NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competencies and with regard for appropriate balance. Part I of this report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine.

The Institute of Medicine was established in 1970 by the National Academy of Sciences to enlist distinguished members of the appropriate professions in the examination of policy matters pertaining to the health of the public. In this, the Institute acts under both the Academy's 1863 congressional charter responsibility to be an adviser to the federal government and its own initiative in identifying issues of medical care, research, and education. Dr. Kenneth R. Shine is president of the Institute of Medicine.

This report was produced under grants DAMD17-92-J-2003 and DAMD17-94-J-4046 between the National Academy of Sciences and the U.S. Army Medical Research and Materiel Command. The views, opinions, and/or findings contained in chapters in Parts II through V that are authored by U.S. Army personnel are those of the authors and should not be construed as official Department of the Army positions, policies, or decisions, unless so designated by other official documentation. Human subjects who participated in studies described in those chapters gave their free and informed voluntary consent. Investigators adhered to U.S. Army regulation 70-25 and United States Army Medical Research and Development Command regulation 70-25 on use of volunteers in research. Citations of commercial organizations and trade names in this report do not constitute an official Department of the Army endorsement or approval of the products or services of these organizations. The chapters are approved for public release; distribution is unlimited.

The serpent has been a symbol of long life, healing, and knowledge among almost all cultures and religions since the beginning of recorded history. The image adopted as a logotype by the Institute of Medicine is based on a relief carving from ancient Greece, now held by the Staatlichemuseen in Berlin.