TheAnatomicalRecord ORIGINALLY FOUNDED BY THE WISTAR INSTITUTE Aaron J. Ladman, Editor Department of Anatomy Mail Stop 408 Hahnemann University Broad & Vine Philadelphia, Pennsylvania 19102-1192 EDITORIAL BOARD Donald J. Donaldson University of Tennessee G. Adolph Ackerman Ohio State University Memphis Ernst Kallenbach University of Florida Gainesville Thomas S. R e e s e m D Y m Elio Raviola Harvard Medical School Gordon I. Kaye National Institutes of Health Peter S. Amenta Georgetown University Albany Medical College Lynn J. Romrell Robert Wood Johnson Medical School Stanley L. Erlandsen University of Minnesota Robert 0. Kelley The University of New Mexico University of Florida Gainesville J o h n V. Basmafian Chedoke Rehabilitation Center McMaster University Dale E. Bockman Medical College of Georgia Robert P. Bolender University of Washington Robert S. Bressler New York College of Pcdiatric Medical School Brown University Davis Linda Saland J o h n F. Fallon University of Wisconsin Eric R. Lacy Gary schoenwolf Madison Donald A. Fischman Cornell University Medical College CharlesJ. F l i c k h g e r William G. Dail, Jr. The University of New Mexico University of Virginia Daniel S. Friend University of California San Francisco Geraldine F. Gauthier The University of Massachusetts Michael D. G e r s h o n Columbia University William J. Gonyea The University of Texas Health Science Center at Dallas Jack L. Haar Medical College of Virginia D u a n e E. Haines University of Mississippi Jackson Damon C. Herbert The University of Texas at San Antonio J o h n C. Herr University of Virginia Robert Hikida Ohio University Dennis M. De Pace David E. H i n t o n University of California Medicine Margaret R. Byers University of Washington Edward C. Carlson University of North Dakota Nikolajs GUM University of Pittsburgh J o h n Clancy, Jr. Loyola University School of Medicine B e n R. Clower University of Mississippi Jackson Richard E. Coggeshall The University of Texas Medical Branch at Galveston Gerald R. Cunha University of California San Francisco Hahnemann University Richard D. Dey West Virginia University Jack Rosenbluth Barry F. King University of California Richard A. Ellis The University of New Mexico Medical University of South Carolina Jeffrey T. Iaitman Mount Sinai School of Medicine N e w York Thomas A. Marino Temple University School of Medicine Roger R. Markwald Medical College of Wisconsin Milwaukee George F. Martin Ohio State University J a m e s L. Matthews Baylor College of Dentistry Dallas Sam G. McClugage Louisiana State University New Orleans R. Peter Meyer Hahnemann University Bryce L. Munger Pennsylvania State University Hershey Charles C.C. O M o r c h o e University of Illinois College of Medicine Urbana-Champaign H e l e n A. Padykula The University of Davis Massachusetts Webster S.S. J e e University of Utah David P. P e n n e y University of Rochester Manuscripts and illustrations intended for publication in The AnatomiGal Record should be sent to Dr.- Aaron J. Ladman, Department of Anatomy, Mail Stop 408, Hahnemann University, Broad & Vine, Philadelphia, Pennsylvania 19102-1192. Please read notice to contributors on inside back cover page for preparation instructions. Officers of the American Association of Anatomists for 1990-91: Karen R. Hitchcock, president; Jerome Sutin, president emeritus; William P. Jollie, president-elect; Donald A. Fischman, first vicepresident; W. Keith O'Steen, second vice-president; Marilyn Zimny, program secretary; Robert D. Yates, secretary-treasurer. Authorization to photocopy items for internal or personal use, or the internal or personal use of specific clients, is granted by Wiley-Liss, Inc. for libraries and other users registered with the Copyright Clearance Center (CCC) Transactional Reporting Service, provided that the base fee of $00.50 per copy, plus $00.25 per page is paid directly to CCC, 27 Congress Street, Salem, MA 01970, 0003-276W90 $00.50 .25. + The paper on which this journal is printed adheres to the requirements for libraryhrchival stability. THE ANATOMICAL RECORD (ISSN 0003-276X), an official publication of the American Association of Anatomists, is published monthly by Wiley-Liss, Inc., 41 East 11th Street, New York, NY New York University University of Utah Arlen R Severson University of Minnesota Duluth Peter J. Sheridan The University of Texas at San Antonio Mike1 H. S n o w University of Southern California Sergei P. Sorokin Boston University A.K. Szakal Medical College of Virginia Bernard Tandler Case Western Reserve University Robert J. Tomanek University of Iowa Jerry S . Trier Peter Bent Brigham Hospital Boston J o h n A. Trotter The University of New Mexico A. Wayne Vogl University of British Columbia H e r s h e y Warshawsky McGill University Robert E. Waterman The University of N e w Mexico Frederick W e z e m a n Loyola University of Chicago Chicago Lawrence C. Zoller Boston University 10003, a division of John Wiley & Sons, Inc. Send subscrivtion inquiries to: John Wiley & Sons, Inc., Subscription Departkent, 7th floor, 605 Third Avenue, New York, NY 10158. For 1990, Volumes 226-228, twelve issues, $813 in US; $915 outside US. All subscriptions outside US will be sent by air. Payments must be made in US dollars drawn on a US bank. Change of address: Please forward to the Subscriptions address listed above six weeks prior to move; enclose present mailing label with change of address. Claims for missing issues: Claims for undelivered copies will be accepted only after the following issue has been received. Please enclose a copy of the mailing label or cite your subscriber reference number in order to expedite handling. Missing copies will be supplied when losses have been sustained in transit and where reserve stock permits. Send claims to John Wiley & Sons, Inc., Customer Service, 605 Third Avenue, New York, NY 10158. If claims are not resolved satisfactorily,please write to Susan Malawski, Director, SubscriptionFulfillment and Distribution,John Wiley & Sons, Inc., 605 Third Avenue, New York, NY 10158. Cancellations: Subscriptioncancellationswill not be accepted after the first issue has been mailed. Volumes published prior to 1980 are available from Swets and Zeitlinger B.V., P.O. Box 810, 2160 SZ Lisse, The Netherlands. Second class postage paid at N.Y., N.Y., and at additional mailing offices. Printed in U.S.A. Copyright 0 1990 Wiley-Liss, Inc. POSTMASTER: Send change of address to The Anatomical Record, Susan Dorato, Subscription Fulfillment and Distribution, John Wiley & Sons, Inc., 605 Third Avenue, New York, NY 10158. Indexed by: BIOSIS Data Base, Chemical Abstracts, Current Contents-e Sciences-Science Citation Index (SCISEARCH), Excerpta Medica, Index Medicus, and Institute of Scientific Information-Soviet Union.