They Experimented on Themselves in Secret. What They Discovered Helped Win a War

The untold, top-secret story of the British researchers who found the key to keeping humans alive underwater—and helped make D-Day a success.
Photo of Haldane at Siebe GormansProf. J. B. S. Haldane at Siebe Gorman UK
Photograph: Hans Wild/The LIFE Picture Collection/Shutterstock

Not long ago, I let a colleague insert an IV line in my hand. He swished saline back and forth between two syringes to create bubbles, then he injected the foamy liquid into my vein. We wanted to know if a new gadget—a small Doppler ultrasound—could hear the bubbles in my bloodstream. We hoped the gadget might be useful in monitoring divers for decompression sickness, otherwise known as “the bends.” When the bubbles passed the ultrasound, we happily heard a waterfall of clicks. Bubbles in the arteries can be deadly, but bubbles in the veins are usually harmless. I knew it was safe, and it was not my first time taking a needle for science.

I’m a biomedical engineer and researcher at Duke University School of Medicine, and I study ways for people to survive in extreme environments like underwater and outer space. I’m not alone in using my own body first in research; in fact—except in fields like chemotherapy and brain surgery—the practice is surprisingly common. One time, Dr. Sherri Ferguson, another diving researcher, needed a chamber that could pressurize the air around only a human subject’s legs. She used her own body to help figure out a good design for such a thing. In the process she found herself popped out of the prototypes by the pressure and rocketed across the room, over and over again, until she made a seal that worked. She has also strapped on a mask and breathed in toxic gases so that she could properly inform and warn prospective test subjects of the symptoms they would experience—and so they couldn’t fake any results.

Dr. Ferguson and I certainly aren’t the only scientists to use ourselves as our first test subjects.

In my field of dive research, there’s one story from eight decades ago that blows the rest of us out of the water. It concerns a group of scientists who conducted a series of tests on themselves so extreme, so dangerous, and so key to the outcome of the Second World War that it got buried under classification markings for generations. This groundbreaking research was so secret, in fact, that professionals in my field will learn about it here for the first time.

In early August of 1942, in a brick warehouse in London a few steps across the Thames from Big Ben and Westminster Abbey, two scientists sat inside a heavy steel tube. A mere 4 feet in diameter, with heavily riveted walls and rounded ends, the tube laid sideways on a platform in the corner of the warehouse. Pneumatic pipes sprouted from the top of it like mechanical antennae. Inside, wood planks formed the floor.

Even when curled up on that floor in a sitting position, Professor John Burdon Sanderson Haldane took up most of the chamber’s space. Six foot one and awkward and imposing, the blunt yet affable middle-­aged geneticist had broad shoulders, a hefty mustache, and a prominent bald forehead that forced his bushy eyebrows downward at the seeming expense of his eyes. Next to him was Dr. Helen Spurway, that day’s test subject. Twenty-­seven-­year-­old Spurway, also a PhD geneticist, was as lanky as Haldane was robust. In the tank, she perched on a small stool, her slim shoulders forced into a curve by the tubular white walls. She had short dark hair with a subtle natural wave in it, cut into a practical bob that would have been easy to dry between underwater experiments. Her pale face offset deep brown eyes. She looked like someone who not only listened but scrutinized.

Spurway’s nose was pinched shut by a spring-­loaded clip. Her lips were sealed around a rubber mouthpiece that was connected through two large corrugated hoses to a square tan bag strapped to her chest—an apparatus designed to deliver pure oxygen to her lungs. As they sat there, a resonant hiss vibrated through the tube as a chamber operator filled the space with pressurized gas. It started to get hot.

Haldane and Spurway’s goal was to see how long she could breathe the oxygen before it began to poison her. They were doing this inside a sealed tank to simulate the pressure of the ocean when diving underwater. Spurway was an eager test subject. The poisonous effects of oxygen—which range from visual hallucinations to seizures—become far worse under high levels of pressure, and she wanted to use her own body to puzzle out how bad they could get.

