The studies presented in this book were originally undertaken at the suggestion of Dr. T. H. Weisenburg. Most of the work was done at the University of Pennsylvania under the guidance of Dr. B. Alexander Randall, whose encouragement will always be affectionately remembered. A sub-department of "Neuro-Otology" was created, in which Dr. Lewis Fisher, Dr. Seth A. Brumm and the writer conducted experiments which constituted the foundation for this study. Acknowledgment is made of the sympathetic co-operation and assistance of Dr. Charles K. Mills, who, with Dr. Weisenburg, guided us from the neurologic standpoint; and also to Dr. William G. Spiller for his unstinted interest and advice. The neurologic chapters, XII and XIII, constitute the presentation of the direct teachings of Drs. Mills and Weisenburg.<br><br>On the otologic side sincere thanks are due to Dr. George E. Shambaugh and to Dr. Eugene R. Lewis for many invaluable suggestions, and on the surgical side to Dr. Cliarles H. Frazier.<br><br>The studies of the relation of the ear to the eye were undertaken with the help of Dr. H. Maxwell Langdon, during a period of four years. The studies in syphilis were originally undertaken in co-operation with the late Dr. Alexander A. Uhle and later with his associate, Dr. William H. Mackinney.<br><br>The dissections of the brain were made by the eminent anatomist, Dr. Addinell Hewson, and the stereoscopic photographs, although taken by the author, were made possible by the equipment and expert guidance of Dr. Matthew H. Cryer.<br><br>The moving pictures were taken and arranged through the courtesy of Mr. S. Lubin, who has shown a most sincere interest in the advancement of the use of moving pictures as a means of medical teaching and research.