00:00:00
Bloodletting, leeches, emetics, coffee
enemas, pretty much every weird old
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medical treatment you’ve heard of was
based off one idea — the four humors.
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When your blood, phlegm, black bile,
and yellow bile were in harmony,
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you were healthy. When they were imbalanced,
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you got sick. So doctors who used this theory
would try to fix you by balancing your humors.
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Too much blood? Let’s poke a hole in your
vein to let some out — that kind of thing.
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So today, I'm going go into depth about
how humoral theory became a thing,
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why it stayed around for so long even though it
didn’t work, and how it was eventually debunked.
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Part 1 | Hippocrates and Galen establish humorism
And to do that, we need to go all the way back to
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the very first systems of medicine, back
when your physician was also your priest.
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See for a long time most doctors around the world
used some version of faith healing. If you got
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sick, it was because you disturbed something
about the universe or got on the wrong side
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of some god. Then sometime around three to four
thousand years ago, early natural-philosophers
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started looking for ways to explain the universe
in terms of things they could look at and study.
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This wasn’t science yet per se, they weren’t
testing hypotheses, but it was revolutionary
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because for the first time, people were separating
phenomena into the things that they could explain,
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and the things that they couldn’t — what
were called the natural or the supernatural.
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By the 6th century BCE, a bunch
of scholars in Ancient Greece,
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or more technically modern day Turkey,
started thinking of the universe as a
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thing made of elements like Fire and
Water. And each of these elements had
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different properties, like fire was hot
and dry while water was cold and wet.
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The most popular version of this theory came
from a Greek philosopher named Empedocles,
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who described four elements — earth, water, wind,
and fire — each of which had opposing properties.
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So water opposed fire, and wind opposed earth.
You know, Avatar the Last Airbender stuff.
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These philosophers then applied this idea of
four elements to the human body and they got
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the four humors.Here's the idea: there
are four properties that describe four
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elements. Each element goes with one of the
four humors — blood, phlegm, black bile,
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and yellow bile. And just like the four elements,
each humor had the properties of that element:
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Phlegm was the humor of water, which
was cold and wet. Blood went with air,
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which was hot and wet. Black bile was cold and dry
and associated with earth. Finally, yellow bile
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was hot and dry and associated with fire.. Every
person had a naturally balanced humoral state,
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and when their humors were balanced, that person
was healthy. But, certain aspects of life like
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diet, exercise, or the weather could alter
the humors. And when they got out of balance,
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they manifested in the body as illness. But
this was just the Greek version of humorism.
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The traditional Indian system of medicine,
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Ayurveda, taught that the universe is made of
five elements (the four Greek ones plus ether,
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or space), and they imagined the body
was made of three doshas: vata, pitta,
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and kapha, which are kind of like their version
of humors. And just like the Greek humoral system,
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the Ayurvedics believe that health
comes from a balance of the doshas.
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Traditional Chinese Medicine, or
TCM uses a similar idea — there’s
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an energy called qi flowing
through the entire universe,
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there are five elements, and opposing
properties represented as yin and yang.
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So the Greeks weren’t using the humoral system
but a humoral system. The difference is that
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theirs was popularized by Hippocrates of Kos,
medicine daddy….sorry, father of medicine.
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Hippocrates gets credited with a lot,
but we actually don’t have a ton of work
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written by Hippocrates himself. Instead,
we refer to the body of work attributed
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to Hippocrates and his disciples, the
Hippocratics, as the Hippocratic Corpus.
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The Hippocratics documented a bunch of diseases
that they attributed to the humors. Like cancer
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was caused by an accumulation of black bile,
while pneumonia was too much phlegm. And you can
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imagine why they thought that. When someone gets
a cut, you can see blood leaving their body,
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or phlegm when someone had a runny nose, or
yellow bile when someone’s infected wound
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started draining pus. And black bile could
be a bunch of things — like dark vomit maybe.
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It’s easy to imagine someone getting severe
diarrhea and an old Greek guy saying “I don’t
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know how much of that fluid you’re supposed
to have, but you’ve got less of it now!”.