Roaring air continued to force its way into the small steel chamber, which was dimly lit by paltry warehouse lights shining through its one pressure-­reinforced porthole. The intruding air drove the internal pressure levels up to those that might be felt by divers swimming deep in the ocean. The temperature climbed as more gas pushed and compressed itself into the small space, and the heat became unmerciful, exacerbated by the syrupy sensation of the increasingly dense atmosphere. Under these conditions, houseflies cannot take flight. People cannot whistle. Voices become cartoonishly high-pitched. Breathing and movement acquire a conscious feeling as air thickens.

Haldane and Spurway reached a pressure level equal to 90 feet beneath the waves, as well as a scorching heat somewhere in the survivable triple digits Fahrenheit. Haldane and Spurway, pressed together by the chamber walls, watched each other sweat. The hiss of the gas, deafening at first, began to taper slowly as the inside of the chamber reached its target pressure. Then an operator outside the chamber spun a valve to halt the inward rush of gas. New sounds pinged through the cooling metal tube, while the temperature inside began to drop. Haldane noted the time.

The tan leather breathing apparatus Spurway wore on her chest was called a Salvus. A year before Jacques Cousteau invented the AquaLung while living in occupied France, she was trying to figure out how long such a device could be used, and at what depths, by swimmers and submariners beneath the surface of the ocean.

After precisely 33 minutes in the chamber, patiently sucking down oxygen, Spurway yanked the rubber mouthpiece from her lips. She vomited. She vomited repeatedly. She gulped down chamber air, no longer on oxygen, and recovered slowly. Her symptoms—visual disturbances, lip twitches, and of course the vomit—were mild. Watching her gulping, gasping face, Haldane noted the time. Spurway later reported that she had seen brilliant flashes of dancing purple lights—“dazzle,” she said—during the experiment. Professor Haldane, Dr. Spurway, and the other members of their small clan of scientists had spent the last three years grinding away in the close confines of these hyperbaric metal tubes, at myriad questions about underwater survival. Their first goal was to enable sailors to escape from submarines.

Five days earlier, on August 19, 1942, in the waters of the English Channel, troops from the Allied nations prepared small vessels offshore to conduct a raid on the beaches of Dieppe, France. The troops were mostly Canadian, peppered with a select few who were tasked with secret intelligence-gathering missions in town.

They’d planned the raid using a small number of photos of the area, most of which were taken during vacations before the war. The beaches themselves were largely unknown. The idea was to land the ships, allow clusters of troops to unload tanks and vehicles, then proceed into the town. What actually happened is considered one of the worst disasters in Canadian military history. Surprised by new German gun emplacements and rock-coated beach terrain that literally wrenched the tracks off their tanks, the Allied troops were mowed down. On some beaches, casualty rates were as high as 94 percent.

The Allied soldiers who weren’t killed limped back from the defeat. It was clear now, they needed to be able to creep up to the beaches days before a raid to get up-to-date information. They needed to know where the Nazis had tunneled into the land, placed explosives, or built machine gun nests. None of their ships or boats could get close enough to the shore without being detected, so the Allies needed miniature submarines—and divers. And they needed science to make those things happen.

By this point, Haldane, Spurway, and the other scientists had already given themselves eight seizures and broken several vertebrae for the cause. That’s because, shortly before the disaster at Dieppe, but not in time to stop it, Haldane and his crew had been asked by the Admiralty to pivot and focus on a new, more specific goal. To help their countrymen and the Allies defeat Hitler, to help end the war, the Allies needed the scientists to use this same work to prepare for missions to scout beaches.

Five days after Dieppe, not yet knowing of its horror, Haldane and Spurway were working on the next amphibious assault plan. There would be another beach landing, this time in Normandy—and it could not fail.

