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YouTube // Tom Scott
YouTube // Tom Scott

What Causes 'Floaters' and Other Visual Phenomena?

YouTube // Tom Scott
YouTube // Tom Scott

You may have seen "floaters" in your vision, especially if you look at a blank wall or a bright blue sky. What are they? And should we be worried about them? What about visual snow, phosphenes, and the blue entoptic phenomenon? Although you may not recognize all the names, chances are you've seen most of these at some point—and now Inés Dawson will explain them in depth. Enjoy:

If you want more detail on this topic, or video isn't your thing, read this blog post by Dawson going into vastly more depth. For more videos from Dawson, check out her channel Draw Curiosity.

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Mary-Lynn, Flickr, CC BY 2.0
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11 Primal Facts About Dian Fossey
Mary-Lynn, Flickr, CC BY 2.0
Mary-Lynn, Flickr, CC BY 2.0

Born in San Francisco on January 16, 1932, Dian Fossey came from a world far removed from the dense jungles of East Africa. She discovered that environment in her thirties and spent the final decades of her life studying the gorillas that lived there. From her groundbreaking primatology work to her mysterious death, here are 11 facts about the scientist behind Gorillas in the Mist.

1. HER LOVE OF ANIMALS BEGAN WITH A PET GOLDFISH.

Though she went on to become one of history's most famous animal-lovers, Fossey didn't grow up in a pet-friendly household. The only animal she was allowed to keep as a child was a single goldfish. She loved her fish, but when it died, her parents barred her from getting another animal to replace it. Even a pet hamster offered to her by a classmate was forbidden from entering the house.

2. SHE WAS A PRIZE-WINNING EQUESTRIAN.

Not permitted to keep pets in the home, Fossey nurtured her passion for animals through equestrianism. She received her first horseback-riding lesson at age 6. By the time she reached her teen years, she was advanced enough to merit an invitation to join the riding team at Lowell High School in San Francisco. Her hobby earned her several awards and pushed her to pursue an education in animal husbandry at the University of California, Davis. Even after she'd shifted career aspirations to occupational therapy, Fossey chose to move to Kentucky to be closer to farm life.

3. SHE SPENT HER LIFE SAVINGS ON HER FIRST TRIP TO AFRICA.

Dian Fossey was 31 when she first stepped foot on the continent where she'd complete her most important work. Inspired by a friend's trip to Africa, she collected her life savings (about $8000), took out a three-year bank loan, and planned a seven-week trip through the wilderness of Kenya, Tanzania, Congo, and Zimbabwe. On her adventures there she met Louis Leakey, the anthropologist famous for sponsoring the all-woman trio of primatology pioneers (the "trimates") that included Jane Goodall, Biruté Galdikas, and eventually Dian Fossey herself. It was also during this period when Fossey saw gorillas in the wild for the first time. She met wildlife photographers Joan and Alan Root and joined them on an expedition to photograph the animals in the Congolese mountains. The vacation wasn't scientific in nature, but as Fossey later wrote, "The seed was planted in my head, even if unconsciously, that I would someday return to Africa to study the gorillas of the mountains."

4. SHE PROVED HER DEDICATION WITH AN APPENDECTOMY.

Leakey reconnected with Fossey back in the States in 1966. The anthropologist had spent the last several years supporting his former secretary Jane Goodall in her chimpanzee research, and now he was in search of a candidate to do for gorillas what Goodall had done for chimps. After getting to know Fossey better, he decided she was the right woman for the job. He offered to gather the funding for her trip back to Africa, but before she left she would need to remove her appendix as a precaution. This didn't scare her off. When Leakey wrote six weeks later to say the surgery wouldn't be necessary and he had just wanted to make sure she was committed, she was already appendix-less.

5. HER FIRST RESEARCH EXPEDITION ENDED ABRUPTLY.

Fossey returned to the Congo toward the end of 1966—just months before a civil war erupted in the already volatile region. Rebel soldiers captured her at her base camp in July 1967. After spending two weeks in military detainment, she was able to bribe her way out with promises of cash and her Land Rover. The guards agreed to drive her to Uganda, and shortly after they arrived, she had them arrested. After the scare, Fossey was ready to resume her research almost immediately: This time she set up camp in Rwanda, ignoring warnings from the U.S. Embassy.