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The Hippocratics did a ton of observation
like this. They’d learn as much as they could
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about their patient’s habits, stress, living
situations, or travels all that so they could
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deduce the problem with their humors.
But the most important factor was diet.
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In their model, food was also made of
the elements and had those wet dry,
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hot cold properties. And the Hippocratics believed
when you ate something, your liver turned the food
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into a substance called chyle which then turned
into humors. Blood was made first, then phlegm,
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then yellow bile and finally black bile.
And according to the Hippocratic school,
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at the end of digestion, every humor was mixed
together in the veins into the substance that
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we’d recognize as blood today. Meanwhile,
a separate substance (that was kind of like air) called pneuma flowed
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through the arteries. And that gave food
a super important role within the humoral
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system. Every food literally became
the humors that determined your health.
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Knowing that this is how humorists thought disease
worked, their treatments make a little more sense.
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Like if you had too much blood, then it totally
made sense to poke a hole in your veins and
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let some out. Or if you have too much bile, it
totally makes sense to give you a substance that
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makes you throw up, or to give you a diuretic
to make you pee and balance out your phlegm.
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But more often, their go-to treatment was some
kind of dietary change. The same properties in
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foods that allowed them to cause disease
could also be used to design treatments.
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Not enough blood, and you’d be recommended
something hot and spicy to balance out the lack
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of heat from the blood. Meanwhile, something like
chamomile is cooling, so it would be the antidote
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to too /much/ blood. Likewise, foods like olives,
garlic, and onions had choleric properties,
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so they’d counter a build up of phlegm. But
foods like cucumbers or spinach had phlegmatic
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properties, they were cold and wet, so they’d
counteract too much yellow bile, or choler.
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Over time, scholars compiled these foods and
herbs into lists, which acted kind of like early
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pharmacology textbooks. And the most popular
of these books was De Materia Medica, which
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was compiled by Dioscorides, a Greek physician.
Materia Medica was the source on medical plants
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throughout the Renaissance, and it was all based
on what plants and foods balanced which humors.
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Your environment also had a big influence on
your health. In On Airs, Waters, and Places,
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a Hippocratic writer detailed how a place’s
Weather could influence humors. For instance,
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a hot summer could elevate
everyone in town’s yellow bile,
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which would lead to diseases like
dysentery, diarrhea, or malaria.
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Now, this is the version of the four humors
that survived, but back in Ancient Greece,
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they couldn’t actually agree on a single system.
Different thinkers listed anywhere from 4 up to 11
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humors. Some of the them believed the humors
were literal liquids moving around the body,
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while some thought they were
something more abstract. And
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plenty of thinkers back then weren’t
on board with humoral theory at all.
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Like two scholars in Alexandria
— Herophilus and his student
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Eristratus. These guys were active
a little after Hippocrates’s time,
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and they preferred dissecting human cadavers,
which was something the Greeks weren’t really
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down with. Herophilus and Eristratus rejected
humoral theory because they thought they’d
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find disease in the flesh and bones under
their knives, not flowing through the veins.
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Even though there were critics,
humoral theory stayed around,
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and one of the reasons it did was
actually Hippocrates’ son-in-law,
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Polybus. He documented the Hippocratic humoral
theory in a text called On the Nature of Man.
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He did such a thorough job and humorism became
so popular that writers in the second century
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CE wanted to change Hippocrates’ original work to
include Polybus’s updates. But without a doubt,
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the biggest factor in popularizing humoral
theory was the surgeon Claudius Galen.
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I covered Galen a bunch in my history of
dissection series, but long story short,
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he was this popular and influential surgeon
and scholar in the second and third century
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CE. He treated Roman royalty and gladiators,
which gave him the occasional peek inside a
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human body. And this, along with some animal
dissections, gave him enough observations to
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put together a model of human anatomy that became
the reference for the next 1300 years. Like he
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showed that arteries actually filled with
blood not air like the Hippocratics thought.