Haldane was born in 1892 into the sort of Scottish family whose summer homes have turrets. Stately portraits of ancestors with carefully trimmed facial hair and dresses with miles of pleated fabric looked down from the high walls of their multiple estates. John, called “Jack” in his youth and later “JBS,” had no patience for such pomp. He insisted on keeping an old bathtub full of tadpoles beneath the branches of one majestic apple tree. He was determined to breed water spiders.

Jack and his sister Naomi were bred into science the way some are bred into royalty.

Their parents, Louisa and John Scott, seem to have gravitated toward each other because of the same fiercely independent, socially irreverent genius they would pass on to their children. She was a brilliant young woman with golden hair, classical beauty, an affinity for small dogs, and an outspoken confidence that, along with her propensity for the occasional cigarette, marked her as a rebel within the prim upper crust of 1800s Britain.

He was a researcher, physician, and reader of physiology at Oxford University, and infamously eccentric. He converted the basement and attic of the couple’s house into makeshift laboratories so he could play with fire and air currents and gas mixtures. So could his children.

By age 3, golden-­haired, chubby-­cheeked toddler Jack was a blood donor for his dad’s research. By age 4, he was riding along with his father in the London Underground while John Scott dangled a jar out the window of the train to collect air samples. The duo found levels of carbon monoxide so alarmingly high, the city decided to electrify the rail lines. The young Haldane was learning how to keep people alive and breathing in worlds where they should not survive.

By the late 1800s, frequent explosions and gas leaks made mining one of the most lethal jobs in the world, and John Scott Haldane became known among the miners of the country for his willingness to clamber into the narrow, dark, coal-­filled passageways on his mission to make the air supplies safer. At 4 years old, Jack was also exploring coal mines with his father to figure out how people breathed in those cramped, dangerous spaces. That common expression “canary in the coal mine”—still used to describe early detection of any threatening situation—is in existence today because it was Haldane’s idea to use the small, chipper birds to detect gas leaks.

With every trip, young Jack watched his father practice firsthand what seemed to be the elder professor’s most important lesson: Volunteer yourself first; then, after you went, exclusively test on “other human beings who were sufficiently interested in the work to ignore pain or fear.”

When Jack was 6 years old and Naomi was on the brink of 2, the quartet moved, along with Kathleen’s mother, to a larger, “comfortable and ugly” custom-­built 30-­room mansion christened Cherwell, near Oxford. This building’s entire design revolved around the pursuit of science. John Scott even insisted that the bathtubs be made of lead for better thermal insulation. He refused to allow the installation of gas lines to the home because he considered gas too chemically explosive. He and Kathleen packed every room with cozy chairs for reading and intellectual curios such as scarab beetles or painted Chinese bowls stocked with goldfish.

John Scott’s large office extended off the back of the house, and it was perpetually coated in a layer of books and papers. It also held a room-­length wooden table big enough to do the glassblowing required to make custom chemistry equipment. From the office, a small step led down to the Haldanes’ in‑home laboratory. The lab had large windows looking out onto flower-filled gardens, and the walls were braced by broad shelves full of chemicals and supplies. The lab always featured at least one airtight gas chamber, just large enough to hold a person, nicknamed “the coffin.” It could be flooded with any gas desired. It often was.

Even the family cat slept curled, tightly but voluntarily, inside a beaker in the lab, and Naomi’s dollhouse was decorated in part by famous scientists—including Nobel Prize–winning physicist Niels Bohr, who brought Naomi a little toy jug for her miniature estate.

Carved into the entryway stonework of the house was the Haldane family motto, a word that would become an ominous portent. All visitors and guests were required to pass under the simple declaration: SUFFER.

As they got older, Naomi and Jack became inseparable; they chased globules of mercury across the laboratory floor, huffed chloroform and giggled at its effects, sucked in a miscellany of strange gases from storage bottles to test the effects on their voices, or simply whirled together dancing Viennese waltzes until the spinning rendered them too dizzy to continue. He called her his “Nou.” She addressed him as “Boy”; “Boydie,” a contraction of “boy dear”; or sometimes just “Dearest.”

