Dr. Eugene D. Brand and Harry S. Marshall, the Grass Polygraph (Left), and the Dual Beam Oscilloscope and Camera (Right)
Online; Still Image
UVa Medical Alumni News Letter
From caption accompanying picture in UVa Medical Alumni News Letter, October-November 1958: "Dr. Eugene D. Brand and Harry S. Marshall [of Pharmacology Department] observe recordings made from the cardiovascular and central nervous systems of an animal as it develops irreversible hemorrhagic shock. Changes in the animals are measured by the Grass Polygraph (left) and the dual beam oscilloscope and camera (right). "These devices operate on the same principal but the speed of response of the oscilloscope is much greater. They can amplify and rec ord electric currents originating either in the animal (electrocardiogram, electroencephalogram, nerve or impluse) or in physical or chemical phenemena (temperature by means of thermocuoples, oxygen tension by the platinum electrode method, etc.). "By means of transducers (whose electrical resistance changes with changes in the variable being measured) and a Wheatstone bridge, they can record physical phenomena such as pressures, volumes, tensions, movement, temperature, and light transmittance."