This book describes the basic electrical properties of a variety of mammalian tissues in scientific terms that even a student who has had little formal training in the physics of electricity should find understandable. Familiarity with Ohm's Law is one of the few basic tenets of physics which a reader of this book is assumed to possess. Mathematical treatment is kept to a minimum and formal thermodynamic reasoning is avoided. Instead, reliance is placed upon intuitive ideas of energy with which any undergraduate student of biology who needs to study electric events should feel comfortable.