“As children we were both in and out of the lab all the time,” Naomi once wrote. They didn’t need to sneak in; other than their father, they were the only two people allowed. Naomi’s job as a child was to monitor the test subjects through the observation window in the gas chamber and, should they fall unconscious, to drag them out and resuscitate them.

The Haldanes chose to make informed consent their policy. (At the time, physicians joked openly that it was easier to find volunteers for experimental surgeries than for experimental medical treatments because the unconscious surgical patients could not decline.) Testing on animals was the absolute last resort, John Scott lectured. He even designed a canary cage that would seal itself and resuscitate the coal mine birds with fresh oxygen the moment they fell off their perch.

From his mine trips, John Scott would send home periodic telegrams to reassure his family, but often the carbon monoxide inside post-explosion mines would temporarily addle him so badly, he would write the same words multiple times in one message, forget he’d already sent a message and send multiple repeats, or write entire messages of gibberish. (Kathleen did not find these telegrams reassuring.) To study the effects in a slightly more controlled manner, he sealed up his home gas chambers and willingly breathed levels of carbon monoxide that pushed him deliriously close to death.

Despite the fact that Naomi grew up to be an extraordinary and prolific author as well as a vital key to adult JBS’s future science, most biographers omit or minimize her. Even Kathleen’s own memoir contains a beefy chapter titled “My Son” while only sparsely describing Naomi. Naomi summarized the end effect: “Certain avenues of understanding were closed to me by what was considered suitable or unsuitable for a little girl.” Young Naomi was denied access to the paradise where Jack got to play.

However, she crept her way in. Naomi might not have been welcome in the mines or on the boats, but within the walls of their homes, she was mostly an equal. (A diary kept by Naomi at age 6 has colorful, meticulous illustrations of begonias with details about counting the petals to tell the sex of the blooms—a “she-­begonia” versus a “he‑begonia”—all written in the large, looping calligraphy of a child.) From her, Jack would learn firsthand the intellectual equality of women—a principle that he would absorb and apply with fervor, and one that would allow him to build a spectacular future lab during a war-­driven shortage of eligible men.

When Jack was 8 years old, John Scott brought him to an evening lecture about Mendelian genetics, a set of mathematical explanations of how physical traits get passed down between generations—why some siblings turn out blond but others brunette; why some pea plants have violet flowers but others white. Science had not yet pinpointed the primary culprit as DNA. Jack became obsessed with the cutting-­edge idea. Naomi had begun keeping guinea pigs after a nasty fall left her afraid of her pet horse, so they started using her carefully trained fuzzy “pigs of guinea” to test the theories of gene propagation themselves, along with mice, lizards, birds, and whatever other fast-­breeding animal they could procure.

Soon the front lawn of their home teemed with a roiling carpet of 300 guinea pigs, all carefully labeled, numbered, and partitioned behind wire fencing. The squeaking fuzz balls had been deliberately bred, observed, and documented so that the young scientists could compare the patterns of their whorls and colorful splotches against Mendel’s math. They executed the calculus to describe the patterns of inheritance in their guinea pigs at a time when most adults were unaware that such fields of research even existed. Through this exploration, Jack Haldane learned statistics. He learned probability. Naomi said her favorite part of the day was opening the mouse cages and letting “the darling silky mice” wander over her in her specially designated blue mouse-­tending frock.

When Jack was 13 years old, his father was testing out a new theory he had about diving. John Scott believed he had a new method for keeping divers safe and avoiding the dreaded “bends,” more formally known as decompression sickness. During the trip Jack calculated for his father a table of logarithms, and as a reward, on the last day of the successful tests, John Scott decided his son should have a dive.

