(Inside Science) -- Around 1780 -- so the story goes -- the Italian scientist Luigi Galvani was dissecting frogs for study when his assistant touched a scalpel to one of the frog's nerves just as a nearby electrical machine sparked. The frog's leg twitched violently. That observation, and Galvani's many subsequent experiments, raised a major question: Did animals generate and store electricity -- could it even be an animal life force -- or did they just respond to it?
About a decade later, shortly after Galvani published his findings, Alexander von Humboldt, a young Prussian scientist with wide-ranging interests, was drawn into the debate. As part of his studies, he blistered his own skin with chemicals and recorded how electrical currents affected the wounds. He noted his sensations, the fluids that oozed from his body, and the twitching of his muscles. He experimented with the hole left in his jaw when he had a tooth pulled, and with an accidental wound on his wrist, which he even reopened to continue the experiment.
The tests on his own body "left him quite mutilated for some time," said Ottmar Ette, a leading Humboldt scholar at the University of Potsdam in Germany.
Yet such painful and potentially deadly experiments were not out-of-the-ordinary for Humboldt, who was born 250 years ago, on Sept. 14, 1769. He risked asphyxiation, infection, drowning, altitude sickness, death by electric eel, and more throughout his decades-long pursuit of new knowledge and experiences.
He was "absolutely curious, to the point of craziness," said Rüdiger Schaper, a cultural affairs journalist at the German newspaper Der Tagesspiegel, who has written a biography of Humboldt. "He would never be afraid of dangerous things to do. That's something very special about Alexander, something very fascinating."
Humboldt's curiosity was a constant throughout his long life, during which he saw science transformed into a plethora of increasingly specialized disciplines, Ette said. Even in old age, Humboldt continued to be amazed by the world. His childlike curiosity and awe may have been key to his more than seventy-years-worth of scientific contributions, which included a modern way of merging disparate points of view, Ette said.
"His curiosity, his thirst for knowledge was really extraordinary," said author Dorothee Nolte, in an interview about Humboldt conducted to honor the 250th anniversary of his birth.
Unconscious in the depths of a mine
The first place Humboldt nearly died from his experiments was probably in the depths of the Earth.
Early in his career, Humboldt worked as a mining official. He attended the Freiberg Mining Academy and ascended the ranks at the Prussian Ministry of Industry and Mines. During that time, he became concerned about mine workers' safety and devised a miner's lamp that would work in the oxygen-poor air of the mines, as well as a respirator that could aid rescue efforts after mine accidents.
He descended into the mines numerous times to test the devices himself, as well as to conduct experiments on the composition of mine air. "At first everything went well," he wrote of one experiment to a friend, "but then things turned out differently." He described what happened after he creeped farther into the mine to test his lamp:
I arrived at the location, set my lamp down and its light gave me immense joy. I became very tired, yes even reeling, I sank to my knees next to the lamp. I supposedly called Killinger [the mining supervisor who had accompanied him part-way], I know nothing of it. He groped after me in the dark and found me unconscious next to the lamp. He pulled me out.
[Translation from Ursula Klein's paper, "The Prussian Mining Official Alexander von Humboldt," Annals of Science, 2012]
"We almost lost him early," Schaper said.
Braving mosquitoes, high altitudes, electric eels, and more
Having survived his early brush with death, Humboldt's curiosity, seemingly as undimmed as his lamp, soon led him far beyond the mines. Even while still working as a mine official, he stayed immersed in the scientific world and conducted his initial experiments with animals and electricity. In 1799, buoyed by a large inheritance, he embarked on the voyage he is perhaps most well-known for, to explore Central and South America. He scaled mountains, navigated vast river systems, and trekked through jungle. He described thousands of new plant species, and made detailed scientific measurements and maps in the areas he visited.
It was dangerous to be an explorer at this time. The transatlantic voyage itself was full of perils, both large and small, but Humboldt claimed he never got seasick.
While in the modern-day country of Ecuador, Humboldt pushed his body to its limits as he climbed a number of peaks in the Andes, including Chimborazo, a dormant volcano that was at the time considered the tallest mountain in the world. Humboldt observed how the properties of water and air and the types of plants change at different elevations as he made his way through the mountains.
