Science History (I): Fungal Disease of Silkworm

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Virginia Postrel, The pioneering Scientist Who Explained Contagious Disease; After decades of experiments in the early 19th century, Agostino Bassi showed that silkworms were being killed by a microorganism, setting the stage for modern germ theory. Wall Street Journal, Sept 23, 2023, at page C3
https://www.wsj.com/science/the- ... us-disease-73e59c73

Excerpt in the window of print: Bassi resolved to 'interrogate nature * * *until she responded sincerely to my question.;

Note:
(a) "Agostino Bassi * * * was the first person to identify the specific microorganism that caused a contagious disease—the first to prove the germ theory of disease. * * * He was born into a well-to-do farming family in a small village in Lombardy in northern Italy. Following his father's wishes, he studied law at the University of Pavia. But his first love was science. During his university years, he supplemented his official studies by informally taking courses in science, medicine and mathematics. Among the professors whose lectures he attended was Lazzaro Spallanzani, famed for his opposition to the theory of spontaneous generation [translated in Taiwan as 自然发生说; because ancient people did not correleate things, and believed tadpoles or flies came from nothing, as I believed in childhood]. Another, with whom Bassi became friends, was Giovanni Rasori, a supporter of the then-unpopular idea that contagious diseases were caused by microorganisms."
(i) Agostino Bassi
https://en.wikipedia.org/wiki/Agostino_Bassi
(1773 – 1856)
(ii) Lombardy
https://en.wikipedia.org/wiki/Lombardy
(regional capital: Milan; section 1 Etymology: "The name of the region derives from the name of the people of the Lombards who arrived in Italy in 568 and made Pavia their capital")
(iii) Pavia
https://en.wikipedia.org/wiki/Pavia
("35 kilometres (22 miles) south of Milan"/ section 8 Education: University of Pavia was founded in 1361)
(iv) germ theory of disease
https://en.wikipedia.org/wiki/Germ_theory_of_disease
("such views [germ theory] were held in disdain in Europe, where Galen's miasma theory remained dominant among scientists and doctors.   By the early 19th century, smallpox vaccination was commonplace in Europe, though doctors were unaware of how it worked or how to extend the principle to other diseases. A transitional period began in the late 1850s with the work of Louis Pasteur. This work was later extended by Robert Koch in the 1880s"/ section 2 Development, section 2.6 19th and 20th centuries, section 2.6.1 Agostino Bassi, Italy: "Bassi published his findings that fungal spores transmitted the disease between [silkworm] individuals. * * * [The fungus is] currently classified as Beauveria bassiana")

Ancient people in Europe believed miasma caused diseases, including malaria. Chinese believed the same, calling it 瘴气.


(b) "Lustrous, soft and easy to dye, silk has been Europe's favorite luxury fabric as far back as ancient Rome, where it arrived from China. It comes from the cocoons of Bombyx mori, a moth domesticated in China thousands of years ago and unable to survive in the wild. By Bassi’s day, sericulture—the raising and harvesting of silkworms—was a major industry in Italy and France."
(i) Bombyx mori
https://en.wikipedia.org/wiki/Bombyx_mori
("is the closest relative of Bombyx mandarina, the wild silk moth. The silkworm is the larva (or caterpillar) of a silk moth. * * * A silkworm's preferred food are white mulberry leaves, though they may eat other species of mulberry, and even leaves of other plants like the osage orange")
(A) Bombyx (etymology: from Ancient Greek)
https://www.merriam-webster.com/dictionary/Bombyx
(B) But what does mori mean?

The hint is it means mulberry, when I read
silkworm. New World Encyclopedia, undated
https://www.newworldencyclopedia.org/entry/Silkworm
("Bombyx mori (Latin: 'silkworm of the mulberry tree') ")

And it is. Latin-English dictionary:
* mōrī (noun): "inflection of mōrus [noun feminine singular, plural  mōrī)]"
https://en.wiktionary.org/wiki/mori
(C) The binomial nomenclature for white mulberry is Morus alba. See the Morus as genus name?  However, what does white mean?

Morus (plant)
https://en.wikipedia.org/wiki/Morus_(plant)
("the genus * * * three of which are well-known and are ostensibly named for the fruit color of the best-known cultivar: white, red, and black mulberry (Morus alba, M. rubra, and M. nigra, respectively) ")
(ii) sericulture (n; from Latin [noun neuter] sericum [silk] + English culture)
https://www.merriam-webster.com/dictionary/sericulture
(A) Latin-English dictionary:
* sericum (noun neuter; NO etymology): "Chinese goods, but especially silk"
https://en.wiktionary.org/wiki/sericum

Why?
(B) English dictionary:
* sericeous  (adj; Did You Know?)
https://www.merriam-webster.com/dictionary/sericeous
(iii) Bombyx mori (L). Mississippi Entomological Museum, undated
https://mississippientomological ... es/Bombyx_mori.html
("The mulberry silkworm (Bombyx mori Linnaeus) was derived by artificial selection in China from the wild silkmoth named Bombyx mandarina (Moore) (see Goldsmith 2009).  The caterpillars of B mori are white and cannot hold on to branches of mulberry, and the white moths cannot fly.  The mottled caterpillars of B mandarina are quite different, and move about freely on the mulberry leaves and twigs.  The brown moths, which like the caterpillars are well camouflaged, fly to lights")


(c) 'The Manner of Feeding Silkworms', 1753. Artist: Benjamin Cole. Getty Images, undated.
https://www.gettyimages.co.uk/de ... ews-photo/463897283

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September 25 marks the 250th anniversary of the birth of the most important scientist you’ve never heard of. His name was Agostino Bassi, and he was the first person to identify the specific microorganism that caused a contagious disease—the first to prove the germ theory of disease. How he did it is a remarkable story of scientific passion and persistence. It deserves to be more widely known.