The towheaded boy peered out of the tiny reinforced window cut into the side of a metal chamber, where he was being pressurized to see if his ears could handle the depths, and he gazed at a handful of adults watching him. This small hyperbaric chamber sat on the deck of a Royal Navy ship that was rolling with the waves off the coast of Scotland. As the hiss of gas filled the chamber, pressure in the tank rose, and Jack practiced moving his jaw and swallowing—to prove to the adults he could open his eustachian tubes and balance the air in his ear canals. He reached maximum pressure safely, and was returned to a normal, surface pressure without harm. When the chamber door swung open, the boy clambered carefully out onto the deck in the hot, late-summer weather. Then his father began to strap him into a sturdy canvas suit (sized for an adult). Sailors and other researchers watched.

Fitted loosely into the adult-sized canvas suit, Jack plodded about the murky sea floor for the maximum time allowed. Frigid water leaked through the seals around his wrists, but he was too entranced by the whirls of dirt that rose upwards around his legs and the beams of sunlight dancing through the water to end his adventure voluntarily. At the end of the dive he was pulled from the water blue, borderline hypothermic, and happy.

It was because of these experiments—the ones the father did on the son, with strange gases and their effects—that made the boy most interested in what would become his wartime work: how breathing gases affected people under the menacing pressures of water. That was how Jack Haldane became the heir in a line of respiratory researchers trying to puzzle out the mysteries of the human body under pressure.

While the clock struck midnight to start the new year of 1944, two clandestine operators crept across the darkened shores of key Normandy beaches, the beaches that would be the targets for D-Day. On their second trip, these operators would use a miniature submarine to get as close to the shore as possible. The crew hid their submarine from the Nazis during the day by using principles from the Haldane lab to recycle their breathing gas as they lurked on the ocean floor. By night, they’d surface and, once ashore, they collected sand and measured and mapped the region. They planned.

On 284 separate days, up to January 28, 1944, Jack—now JBS—Haldane, Helen Spurway, and the other members of their scientific lab took turns running at least 611 experiments on themselves in the enclosed steel chambers in London. Haldane and Spurway put their own bodies at risk for 438 of them. When their original factory test site east of the Thames from Westminster Abbey was hit by Luftwaffe bombs, the group relocated the hyperbaric chambers to just north of the city, dusted them off, and restarted.

The number of diving principles the group of geneticists had discovered and proved was stunning, and most are used by divers today. They proved that adding more oxygen to a diver’s air is safe, and can reduce the risk of the bends. They tested how deep divers could breathe pure oxygen without seizing, and proved that the safe limits underwater were shallower than in the air. They gave themselves stimulant drugs issued to the Allied troops, and showed that the drugs would not affect underwater abilities. They figured out what was needed to survive inside miniature submarines, how to let people live inside such tiny enclosed volumes without asphyxiating.

By the end of their experimental series in January, British special operations personnel had used their scientific discoveries to lurk in miniature submarines off the coast of specific, handpicked, highly classified beach locations in Normandy. By the day of the invasion, June 6, 1944, amphibious divers used the same science to inspect the same waters for ordnance and dispose of obstacles like the infamous six-pointed hedgehogs. These divers expanded the safe landing channels for the increasing numbers of incoming ships, which brought more and more Allied troops to fight Hitler on the mainland. Because of the Haldane group’s science, the divers succeeded, and without a single diving casualty. At the end of the war, Jacques Cousteau would write a letter to Spurway, Haldane, and the others, thanking them for hosting him at their lab to teach him about the principles of surviving underwater.

All of those achievements were buried under classification markings for two generations. All of them came from hard work, genius, and the self-sacrifice of self-experimentation.

From Chamber Divers: The Untold Story of the D-Day Scientists Who Changed Special Operations Forever by Rachel Lance, published April 16, with permission from Dutton, an imprint of the Penguin Publishing Group, a division of Penguin Random House, LLC. Copyright © 2024 by Rachel Lance

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