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I mean he efinitely wasn’t 100 percent
accurate, but we’ll get to that later.
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Galen was a humorist and a big fan of
Hippocrates, so when he looked inside a body,
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he looked at it through the lens of humoral
theory. And most of his actual doctoring was
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traditional humoral medicine too. Like
he’d feel for temperature and pulse,
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look at changes in skin color, or examine his
patients’ poop and pee to look for imbalances.
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Then he’d make a diagnosis and document. But
where Galen really pushed the humoral theory
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was in psychology. He popularized the idea
that your humoral balance influenced your
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personality and mood. He thought that too much
anxiety could create a build up of black bile,
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which he called melancholy. In Greek, melan
translates to Black, and chole to Bile. So
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melancholy, or what eventually got renamed
depression, owes its origin to the humors.
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The other humors had roles in your mental
health and temperament too. Like too much
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blood made you sanguine, yellow bile
made you colic, phlegm, phlegmatic.
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And since Galen thought about mental illness in
the same way as he thought of physical illness,
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Galen would treat everything with humoral
medicine. He’d modify diets and lifestyle
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factors, prescribe medicines
that made people poop or puke,
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and he was a big fan of bloodletting.
There’s a story of Galen letting out
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so much blood that a nearby doctor joked
that Galen “had slaughtered the fever”.
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Galen was massively popular while he was alive.
He even got a smallpox plague named after him,
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which is like, maybe not what you want
your legacy to be. But he was popular,
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in part, because he was a man of the people.
While Galen mostly treated athletes, royalty,
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and affluent men, he also treated
women and other normal civilians,
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and interacted with people of all socioeconomic
classes. And he supposedly never charged a fee.
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But what made Galen a legend was ultimately his
scholarship. He wrote more than any writer in
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antiquity, an estimated 600 treatises totaling
over 2.6 million words. That’s the equivalent of
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2 copies of the Harry Potter series worth
of work. And in a time before Wikipedia,
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that would’ve seemed like a comprehensive
account of the human body, which ended up
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being problematic, because nobody corrected
Galen’s work for over a thousand years.
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Part 2 | Challenging Galen
Galen’s popularity started
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declining a little by the 600s. But by
the 10th century, the Islamic world was
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enjoying their Golden Age, and scholars
in the eastern part of the Roman Empire
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started getting a lot more interested
in Ancient Greek and Roman scholarship.
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They already preserved a bunch of writings,
including Arabic translations of some of
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Galen’s writings, in a famous library, the
Bayt al-Hikma, or House of Wisdom, in Baghdad .
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But the Islamic scholars weren’t just
translating books. They were building
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on the old scholarship and adding their own
work . Like tenth century Persian Haly Abbas
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synthesized a bunch of old medical books
into “The Royal Book of All Medicine”
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It was a super valuable resource for medical
students at the time, and definitely based
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on the humors. Meanwhile, other books
offered criticism with their synthesis.
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Al-Razi, or Rhazes, wrote another
massive treatise called Kitab al-Mansuri,
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or what gets Latinized as the Almansor.
Like Haly Abbas, he synthesized Galen,
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Hippocrates, Indian scholars, and a few
others, but unlike his predecessors,
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he was critical of their work. Like he disagreed
with Galen about some specific neuroanatomy.
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Meanwhile, other Islamic scholars added
new knowledge, still using the humoral
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system. The most well known was Ibn Sina,
or Avicenna, who was a Persian philosopher,
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physician and polymath who wrote an influential
book called The Canon of Medicine.. And it’s
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textbook humoral medicine. He writes “every
organ is endowed with a hot, cold, moist,
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or dry temperament appropriate to its functional
requirements”. Like other humoral physicians,
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he’d feel the pulse, examine bodily
fluids, and use food and herbs in his
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treatments. Ibn Sina also added a ton
of his own observations into Canon,
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including a massive section on pharmacology
and diagnoses not even Galen had described.
