Solving Scurvy
During the Age of Sail, conquering the seas meant conquering scurvy, a disease that frequently afflicted sailors on long journeys. In 1541, Dutch physician Johannes Echthius wrote one of the earliest known descriptions of scurvy’s gruesome symptoms:
…[A] spongy swelling of the gums, which are apt to bleed, with a loosening of the teeth; an eruption of leaden coloured, purple or livid spots on the legs…
As the disease develops the patients lose the use of their legs and are subject to a difficulty of breathing.
Scurvy frequently led to death, and the disease could decimate a ship’s crew; one particularly disastrous example was Commodore George Anson’s 1740 circumnavigation of the globe:
Anson’s six warships and two supply ships sailed with 1,854 men.
One ship and 188 men returned; 997 of the 1,415 deaths were from scurvy.
In this manner, scurvy would claim the lives of millions of sailors of that era. It is sometimes theorized that the British lost the Revolutionary War in large part because of scurvy’s impact on the British navy. Shortly thereafter, the British figured out how to prevent scurvy on their ships, and they used this knowledge to triumph over the French in the Napoleonic Wars.
Scurvy is intriguing because the knowledge of how to prevent it and treat it was seemingly found and lost and found again and lost again, over and over, throughout the centuries. Many sailors knew how to treat scurvy hundreds of years before the British tamed it throughout their navy in the early 19th century. Remarkably, scurvy would rise again to plague polar explorers as late as the early 20th century, long after it had supposedly been conquered.
Scurvy may seem like an unusual topic for a blog about economics and investing, but it is a fantastic case study about the different ways people throughout the ages approached a difficult problem involving a very complex system beyond their understanding (the human body) with lots of confounding variables to lead them into blind alleys. We can see now what strategic approaches worked best to solve the problem, and why. The problem of scurvy is worth studying today because it is analogous to the problems we confront every day in economics, investing, and even at the office.
We now know that scurvy is caused by a deficiency in vitamin C, which the human body needs to produce new tissue. (Hence the gruesome symptoms.) Vitamin C is found in various concentrations in a wide variety of fresh foods, particularly in vegetables and fruits, but also in fresh meat. It makes sense to us today that sailors with no access to fresh foods would be susceptible to the disease, while land-dwellers would only encounter it under rare circumstances.
No one knew that scurvy was a deficiency disease until a pair of Norwegian researchers stumbled into the finding while experimenting on guinea pigs, publishing their studies in 1907. No one was aware of the concept of vitamins until 1912. Albert Szent-Györgyi isolated vitamin C in 1931, and won the Nobel Prize for his efforts in 1937. By WWII, vitamin C was being distributed in tablet form, and scurvy was a thing of the past.
Before 1907, no one knew what caused scurvy — many believed it was an infectious disease, or it was caused by tainted food. Regardless, as far back as recorded history goes, people found ways to deal with scurvy when they did not have access to fresh food, whether it was because they were under siege from invaders or because they had to deal with a long winter.
Anton Howes documents that the residents of northern climates had, over the ages, developed methods of making it through the winter without getting scurvy:
The Iroquois ate the bark, needles or sap of evergreen trees — most likely white cedar, or some other kind of spruce, fir, juniper or pine, all rich in vitamin C…
Cloudberries became something of an obsession for the common people of sixteenth-century Bergen, in northern Norway…and [they] otherwise subsisted almost entirely each winter on honey-sweetened cloudberry jams, which they covered with a butter to preserve it from the air.
Howes tells us that the sailors on the earliest long range voyages quickly discovered the value of oranges and lemons in treating scurvy:
The voyage of Vasco da Gama, having been the first to round the Cape and reach the eastern coast of Africa, was then stricken with scurvy. They were only inadvertently saved when they traded with some Arabian ships laden with oranges, before landing at Mombasa…
[The] status of oranges as a scurvy wonder-cure had entered sailors’ lore. When Pedro Alvares Cabral repeated da Gama’s feat of rounding the Cape of Good Hope in 1500, his crew purposefully treated their scurvy using oranges.
This knowledge spread to other countries during the 1500s:
The first Dutch East Indies Fleet sailed in 1595 with 249 men and returned in 1597 with only 88. The 1598 fleet took lemon juice, grew horseradish and scurvy-grass (a corruption of “scurvy-cress”) on board, and lost only 15 men.