6. SHE UNCOVERED THE GORILLAS' TRUE NATURE.

Prior to Fossey's research, the public viewed gorillas as beasts similar in temperament to King Kong. She quickly disproved the notion that gorillas were bloodthirsty animals that would attack humans when given the chance.

To infiltrate their society, she adopted their habits. Walking on her knuckles and chewing on celery stalks allowed her to gain the apes' trust. As long as she maintained a nonthreatening profile and made her presence known at all times, she was safe around the gentle behemoths. Today we know that despite their intimidating size, gorillas are some of the least violent members of the great ape family.

7. SHE EARNED A UNIQUE NICKNAME FROM LOCALS.

Dian Fossey spent enough time at her research center in Rwanda to garner a reputation. To the locals she was Nyiramachabelli, a Swahili name that when roughly translated means "the woman who lives alone on the mountain."

8. SHE USED THE GORILLAS' NOSES TO TELL THEM APART.

Many of the gorillas Fossey studied were given names, such as Peanut, Rafiki, and Uncle Bert. Fossey used another method to tell her subjects apart: She drew sketches of their noses. Each gorilla has a unique pattern of wrinkles around its nose that makes it easy to identify. These nose prints are the equivalent of fingerprints in humans, but instead of getting up close to study them, Fossey was able to document them from far away using binoculars and a sketchpad.

9. ONE OF HER GORILLAS IS ALIVE TODAY.

Hundreds of gorillas made it into Dian Fossey's body of research. In 2017, only one specimen from that original pool is still alive. Poppy was born into a group of gorillas on Fossey's radar in 1976. The researcher documented the animal's birth and childhood in her journals. Today, at 41, Poppy is the oldest gorilla currently monitored by the Dian Fossey Fund.

10. HER WORK IS THE SUBJECT OF A BOOK, A MOVIE, AND AN OPERA.

In 1983, Fossey published the book that helped make her famous. Gorillas in the Mist is the autobiographical account of her first 13 years in the African jungle and the scientific discoveries she made about the gorillas living there. The title went on to become a bestseller. Five years later, Sigourney Weaver starred as Fossey in a film of the same name. The biopic snagged five Oscar nominations and converted Weaver into a gorilla conservationist.

There's another dramatization of Fossey's life that's not so widely known: In 2006, the Kentucky Opera VISIONS! program staged an opera called Nyiramachabelli—a nod to the researcher's nickname.

11. HER DEATH REMAINS A MYSTERY.

Next to her groundbreaking gorilla research, Fossey is perhaps best known for her mysterious and tragic murder. On December 27, 1985, she was found dead in her cabin at her Rwandan research camp. The cause of death was a machete blow to the head, but the identity of her assailant remains unknown to this day. (A Rwandan court convicted in absentia her American research assistant, Wayne McGuire, for her murder and sentenced him to death. McGuire, who fled Rwanda before the conviction, has always maintained his innocence.) Fossey was buried in the nearby mountains beside the grave of her favorite gorilla Digit, who had been slaughtered by poachers years earlier. Before she was killed, Fossey wrote one final entry in her diary. It reads:

“When you realize the value of all life, you dwell less on what is past and concentrate on the preservation of the future.”

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The Body
12 Fantastic Facts About the Immune System
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The human body is an amazing thing. For each one of us, it's the most intimate object we know. And yet most of us don't know enough about it: its features, functions, quirks, and mysteries. Our series The Body explores human anatomy, part by part. Think of it as a mini digital encyclopedia with a dose of wow.

If it weren't for our immune system, none of us would live very long. Not only does the immune system protect us from external pathogens like viruses, bacteria, and parasites, it also battles cells that have mutated due to illnesses, like cancer, within the body.

Here are 12 fighting facts about the immune system.

1. THE IMMUNE SYSTEM SAVES LIVES.

The immune system is a complex network of tissues and organs that spreads throughout the entire body. In a nutshell, it works like this: A series of "sensors" within the system detects an intruding pathogen, like bacteria or a virus. Then the sensors signal other parts of the system to kill the pathogen and eliminate the infection.

