Ruska, Ernst WORLD OF MICROBIOLOGY AND IMMUNOLOGY496•
tried on humans, and Pasteur was reluctant to give it to the
boy; but when two physicians stated that Meister would die
without it, Pasteur relented and administered the vaccine.
Pasteur stated that he utilized the attenuated strain of the
vaccine; his lab notes, however, confirm that he treated
Meister with the dead strain that Roux had been working on.
(Why Pasteur maintained that he used his attenuated strain is
not clear.) In any case, Meister received 13 shots of the rabies
vaccine in the stomach in 10 days and was kept under close
observation for an additional 10 days. The boy survived and
became the first person to be immunized against rabies.
In 1883 Roux became the assistant director of Pasteur’s
laboratory. He undertook administrative responsibilities to
help establish the Pasteur Institute, which opened in 1888 with
Roux serving as director (from 1904) and teaching a class in
microbiology.
Also in 1883 Roux and Yersin discovered the diphtheria
toxin secreted by Corynebacterium diphtheriae. The two sci-
entists filtered the toxin from cultures of the diphtheria bac-
terium and injected it into healthy laboratory animals. The
animals exhibited the same symptoms (and eventual death) as
those infected with the bacterium. Other data to support their
discovery of the diphtheria toxin included urine obtained from
children infected with the microorganism. Toxin excreted in
the urine was sufficient to produce the same symptoms of the
disease in laboratory animals. In 1894 Roux and Louis Martin
began to study the immunization of horses against diphtheria
in order to create a serum to be used in humans. The outcome
of their research led them to successfully treat 300 children
with the serum.
Beginning in 1896 Roux researched different aspects of
diseases such as tetanus, tuberculosis, bovine pneumonia, and
syphilisuntil he became the director of the Pasteur Institute in- At that time Roux ceased all personal research and
focused solely on running the Pasteur Institute until his death
from tuberculosis in 1933.
See alsoBacteria and bacterial infection; History of microbi-
ology; History of public healthRRuska, Ernst USKA, ERNST(1906-1988)
German physicistThe inventor of the electron microscope, Ernst Ruska, com-
bined an academic career in physics and electrical engineering
with work in private industry at several of Germany’s top elec-
trical corporations. He was associated with the Siemens
Company from 1937 to 1955, where he helped mass produce
the electron microscope, the invention for which he was
awarded the 1986 Nobel Prize in physics. The Nobel Prize
Committee called Ruska’s electron microscope one of the
most important inventions of the twentieth century. The bene-
fits of electron microscopy to the field of microbiology and
medicine allow scientists to study such structures as viruses
and protein molecules. Technical fields such as electronics
have also found new uses for Ruska’s invention: improvedversions of the electron microscope became instrumental in
the fabrication of computer chips.
Ruska was born in Heidelberg, Germany, on December
25, 1906. He was the fifth child of Julius Ferdinand Ruska, an
Asian studies professor, and Elisabeth (Merx) Ruska. After
receiving his undergraduate education in the physical sciences
from the Technical University of Munich and the Technical
University of Berlin, he was certified as an electrical engineer
in 1931. He then went on to study under Max Knoll at Berlin,
and received his doctorate in electrical engineering in 1933.
During this period, Ruska and Knoll created an early version of
the electron microscope, and Ruska concurrently was
employed by the Fernseh Corporation in Berlin, where he
worked to develop television tube technology. He left Fernseh
to join Siemens as an electrical engineer, and at the same time
accepted a position as a lecturer at the Technical University of
Berlin. His ability to work in both academic and corporate
milieus continued through his time at Siemens, and expanded
when in 1954, he became a member of the Max Planck Society.
In 1957, he was appointed director of the Society’s Institute of
Electron Microscopy, and in 1959, he accepted the Technical
University of Berlin’s invitation to become professor of elec-
tron optics and electron microscopy. Ruska remained an active
contributor to his field until his retirement in 1972.
Prior to Ruska’s invention of the electron microscope in
1931, the field of microscopy was limited by the inability of
existing microscopes to see features smaller than the wave-
length of visible light. Because the wavelength of light is
about two thousand times larger than an atom, the mysteries of
the atomic world were virtually closed to scientists until
Ruska’s breakthrough using electron wavelengths as the reso-
lution medium. When the electron microscope was perfected,
microscope magnification increased from approximately two
thousand to one million times.
The French physicist, Louis Victor de Broglie, was the
first to propose that subatomic particles, such as electrons, had
wavelike characteristics, and that the greater the energy exhib-
ited by the particle, the shorter its wavelength would be. De
Broglie’s theory was confirmed in 1927 by Bell Laboratory
researchers. The conception that it was possible to construct a
microscope that used electrons instead of light was realized in
the late 1920s when Ruska was able to build a short-focus
magnetic lens using a magnetic coil. A prototype of the elec-
tron microscope was then developed in 1931 by Ruska and
Max Knoll at the Technical University in Berlin. Although it
was less powerful than contemporary optical microscopes, the
prototype laid the groundwork for a more powerful version,
which Ruska developed in 1933. That version was ten times
stronger than existing light microscopes. Ruska subsequently
worked with the Siemens Company to produce for the com-
mercial market an electron microscope with a resolution to
one hundred angstroms (by contrast, modern electron micro-
scopes have a resolution to one angstrom, or one ten-billionth
of a meter).
Ruska’s microscope—called a transmission micro-
scope—captures on a fluorescent screen an image made by a
focused beam of electrons passing through a thin slice of met-
alized material. The image can be photographed. In 1981,womi_R 5/7/03 8:17 AM Page 496