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By the Renaissance, Canon of Medicine was
the second most printed book in Europe,
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just behind the Bible. That’s how
popular the humoral system was.
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These medieval medical books were
required reading at some of the
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first universities in the world like the
Al Quaraouiyine in modern day Morocco,
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or in some of the first European
universities like in Bologna. Which
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meant that university-trained physicians were
learning and practicing humoral medicine.
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Leeches are probably the most well
known of their treatments, and actually,
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leeches do have medical applications in
modern day, but back then, doctors would
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use them to balance out the blood humor. Then
there were less drastic, gentler remedies like
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the herbal remedies in Dioscorides’ old Materia
Medica. A popular treatment was black hellebore,
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a gorgeous but super poisonous flower that
medieval doctors would use to make you throw
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up. They might also prescribe something
from Pliny the Elder’s Natural History,
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a book that is so comically inaccurate that
I’m going to dedicate a future video to it.
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So at this point, it’s the early 1500s and we’ve
been bloodletting and purging people for over two
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thousand years. It doesn’t work, but it
survived because it was a big part of
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academic culture like we just saw, and
also a big part of religious culture.
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The humoral theory fit in really well within
monotheistic religion — especially with the
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Catholic Church, and in the Middle Ages,
you did not want to be a scientist who got
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on the church’s bad side. Just ask those guys who
thought the earth revolved around the sun. Plus,
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the Church had outlawed dissection, so any
anatomists that would have challenged
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humoralism didn’t have the chance to show
their work. But by the time of the Renaissance,
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the humoral theory was starting to fall apart
thanks to scientific advancements in Italy.
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Sometime in the 14th century, a few
anatomists started dissecting again,
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then soon after that it became mandatory in
medical schools. And by 1480, Pope Sixtus
00:12:52
the fourth... Pope Fourth's the Sixth?....
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Pope Sixtus the Fourth formally legalized dissection. You could say that dissection was…back on the table. [I'm so sorry for that]
00:13:01
The most important development
happened at the University of Padua,
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with an anatomist named Andreas Vesalius.
Like a lot of anatomists of the time,
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Vesalius started out as a fan of
Galen, and his first published work,
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Tabulae Anatomicae Sex, repeated a
lot of Galen’s anatomical mistakes,
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including the ones based on the four humors.
But as Vesalius did more and more dissections,
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he started to notice some inconsistencies
between Galen’s writings and his cadavers.
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So in 1543 he released this massive 7 book
series called De Humani Corporis Fabrica.
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And in it, he calls out some of Galen’s
mistakes and includes these massive,
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detailed illustrations. And it immediately became
the most important anatomy book of its time.
00:13:40
Now, Vesalius noticed something strange when it
came to the humors. He was able to find blood,
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even though he found some errors in Galen’s
descriptions of the heart. He was able to
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find yellow bile in the liver and gallbladder.
And he even found lymphatic vessels and lymph,
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which could’ve been interpreted as
phlegm. But he couldn’t find black
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bile. Vesalius wrote down his doubts, but
never published them which is kind of weird
00:14:01
from our perspective. He had no trouble
debunking the obvious, visible version of
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Galen’s anatomy. But when it came to the more
invisible physiology, he was more reserved.
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So Fabrica goes on to become one of the
most famous anatomy books of all time,
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and gives other anatomists
the idea that dissection and
00:14:16
observation were good and Galen and
humoral theory weren’t always right.
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Our next big shake up came in 1622, when
an anatomist named Gaspare Aselli was
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doing some dog dissections or more accurately,
vivisections — dissections on a living thing,
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which I know, seems brutal, but it was your
only option for seeing physiology in real
00:14:35
time back then. After all, you couldn’t see a
ton of activity if all you had was a corpse.
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So one day, Aselli noticed this clearish
white substance leaking out of the dogs’
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lymphatic vessels. He called these structures
lacteal vessels since the fluid looked like
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milk. Aselli noticed that these vessels
filled up right after digesting food,
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but were otherwise empty most of the time. And
while he ended up interpreting his findings wrong,
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this experiment inspired future
anatomists to connect these vessels
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to a larger system of vessels that
we now know as the lymphatic system.