Sir Richard Hawkins in 1590 bought hundreds of oranges and lemons in Brazil for his men, perhaps based on his experience as a prisoner-of-war in Spain: “that which I have seene most fruitful is sower oranges and lemons . . . I wish that some learned man would write of it, for it is the plague of the sea, and the spoyle of mariners.
The efficacy of lemons, oranges, and other similar foods in preventing and treating scurvy was documented in textbooks of the era (together, these foods were dubbed “antiscorbutics”), but adoption of these proven treatments was still spotty. Part of the problem was misinformation spread by medical professionals:
[O]rthodox physicians, such as Thomas Willis, Gideon Harvey, Boerhaave, Meade, and Cullen, wrote copiously and learnedly about scurvy, but without any maritime experience, simply listing the many standard theories of the cause of scurvy, and the many standard medical treatments such as bleeding, purging, and polypharmacy.
Remember Commodore Anson’s fateful 1740 journey, where he lost a thousand men to scurvy? Well, here is how it happened:
The admiralty ignored the centuries of experience of seamen and instead took advice from the College of Physicians and supplied Anson’s ships with elixir of vitriol (sulphuric acid, alcohol, sugar, and spices) as a substitute for acid fruits on the concept that the efficacy of citrus fruits was related to their acidity.
The traditional story of the triumph over scurvy takes place in the 1750s. Here is how the (US) Military Health System tells it on their website today:
[The] Royal Navy cracked the mystery of the disease in the 18th century thanks to surgeon James Lind. The British began storing citrus fruits on board all of its ships. The British Navy gave its sailors limes or lemon juice rations to ward off scurvy – earning them the nickname of "Limeys" among the American sailors who didn't know about or believe in the preventative treatment.
In this simple telling, a heroic Scottish doctor named James Lind, when confronted with cases of scurvy on a ship, conducts the first clinical trial in history, correctly deducing that oranges and lemons cure scurvy. The Royal Navy is very slow to react to this new information, but a half century later, they get around to giving lemon juice to their sailors, before later switching to their famous limes. The British conquer scurvy, and then conquer the world.
This story is almost completely false.
There is no evidence that Lind’s clinical trial ever happened; on the journey where he supposedly conducted his study, the ship’s logs contain no record of sick passengers. Lind’s Treatise of the Scurvy does not give a clear recommendation that oranges and lemons should be the main treatment for scurvy. Moreover, Lind’s actual proposed treatment was useless:
Lind was well aware that it was impractical to carry citrus fruits on long sea voyages because, as Woodall noted, “oranges and lemons are liable to spoil”, as indeed would lemon juice. Lind therefore devised a system of almost boiling purified citrus juice, so that 24 oranges or lemons were reduced to a few ounces…
Hughes (correctly) joined others in asserting that Lind’s rob [fruit syrup] was later shown to be ineffective in preventing scurvy (now known because he had boiled the heat-labile ascorbic acid), and (correctly) that Lind was unscientific in presenting no evidence for his rob, merely “by my own experience”,“the most incontestable experience”,“remains good for several years”, and “preserving their virtues for years”.
The late Jeremy Hugh Baron argues that the credit should actually go to a subsequent pair of Lind-inspired Scottish doctors, Thomas Trotter and Gilbert Blane. Trotter was assigned to a slave ship in 1779, and calculated that he could improve the slavers’ financial returns by convincing them to invest in a bit of citrus. More importantly, he figured out that lemon juice can be preserved for a long journey by straining it, bottling it, and covering it with olive oil.
Meanwhile, Blane joined the Royal Navy in 1779, and he made similar calculations for his own bosses, who had been suffering great losses from scurvy during the Revolutionary War. Blane calculated that a mere 50 oranges and lemons could effectively “buy” them an extra sailor by reducing mortality from scurvy.
His method of preserving lemon juice involved mixing it with spirits, but it was equally effective, and it began to gain adoption throughout the British fleets. Thanks to the efforts of Blane and Trotter, by 1796, all British naval ships on foreign service were issued lemon juice.
Here, finally, the British defeat scurvy, and they defeat the French in the Napoleonic Wars:
Between 1795 and 1814 the admiralty issued 1.6 million gallons of lemon juice. Sweet lemons were imported, especially from the Mediterranean region. Nelson turned Sicily into a vast lemon juice factory. Scurvy then more or less disappeared from ships of the navy.
Or did it?
