The Microscope

What is the history behind one of the most helpful technological advances of our time, the microscope?

A cheek cell. An onion cell. An upside-down e. A drop of green pond water, teeming with writhing shapes. Most of us, at some point in our education, have peered into a microscope at the miniscule, silent world at the end of the lens. In fact, it would be hard to imagine a complete science classroom without one of these valuable instruments.

“ It would be difficult to overestimate the immense impact the invention of the microscope has had on the world these past several centuries, or to fully realize the number of scientific breakthroughs and technological advances allowed by its peering lenses. ”

While ancient writings mention the use of glass and possibly even forms of crude lenses to magnify objects, the microscope as we know it is relatively new technology, developed and perfected over the past several centuries. Though there is some debate over the exact beginnings of the modern microscope, the story typically begins in a small spectacle shop in Holland.
A New Way of Looking At Things

During the late sixteenth century, the young Dutch spectacle maker Zacharias Janssen and his father, Hans, experimented with glass by lining up several convex lenses in a tube and focusing the tube on a nearby object. Light would bend and magnify the image, making the object appear more detailed and three to nine times larger. Their discovery led to the development of the compound microscope, in which an objective lens is fixed near the specimen and the eyepiece lens is placed near the eye. Independent work done with magnifying tubes by fellow Dutch optician Hal Lippershey and the Italian scientist, Galileo, also played a part in developing the compound microscope.

The following decades brought a heightened interest in the microscope, primarily as a novelty to amuse the rich, but also increasingly as a scientific tool. In 1661, the Italian physiologist Marcello Malpighi was able to describe the network of pulmonary capillaries in the human body based on his microscopic observations. The brilliant scientist and creationist Robert Hooke improved the design of the compound microscope and used it to observe and record unique microscopic details of nature. He published the results in 1665 in his landmark volume Micrographia, a collection of thirty-eight copper plate illustrations of observations such as the detailed structures of a flea and body lice and the minuscule units of cork tissue, for which he coined the term “cells.”

In 1673, while Hooke worked as the Curator of Experiments for the newlyformed Royal Society of London, the organization began receiving insightful and lively letters from a Dutch tradesman named Antony van Leeuwenhoek, who reported observing “Animals” (bacteria and protozoa) in pond water and teeth scrapings, as well as blood cells, yeast, and other single-celled entities. Inspired by Hooke’s Micrographia, van Leeuwenhoek made over five hundred single-lens microscopes as a hobby, and although they were very simple structures, the lenses he grinded were the best in Europe—with a magnification of up to 270 times—producing microscopic images never before seen.

For fifty years, Van Leeuwenhoek’s long, descriptive letters were published in the periodical Philosophical Transactions of the Royal Society of London,inspiring other scientists to look through an eyepiece as well. He wrote in one letter to the society:

took some of this flower and mixt it . . . with pure rain water wherein were no Animals . . . and then to my great surprize perceived that the aforesaid matter contained very many small living Animals, which moved themselves very extravagantly.

[T]heir motion was strong & nimble, and they darted themselves thro the water . . . as a Jack or Pike does thro the water. (Philosophical Transactions of the Royal Society of London,Vol. 14, 1684, no. 159, pages 568–74; reprinted inMilestones in Microbiologyby Thomas D. Brock, American Society for Microbiology, 1999)

Though Van Leeuwenhoek was thorough in reporting what he observed, he was very secretive about his process for grinding and illuminating his superior lenses, and consequently it was over a century after his death before compound microscopes were as excellent as the single-lens ones made by Van Leeuwenhoek.
Technological Advances

Some important discoveries were made with early microscopes, and great advances were made in their quality, but the lenses were still relatively weak. There was also often a blurred ring of color, a “halo,” around the edge of the image. These problems, which hindered the scientists’ ability to undertake more sophisticated research, were resolved in 1830 when Joseph Jackson Lister, a wine merchant by trade, proceeded to create a specialized lens for the microscope by layering several weak lenses together, enlarging the view of the specimen while eliminating the hazy images that blurred the view. With these improvements, Lister ushered in the modern era of microscopy.

Other advancements in the construction and use of microscopes during the 1800s include Ernst Leitz’s invention in 1873 of a revolving mount for five objective lenses, as well as August Köhler’s superior illumination technique, developed in 1893, and still referred to today as “Köhler illumination”. Much of the rapid progress in medical research that began during the late nineteenth century, such as the monumental work done by Louis Pasteur and Robert Koch regarding the role of bacteria in the spread of disease, was made possible by the new advances in the technology of manufacturing microscopes.

All of the microscopes used into the early part of the twentieth century were optical microscopes, which use light beams to create a magnified image, but the wavelength of light limits the visibility of even the most specialized optical microscopes. Max Knoll and Ernst Ruska broke past this barrier in 1931 by inventing the electron microscope, which can now magnify an object up to two million times by focusing a beam of electrons onto an object, allowing smaller units such as cellular ribosomes and viruses to be viewed and studied. Many of the detailed photos of microscopic organisms and structures published in contemporary science books have been taken with some type of electron microscope.

Those early researchers would probably be impressed, or even awed, by what can be seen today with just a common student microscope. Yet there are now over forty types of microscopes to choose from which they could choose in essentially every field of science, utilizing not only light or electrons to produce images, but also technologies such as magnetic forces and X-rays.

It would be difficult to overestimate the immense impact the invention of the microscope has had on the world these past several centuries, or to fully realize the number of scientific breakthroughs and technological advances allowed by its peering lenses. This revolutionary tool has taken us to hidden places beneath our feet, within our food, and even inside our own bodies, revealing to us a realm of God’s creation that, without the microscope, would still be unknown.

For merely to say that the discovery of the microscope enlarged the scope of our vision sounds utterly pedestrian. It did much more that that: it replaced the world we lived in with a “plurality of worlds,” each of them an abyss, a labyrinth, a universe replete with its own beauties and its own terrors. We used to see from the elephant down to the mite: thenceforth we had a world populated with tiny animalcules to whom the mite was elephant.Introduction by F. Gonzalez-Crussi, M.D., toMicrobe Huntersby Paul DeKruif, Harcourt Brace & Company, 1926)

by Laura Phipps
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