One of our basic aims here at Medical Museion is to put current trends in biomedicine in a longer historical perspective. Last Friday, we got yet another opportunity for doing this, when the new Core Facility for Integrated Microscopy at the Faculty of Health Sciences opened together with an international research symposium on the state-of-the-art of microscopy.
In the hallway outside the symposium room, we displayed a selection of six of our most beautiful old microscopes that represent the development from early simple single lenses to end of the 19th century compound microscopes. The aim was to make the symposium participants better appreciate the beauty of early microscopes and the craftsmanship that has gone into constructing them.
During the lunch break, I had a chat with Peter Evennett, who has edited the English version of Harald Moe’s classical The Story of the Microscope together with Chris Hammond. Peter and Chris, who are members of the Royal Microscopical Society’s outreach and education committee, has helped us select the displayed items from our large collection of microscopes and write the showcase texts for the exhibition, which was designed and put together by Bente and Ion.
The oldest microscope (or rather replica of a microscope) selected is actually only a lens in a brass fitting, made in 1670 by Anthony van Leuwenhoek of Delft, who for the first time ever was able to clearly observe life on an incredibly small scale. Holding the lens at a slant towards the light, he was able to see living bacteria and wriggling, human sperm cells. It was the beginning of a whole new era for science.
Peter went on to tell me how early microscopes weren’t used for science, as I thought, but were a kind of intellectual hobby and prestige objects for wealthy gentlemen. Consequently many of the microscopes from this period are quite charming and exquisite. It wasn’t until the 1830s — when the wine merchant J. J. Lister was able to produce objectives that minimised the colour fringing — that the microscope was seriously introduced into science. And so in 1839 a group of scientists got together to propose a toast to the instrument and to found the Royal Microscopical Society.
On display was also a modern single lens microscope from 1848, just like the one Darwin brought with him on the Beagle. The newest microscopes in the exhibition were compound microscopes from the end of the 19th century. They had a double lens system, with an objective lens that projected the image from the sample up through the tube to the eye lens, which worked as a magnifying glass. The light was redirected from a window or an oil lamp via a small built-in mirror, to hit the sample from below and carry the image up the tube, to the pupil of the scientist’s eye.
And then Peter’s efforts to educate me became technical …
Though it was by means of light that the microscope functioned, light was also the factor setting the limit for how detailed the samples could be shown. Opposed to what many people think, the basic principle in microscopy is not magnification, but resolution. In the 1860s and 1870s, the German physician Ernst Abbe (co-owner of the Carl Zeiss AG, the famous microscope producer) discovered that the smallest distance you can have between two things before the images of them merge — and thereby determining how detailed a picture you can see in a microscope — is limited by three factors: 1) the angle of the light entering the microscope, 2) the substance through which the light has to pass, and 3) the wavelength of the light.
Of these three limiting factors the last is now being contested by using electrons with a wavelength 100.000 times smaller than visible light. But, as Peter puts it, that’s using tricks.