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But this meant that there were humors flowing
through the body in vessels other than the veins,
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which contradicted Galen’s model
of humor transport. Remember,
00:15:10
the humoral theory said that every humor got
mixed up and distributed through the veins,
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which Galen said originated in the liver.
00:15:16
And ever since the resurgence
of dissection, anatomists were
00:15:19
noticing more inconsistencies with Galenic
anatomy, especially in the circulatory system.
00:15:25
Vesalius showed that the vena
cava, the widest vein in the body,
00:15:28
did not in fact originate in the
liver, and a Spanish anatomist got
00:15:32
really close to correctly figuring out
how the pulmonary blood vessels worked.
00:15:35
But it was an English scientist
named William Harvey who made the big
00:15:39
breakthrough. Harvey continued contemporary
cardiovascular curiosity and systematically tested
00:15:45
both humans and animals, recorded his observations
and published them in 1628’s An Anatomical Essay
00:15:52
Concerning the Movement of the Heart and the Blood
in Animals, or what gets called De Motu Cordis.
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His big takeaway was that blood stayed
in circulation unless it was let out.
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It was a closed system and the heart acted like
a pump that moved all the fluid around. This dude
00:16:07
invented modern cardiology and destroyed humoral
theory in the process. Like he calculated that It
00:16:12
wasn’t mathematically possible for the food we ate
to be turned into blood like Hippocrates thought.
00:16:18
To quote Harvey: “The beat of the heart is continuously driving through that organ more blood
00:16:22
than the ingested food can supply, or all the
veins together at any given time contain”.
00:16:27
He was saying that our veins would literally burst open if
our food turned into humors. And this meant that
00:16:32
one, Bloodletting wasn’t releasing a surplus of
blood, it was wasting a fixed resource, and two,
00:16:38
humoral theory couldn’t be right because it said
that blood was constantly in and out of balance.
00:16:43
Now, histories of humoral theory usually end
here. Harvey and all these past scientists had
00:16:48
shown without a doubt that humoral theory
didn’t work. But it wasn’t that easy.
00:16:51
Yes, they revolutionized how physicians
understood healthy bodies, but physicians
00:16:56
still didn’t understand how healthy bodies
became diseased bodies. So for the time being,
00:17:01
humoral theory was still the best
model they had for understanding
00:17:05
illness. Like Aselli thought that
maybe build up of lymph could become
00:17:08
cancer — which was basically Galen’s idea
but substituting black bile with lymph.
00:17:13
We would need an entirely new way of
thinking about the physiology of disease.
00:17:17
We would need to invent pathology.
Part 3 | Foundation of Pathology
00:17:19
If you wanted to figure out where disease
came from back then, you had one real option:
00:17:24
record someone’s symptoms when they were alive,
00:17:26
then wait for them to die and poke around
their body looking for anything out of place.
00:17:30
In the 1670s, a physician named
Théophilus Bonet used this method
00:17:34
to write thousands of case reports
and compile them into a big book.
00:17:37
17th century physicians might
have used it as a reference book,
00:17:40
but according to an article in Clinical
Cardiology, the book was pretty much useless.
00:17:44
“There were several deficiencies in the
Sepulcretum [Bonet’s book] which made the
00:17:49
work virtually useless to scholars. These
included misquotations, misinterpretations,
00:17:53
inaccurate observations, and the lack of a proper
index”. And in 1740 an Italian anatomist named
00:17:59
Giovanni Batista Morgagni is like “yeah, I can’t
use this book” and decided to make his own. He
00:18:05
actually worked at the University of Padua, the
same university that Vesalius did. So over the
00:18:09
next 20 years, Morgagni compiled hundreds of case
reports along with two big pieces of information:
00:18:14
the patients’ symptoms while they were alive,
and what doctors found in their bodies during
00:18:18
autopsy. Like take the case of “the wife of a
certain painter at Padua, of forty years of age,
00:18:23
and the mother of four children” who “began
to complain of a palpitation at her heart,
00:18:28
with which she was troubled to the
very day of her death”...”as to the
00:18:31
other symptoms which attended the disorder,
an oedemous tumor began also to come on,
00:18:36
that was particularly conspicuous in the
lower limb on the right side and by this,
00:18:40
among many even eminent physicians, the opinion
of an aneurysm of the aorta was confirmed”.
