This book makes available, for interested scientists to procure, absorb, and evaluate, the vast body of information on the research and results of the work on the chemistry of penicillin done in England and the United States during the war. The National Academy of Sciences arranged for the preparation of this summary, Dr. H. T. Clarke and Dr. J. R. Johnson representing the United States on the editorial board, and Sir Robert Robinson representing Britain. The body of the work was prepared by more than 60 outstanding biochemists and biophysicists, who describe the phases of research to which they contributed the most. The work of 23 academic, medical, industrial, and government laboratories is reported. Originally published in 1949. The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These editions preserve the original texts of these important books while presenting them in durable paperback and hardcover editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.