Word: cardiogram
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Dates: during 1930-1939
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...James Franklin Yeager of the Department of Agriculture projected on a screen a cardiogram from the beating heart of a cockroach. This was obtained by exposing the heart of the insect and placing on it a minute drop of wax. A human hair inserted in the wax was connected through a lever to a fine wire. The heart beats thus jerked the wire and a light beam passing across it translated them into a pulsating graph. The Department uses this method to study the cardiac effect of insecticides...