Somehow, scurvy would make a comeback. The British would switch from imported Mediterranean lemons to limes from the West Indies in 1860. This was an unfortunate choice, as we now know that limes contain only half the vitamin C of lemons. Moreover, tests conducted in 1918 demonstrated that the lime juice issued by the British was almost totally ineffective, probably because it came into contact with copper (which oxidizes vitamin C) when it was manufactured.
There were reports of increased cases of scurvy in the Royal Navy in the 1860s, but nothing approaching an epidemic. This is because at the same time, the advent of the steam engine made voyages much shorter, meaning that sailors usually no longer spent enough time between ports to develop scurvy. (It turned out that under the right circumstances, the steam engine prevented scurvy just as effectively as lemon juice did.)
This all changed in 1875, when the British sent George Nares to lead an Arctic expedition, where they would be away from fresh food for months. Maciej Cegłowski picks up the story:
The expedition was a fiasco. Two men in the sledging party developed scurvy within days of leaving the ship. Within five weeks, half the men were sick, and despite having laid depots with plentiful supplies for their return journey, they were barely able to make it back. A rescue party sent to intercept them found that lime juice failed to have its usual dramatic effect. Most damning of all, some of the men who stayed on the ship, never failing to take their daily dose, also got scurvy.
The failure of the Nares expedition provoked an uproar in Britain. The Royal Navy believed itself capable of sustaining any crew for two years without signs of scurvy, yet here was an able and adequately supplied crew crippled by the disease within weeks. For the first time since the eighteenth century, the effectiveness of citrus juice as an absolute preventative was in doubt.
Scurvy would plague polar expeditions for the next forty years, which Ceglowski describes in detail. Three wrinkles made late 19th century / early 20th century polar scurvy particularly difficult for scientists to solve:
Many explorers managed to avoid scurvy by eating fresh seal or polar bear meat. We now know that this is because fresh meat also contains vitamin C, but again, they had no way of knowing this.
By now, scientists are aware of bacteria and germs, and are more inclined to attribute diseases to those causes.
Explorers are regularly consuming lime juice and still coming down with scurvy.
They used these observations to come up with a dramatically incorrect theory of scurvy, which was that antiscorbutic substances such as lemon juice are actually useless placebos, and that scurvy is really caused by tainted meat or other tainted foods. This theory actually mostly fit the observed data from the time, but on the other hand, it could not have been more wrong.
Ceglowski summarizes the problem well:
This pattern of fresh meat preventing scurvy would be a consistent one in Arctic exploration. It defied the common understanding of scurvy as a deficiency in vegetable matter. Somehow men could live for years on a meat-only diet and remain healthy, provided that the meat was fresh.
This is a good example of how the very ubiquity of vitamin C made it hard to identify. Though scurvy was always associated with a lack of greens, fresh meat contains adequate amounts of vitamin C, with particularly high concentrations in the organ meats that explorers considered a delicacy. Eat a bear liver every few weeks and scurvy will be the least of your problems.
But unless you already understand and believe in the vitamin model of nutrition, the notion of a trace substance that exists both in fresh limes and bear kidneys, but is absent from a cask of lime juice because you happened to prepare it in a copper vessel, begins to sound pretty contrived.
In 1904, the Norwegian bacteriologist Axel Holst set out to find the microbe that causes the disease known as beriberi; an impossible task, because as we now know, beriberi is actually caused by a vitamin B1 deficiency. After a couple of fruitless years, he began to do studies on guinea pigs with his colleague Theodor Frolich, a pediatrician who had been studying infantile scurvy. This was a fortunate choice, as guinea pigs are one of the very few animals besides humans that need to consume vitamin C.
In 1907, the pair published a study showing that guinea pigs fed a diet of pure grain would exhibit all of the symptoms of human scurvy and die, but when antiscorbutics like cabbage and apples were added to their diet, they showed no scurvy symptoms. (They even managed to find that fresh cabbage and fresh potatoes work against scurvy, but boiled cabbage and dried potatoes do not.)
Based on their guinea pig experiments, they concluded, accurately, that scurvy was a deficiency disease. Holst and Frolich had cracked the code, and within a little over a decade, their findings would be universally accepted, and scurvy would be a thing of the past.
