when leeuwenhoek discovered microorganisms-- 4/21/17

Today's selection -- from I Contain Multitudes by Ed Yong. The Dutch amateur scientist Antony van Leeuwenhoek was the first person to observe and describe microorganisms:

"In 1632, Antony van Leeuwenhoek was born in the city of Delft, a bustling hub of foreign trade permeated by canals, trees, and cobbled paths. By day, he worked as a city official and ran a small haberdash­ery business. By night, he made lenses. It was a good time and place to do so: the Dutch had recently invented both the compound micro­scope and the telescope. Through small circles of glass, scientists were peering at objects too far or too small to see with the naked eye. The British polymath Robert Hooke was one. He gazed at all manner of minute things: fleas, lice clinging to hairs, the points of needles, pea­cock feathers, poppy seeds. In 1665 he published his observations in a book called Micrographia, complete with gorgeous and extraordinarily detailed illustrations. It became an instant bestseller in Britain. Small things had hit the big time.

A portrait of Antonie van Leeuwenhoek
(1632-1723) by Jan Verkolje

"Leeuwenhoek ... never went to uni­versity, was not a trained scientist, and spoke only Dutch rather than the more scholarly Latin. Even so, he taught himself to make lenses with a skill that no one else could match. The exact details of his tech­nique are unknown but, broadly speaking, he would grind a bauble of glass into a smooth and perfectly symmetrical lens, less than two mil­limetres across. This he sandwiched between a pair of brass rectan­gles. He would then fix a specimen in front of the lens with a tiny pin, and adjust its position with a couple of screws. The resulting micro­scope looked like a glorified door hinge, and was little more than an adjustable magnifying glass. To use it, Leeuwenhoek had to hold it so that it was practically touching his face, while squinting through the tiny lens, preferably in bright sunlight. These single-lens models were much harder on the eye than the multi-lens compound microscopes that Hooke championed. But they produced clearer images at higher magnification. Hooke's instruments magnified objects by 20 to 50 times; Leeuwenhoek's did so by up to 270 times. In their day they were easily the best microscopes on earth.

"But Leeuwenhoek was 'more than a good microscope maker', observes Alma Smith Payne in The Cleere Observer. 'He was also an excellent microscopist -- a user of microscopes.' He documented everything. He repeated observations. He conducted methodical experiments. Even though he was an amateur, the scientific method instinctively ran deep within him -- as did a scientist's untrammelled curiosity about the world. Through his lenses, he gazed at animal hairs, fly heads, wood, seeds, whale muscle, skin flakes, and ox eyes. He saw marvels, and he showed them to friends, family, and scholars in Delft. ...

Van Leeuwenhoek's microscopes by Henry Baker

"And then, Leeuwenhoek looked at some water -- specifically, water of Berkelse Mere, a lake near Delft. Sucking some of the turbid liquid into a glass pipette and mounting it on his microscope, he saw that it was teeming with life: 'little green clouds' of algae, along with thousands of tiny, dancing creatures. 'The motion of most of these animalcules in the water was so swift, and so various upwards, down­wards and round about that 'twas wonderful to see,' he wrote, 'and I judged that some of these little creatures were above a thousand times smaller than the smallest ones I have ever yet seen upon the rind of cheese.' They were protozoa -- the diverse group of organisms that includes amoebas and other single-celled eukaryotes. Leeuwenhoek had become the first person ever to see them.

"In 1675, Leeuwenhoek used his lenses to look at rainwater, which had gathered in a blue pot outside his house. Again, a delightful menag­erie appeared. He saw serpentine things that wound and unwound themselves, and ovals 'furnished with diverse tiny feet' -- more proto­zoa. He also saw examples of an even tinier class of creature, a thousand times smaller than a louse's eye, which would 'turn themselves about with that swiftness as we see a top turn round' -- bacteria! He looked at more water, from his study, his roof, Delft's canals, the nearby sea, and the well in his garden. The little 'animalcules' were everywhere. Life, it turned out, existed in untold numbers beyond the threshold of our perception, visible only to this one man and his superlative lenses. As historian Douglas Anderson later wrote, 'Almost everything he saw, he was the first human ever to see.' And more to the point, why did he look at the water in the first place? What on earth possessed this man to scrutinise rain that had collected in a pot? A similar question could be asked of many people throughout the entire history of microbiome research: they were the ones who thought to look. ...

"Leeuwenhoek['s] missives ... [contain] fascinatingly detailed accounts of the animalcules. They were 'incredibly small; nay, so small, in my sight, that I judged that even if 100 of these very wee animals lay stretched out one against another, they could not reach the length of a grain of coarse sand; and if this be true, then ten hundred thousand of these living crea­tures could scarce equal the bulk of a coarse grain of sand'. (He later noted that a sand grain is around 1/80th of an inch across, which would make these 'wee animals' 3 micrometres long. That is, more or less, the length of an average bacterium. The man was astonishingly accurate.)"

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