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You can go to linode.com/scishow to learn more and get a $100 60-day credit on a new Linode account. [♪ INTRO] Smart people can make misguided decisions just like the rest of us. Some extreme examples are the scientists who used their own bodies as subjects in their experiments.

Now, in some cases, these scientists earned the Nobel Prize. But in other cases, these experiments led to their death. So don’t try it at home!

They did these high stakes experiments so you don’t have to. Regardless of how the experiment ended for the researcher, each of their sacrifices led to a new scientific discovery. I’m your host, Stefan, and here are our scientists: In 1923, George de Hevesy published his observations on how a substance can be traced as it passed through a plant, from absorption to metabolic breakdown.

And to do that, he used radioactive lead. Plants can absorb lead through soil or water, so he just had to “feed” lead that contained radioactive isotopes to a plant, and then take samples from different parts of the plant to identify which areas of the plant contained the lead and which didn’t. He used this method to determine where the lead went once it was absorbed by the plant.

After 22 hours, he found that most of the lead remained in the roots, followed by a much smaller amount in the fruit, an even smaller amount in the stem, and the smallest amount in their leaves. He concluded that when exposed to dilute solutions of lead, plants will use their roots to absorb the lead and keep it from reaching other parts of the plant. Now, once he figured out how lead moves through a plant, he decided to use a similar technique to determine how molecules of water move through a human.

For this study, instead of lead isotopes as his tracer he used heavy water. Heavy water isn’t radioactive, but it has properties that make it equally easy to track. That’s because heavy water is water that contains deuterium instead of hydrogen.

Deuterium is an isotope of hydrogen that has a proton in its nucleus just like hydrogen, but it also has a neutron in there. This extra particle makes deuterium denser than hydrogen, thus the name “heavy water.” And then Hevesy, or maybe his assistant, named Erich Hofer, drank the heavy water. It’s a bit of a mystery which one of them was the test subject, because the paper they published together was careful not to disclose that detail.

But one of them drank different amounts of heavy water and then had their pee sampled afterward. Because, after all, your pee is mainly water. So after you drink tap water, your pee has almost the same density as the tap water itself.

But if you drink heavy water, your pee becomes denser. How dense depends on the percentage of heavy water to regular water in your body. Since density is mass divided by volume, all they had to do was take note of how much pee they collected after drinking heavy water and weigh the samples.

Easy as one, two, pee. So after drinking different amounts of heavy water, Hevesy and Hofer found that water stays in a human body for days. They calculated that it should take about nine days for half of the heavy water to leave the body.

And while Hevesy and Hofer didn’t report any negative effects from drinking heavy water, later experiments on mice showed that a large enough quantity could be lethal. So it didn’t kill them, but theoretically it could have at high enough doses. But instead, nine years later, Hevesy won a Nobel Prize, primarily for the lead isotope tracer technology that led to this self-experiment.

Hofer got nothing but a publication out of it. Although, the experiment didn’t kill him, so there’s that. Now onto another person who liked to consume things from the lab: Carl Wilhelm Scheele, who worked with cyanide and arsenic.

We have a lot of laboratory guidelines today that tell us not to eat the chemicals we make in the lab. But in the 1700s, Scheele likely considered it a part of the job. Back then, scientists didn’t have many of the fancy chemical identifying machines that we have today.

So, when Scheele completed a chemical reaction, he studied the products of that reaction by sniffing them, and tasting them! One of his projects involved finding ways to synthesize oxygen gas. He did that by heating up compounds like silver carbonate to break it down into silver, carbon dioxide, and oxygen.

So then he separated out the oxygen, sniffed it, tasted it, and sensed… nothing. Which is how he figured out that oxygen is an odorless, tasteless gas. He was the first person to describe oxygen’s sensory properties.

And he didn’t stop at oxygen. He discovered and possibly sampled at least seven elements and 18 compounds. So these risky methods were working for him… until they didn’t.

Scheele also taste-tested other compounds, like copper arsenite, which is a poisonous green pigment now known as Scheele’s Green, and hydrogen cyanide. At the age of 43, Scheele died, possibly from overexposure to arsenic and cyanide. But he seemed to consider it the table stakes of his profession.

And we’re definitely better off knowing about oxygen. Now another Karl in science history took a different approach. Instead of sniffing and tasting the chemicals in his lab, Karl Landsteiner experimented on his own blood and the blood of his peers.

He did that to figure out why blood transfusions sometimes fail. In 1901, people knew that when you give a human some blood from, say, a sheep, it often clumped up and ended in death. They understood that the blood of different animals can be incompatible with ours.

But what they didn’t know was why the blood from two different humans could also be incompatible. To try to figure that out, Landsteiner drew blood from himself and five of his colleagues. Now, thankfully, he tested the blood after he removed it from his subjects’ bodies, so the risk was already lower than it was for some of the other researchers on this list.

First, he noted that each blood sample was totally fine when it was just exposed to the blood cells of that same person. But then, he started mixing samples from different people. And that’s when it was a really good thing that they did this experiment outside of their bodies.

