The Dogma of the Flies

Francesco Redi
Omne Vivum Ex Ovo
The Swedish Method

Abstract

Redi wrote, “I started to doubt whether the worms were generated directly from the putrefying flesh, rather than being the consequence of egg deposition by flies”. Flesh and plant never become verminous if they are kept where flies and mosquitoes cannot enter. Animal and plant tissues play no other part, nor have any other role in the generation of insects, than to prepare a suitable place or nest into which, during the period of generation eggs and other seeds of worms are laid and hatched by the animals. But, Aristotle, who was the authority on science believed by the Church, had declared flies and lower animals, such as worms, sprang directly from decaying flesh. Belief in the incarnation of flies was as obligatory as belief in the incarnation of God.

Francesco Redi

Paolo Mazzarello writes in Nature that there are few examples of scientific research inspired by art. Art owes more to science than science to art. The best case of a scientific discovery inspired by art took place in Florence, at the Medici court, in 1668 AD. The head physician and superintendent of the ducal pharmacy and foundry was Francesco Redi (l626-98), whose scientific reputation was built on his studies of viper’s venom.

Redi was also a poet and aficionado of classical literature. One day, while reading the nineteenth book of the Iliad, he was puzzled by Achilles’ request to his mother Thetis to take care of the corpse of his friend Patroclus:

I much fear that flies will settle upon the son of Menoetius (Patroclus) and breed worms about his wounds, so that his body, now he is dead, will be disfigured and the flesh will rot.

Thetis answered:

My son, be not disquieted about this matter. I will find means to protect him from the swarms of noisome flies that prey on the bodies of men who have been killed in battle.

But, Aristotle, who was the authority on science believed by the Church, had declared flies and lower animals, such as worms, sprang directly from decaying flesh. Redi wrote, “I started to doubt whether the worms were generated directly from the putrefying flesh, rather than being the consequence of egg deposition by flies”.

Omne Vivum Ex Ovo

He launched a formidable attack on the doctrine of spontaneus generation. Redi exposed meat, cheese and other organic substances in jars, some covered with wire gauze, others uncovered. In due course, he observed the development of maggots on top of the gauze in the first cases and directly in the meat and cheese in the second.

The Swedish Method

C H Parker of Sherborne in Dorset, England, was lying in Winterton Hospital, Durham in August 1944, having been shipped back wounded from the Normandy landings. In a nearby cot was a young man with a bad case of gangrene. In attendance were nurses from the Swedish Red Cross, and the doctors informed the young soldier:

Before we take your leg off, we will try to clean it up using a Swedish method.

The nurses applied a poultice of maggots to the stinking wound, and then the leg was enclosed in a plastic sleeve through which was passed oxygen gas. Periodically the tube was flushed with a saline solution. After two months new flesh was forming, and the young man finished up with a functioning, if badly scarred leg.

With these and other experiments he established that flesh and plant “never become verminous if they are kept where flies and mosquitoes cannot enter”. Thus animal and plant tissues “play no other part, nor have any other role in the generation of insects, than to prepare a suitable place or nest into which, during the period of generation eggs and other seeds of worms are laid and hatched by the animals”.

When the worms were born, they found sufficient food in this “nest” to “nourish themselves very well”. Thus Redi gave experimental support to the principle of omne vivum ex ovo (every living being from an egg). In 1668, Redi’s master piece Experiences about the Generation of Insects was published in Florence. It collected his experiments and results, and dealt a blow to the doctrine of spontaneous generation.

But the blow was not fatal. Phoenix-like, the idea was reborn after Anton van Leeuwenhoek’s discovery of microorganisms. Microscopic beings were seen as a bridge between inanimate matter and organisms visible to the naked eye. Only after the discoveries of Lazzaro Spallanzani, Louis Pasteur and others was the dogma laid to rest.

So, the first serious blow to spontaneous generation came from the Iliad, a book which also inspired Heinrich Schliemann’s discovery of Troy. Mathematicians and logicians know Achilles for his race with the tortoise, and anatomists for the Achilles’ tendon. With his part in firing Redi’s imagination, he is certainly the most influential mythological figure in the history of science.

The central point though, is that the ancient Greeks knew what Redi had to rediscover 2000 years later, because the Church took one man’s incorrect hypothesis about spontaneous generation as dogma!