. Uh and uh. Basically on both sides, it's sort of a mirror image with a

few differences. So you've got the normal range, but then you start getting away from it, you get things like irritability, lethargy, aussia, a taxia, trembling, hypothermia, and then in both cases you end up in the seizures and death territory. So yeah, so basically, yeah, we have this this thin little realm

of stability and to either extreme it's just madness and death. Right, So the body has to very carefully keep that concentration of osma lights in the right range, and if it gets off there, there are it will take drastic measures to get it right again. But then the authors identify another major reason that the body has to keep fluid volume and osmalality at the right levels, which is blood pressure.

You know, they say, your body uses blood to transport oxygen and other essential nutrients to all of its tissues. Everything in the body needs to get oxygen, uh that, you know, from the lungs in the heart, and the blood has to get there to do its work. If the volume of water in the body drops below ideal levels,

blood volume actually decre recess. There's not enough blood, which means the circulatory system has to work harder and harder to keep blood pressure up where it needs to be to get to all the parts of the body and deliver those nutrients. So, in addition to maintaining the right concentration of those dissolved things like sodium, you also just need to have enough water in your body to keep your blood pressure up to allow your heart to keep

getting blood to all the parts of the body. It just it kind of comes back to what you said earlier about it. You know that we're there's water bags, we're creatures made out of water, and if we don't have enough water, we don't have enough of us, right, Yeah, nothing nothing works without it anyway. The authors say that the bodies of animals have evolved to carefully preserve blood volume and blood osmality, and then they describe some of

the main components of this system that we know about. So, first of all, there are neurons that monitor blood osmalality and volume. You've got especially dedicated cells in the central nervous system that pay attention to this stuff, and when they detect a problem, they quote trigger a coordinated set of autonomic, neuroendocrine, and behavioral responses that defend these parameters against change. So one of the main measures the body can take to defend against changes in OSM reality is

modulating kidney function. So as OSM reality increases, you get a surge of anti diuretic hormone, which makes the kidneys change tack to keep more water inside the body and make the urine more highly concentrated, make it less deluded with water. Of course, the kidneys can't do their job alone because they also have to do other things. In addition to that, they have to help purge the body of toxic substances and other kinds of waste and of course,

some some water volume will necessarily be lost in that process. Also, the body loses water through these other means we mentioned a minute ago, sweating, breathing, and so forth, So eventually the body will be forced to consume new water to restore the balance and the volume of the blood plasma. So so that's the chemistry and the physiology. But eventually you have to get to behavior. At some point, the brain has to trigger behaviors to get new water in

so an animal thinks I need to drink water. Of course, this behavior can be costly there you know, there are factors working against an animal's motivation to do it because it might involve spending energy finding and traveling to a water source. It might involve taking big risks. I mean, think of all the nature documentaries you've seen where predation happens at the water's edge, whether it's a crocodile jumping out of the water or a predator sneaking up while

an animal is distracted by lapping up water. And then some of those predators have been traditionally been human beings. Oh totally. And of course drinking water just involves temporarily de prioritizing other important things. Like you know, in the natural context, maybe forging for food or pursuing reproduction, but even think you know, it might force you to get

up from gaming or whatever. Well, I mean, this is one of those areas again where like with humans, so many of us are are are fortunate that we never have to hunt for water. You know, the drinking water is readily available to us. We have all that we need. And likewise, through human civilization we we tend to have

the food situation knocked as well. Again, and ideal circumstances, you're not going to have to spend um most of your day foraging for food, which is going to be the case with many different species of animals, you know, where most of the day is about just finding the food, eating the food, and of course there's no there's no room for anything else. And if you're having to hunt for extra water along the way, then you're that's getting

in the way potentially of this this vital food hunt. Yeah, just as an aside, easy access to clean, drinkable running water is like my go to example of what's good about modern civilization. You know, there are a lot of people who kind of demonize modern civilization, and there are

a lot of things about it not to like. But but easy access to clean water is like, that is the most unambiguous good thing I can think of, right, I mean, to the to the to the extent that it's ridiculous in some in many cases you know where someone might ask, what what is this? What is this water in your toilet? Well, this is drinking water, the drinking water that comes into the house, he goes into the toilet. We just make sure that the water in

there it's perfectly fresh and drinkable. Um, which I guess is good for the dogs and the cats. But um, you know certainly that I think you see these various you know, gray water models, Um, that certainly make a lot more sense, Like why should the drinking water be the water in the toilet. Can't the water from the washing of my hands be the water in the toilet?

Wouldn't that make more sense? Of course it requires more work, right, But to come back to the the wild context, I mean, obviously there are all these things that would be factors pushing against your your acquisition of water, and your body needs it. So of course what an animal needs is intrinsic motivation. Actually, they're demotivating factors that are just natural parts of the environment. So acquiring water needs its own

intrinsic motivation, hence the motivating desire of thirst. It is a moment to moment drive to acquire water that's calibrated by the constantly updated feedback on blood volume and osmality, though there may also be some other interesting and more surprising inputs on it that will get to in a

bit now. The authors point out that thirst appears to have both positive and negative motivating mechanisms, and I think you can think about food, food and hunger as an analogy here, because there's something sort of along the same line. So you've got positive reinforcement of fluid drinking behavior by just making drinking water when you're thirsty feel really good, you know, when you're very thirsty, that glass of water,

it's it's delicious, it's wonderful, it feels great. And then you've got the negative reinforce smith side, which is that thirst is inherently unpleasant. It is experienced as a type of discomfort or pain that has to be alleviated by drinking fluid. So we all know from experience that these things are true. That you have this positive and negative reinforcement mechanism within the brain for thirst and the drinking

of water. But what's very interesting is that, at least at the time of this paper in two sixteen, how these two mechanisms of thirst are instantiated in the brain

is still not fully understood. There are some major question marks remaining, and I think there are at least a few other studies that we can refer to in subsequent parts of the series about that where where some ideas have developed since then, but there's still a lot of questions out there, and this is This is one of the reasons that I thought it would be so interesting to pursue Thirst as a series on the show, because it's surprising that there are things we still don't know

about it. It seems like one of those things that would be absolutely totally understood at this point. But but there's some great outlining questions about thirst and and UH, how we experience thirst, what are the neural pathways there, how is thirst SAYD and so forth, So maybe we'll

have to call it for this first part here. I know I'm only halfway through discussing this uh from repaper, but if we go on through the end of this one this first episode is going to be two hours long or something, so so maybe we should call it What do you think, Rob? I think so, yeah, I'm actually almost out of water here and I'm going to have to refill. But yeah, I'm excited to keep going

with this. There are a number of little areas I'm hoping we'll get into the manipulation of thirst by other organisms the end and life forms the I want to get back to the taste of water. Uh, this is something that's always fascinated me. I'm granted water, the taste of of of water will change depending on where you're getting the water. But you'll sometimes hear people say, well, I don't like the taste of water, or we'll think

of water as having no taste at all. Um. I actually found some some some some papers dealing with this topic a little bit, so I think they could be fun to discuss. People who don't like the taste of water. That is a telltale sign of vampororism. Just add some red food coloring to it. Then then you're then you're like, oh,

this is great, this is wonderful. Okay, well, all veins to drink from when we return, All right, in the meantime, if you want to check out other episodes of Stuff to Blow Your Mind, you'll find them in the Stuff to Blow your Mind podcast feed wherever you get your podcast. Core episodes on Tuesdays and Thursdays, Artifact episodes on Wednesdays, listener mail on Mondays, and on Fridays, we do Weird how Cinema. That's our time to set aside most serious

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