"The immune system is being bombarded by all sorts of microbes all the time," Russell Vance, professor of immunology at University of California, Berkeley and an investigator for the Howard Hughes Medical Institute, tells Mental Floss. "Yet, even though we're not aware of it, it's saving our lives every day, and doing a remarkably good job of it."

2. BEFORE SCIENTISTS UNDERSTOOD THE IMMUNE SYSTEM, ILLNESS WAS CHALKED UP TO UNBALANCED HUMORS.

Long before physicians realized how invisible pathogens interacted with the body's system for fighting them off, doctors diagnosed all ills of the body and the mind according to the balance of "four humors": melancholic, phlegmatic, choleric, or sanguine. These criteria, devised by the Greek philosopher Hippocrates, were divided between the four elements, which were linked to bodily fluids (a.k.a. humors): earth (black bile), air (blood), water (phlegm) and fire (yellow bile), which also carried properties of cold, hot, moist, or dry. Through a combination of guesswork and observation, physicians would diagnose patients' humors and prescribe treatment that most likely did little to support the immune system's ability to resist infection.

3. TWO MEN WHO UNRAVELED THE IMMUNE SYSTEM'S FUNCTIONS WERE BITTER RIVALS.

Two scientists who discovered key functions of the immune system, Louis Pasteur and Robert Koch, should have been able to see their work as complementary, but they wound up rivals. Pasteur, a French microbiologist, was famous for his experiments demonstrating the mechanism of vaccines using weakened versions of the microbes. Koch, a German physician, established four essential conditions under which pathogenic bacteria can infect hosts, and used them to identify the Mycobacterium tuberculosis bacterium that causes tuberculosis. Though both helped establish the germ theory of disease—one of the foundations of modern medicine today—Pasteur and Koch's feud may have been aggravated by nationalism, a language barrier, criticisms of each other's work, and possibly a hint of jealousy.

4. SPECIALIZED BLOOD CELLS ARE YOUR IMMUNE SYSTEM'S GREATEST WEAPON.

The most powerful weapons in your immune system's arsenal are white blood cells, divided into two main types: lymphocytes, which create antigens for specific pathogens and kill them or escort them out of the body; and phagocytes, which ingest harmful bacteria. White blood cells not only attack foreign pathogens, but recognize these interlopers the next time they meet them and respond more quickly. Many of these immune cells are produced in your bone marrow but also in the spleen, lymph nodes, and thymus, and are stored in some of these tissues and other areas of the body. In the lymph nodes, which are located throughout your body but most noticeably in your armpits, throat, and groin, lymphatic fluid containing white blood cells flows through vein-like tubules to escort foreign invaders out.

5. THE SPLEEN HELPS YOUR IMMUNE SYSTEM WORK.

Though you can live without the spleen, an organ that lies between stomach and diaphragm, it's better to hang onto it for your immune function. According to Adriana Medina, a doctor who specializes in hematology and oncology at the Alvin and Lois Lapidus Cancer Institute at Sinai Hospital in Baltimore, your spleen is "one big lymph node" that makes new white blood cells, and cleans out old blood cells from the body.

It's also a place where immune cells congregate. "Because the immune cells are spread out through the body," Vance says, "eventually they need to communicate with each other." They do so in both the spleen and lymph nodes.

6. YOU HAVE IMMUNE CELLS IN ALL OF YOUR TISSUES.

While immune cells may congregate more in lymph nodes than elsewhere, "every tissue in your body has immune cells stationed in it or circulating through it, constantly roving for signs of attack," Vance explains. These cells also circulate through the blood. The reason for their widespread presence is that there are thousands of different pathogens that might infect us, from bacteria to viruses to parasites. "To eliminate each of those different kinds of threats requires specialized detectors," he says.

7. HOW FRIENDLY YOU'RE FEELING COULD BE LINKED TO YOUR IMMUNE SYSTEM.

From an evolutionary perspective, humans' high sociability may have less to do with our bigger brains, and more to do with our immune system's exposure to a greater number of bacteria and other pathogens.

Researchers at the University of Virginia School of Medicine have theorized that interferon gamma (IG), the immune cytokine that helps the immune system fight invaders, was linked to social behavior, which is one of the ways we become exposed to pathogens.

