Measurements of skin conductivity using silver disc and multtplint electrodes have been described. Comparisons with skin temperature measurements using thermistor probes have been made, and a parallel between the two parameters demonstrated. A connection between skin conductivity and blood flow was suggested, and confirmed by the effects on conductivity of exercise and the intradermal injection of adrenaline and histamine under the electrode site. The implications of this are discussed and a possible role of such measurements in the clinic is mentioned.IT is customary to consider the resistance of the skin to the passage of direct current as a function of the thickness of the stratum corneum and its moisture content (Tregear, 1966). Thus, the skin galvanic responses investigated by psychologists are said to have their origin in a temporary increase of permeability of the cells of the sweat glands. There is, however, the evidence from earlier German workers that epidermal cell permeability changes are involved (Gildermeister, 1912; Kbbecke, 1912), and Shaver ei a^ (1962) observed an epidermal component in their experiments to investigate the .site of the skin potential response, in addition, Darrow (1927Darrow ( , 1929 reported observing maximal sweating with poor response amplitude and vice-versa, while Richter (1929) conchuled one of his many papers with tlie coinmcnt that factors involved with temperature control appear to play a role.Thus, despite the accepted view regarding thickness and moisture content of the stratum corneum. there are grounds for considering that some other factor might play a role. The most likely one to be involved here VA the circulation with respect to either the diameter of, or rate of flow of blood, in the small vessels of the skin. This is because the body is a volume conductor and the bulk of resistance lies therefore in the skin innnediateiy under the electrodes (Sucklhig, 1901), In this region, therefore, blood flow is the parameter most likely to be capable of undergoing sudden rapid changes such as are seen in the skin resistance response, etc. In support of this theory it is interesting that the areas of lowest resistance and maximum response are the fingertips; the palms, then the dorsum of the hand, and finally the forearm follow. Not only does the density of sweat glands follow this order but also the density of the arterio-venous shunts, which can be up to 250/mm'^ on the fingertips (Rothman, 1954). On the forearm there are probablj' none at all. These shunts are also found between artcrioles and venules and at metarteriole level. The calibre of these smaller vessels is under both local metabolic and central nervous control.Aocepted for publication April 20th, 1972.