Bassi wasn’t meant to be a scientist. He was born into a well-to-do farming family in a small village in Lombardy in northern Italy. Following his father’s wishes, he studied law at the University of Pavia. But his first love was science. During his university years, he supplemented his official studies by informally taking courses in science, medicine and mathematics. Among the professors whose lectures he attended was Lazzaro Spallanzani, famed for his opposition to the theory of spontaneous generation. Another, with whom Bassi became friends, was Giovanni Rasori, a supporter of the then-unpopular idea that contagious diseases were caused by microorganisms.

After receiving his law degree in 1798, Bassi settled in Lodi, a town about 20 miles southeast of Milan. Plagued by recurring bouts of an eye inflammation that made reading and writing difficult, he moved in and out of bureaucratic posts. On the side, and between positions, he used the family farm as a laboratory. Over the years, he conducted experiments and published treatises on breeding sheep, cultivating potatoes, aging cheese and making wine. His most important—and time-consuming—research was on silkworms.

Lustrous, soft and easy to dye, silk has been Europe’s favorite luxury fabric as far back as ancient Rome, where it arrived from China. It comes from the cocoons of Bombyx mori, a moth domesticated in China thousands of years ago and unable to survive in the wild. By Bassi’s day, sericulture—the raising and harvesting of silkworms—was a major industry in Italy and France.

Sericulture is a precise and demanding process. Cultivators raise silkworms on trays protected from the weather and supply them with fresh mulberry leaves, the only food they will eat. Mulberry orchards are as essential to sericulture as the insects themselves. When the caterpillars are ready to build cocoons, cultivators provide them with sticks and monitor their hibernation. Just before the moths emerge, they harvest the cocoons and heat them to kill the insects before they can break the precious silk. Each intact cocoon is a continuous filament that can be reeled off, combined with others and turned into fine thread. Each sericulture stage requires precision: just the right density of silkworms and leaves, just the right temperatures, just the right timing. Disease can devastate a harvest.

In late 1807, Bassi embarked on what turned out to be 30 years of experiments aimed at identifying and countering the cause of a mysterious ailment that was wiping out silkworms. They would stop eating, become limp and die. Their corpses would then grow stiff, brittle and coated in white. The disease was variously known as mal del segno, muscardine or, in a nod to the white powder, calco, calcino or calcinaccio. Breeders believed that it must be caused by a toxin in the insects’ environment, and Bassi set out to figure out what that was.

His first eight years of experiments proved frustrating and apparently futile. He later wrote: “I used many different methods, subjecting the insects to the cruelest treatments, employing numerous poisons—mineral, plant and animal. I tried simple substances and compounds; irritating, corrosive and caustic; acidic and alkaline; soils and metals; solids, liquids and gases—all the most harmful substances known to be fatal to animal organisms. Everything failed. There was no chemical compound or pest that would generate this terrible disease in the silkworms.”

By 1816, Bassi was deeply discouraged. He had expended enormous effort and nearly all his money on fruitless studies. He was losing his eyesight. “Oppressed by a great melancholy,” he abandoned his research. But a year later, he rallied and resolved to “defy misfortune, turning to interrogate nature in new ways with the firm resolution of never abandoning her until she responded sincerely to my questions.”

[photo caption: (wording in the engraving: The Manner of Feeding Silkworms Engraved for the New Universal Magazine, 1753.)
A 1753 illustration of a silkworm farm shows the trays and mulberry leaves used to cultivate the delicate caterpillars. PHOTO: GETTY IMAGES]

A major clue came when Bassi observed that silkworms raised in the same conditions and fed the same food but housed in adjacent rooms had different outcomes. The disease would sweep through one room while its neighbor suffered little or no damage. The difference, he concluded, was that “there was no calcino germ, or very few, in one room and large numbers in the other. The mal del segno or muscadine is never born spontaneously” in reaction to a toxin, as everyone had previously believed.

After more experiments, Bassi realized that living insects wouldn’t infect one another. Rather, the disease was carried by the corpses’ white coating. Introduced into the body of a living insect, whether caterpillar, pupa or moth, the powder would multiply inside, feeding on the insect’s body until it killed it. Only then would it spread. Bassi concluded that the invader was a fungus and the white substance its spores. It was the first experimental proof that a contagious disease would spread as microorganisms traveled from an infected to an uninfected animal.

By placing a dead insect in a warm, humid environment, Bassi found he could cultivate the fungus enough to detect hints of stems with the naked eye. Under a simple microscope, he could see the curves that marked the invader as a living organism rather than a crystal.

Having determined the culprit, Bassi experimented with ways of killing the fungi without harming the silkworms, identifying several effective disinfectants. He advised sanitary measures that included treating all silkworm eggs with disinfecting solutions; boiling instruments; disinfecting trays, tables and workers’ clothing; and requiring everyone tending the silkworms to wash their hands with disinfectants.

As these hospital-style measures suggest, Bassi’s discovery was a breakthrough with implications beyond sericulture. His research anticipated the more famous work of Louis Pasteur and Robert Koch in developing the germ theory of disease. In 1856, nine years after Bassi’s death, the well-funded, publicity-savvy Pasteur turned his own attention to silkworms, conducting his first research on animals. Among the resources he had at his disposal were French translations of Bassi’s work. The provincial lawyer was a scientist ahead of his time.

Virginia Postrel is the author of “The Fabric of Civilization: How Textiles Made the World” and a contributing editor for Works in Progress magazine.