This edition of The Principles and Practice of Medicine is the sixth that we have edited in the past 20 years.

In preparation for this edition each section of the Twenty-First Edition was sent to two external reviewers for their comments and expert criticism. This detailed outside review was helpful to us in planning our revisions for this new edition. It prompted us to address issues which they raised as well as a host of related issues.

This textbook continues to reflect the coherent view of a single institution—Johns Hopkins. Nevertheless, institutions change and evolve from edition to edition and certainly the practice of medicine advances rapidly between editions. There are also fresh approaches to clinical problem-solving and new insights into patient management, that is, there are advances in principles as well. This edition has been extensively revised in response to these advances and changes. In addition, the sequence of sections has been changed to reflect newly developed connections between clinical problem areas.

In this edition we have a number of new section editors: Joseph T. Coyle, Jr., H. Franklin Herlong, Dudley P. Jackson, Paul W. Ladenson, Simeon Margolis, John R. Michael, William E. Mitch, Mack C. Mitchell, Mark C. Rogers, J.T. Sylvester, and Peter B. Terry.

We also welcome 59 new contributors to this edition. They include: Elaine L. Alexander, A. Michael Borkon, Jason Brandt, Barbara L. Braunstein, Henry Brem, Roy G. Brower, Philip J. Burke, John R. Burton, David S. Cooper, David R. Cornblath, Robert S. Fisher, William R. Furman, Francis M. Giardiello, Vincent L. Gott, Stuart S. Grossman, Thomas Guarnieri, Alan D. Guerci, Bruce Hamilton, Douglas A. Jabs, Dudley P. Jackson, Donald R. Jasinski, David B. Kafonek, Allan Krumholz, Paul W. Ladenson, W. Lowell Maughan, Andrew R. Mayrer, Justin C. McArthur, Esteban Mezey, William E. Mitch, John F. Modlin, Cheryl L. Newman, Godfrey D. Pearlson, David B. Pearse, Thomas A. Pearson, Stephen P. Peters, Marshall Plaut, Leonard R. Proctor, Peter Rock, Mark C. Rogers, Barry W. Rovner, Chester W. Schmidt, Jr., Marvin M. Schuster, Stephen S. Selinger, James V. Sitzmann, Keith T. Sivertson, Barney J. Stem, Mark L. Teitelbaum, Melvyn S. Tockman, Larry E. Tune, Martin D. Valentine, Sandra M. Walden, Gary D. Walford, Patrick C. Walsh, Gary S. Wand, Andrew C. Warren, Gail G. Weinmann, Paul S. Wheeler, Howard A. Za- cur, and Carol M. Ziminski.

We also wish to thank the section editors and authors who have contributed not only to this edition but to previous editions as well. Their experience is invaluable, and their continued interest, effort, and tolerance are warmly appreciated.

As in the last edition Ms. Christine D. Young prepared the illustrative material. We appreciate her skill in communicating complex topics clearly and artistically.

Finally, we are grateful to those who assisted us so ably in the preparation of this edition, particularly Mrs. Sandra M. Sann.

THE EDITORS

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