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The Time Travel Interviews with Famous Scientists: Antonie Van Leeuwenhoek

About this Daily Classroom Special
The Time Travel Interviews with Famous Scientists is written by Judy Jones, teacher at East Chapel Hill High School (NC) and Teachers Network web mentor.  Judy is also responsible for the popular Critter Corner Daily Classroom Special. E-mail Judy.

  Antonie Van Leeuwenhoek

Antonie Van Leeuwenhoek Hello everyone, Jurna List, here. Today, I have traveled back into the 17th century to interview Antonie van Leeuwenhoek, the first person to discover bacteria. We are in Delft, Holland (Kingdom of the Netherlands) where van Leeuwenhoek was born. (Some of you may have seen the beautiful blue china that comes from Delft.) In the 17th century, Delft was a major trade center. We are sitting outside the medieval Oude Kerk (old church), a Gothic church, that contains a memorial to Antonie van Leeuwenhoek. This beautiful old church stands by a canal in the old inner part of Delft and is surrounded by elegant old trees. Jan Vermeer, a famous painter, was born in Delft in the same year and on the same day as his good friend, van Leeuwenhoek.

Jurna List: Mr. Leeuwenhoek, please tell us when you were born.

Antonie van Leeuwenhoek: I was born on October 24 in 1632.

JL: What did your parents do?

AL: My family were tradesmen. My stepfather made baskets and my mother's family were brewers. We were simple people and we never had much money.

JL: Did you go to school?

AL: Yes, I attended school in the town of Warmond. But I never went to the university.

JL: What did you do after you finished school?

AL: When my stepfather died, I went to live with my uncle in Benthuizen and in 1648 I became an apprentice in a linen-draper's shop. In 1654, I returned to Delft and set myself up in business as a fabric merchant (draper) and a haberdasher. At various times in my life, I also worked as a surveyor, a wine assayer, and I even served as a minor city official in 1660; I was a chamberlain to the sheriff of Delft.

JL: How did you become interested in lenses?

AL: After I moved back to Delft, I learned to grind lenses and make very simple microscopes. I was very inspired by a book that I read by Robert Hooke called Micrographia. In this book, Hooke described and made illustrations of his own observations with the microscope.

JL: In 1998, we have 10 microscopes that you made in the 17th century. How many did you actually make?

AL: Oh, I made over 500 microscopes. But my microscopes were not like the ones you use today. They were really more like very powerful magnifying glasses. There was only one lens that I mounted in a tiny hole on a brass plate. The specimen would be mounted on a sharp point in front of the lens and two screws were used to move the specimen around and focus it. I had to hold the instrument up very close to my eyes and I needed very good light. Luckily, I had very good eyesight and was able to see some quite amazing things. By adjusting my lenses carefully, I could magnify well over 200 times. And my resolving power was very good for the times. My best instruments had a resolving power of 1.4 micrometers.

JL: What is resolving power, Mr. van Leeuwenhoek?

AL: Resolving power is the ability of the instrument to show two objects as two rather than one. Two objects that were 0.0014 millimeters or more apart would be seen as two objects but objects that were closer together than 0.0014 meters would be seen as one object.

JL: When did you find time to work with your lenses?

AL: I built my lenses and made my observations during my spare time. It was my passionate hobby that I pursued when I was not selling buttons and ribbons! I taught myself how to make the lenses.

JL: Tell us about some of the things that you saw.

AL: In 1673, I began writing letters to the newly-formed Royal Society of London and I continued writing for the next 50 years. In those letters I described little organisms that live in the bile of animals, the eggs and spermatozoa of insects, and protozoa in the gut of a horsefly. I even described the organisms I found in my own diarrhea. In my letter, I said, "their bodies were somewhat longer than broad, and their belly, which was flat like, furnisht with sundry little paws, wherewith they made such a stir in the clear medium and among the globules....."

JL: Mr. van Leeuwenhoek, today we know that you were describing a protozoan with a long tail-like flagellum, called Giardia lamblia, that causes diarrhea. What else did you see?

AL: I saw some very small animalcules that had bent bodies like serpents and traveled through the liquid very quickly.

JL: We know now that you were looking at spirochetes which are bacteria. Tell us more of what you saw.

AL: I also looked at the material that I found around my teeth. I wrote to the Royal Society, "For my part I judge, from myself, that all the people living in our United Netherlands are not as many as the living animals that I carry in my own mouth this very day." I rubbed my teeth each morning with salt and swilled my mouth out with water and I even cleaned my back teeth with a toothpick and rubbed them with a cloth, but in spite of that, the little white matter that I could still find in my teeth, when mixed with clean water had hundreds of little living animalcules very prettily a-moving.

