We define biomagnetism broadly as the science of processes and functions in living organisms induced by static magnetic fields. Biomagnetic research has greatly increased since the publication of the first volume of this series. While much of this work has been reported in various international journals, there exists a need for this work to be collected together in one place. This book covers a rather wide area of research, both with respect to the strength of the field, ranging from "zero" to 150,000 oersteds, and with respect to the various specimens and their biological functions. It is designed primarly to help clarify the action of magnetic fields on biological systems with the hope of achieving a better understanding of the fundamental physiological processes occurring in them. In some chapters it is suggested that magnetic fields could ultimately be used in the treatment of disease. I would like to take this occasion to thank the contributors for their generous interest and willing cooperation. M. F. B. June 1969 Chicago, Illinois v CONTRIBUTORS Robert A. Abler, Varian Associates, Palo Alto, California (page 1). M. M. Alexandrovskaya, Institute of Higher Nervous Activity and Neuro­ physiology, Academy of Sciences, Moscow, USSR (page 215). Jena M. Barnothy, Biomagnetic Research Foundation, Evanston, Illinois (page 61). Madeleine F. Barnothy, College of Pharmacy, University of Illinois, Chicago, Illinois (pages xi, 103). Robert O. Becker, State University of New York, Upstate Medical Center, Syracuse; Veterans Administration Hospital, Syracuse, New York (page 207).