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. In preparing its report, the committee invited people with different perspectives to present their views. Such invitation does not imply endorsement of those views.

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.

This study by the National Research Council’s Commission on Life Sciences was sponsored by the National Institutes of Health and the National Science Foundation under contract no. N01-OD-4-2139. Points of view in this document are those of the authors and do not necessarily represent the official position of the sponsoring agencies.

Library of Congress Catalog Card Number 97-75390

Cover art created by Vivianna Padilla.