Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. Resentin G the substance of some of the public lectures delivered at the Medical School of Harvard Univer sity, this series aims to provide in easily Q accessible form modern and authorita fz tive information on medical subjects of general importance. The following committee, composed of members of the Faculty of Medicine, has editorial supervision of the volumes published.