It is worth highlighting that their study was not universally embraced at first. One of the loudest skeptics was a fellow Norwegian scientist, Fridjtof Nansen. Nansen was not just any scientist; he was actually the most famous scientist in all of Norway, a successful polar explorer and national hero who would later win the Nobel Peace Prize. His Fram expedition in 1893-96 reached a record northern latitude (although it fell short of the North Pole), and he accomplished it without suffering issues with scurvy.
He believed wholeheartedly in the theory that scurvy was caused by tainted foods, and that his expeditions were proof that scurvy could be avoided by proper precautions and sanitation. In his mind, he was a real life explorer who had prevented scurvy in humans in the field, while Holst and Frolich were merely doing studies on rodents in a lab. (It didn’t help that Nansen had a personal beef with Holst dating back many years, when Professor Holst attacked then-grad student Nansen’s dissertation.)
Holst replied that despite Nansen’s extensive field experience, he had never done anything approaching a controlled experiment, and logically, he had no way of knowing how he actually avoided scurvy on his trips. Holst was of course completely correct. As it turns out, Nansen had inadvertently avoided scurvy on his Fram expedition in a very traditional Norwegian way – by bringing along a half ton of cloudberry preserve!
What can we learn from this whole episode?
Vitamin C Knowledge vs. Cloudberry Knowledge
Anton Howes has the main conclusion nailed:
It is possible to discover that a thing works, and even to use it for hundreds upon hundreds of years. But without knowing why it works, its potential will never be realised. In fact, the lack of understanding can make a perfectly useful method of solving a problem extremely vulnerable to being discredited and lost.
Scurvy was only truly defeated once we had an accurate theoretical framework for what caused it. Once you know exactly what causes it, you can go on multi-year voyages, you can go to the South Pole, you can go to space, all without worrying about scurvy. You just need to bring along some stable source of vitamin C.
It is true that the ancients had, through trial and error, found some ways of preventing and treating scurvy, but knowledge they acquired was in practice a bit more limited in utility than one might imagine.
For example, we might think, “the Norwegians knew centuries ago that cloudberry preserves prevented scurvy”, but that statement is far too broad to describe what was actually known at the time.
It might be more accurate to say “the Norwegians knew that Norwegian cloudberries, preserved and stored and the Norwegian way, when consumed in Norway during the Norwegian winter, prevented scurvy.” They had no way of knowing if their methods would work at all outside of Norway, or if they would work with any substitutions in the preparation process, or even if conditions might change somehow in Norway in the future to make their methods useless.
If this seems excessively nitpicky, consider what happened to the British. They figured out that lemon juice sourced from the Mediterranean and prepared and stored in a certain way works to prevent scurvy on long warm sea voyages. This was useful, but had some limitations:
First, you need a way of reliably sourcing incredible quantities of lemons every year, lemons being a fruit that only grows in warm Mediterranean climates.
Also, you need a way of consistently preparing and storing that much lemon juice, because you don’t know what parts of the preparation and storage process are crucial to its effectiveness.
Finally, if it stops working, you have no way of figuring out a potential alternative solution, or even of knowing if lemon juice was ever a key part of the solution in the first place.
In practice, their lemon juice solution eventually failed on all of these points: they had to switch to limes, the preparation and storage process broke down undetected, and they never managed to figure out an alternative to lime juice when polar expeditions revealed the gaps in their knowledge.
There is a massive gap between the utility of what we might call “vitamin C knowledge”, where we know precisely why and through what channels a solution works, and what we might call “cloudberry knowledge”, where we observe compelling evidence that a solution works in a specific environment, but without any idea why it works, or if it will work in any other environment, or even if the solution will be available in the future.
Even the most basic pieces of vitamin C knowledge are powerful when utilized correctly. We talk here sometimes about value investing, which as taught by Ben Graham in the 1930s, is simply based around the idea that stock represents ownership in a business, and that if you are able to estimate the cash that will be distributed to its owners in the future with any accuracy, you can use that knowledge to buy stock when it is cheap relative to projected future cash distributions.
There are a lot of ifs in that statement, but the statement itself is known to be correct. It must be true over time that the owners of a business will receive all of the cash distributed by the business, no more and no less.
Everyone else can trade in and out of their shares as they like, pursuing Keynes’ “beauty contest” of guessing the next meme stock or any other macro or trading strategy that strikes their fancy. If you can reliably buy undervalued stocks and hold them as long as necessary to realize their cash flows, you will make money at everyone else’s expense.
