Depth of Field in Microscope Objectives

Abstract

Improved surface electrodes for recording biolelectric potentials made from sponge rubber are described. The sealed side of the rubber is pressed to a piece of surgeon''s tape or Scotch tape, and the rough side is applied to the skin. The sponge is moistened with saline. Forty subjects were tested for change in resistance for periods up to 5 hrs. If the electrode has enough fluid to wet the skin completely, the resistance between 2 electrodes, placed 2.25 inches apart on the forehead, usually decreases slightly with time. Initial resistance varied from 4,000-41,000 ohms, and final resistance from 2,000-38,000 ohms.