Electrical potential difference across blood vessels.

• Over the past decade, several types of experiments characterizing the electrical properties of blood vessels have been carried out.' 2 Some of these experiments were done to determine the possible existence, magnitude, and polarity of the normal potential difference across the aortic and vena caval wall using in vivo and in vitro preparations." The first group of experiments was done in the living dog where saline-filled polyethylene tubes were implanted across canine blood vessel walls for periods up to several weeks. Measurement of the potential difference using these catheters as salt bridges gave values as high as 30 to 40 millivolts (mv.) with the intimal side of the blood vessel ordinarily negative to the adventitial side. We were able to determine, by mathematical treatment of the data at that time, that the potential difference was in large degree produced by tissues surrounding the aorta. This finding has since been substantiated by additional experimental work. Since then, in vitro experiments have been developed to measure the transniural potential difference across membranized aortic wall. As the techniques of measurement improved, it became apparent that if an electrical potential existed across the exteriorized, but otherwise uninjured, blood vessel, it was quite amall.