This particular bit of knowledge happens to be much more useful if fewer people believe it – after all, you need people to sell you the stock at attractive prices – but investors have used this simple insight to make money in the past, including Ben Graham himself.
Investors have to rely on cloudberry knowledge as well, approaches and relationships that they have found to work in practice, even if they don’t necessarily understand why. Some of these are statistical in nature, like the tendency of momentum stocks to outperform, while others are more qualitative, tendencies they have noticed from their extensive experience that they might talk about on Invest Like the Best.
We treasure the cloudberry knowledge we possess, which is often proprietary and learned from hard experience. But because we lack the “why”, the knowledge is evanescent. Specific investment strategies from the 1990s do not necessarily work at all today, while The Intelligent Investor is timeless.
The more quickly an environment changes, the more quickly that knowledge based only on specific experience will become obsolete. (We have all had the experience of receiving well-meaning but obsolete advice from our parents, and we can all look forward to dispensing the same to our own children.) Cloudberry knowledge is fantastic, but only if we understand its limits.
Vitamin C knowledge describes Elon Musk’s favored method of working through problems from “first principles”, stripping things down to the basic building blocks of theoretical knowledge we fully understand and know to be true, and working to solve problems from there. As the story goes, first principles thinking was key in building Tesla and SpaceX.
First principles thinking is an especially powerful tool for a new venture in a fast-changing market, which lacks the experience and know-how that incumbents possess, but will be unencumbered by increasingly obsolete processes and ideas.
False Theories
Here is Ceglowski’s top observation about scurvy, which is equally on the mark:
[F]rom the fifteenth century on, it was the rare doctor who acknowledged ignorance about the cause and treatment of the disease. The sickness could be fitted to so many theories of disease—imbalance in vital humors, bad air, acidification of the blood, bacterial infection—that despite the existence of an unambiguous cure, there was always a raft of alternative, ineffective treatments. At no point did physicians express doubt about their theories, however ineffective.
Before 1907, doctors never had an accurate theory of what caused scurvy. It would have been almost impossible given their knowledge of biology. Naturally, this did not stop them from coming up with inaccurate theories, and prescribing treatments based on those theories instead of the actual evidence.
This is a theme we have covered before, with the famous story of Ignaz Semmelweiss:
As a recent medical school graduate in Vienna in the 1840s, Semmelweis learned that the one of the two maternity clinics at his hospital had an extremely high mortality rate from childbed fever.
One day, his friend was accidentally cut with a scalpel during an autopsy and died of something similar to childbed fever. He realized that the maternity clinic with the high mortality rate was staffed with medical students who performed autopsies, and he worked out that childbed fever could be eliminated if doctors were forced to wash their hands before attending to patients.
He introduced hand washing to the maternity clinic, and childbed fever rates immediately plummeted. Armed with this evidence, he and his colleagues spread the word. To their surprise, they were met with ridicule and rejection from the leading doctors of the time.
The medical community objected that his explanation of how childbed fever is transmitted did not match leading theories of disease at the time (this was before germ theory was developed)...
Semmelweis eventually died in an insane asylum, and it would be decades before hand-washing was widely adopted in the medical community.
Humans are emotional creatures, and we get wrapped up in the stories we tell ourselves and the theories we embrace. They become part of our identity, central to our ego and our status in society. We are suckers for an attractive story, and we find it very comforting to believe that we understand something.
When confronted with incontrovertible evidence that our theories are wrong, do we just abandon them? Of course not. We dismiss the offending evidence, or we seek to find evidence that confirms our original theories. This is easier than one would think, especially if we are willing to use incorrect logic, or if we are intentionally careless about checking the veracity of any new “evidence” that supports our original, disproven theories.
In hindsight, it would have been best if everyone just admitted they had no verifiable theory for what caused scurvy, and simply proceeded based on the known effective treatments, which were plentiful going back for centuries: again, the word “antiscorbutics” was coined in the 1600s to describe foods that cured scurvy. Theories are valuable if they are true, but backfire if they are inaccurate.
It is very common to learn with a high level of certainty that something works, before knowing exactly why. That’s fine! Cloudberry knowledge might have its limits, but it is still effective. Solutions don’t stop working just because you don’t understand how they work. Especially when the stakes are life or death, it makes sense to go purely on the evidence collected.
No one needed to know about vitamin C to be able to treat scurvy with oranges, and no one should have needed to wait for germ theory before deciding to wash their hands before they delivered babies.
