7 Paul Müller 7

rapid, potent toxicity for the greatest number of insect

species but would cause little or no damage to plants and

warm-blooded animals. He also required that it have a

high degree of chemical stability, so that its effect would

persist for long periods of time and its manufacture

would be economical. Four years later Müller tested a

substance known as dichlorodiphenyltrichloroethane

(DDT) and found that it satisfied these requirements. The

German chemist Othmar Zeidler had first synthesized

the compound in 1874 but had failed to realize its value as

an insecticide.

In 1939 DDT was tested successfully against the

Colorado potato beetle by the Swiss government and by

the U.S. Department of Agriculture in 1943. In January

1944 DDT was used to quash an outbreak of typhus carried

by lice in Naples, the first time a winter typhus epidemic

had been stopped.

Although Müller had required his ideal insecticide to

be relatively nontoxic to warm-blooded animals, the

widespread use and persistence of DDT (in 1968 it was

estimated that 1,000,000,000 pounds [453,000,000 kg]

of the substance remained in the environment) made it a

hazard to animal life, and it showed signs of disrupting

ecological food chains. By 1970 DDT was rapidly being

supplanted by more quickly degraded, less toxic agents; its

use was banned in a number of countries.

Ernest O. Lawrence

(b. Aug. 8, 1901, Canton, S.D., U.S.—d. Aug. 27, 1958, Palo Alto, Calif.)

E

rnest Orlando Lawrence, an American physicist, was

awarded the 1939 Nobel Prize for Physics for his

invention of the cyclotron, the first particle accelerator to

achieve high energies.