The Undiscovered Country: The Development of the Electron Microscope

By: Julie Stoehr

A clear succession of ideas and discoveries across the globe led to the development one of the most significant contributions to the study of the biological and medical sciences – the electron microscope. However, very few people realize that there were several notable Canadian connections to the development of the instrument that has allowed scientists to visualize and resolve structures previously undiscovered using the light microscope.

The summer of 1935 was a pivotal one for the involvement of Canadians in the field of electron optics. It was at this time that E. F. Burton, Chairman of the Physics department at the University of Toronto, visited Berlin to attend a meeting on Possible Areas for the Application of the Electron Microscope. Just three years previously, an electron microscope with a resolving power of 500 Å, (better than that of the light microscope), was fashioned in 1932 by a team of scientists including Ernst Ruska who had also constructed a crude model in 1931 (recognized as the first electron microscope). Unfortunately this instrument held little practical application for research since it was a complicated apparatus and inevitably destroyed the specimens it magnified. After attending the meeting Burton became certain that, once perfected, the electron microscope would be a key tool in biological and medical research and he came back to Canada determined to construct such an instrument. Over the next two and a half years, he persuaded three graduate students, Cecil Hall (University of Alberta), Albert Prebus (University of Alberta), and James Hillier (University of Toronto) to become involved in designing and constructing the first electron microscope of practical application in North America. In 1938 Prebus and Hillier, developed an instrument at the University of Toronto, which had a resolving power of 140 Å. Further work on the instrument resulted in a resolving power of better than 60 Å just ten months later. The design of this ground-breaking instrument was largely based on the crude microscope designed as part of Hall’s 1935 Master’s thesis, yet his results were never published in a scientific journal. After leaving Toronto for financial reasons, Hall designed and built the first electron microscope in the United States as part of his work for the Eastman Kodak company in 1938. This instrument was not marketed as management decided it did not represent a suitable product line for the company.

The design of Prebus and Hillier became the basis of the first commercial series of electron microscopes developed in 1941 by the Radio Corporation of America. Interestingly enough, Hillier was a key contributor to this project as he joined the RCA in 1940, yet several textbooks and publications neglect to even acknowledge the assistance of Canadians in the discovery of the electron microscope.

Questions:

1. Despite the clear timeline establishing the development of the electron microscope, none of the above scientists is credited in patent law for its creation. Instead a gentleman named Rudolf Ruedenberg employed by the Siemens Corporation in Germany filed a patent in 1931 and receives credit for being the inventor of the electron microscope. Is Ruedenberg a shrewd opportunist, simply acting in the best interests of his company who hoped to develop the first commercially available electron microscope, or should his credit for the invention be revoked? To whom should the credit belong?

2. After his visit to Berlin in 1935, Burton persuaded at least two of his graduate students to switch from the study of spectroscopy to that of electron optics in his quest to develop the first North American electron microscope. Is this the mark of a passionate leader or was Burton taking advantage of his supervisory position to further his own research aspirations?

3. Rarely does the history of the electron microscope mention the work of Cecil Hall who not only contributed to the production of the Toronto microscope, but who also constructed the first electron microscope in North America. Should Hall have been credited as a contributor in the Toronto publication of 1939 since his initial microscope served as a stepping stone for Prebus and Hillier?

4. The Radio Corporation of America constructed the first commercially marketed electron microscope, yet rarely is it mentioned that the design was founded at the University of Toronto. Are Canadians being denied historical credit? Consider that nearly all historical accounts mention the findings of Ruska’s lab in the course of commercial development.

Curriculum Fit:

Science 10 Unit 2: Energy and Matter in Living Systems –

Attitude: students will be encouraged to appreciate that our knowledge of biology has been enhanced by the application of technology.

Concept 1: The cell is the basic unit of living systems –STS connection: describe how advancements in knowledge of cell structure increased as a direct results of developments in microscope technology, including electron microscopes (eg. Nobel Prize in Physiology / Medicine, 1974).

References:

http://helios.physics.utoronto.ca/~interact/microsco/microscopy.htm

http://www.nobel.se/medicine/laureates/1974/press.html

Bradbury, S. The Evolution of the Electron Microscope. 1967. Pergamon Press Ltd.

Burton, E.F. and W.H. Kohl. The Electron Microscope. 1942. Reinhold Publishing Corporation.

Doane, F.W., G.T. Simon, J.H.L. Watson. Canadian Contributions to Microscopy. 1993. Microscopical Society of Canada.

Grimstone, A.V. The Electron Microscope in Biology. 1968. Edward Arnold Ltd.

Meek, M.A. Practical Electron Microscopy for Biologists. 1970. William Clowes and Sons Ltd.

Prebus A. and J. Hillier. The construction of a magnetic electron microscope of high resolving power. 1939. Can. J. Res. Vol. A17. pp 49-63.

Zworykin, V.K., G.A. Morton, E.G. Ramberg, J. Hillier, A.W. Vance. Electron Optics and the Eletron Microscope. 1945. John Wiley and Sons, Inc.

Zworykin, V.K., J. Hillier, A.W. Vance. An electron microscope for practical laboratory service. 1941. Elec. Eng. Vol. 60. pp 157-161.