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 Board responsible for the report were chosen for their special competences and with regard for appropriate balance.

Support for this project was provided by the National Cancer Institute; the Centers for Disease Control and Prevention; the American Cancer Society; American Society of Clinical Oncology; Abbott Laboratories; Amgen, Inc.; and Aventis. The views presented in this report are those of the Institute of Medicine and Commission on Life Sciences National Cancer Policy Board and are not necessarily those of the funding agencies.

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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 serpent adopted as a logotype by the Institute of Medicine is a relief carving from ancient Greece, now held by the Staatliche Museen in Berlin.