Courage, curiosity or complete hubris? It's probably a mixture of all these things that causes many scientists to test their own inventions on themselves first. According to the Global Times, a Chinese doctor not only developed an oral vaccine against the SARS-CoV-2 but also tried it out himself. So far, he hasn't seen any side effects.

Scientific knowledge and private pleasure can go hand in hand. The British chemist Sir Humphry Davy experimented with nitrous oxide between 1795 and 1798. With the help of his self-experiments, he discovered not only the pain-relieving effect of the gas but also its intoxicating qualities.

The German physicist Johann Wilhelm Ritter not only discovered ultraviolet radiation in 1801, but also invented the first battery the following year. Ritter was also interested in galvanism — a term applied to muscle contractions caused by electric shocks. The fact that he died at the age of 33 is said to have been due in part to the galvanic self-experiments with which he maltreated his body.

The Austrian psychologist and doctor Sigmund Freud is known as the founder of psychoanalysis. His methods are still used, discussed and criticized today. Less well known is that Freud researched the effects of cocaine during his time as a doctor at the Vienna General Hospital. Published letters show that Freud himself consumed coke for a long time and in large quantities.

"I believe that I am on the trail of the true pathogen," wrote the American physician Jesse Lazear on September 8, 1900, in a letter to his wife. Lazear researched malaria and yellow fever. He confirmed that the latter is transmitted by mosquitoes. To study the disease, he intentionally allowed himself to be stung, fell ill and died 17 days after writing the letter. Lazear was only 34 years old.

John Paul Stapp became known as the "fastest man on earth" because of his research on the effects of acceleration forces on the human body — including his own: He had himself accelerated on a so-called rocket sled up to more than 1,000 kph (621 mph) and decelerated completely in 1.4 seconds. It is the highest acceleration that a human being has ever voluntarily withstood.

Werner Forssmann was already considered a troublemaker during his medical training. The German surgeon was determined to prove that a long, flexible catheter could be inserted safely from the crook of the arm to the heart. Although his superiors had expressly forbidden him to carry out the experiment, in 1929 Forssmann was the first person to try it out — on himself. Secretly, of course.

The Canadian physician Ralph Steinman fell ill with pancreatic cancer and underwent an immunotherapy he developed himself. According to his physician, this therapy was unable to prevent Steinman's death, but — contrary to the prognosis — could possibly have prolonged his life by over four years. Steinman died in 2011, a few days before the Nobel Prize was awarded, which he received posthumously.