00:18:45
Unfortunately, this woman didn’t turn out so hot,
because “Others, on the contrary…attributed all
00:18:51
these symptoms of a hysterical disorder…and
while these controversies were agitated,
00:18:55
the woman, finally, having her pulse already
diminished, died as she was speaking”.
00:19:00
Basically, doctors argued whether this
woman was crazy or not and it turns out
00:19:03
not. But hey, now that we’ve got a
dead body, it’s time to open it up.
00:19:07
If you’re wondering, ethical
review boards didn’t exist yet.
00:19:10
“Both the cavities of the thorax,
but particularly the right,
00:19:13
contained a considerable quantity of water,
which had not the least disagreeable smell”.
00:19:17
“I looked upon this artery and the heart
externally, and compared them one with another,
00:19:21
and with the other parts of the body, the artery
seemed to be somewhat more contracted than it
00:19:26
ought to be, and the heart enlarged, yet neither
in a very great degree. The heart being soon
00:19:31
dissected…I observed that the corpuscles in the
middle of the border of the valves, placed at
00:19:36
the beginning of the arteries, were harder, and
at the same time larger, than they usually are”.
00:19:40
I’m glossing over some details, but you get the
idea: symptoms followed by autopsy information.
00:19:44
Morgagni compiled 20 years of these into a 5 book
series that he published in 1761 called On the
00:19:51
Seats and Causes of Disease, or what sometimes
gets called its Latin name of De Sedibus.
00:19:55
So what made this a big deal? And what
does it have to do with the humors?
00:19:59
Well, throughout all his observations,
Morgagni noticed a link between some
00:20:02
kind of pathologic anatomy during autopsy, and
the patient’s symptoms while they were alive.
00:20:06
So he concluded that the patients’ symptoms were
caused by damage to specific organs, not humors.
00:20:12
And this seems super obvious with
our understanding of disease today,
00:20:15
but back then this was a massive deal. According
to humoral theory, disease was system wide because
00:20:21
humors flowed through your entire body, but here
was Morgagni showing disease could be localized.
00:20:25
As Morgagni said, each symptom was “the
cry of the suffering organs”. Which is
00:20:31
an absolutely incredible line. I love it so much.
00:20:33
This kind of case study of symptoms
followed by autopsy results got much
00:20:37
more popular after Morgagni. But there
was an exception I want to talk about.
00:20:40
This is Scottish anatomist Matthew
Baillie. In the late 1700s,
00:20:45
he was interested in pinpointing
disease in the body, so like Morgagni,
00:20:49
he took symptoms while a person was alive and did
an autopsy. But unlike pathologists of his time,
00:20:54
his work centered the pathologic anatomy,
not the patient’s story or treatment.
00:20:59
In his own words “The object
of this work is to explain,
00:21:02
more minutely than has hitherto been done,
the changes of structure arising from morbid
00:21:07
actions in some of the most important parts of
the human body. This, I hope, will be attended
00:21:12
with some advantages to the general science
of medicine, and ultimately, its practice”
00:21:16
Baillie thought that a deeper understanding
of the “morbid anatomy” as he called it,
00:21:21
would help doctors understand how that change
in the organs caused symptoms, and eventually
00:21:25
how they could come up with treatments. So in
1793, he released this massive book called The
00:21:31
Morbid Anatomy of Some of the Most Important
Parts of the Body. And in it, he describes a
00:21:35
bunch of different diseases. Among them were
different types of tumors and none of them
00:21:40
looked anything like what they imagined black bile
to be. That was Strike 2 against Galenic causes of disease.
