ABSTRACT
A living subject consists of tissues and fluids with differing conducting properties. Current injected into a subject will seek the tissues and fluids with the lowest resistivities. Because cell membranes have dielectric properties, a tissue specimen can exhibit a small capacitive component, depending on the frequency used for measurement. The resistivity for direct current represents current flowing mainly in the fluid surrounding the cells. Resistivity is measured with the bipolar or tetrapolar method. Typical values for tissue resistivity are presented in the accompanying tables. Many of the values were derived from the review presented by L. A. Geddes and L. E. Baker. Many different electrolytic preparations have been used to establish electrical contact between a metal electrode and the skin. The low-resistivity preparations are used when current is delivered, as for example in stimulation, cardioversion and ventricular defibrillation. High-resistivity preparations are used for recording bioelectric events, such as the electrocardiogram.
