This is the 1st new series of monographs which will be dedicated to current interest of methods in medical research. It is desirable to call this volume to the attention of medical research workers, including those in pediatrics, although it is obviously a volume of interest to specialists in the various fields represented. As stated in the preface, "Each volume will be divided into four or five principal self-contained sections, each of which shall, for that volume, represent one of the broad fields of medical research; biochemistry, physiology and pharmacology, microbiology and immunology, and biophysics including radiobiology. Within each of these broad fields we shall try, year by year, to select narrower topics wherein a restatement of technic seems timely."