Landsteiner combined the blood from one of his colleagues with the blood of another, and noticed that the mixture started to form visible clumps. The team decided to call these two blood types A and B. What they found was that different types of blood contain their own specific antigens, which were in turn recognized by the other blood type’s antibodies.

The response of the antibodies to those antigens resulted in the clumping. So when you mix type A with type A or type B with type B, everything flows smoothly. But not so much when type A mixes with type B.

AND! When Landsteiner added both of the other kinds of blood to his own, there was also clumping! Which meant he couldn’t have type A or type B, because they both produced a response from his blood’s antibodies.

It turned out that Landsteiner’s blood was a third type. His blood had the antibodies against both type A and type B blood but had no antigens to provoke either A or B antibodies. So they eventually called it type O, short for Ohne, which means “without” or “zero” in German, and it’s now considered the universal donor type.

Now, there’s also a blood type called AB that can accept a transfusion from anyone else because it doesn’t have antibodies against any other blood type. But none of the scientists that Landsteiner sampled in this experiment happened to be type AB, so that type wasn’t discovered for another year. If Landsteiner had done experimental transfusions, well, he would have died.

Because type O folks are universal donors, but not universal recipients. And some of his colleagues would have died as well, depending on what type of blood they got. Because when incompatible blood types mix, the blood clumps up and gets destroyed by the immune system so it can’t do its job.

But by conducting experiments on a sample from himself, he lived to publish the tale and earned a Nobel Prize for that work. He even lived 13 more years, until he died in his lab from an unrelated heart attack.. Now, Daniel Carrion, on the other hand, gave himself the full body treatment.

Back in 1885, Carrion was working to understand verruga peruana. It’s a chronic disease that literally translates to “Peruvian warts” because it’s endemic to Peru and patients have bumps on the skin. He wanted to identify the symptoms and stages of verruga peruana, and he couldn’t do that because most patients who reached the acute stage of the disease either recovered or died before they could get to the hospital.

So, since the disease is rarely fatal, Carrion figured the best way to study it was to inoculate himself with the juices from a lesion on a patient’s face. And it definitely gave him some symptoms to study, but they didn’t match up with what was known about verruga peruana. As his illness progressed, Carrion and his doctors took detailed notes of his fever, anemia, and other symptoms.

And they were much more aligned with a seemingly unrelated illness called Oroya fever. Now, verruga peruana and Oroya fever have totally different symptoms. Oroya fever is very quickly deadly, while verruga peruana is rarely fatal.

But, as Carrion showed in this experiment, these two diseases are really two stages of the same illness. Some people are killed by the first acute phase, while others live through it to later develop the chronic lesions. And some people go straight to the verruga stage without an acute fever.

It’s still not entirely clear what leads Oroya fever to such drastically different outcomes. It’s possible that it comes down to each individual’s immune system. But today, we know that both stages are caused by the same bacterium, which infects human blood cells and makes dangerous proteins that trigger the cells to break apart.

So we can usually treat it with antibiotics. However, Carrion never took these antibiotics because people didn’t know at the time that it was a bacterial disease. And, even if he did, antibiotics didn’t exist yet.

So a few weeks after he gave himself Oroya fever, it killed him. But his experiment provided a link between the two stages of a complicated disease. Now our last scientist for today, Niels Finsen experienced symptoms of a condition known as Niemann-Pick disease starting when he was at least 23 years old in 1883.

It’s a degenerative disease that thickens the connective tissue in your organs, making it hard for them to function. Finsen showed signs of heart trouble, which may have been due to plaque buildup in his arteries. But this disease led him to what would become his entire career in research, specifically an interest in phototherapy, or the therapeutic use of light in the treatment of certain diseases.

He first started experimenting on himself by sunbathing in the hopes that it would alleviate his symptoms. But he didn’t record his experiences, so it’s hard to say whether or not it worked. People had been studying the bacteria-killing effects of light since at least the 1880s.

And Finsen made it his mission to determine which wavelengths of light brought about positive effects so he could reduce the negative effects like burning your skin. And those experiments resulted in the creation of an artificial light that had the bacteria-killing effects of UV rays without burning the skin the way natural light would. Aside from looking for a cure for his own disease, he used himself as a subject in calibration tests to see how much exposure you could get before causing a condition called erythema, or a flushing of the skin, which is different from your run-of-the-mill sunburn.

While he was unable to cure himself of Niemann-Pick disease, by 1902, the Finsen Institute, which he started, used phototherapy to cure over 400 people of the condition known as lupus vulgaris, which is a painful skin infection caused by tuberculosis. And for that work, he was awarded the Nobel Prize in 1903. He then continued to research a cure for himself until the day he died, one year later, at age 44.

Finsen is the perfect researcher to end this list of self-experimenters, because he first experienced symptoms of the disease that led to his death at the start of med school, before he started conducting his experiments. So rather than the experiment causing his death, the ultimate cause of his death actually led him to self-experiment. In the end, all of these scientists were just looking for answers.

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