JL: We have looked at your pictures of these "animalcules" and determined that they are bacteria (rod-shaped, spirillum, and coccus). We have also learned that our own mouthwashes do not get rid of all these bacteria any more than your salt, water, and vinegar washes did!

Tell me, what else did you observe?

AL: I made many observations of lake water. I found green streaks, spirally wound serpent-wise that were no thicker than the hair on one's head.

JL: We think these were a green alga called Spirogyra. Tell us more.

AL: One day, I watched a most amusing little animalcule for quite some time. It was fashioned like a bell and at the round opening, it made such a stir that the particles in the water were set in motion. If they were disturbed, they would contract their bodies and tails and then slowly begin to stretch out again. I found their gentle motion mightily diverting.

JL: These were probably the protozoan, Vorticella. Biology students today still enjoy watching these interesting organisms. Did you ever become a member of the Royal Society?

AL: Yes, in 1680, I was elected a full member of the Royal Society even though I had never attended a meeting! The Society had been publishing my discoveries in their Philosophical Transactions.

JL: What do you think was one of your most important discoveries?

AL: In the 1700's most people believed that lower organisms could arise from unusual things. For example, some people believed that weevils could arise from wheat or fleas from sand. I was able to show that weevils and fleas have larval forms that are microscopic and that they breed just like other insects. I was definitely in opposition to the idea of the spontaneous generation of lower organisms. I also observed the eggs of ants and of freshwater mussels and was able to show the stages of their life cycles.

JL: What was one of your most interesting experiences?

AL: In 1698, I got the opportunity to show how blood circulates in the capillaries of an eel to Tsar Peter the Great of Russia. I was always welcoming interesting visitors to my home to see the strange things that I was describing. Both James II of England and Frederick II the Great of Prussia came to visit me. But probably my most interesting experiences were the most amazing animalcules that I observed with my lenses.

JL: Were you always admired by people in your town?

AL: The people in my town thought I was a big joke because I spent my free time making lenses and looking at my animalcules. I could find no one who wanted to learn my secrets of lens making. I became unwilling to share my work and I have kept some secrets about lighting my specimens in my head. These secrets died with me. Even my very good friend, Jan Vermeer, wrote me a letter expressing his concern that I was "setting out on a dangerous journey that might bring humanity not only advantage but also irreparable harm." He said that the wonderous things that I showed him in a drop of water were "strange creatures that swirl in the water like in Bosch's transparent hell."
(Editor's Note: Jan Vermeer frequently employed a device known as the camera obscura, a kind of primative camera, when painting. It is not unreasonable to imagine that he acquired the required lens from van Leeuwenhoek.)

JL: Did you continue to be friends with Jan Vermeer.

AL: Oh, yes. He also wrote that he knew he could not convince me to "abandon polishing my lenses" but he wanted to continue "speaking joy from recovered harmony."

JL: It is true that is was not for 100 years that someone finally discovered a way to make lenses that could reveal the animalcules called bacteria. Until then, no microscopes were as good as yours.

Tell us how long you lived?

AL: I died on August 30, 1723 when I was 91 years old - a very long life for someone born in the 17th century.

JL: Why do you think you managed to live such a long life?

AL: I think that my curiosity and my persistence kept life very interesting for me. Each day, I wanted to see more new things with my instruments. People who are passionately interested in something have a reason to live.

JL: Mr. van Leeuwenhoek, when you died, the pastor of the New Church at Delft wrote the following to the Royal Society:

Antonie van Leeuwenhoek considered that what is true in natural philosophy can be most fruitfully investigated by the experimental method, supported by the evidence of the senses; for which reason, by diligence and tireless labour he made with his own hand certain most excellent lenses, with the aid of which he discovered many secrets of Nature, now famous throughout the whole philosophical World.

You are a very famous person in the scientific world of 1998. Biology students are using modern compound microscopes to observe the same animalcules that you described in the 1700's! Thank you so much for spending time with us today. I am returning now to 1998, to write up my interview and share it with other people.

AL: Thank you. And should you see my good friend Vermeer, tell him I say hello.

Helleman, Alexander and Bryan Bunch, The Timetables of Science, Simon and Schuster, NY, 1988.

Rosebury, Theodor, Life on Man, The Viking Press, New York, 1969.

(Includes pictures of simple lens built by Leeuwenhoek.)

(Has many links to other sites about Leeuwenhoek.)


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