Francesco Redi’s was an innovative scientist, physician, and poet. His scientific work resulted in a number of significant milestones: he showed that flies breed and lay eggs and do not, as was popularly believed, spontaneously generate; his microscopic examination of parasites marked the founding of modern parasitology; and in studying chemical treatments to kill parasites, he devised and performed the first controlled experiments in scientific history.
Francesco Redi was born on February 18, 1626 in the city of Arezzo in Tuscany, Italy. Francesco’s father was Gregorio Redi, an eminent physician of noble birth, and his mother was Cecilia de Ghinci.
Francesco was educated from an early age in a Jesuit school in the city of Florence about 50 miles (80 km) from his hometown.
His education placed special emphasis on theology and “polite literature” – literature the Jesuits found acceptable. Francesco would have learned nothing officially about the momentous scientific work of his fellow Tuscan, Galileo Galilei, who, just a few miles from Francesco’s school, was nearing the end of a remarkable life. Galileo’s work, which transformed our world, had incurred the wrath of the Catholic Church, which had prohibited his writings. The Jesuits were among the Church’s most fearsome defenders, zealously enforcing the prohibition.
At perhaps the age of 15 or 16, Francesco left Florence for the University of Pisa, where he graduated in 1647, aged 21, with doctorates in both medicine and philosophy.
Francesco Redi – Physician
Within a year of graduating, Redi returned to Florence as physician to Ferdinand II, Grand Duke of Tuscany. Ferdinand was a member of the famous – or infamous – Medici family. No doubt Redi’s father helped him get the job: six years earlier, in 1642, he himself had been appointed physician to the Medici court.
Francesco Redi’s Contributions to Science
Redi maintained a lifelong loyalty to the Jesuits, but word reached him of the importance Galileo had placed on gathering evidence to support scientific ideas. Galileo’s viewpoint sounded so legitimate to Redi that he applied it in his own investigations.
Also, while studying medicine in Pisa, Redi had learned about the rational experiments carried out by William Harvey. These experiments provided Harvey with the data he needed to correctly describe blood circulation around the body for the first time. Redi was highly impressed by Harvey’s research work.
Scientific Approach to Snakes and their Venom
At the age of 38, in 1664, after making a study of snakes, Redi wrote his first major work: Observations about Vipers.
In Redi’s era, people commonly believed all sorts of nonsense about snakes, such as: snakes enjoy drinking wine; it’s deadly to eat the flesh of an animal killed by snake venom; snakes produce venom in their gallbladders; and eating a snake’s head is an antidote to its venom.
Redi used observations and experiments to disprove these myths.
For the snakes he observed, he established that venom must be injected into the victim’s bloodstream to be deadly. He showed the source of snake venom is two small bladders covering their fangs, which are compressed when the snake bites, squeezing out the venom. And, as Galileo had done in physics, he refuted the biology of Aristotle, who had claimed that snakes are killed by human spittle.
Aristotle had also promoted the idea that life is generated spontaneously: he said simpler lifeforms such as worms and maggots need no parents – they emerge alive from the earth and from rotting organic matter. This idea had been accepted for over 2,000 years.
Again, Redi used experiments to research this subject. He observed that flies laid eggs on meat. These eggs hatched into maggots. If the meat was protected from flies, no eggs were laid and no maggots appeared.
He described his work in 1668 in Experiments on the Generation of Insects.
A little over a decade later, Antonie van Leeuwenhoek confirmed Redi’s maggot and fly work, observing the entire lifecycle. In the 1830s, Theodor Schwann showed that microorganisms do not spontaneously generate. Finally, in 1862, Louis Pasteur completely killed off the idea of spontaneous generation in mainstream science. Redi had been the first person to use experiments to show fellow scientists the path, but it took them a long time to follow it to its natural conclusion.
In addition to his refutation of spontaneous generation, Experiments on the Generation of Insects contained Redi’s detailed drawings of a large variety of insects, eggs, and maggots, such as these below.
Redi documented over 100 parasite species, observing once again that creatures popularly believed to generate spontaneously actually hatched from eggs. He documented his observations in his 1684 book Observations on living animals, that are in living animals. He made drawings of a large number of parasites, recording the places they had been found. This comprehensive work marked the beginning of modern parasitology.
The Controlled Experiment
In his 1684 book, Redi also discussed laboratory trials of chemicals used to treat parasites. Experimental science was in its infancy, and Redi came up with a brilliant new idea: the controlled experiment.
He compared the health outcomes for animals given chemical treatments for their parasites versus animals kept under the same conditions but given no treatment for their parasites. He found that santonin and copper sulfate were particularly effective in treating parasitic worms.
Some Personal Details and the End
After studying literature at school, Redi remained a lifelong enthusiast, building a collection of many old manuscripts. He was also a celebrated poet, famous for his lengthy work Bacchus in Tuscany dedicated to the joy of wine drinking.
According to Bigelow, (see further reading) Redi did not marry and had no children of his own, although he did have nephews. According to Hunt, Redi had a least one son, who achieved some renown in literature; if Redi married, the name of his wife has been lost in the mists of time.
From an early age Redi was prone to hypochondria, but took comfort from his personal belief that hypochondriacs seldom die at an early age. In his later years he suffered from epilepsy.
Francesco Redi died at the age of 71 on March 1, 1697 in Pisa. He was buried in his hometown of Arezzo.
The Duke of Tuscany, Cosmo III, to whom Redi had been a valued physician struck three medals to honor Redi: one for his work in medicine; one for his contributions to natural history; and one for his Bacchanalian poem.
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Osservazioni intorno agli animali viventi che si trovano negli animali viventi
Per Piero Matini, all’insegna del Lion d’Oro, Florence, 1684
Francesco Redi, translated by Leigh Hunt
Bacchus in Tuscany
John and H. L. Hunt, London, 1825
Francesco Redi, translated by Mab Bigelow
Experiments on the Generation of Insects
The Open Court Publishing Company, Chicago, 1909
The Spontaneous Generation Controversy from Descartes to Oparin
The Johns Hopkins University Press, 1974
Raffaele Roncalli Amici
The History of Italian Parasitology
Veterinary Parasitology Vol. 98, pp. 3–30, 2001