00:21:46
This was a big deal because now instead
of thinking of cancer as just part of
00:21:50
your personality, we could imagine
cancer as physical tumors that could
00:21:55
be removed from the body. We’ll see
this in my video about breast cancer,
00:21:58
but this is when cancer surgery starts to
take off, and not entirely for the better.
00:22:02
At this point, we’re finally starting to
replace humoral theory’s idea of disease.
00:22:06
We kept narrowing it down from system wide, to
organ level, to tissue, but we’d still need to
00:22:12
get even smaller. And for that, we would need
microscopes. You probably learned about
00:22:17
Robert Hooke and Antonie van Leeuwenhoek in
middle school science class, they get credited
00:22:21
with popularizing microscopes and discovering
cells back in the 1600s. For now, just know that by
00:22:26
the end of the 1700s, scientists knew that cells
existed and that there were microbes everywhere.
00:22:30
And then by the beginning of the 1800s, most
doctors knew their way around a microscope.
00:22:35
But we still didn’t really know the
cell’s role in pathology And that’s
00:22:38
where these two Germans come in: Matthias
Jakob Schleiden and Theodor Schwann.
00:22:42
(I'm certainly butchering that German)
00:22:44
Schleiden was a scientist who spent years
looking at plants under the microscope, and in doing so, proposed that
plants are made up of cells.
00:22:51
He wasn’t the first to propose that a big
life form was made up of tiny life forms,
00:22:55
but he for sure popularized it. And one day, he
had dinner with our other German, Theodor Schwann,
00:23:01
who anatomy students might recognize as the
namesake behind the Schwann cells around nerves.
00:23:05
Schwann basically copy pasted Schleiden’s
observations about plants to animals and
00:23:10
thought that the human body must be composed
of cells too. And in 1839, both men published
00:23:15
their respective work that became the
foundation of an idea called cell theory.
00:23:19
They came up with three main tenets for cell theory: Number one,
all living things are made of one or more cells,
00:23:25
and number two, the cell is the
most basic unit of life. Number
00:23:29
three was that cells formed from a kind
of crystallization process, which isn’t
00:23:33
really a thing. The crystallization idea was
debunked by a team of other German doctors,
00:23:37
one of whom was Rudolf Virchow.
He applied this new idea of cell
00:23:42
theory to the field of pathology to
get a new field — cellular pathology.
00:23:46
Virchow’s experiments were kind of like Morgagni
and Baillie’s but microscopic. He’d take cell
00:23:51
samples from patients with a disease, look
at them under a microscope, and compare them to
00:23:55
healthy cells. This means he didn’t have to do a
full autopsy, which is great. No corpses required.
00:24:00
Virchow spent years studying
and lecturing on the topic,
00:24:03
and published a massive collection of
his lectures in 1858 titled Cellular
00:24:07
Pathology as bases upon physiological
and pathological histology. I’ve linked
00:24:11
a pdf and all my other sources in the
description if you want to check them out.
00:24:14
He spends the first Lecture explaining the logic
for cellular theory, and giving the history of
00:24:18
Schleiden and Schwann. But from there, it’s
a lot like a modern pathology book — again,
00:24:22
doesn’t seem out of the ordinary by our standards,
but this was a brand new thing back then.
00:24:26
What I love thought is that Virchow knew
he was writing something important.
00:24:31
In the preface, he writes that cellular pathology
00:24:33
is “in opposition to the one-sided
humoral and neuristical (solidistic)
00:24:38
tendencies which have been transmitted
from the mythical days of antiquity”.
00:24:42
Humoral theory was dead, and we finally
had the anatomical and pathological
00:24:46
replacements for it. Unfortunately,
cell theory had a major weak point.
00:24:50
It couldn’t explain why a bunch of different
people living in the same area would get sick with
00:24:55
the same disease at the same time. For that, we’d
need an entirely separate revolution in medicine.
00:25:01
We would need germ theory. Check out this
video if you want the next part of this story.
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