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 competences and with regard for appropriate balance.

The activity was supported by a grant between the National Academy of Sciences and Kaiser Permanente. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the organizations or agencies that provided support for the project.

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Cover credit: Carmen Lomas Garza, Tamalada (making tamales). Oil on linen mounted on wood, 24 × 32 inches.

© 1988 Carmen Lomas Garza, used with permission.

www.carmenlomasgarza.com

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.