Even outside of medicine, false theories have always dictated human behavior long after they were disproven by real world evidence. As Keynes famously put it:
The ideas of economists and political philosophers, both when they are right and when they are wrong, are more powerful than is commonly understood. Indeed the world is ruled by little else. Practical men, who believe themselves to be quite exempt from any intellectual influences, are usually the slaves of some defunct economist. Madmen in authority, who hear voices in the air, are distilling their frenzy from some academic scribbler of a few years back.
Economics and investing are particularly fertile territory for disproven but seductive theories to gain popular traction. Economics also features complicated systems and confounding factors, which make it easier for people to “prove” any lie they wish with distorted statistics and incorrect logic. Thus people are able to justify their support of policies guided by their mistaken beliefs, policies which so often coincidentally happen to fulfill some selfish interest of theirs.
This newsletter has often looked at NIMBYism, which is based around a central myth that the quantity of housing we construct does not affect the price of housing or the quantity of housing we can consume, something that has been disproven by every careful study, as well as by basic logic. But NIMBYism is hardly unique – economic policymaking is dominated by incorrect populist theories that never seem to go away, from the lump of labor fallacy to greedflation.
Facts and Analysis
One painful recurring theme from the story of scurvy is that even with no knowledge of vitamins, people with authority often still had enough evidence about effective treatments to be able to control the disease, but they usually failed to successfully implement them.
The problem was not the failure to listen to experienced and credentialed practitioners. Reputable doctors published all sorts of misinformation for centuries, without a hint of self-doubt. James Lind had years of experience as a doctor at sea, and for most of his life, he propounded a completely useless treatment, “based on his own experience”.
As late as 1900, scientists were publishing papers that said things like: “Neither lime juice nor fresh vegetables will either prevent scurvy or cure it; it is a disease produced through the eating of tainted food.” Even after the solution was discovered, Fridjtof Nansen, a scientist and successful explorer, was still pushing a false theory based on incorrect logic.
How did all of these experienced and credentialed practitioners end up so far off base? We speculated previously that a likely cause was confirmation bias, and that is certainly part of it. However, an equally important likely cause is that they were not skilled or disciplined when it came to proper logical reasoning and analysis. There is nothing about first-hand experience or success that confers knowledge and wisdom by osmosis – it still has to be gained by disciplined study and correct analysis.
What worked to treat scurvy were careful studies and sound reasoning. Even if Lind’s supposed first clinical trial in history never happened, his immediate successors took a more rigorous approach. Here is what Baron tells us about Sir Gilbert Blane, the man who convinced the Royal Navy to adopt lemon juice in the 1790s:
Blane persuaded his admiral to instruct all ships’ surgeons to keep precise daily records of the numbers, diagnoses, and fates of sick sailors for Blane to tabulate…
[H]is colleagues admitted he was “a painstaking physician . . . he was so cold in temperament, that we called him “Chilblaine”...
Blane had a reputation in the navy of being unflappable, and his statistical analyses were unanswerable.
And here are Blane’s own words in 1799:
Lemon juice may be deemed a medicine . . . better as a dietetic modifying the alimentary matter. I am glad thus to escape from the slippery paths of theory, having no great confidence in the accuracy, nor the utility of such speculations.
That was all it took. Careful data gathering, careful reasoning, and the discipline to admit that he didn’t know what he didn’t know.
In a much different context, Ben Graham once said:
The stock investor is neither right or wrong because others agreed or disagreed with him; he is right because his facts and analysis are right.
What is true in finance is true in medicine, and is true everywhere else. Scurvy does not care about credentials, experience, past successes, or seductive stories. It only responds to effective treatments. If we truly desire to achieve a successful outcome, what matters most is that we get our facts and analysis right.
Further reading:
This essay is inspired by Plague of the Sea, a post written by Anton Howes last year. Even if you’re not sure if you’re interested in the history of innovation, you should consider subscribing to his Substack, which is consistently interesting and thought provoking.
Much of the history of scurvy in this essay comes from this excellent journal article published in 2009 by the late Jeremy Hugh Baron, a respected physician and writer.
The history of polar scurvy comes from Maciej Ceglowski’s excellent 2010 essay, which is very much worth reading in its entirety as well.
Great article!
I've seen before the 2 types of knowledge being called episteme (the humors/bacteria/vitamin C type of knowledge) and metis (the lemon/cloudberry type of knowledge).