In mice, they found IG acted as a kind of brake to the brain's prefrontal cortex, essentially stopping aberrant hyperactivity that can cause negative changes in social behavior. When they blocked the IG molecule, the mice's prefrontal cortexes became hyperactive, resulting in less sociability. When they restored the function, the mice's brains returned to normal, as did their social behavior.

8. YOUR IMMUNE SYSTEM MIGHT RECRUIT UNLIKELY ORGANS—LIKE THE APPENDIX—INTO ITS SERVICE.

The appendix gets a bad rap as a vestigial organ that does nothing but occasionally go septic and create a need for immediate surgery. But the appendix may help keep your gut in good shape. According to Gabrielle Belz, professor of molecular immunology at the Walter and Eliza Hall Institute of Medical Research in Melbourne, Australia, research by Duke University's Randal Bollinger and Bill Parker suggests the appendix houses symbiotic bacteria that are important for overall gut health—especially after infections wipe out the gut's good microbes. Special immune cells known as innate lymphoid cells (ILCs) in the appendix may help to repopulate the gut with healthy bacteria and put the gut back on track to recovery.

9. GUT BACTERIA HAS BEEN SHOWN TO BOOST IMMUNE SYSTEMS IN MICE.

Researchers at the University of Chicago noticed that one group of mice in their lab had a stronger response to a cancer treatment than other mice. They eventually traced the reason to a strain of bacteria—Bifidobacterium—in the mice's guts that boosted the animals' immune system to such a degree they could compare it to anti-cancer drugs called checkpoint inhibitors, which keep the immune system from overreacting.

To test their theory, they transferred fecal matter from the robust mice to the stomachs of less immune-strengthened mice, with positive results: The treated mice mounted stronger immune responses and tumor growth slowed. When they compared the bacterial transfer effects with the effects of a checkpoint inhibitor drug, they found that the bacteria treatment was just as effective. The researchers believe that, with further study, the same effect could be seen in human cancer patients.

10. SCIENTISTS ARE TRYING TO HARNESS THE IMMUNE SYSTEM'S "PAC-MAN" CELLS TO TREAT CANCER.

Aggressive pediatric tumors are difficult to treat due to the toxicity of chemotherapy, but some researchers are hoping to develop effective treatments without the harmful side effects. Stanford researchers designed a study around a recently discovered molecule known as CD47, a protein expressed on the surface of all cells, and how it interacts with macrophages, white blood cells that kill abnormal cells. "Think of the macrophages as the Pac-Man of the immune system," Samuel Cheshier, lead study author and assistant professor of neurosurgery at Stanford Medicine, tells Mental Floss.

CD47 sends the immune system's macrophages a "don't eat me" signal. Cancer cells fool the immune system into not destroying them by secreting high amounts of CD47. When Cheshier and his team blocked the CD47 signals on cancer cells, the macrophages could identify the cancer cells and eat them, without toxic side effects to healthy cells. The treatment successfully shrank all five of the common pediatric tumors, without the nasty side effects of chemotherapy.

11. A NEW THERAPY FOR TYPE 1 DIABETES TRICKS THE IMMUNE SYSTEM.

In those with type 1 diabetes, the body attacks its own pancreatic cells, interrupting its normal ability to produce insulin in response to glucose. In a 2016 paper, researchers at MIT, in collaboration with Boston's Children's Hospital, successfully designed a new material that allows them to encapsulate and transplant healthy pancreatic "islet" cells into diabetic mice without triggering an immune response. Made from seaweed, the substance is benign enough that the body doesn't react to it, and porous enough to allow the islet cells to be placed in the abdomen of mice, where they restore the pancreatic function. Senior author Daniel Anderson, an associate professor at MIT, said in a statement that this approach "has the potential to provide [human] diabetics with a new pancreas that is protected from the immune system, which would allow them to control their blood sugar without taking drugs. That's the dream."

12. IMMUNOTHERAPY IS ON THE CUTTING EDGE OF IMMUNE SYSTEM RESEARCH.

Over the last few years, research in the field of immunology has focused on developing cancer treatments using immunotherapy. This method engineers the patient's own normal cells to attack the cancer cells. Vance says the technique could be used for many more conditions. "I feel like that could be just the tip of the iceberg," he says. "If we can understand better what the cancer and immunotherapy is showing, maybe we can go in there and manipulate the immune responses and get good outcomes for other diseases, too."

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