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# Louis Pasteur

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French scientist.

In his early work as a chemist he resolved a problem about the nature of tartaric acid. A solution of this compound derived from one source rotated the plane of polarisation of light passing through it. The mystery was that tartaric acid derived by synthesis? had no such effect, even though its reactions were identical and its composition was the same. Pasteur noticed on examination of the tiny crystals of tartaric acid that the crystals came in two asymmetric forms that were mirror images of one another. Tediously sorting the crystals by hand gave two forms of tartaric acid: solutions of one form would rotate polarised light clockwise, the other form would rotate light anticlockwise; an equal mix of the two would have no effect. Pasteur correctly deduced that the tartaric acid molecule was asymmetric, and could exist in two different forms that resemble one another as a left and right handed glove resemble one another. As the first demonstration of chiral? molecules, it was quite an achievement, but Pasteur then went on to his more famous work in the field of biology/medicine.

He demonstrated that fermentation and the growth of microorganisms in nutrient broths was not caused by [spontaneous generation]?. He exposed freshly boiled broths to air in vessels that contained a filter to stop all particles passing through to the growth medium: and even with no filter at all, with air being admitted via a long tortuous tube that would not pass dust particles. Nothing grew in the broths, therfore the living orgainsms that grew in such broths came from outside, as spores on dust, rather than being generated within the broth.

With this established, he invented the process of pasteurization.

His later work on diseases included work on chicken cholera; during this work, a culture of the responsible bacteria had spoiled, and failed to induce the disease in some chickens he was infecting with the disease. Re-using these healthy chickens, Pasteur discovered that he could not infect them, even using fresh bacteria; the weakened bacteria had caused the chickens to become immune to the disease, though they had not actually caused the disease .

The notion of a weak form of a disease causing immunity to the virulent version was not new: this had been known for a long time in the case of smallpox. Inoculation with smallpox was known to result in far less scarring and greatly reduced mortality, compared with the naturally acquired disease. Edward Jenner had also discovered vaccination using cowpox? to give cross-immunity to smallpox, and by Pasteur's time this had generally replaced the use of actual smallpox material in inoculation. The difference in chicken cholera was that the weakened form of the disease had been generated artificially, and so a naturally weak form of the disease did not need to be found.

This discovery revolutionised work in infectious diseases: Pasteur produced the first vaccine for rabies?, and laid the foundations for the manufacture of many other vaccines.

Also work on anthrax, silk worm diseases and brewing that I can't remember offhand. Perhaps someone else can fill in.

If they'd had the Nobel Prize back then, there's no doubt Louis would have been a hot contender for the Chemistry, Biology and Medicine prizes.

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Last edited June 7, 2001 9:11 am (diff)
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