Microbiology and Immunology

WORLD OF MICROBIOLOGY AND IMMUNOLOGY Electron microscope, transmission and scanning

179

•

ten or twenty thousand more patients. There was no halting the

demand, however, and the Georg Speyer Haus ultimately

manufactured and distributed 65,000 units of 606 to physi-

cians all over the globe free of charge. Eventually, the large-

scale production of 606, under the commercial name

“Salvarsan,” was taken over by Höchst Chemical Works. The

next four years, although largely triumphant, were also filled

with reports of patients’ deaths and maiming at the hands of

doctors who failed to administer Salvarsan properly.

In 1913, in an address to the International Medical

Congress in London, Ehrlich cited trypan red and Salvarsan as

examples of the power of chemotherapy and described his

vision of chemotherapy’s future. The City of Frankfurt hon-

ored Ehrlich by renaming the street in front of the Georg

Speyer Haus “Paul Ehrlichstrasse.” Yet in 1914, Ehrlich was

forced to defend himself against claims made by a Frankfurt

newspaper, Die Wahrheit(The Truth), that Ehrlich was testing

Salvarsan on prostitutes against their will, that the drug was a

fraud, and that Ehrlich’s motivation for promoting it was per-

sonal monetary gain. In June 1914, Frankfurt city authorities

took action against the newspaper and Ehrlich testified in

court as an expert witness. Ehrlich’s name was finally cleared

and the newspaper’s publisher sentenced to a year in jail, but

the trial left Ehrlich deeply depressed. In December, 1914, he

suffered a mild stroke.

Ehrlich’s health failed to improve and the start of World

War I had further discouraged him. Afflicted with arterioscle-

rosis, his health deteriorated rapidly. He died in Bad

Homburg, Prussia (now Germany), on August 20, 1915, after

a second stroke. Ehrlich was buried in Frankfurt. Following

the German Nazi era, during which time Ehrlich’s widow and

daughters were persecuted as Jews before fleeing the country

and the sign marking Paul Ehrlichstrasse was torn down,

Frankfurt once again honored its famous resident. The

Institute for Experimental Therapy changed its name to the

Paul Ehrlich Institute and began offering the biennial Paul

Ehrlich Prize in one of Ehrlich’s fields of research as a memo-

rial to its founder.

See alsoHistory of immunology; History of microbiology;

History of public health; History of the development of antibi-

otics; Infection and resistance

ELECTRON MICROSCOPE, TRANSMISSION

AND SCANNINGElectron microscope, transmission and scanning

Described by the Nobel Society as “one of the most important

inventions of the century,” the electron microscopeis a valu-

able and versatile research tool. The first working models

were constructed by German engineers Ernst Ruskaand Max

Knoll in 1932, and since that time, the electron microscope has

found numerous applications in chemistry, engineering, medi-

cine, molecular biologyand genetics.

Electron microscopes allow molecular biologists to

study small structural details related to cellular function.

Using an electron microscope, it is possible to observe and

study many internal cellular structures (organelles). Electron

microscopy can also be used to visualize proteins, virus parti-

cles, and other microbiological materials.

At the turn of the twentieth century, the science of

microscopy had reached an impasse: because all optical

microscopes relied upon visible light, even the most powerful

could not detect an image smaller than the wavelength of light

used. This was tremendously frustrating for physicists, who

were anxious to study the structure of matter on an atomic

level. Around this time, French physicist Louis de Brogliethe-

orized that subatomic particles sometimes act like waves, but

with much shorter wavelengths. Ruska, then a student at the

University of Berlin, wondered why a microscope couldn’t be

designed that was similar in function to a normal microscope

but used a beam of electrons instead of a beam of light. Such

a microscope could resolve images thousands of times smaller

than the wavelength of visible light.

There was one major obstacle to Ruska’s plan, how-

ever. In a compound microscope, a series of lenses are used

to focus, magnify, and refocus the image. In order for an

electron-based instrument to perform as a microscope, some

device was required to focus the electron beam. Ruska knew

that electrons could be manipulated within a magnetic field,

and in the late 1920s, he designed a magnetic coil that acted

as an electron lens. With this breakthrough, Ruska and Knoll

constructed their first electron microscope. Though the pro-

totype model was capable of magnification of only a few

hundred power (about that of an average laboratory micro-

scope), it proved that electrons could indeed be used in

microscopy.

A transmission electron microscope.

womi_E 5/6/03 2:12 PM Page 179