A picture of an electric eel, appearing in the book "Humboldt's Travels and Discoveries in South America."
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He also returned to his experiments on animals and electricity. Part of the motivation for the trip was to get fresh specimens of electric eels, to study the biological structures of the fish -- which might yield insights into how they stored their charges -- and to experiment with how the electricity they produced affected animals and human bodies. At one point, while accompanying natives on a hunt for eels, Humboldt collapsed after fish were loaded into the boat with wooden sticks. Their shocks had reached him through water that had collected in the bottom of the vessel. It took almost half a day for him to regain consciousness.
The first thing he did when he revived was to ask for paper to write down his observations, said Frank Stahnisch, a science historian at the University of Calgary in Canada. Humboldt noted "the tingling in his fingers, the pain that goes up to his shoulder, the various levels of consciousness that he was regaining. It's amazing from a neurological perspective, how he was doing that."
Humboldt also used eels to shock various parts of his body, including his eyes and the mucus membrane of his anus, and recorded what he felt.
Although Humboldt's self-experiments with electricity may seem bizarre and extreme from a 21st-century perspective, they fell within an accepted approach to science at the time, said Stahnisch.
For followers of the popular German Romantic movement, one of the prime motives was to observe with their senses as best they could, Stahnisch said. "Some of this meticulous writing down of observations, impressions, and experiences was the gold standard of the time," he said. It was also a period when there were not many sophisticated recording instruments available, he said.
Humboldt doesn't rise to the highest levels in the ranks of scientific self-experimenters -- a designation Stahnisch would rather award to people like Humboldt's contemporary, the German scientist Johann Wilhelm Ritter, whose relentless self-experimentation with electricity may have even contributed to his early death. But when Humboldt did use his own body for experiments, he "really went at it," Stahnisch said.
A modern legacy
It's lucky for Alexander von Humboldt -- and for the world -- that he survived his many life-threatening adventures. After coming back from the Americas, he wrote up his discoveries, worked to reform the Berlin Academy of Sciences, and traveled and lectured widely. He continued to experiment in various fields. His interests spanned disciplines from astronomy to zoology. He was a charismatic figure at salons in Paris and Berlin, famous for his witty and sarcastic remarks.
At the end of his career, he was one of the most famous scientists in the world. He died at the highly respectable age of 89, following a minor stroke he had suffered two years earlier.
Humboldt had a strong belief that things would work out, Ette said, and perhaps that's partly why he took risks. "In German, we have a word for this: Ur-Vertrauen. You are confident in a very general way, from the very moment you are born. You have trust that someone will always pick you up, will always find you, will always help you. And in fact, it was often the case with Humboldt."
Although Humboldt is often popularly called one of the last Renaissance men, or Universalgelehrter, Ette has a different view. "Humboldt was not the last in the line, he was the first in a line," he said. He sees Humboldt as the first transdisciplinary researcher, bringing together very different approaches, scientific disciplines, and specializations. More than any particular discovery Humboldt made, this was his most important legacy, Ette said. "He changed completely the sciences he was working on," he said. Humboldt's final treatise on science, called Kosmos, presents a unifying view of nature, humanity, and the universe.
Humboldt eased off on the most extreme risk-taking as he passed middle age, but he didn't give it up completely. One of Schaper's favorite Humboldt stories, he said, occurred when the scientist was 57 years old, visiting London as the city was constructing the first tunnel under the Thames River -- a perilous undertaking that killed and sickened many workers.
People could descend to the bottom of the river in a diving bell, a huge, metal contraption with a leather hose to feed air to the occupants.
"He decided in 1827 to dive into this cold and stinky river, 13 meters deep. They sit in this capsule -- 3 men -- in the cold, in the dark, just to see what they can see," said Schaper. Humboldt's nose began to bleed from the changes in pressure. Any number of things could have gone horribly wrong. But Humboldt wanted to experience what it was like at the bottom of the river. And so he went.