Dr. Kendall's distinguished career spans over half a century of research into the structure of major hormones of the body: thyroxin produced by the thyroid gland, and the steroids produced by the adrenal cortex. In this brief autobiographical memoir he not only describes the methods by which the essential compounds were extracted, isolated and crystallized but he conveys a picture of an era: the rise of biochemistry as an essential arm of medical science. As recently as the first decade of the century chemists without medical degrees were spurned in hospitals. Clinical research was not exactly respectable and drug companies employed Ph.D. chemists for essentially menial tasks. It was individuals like Kendall with his marvelously prototypical New England Protestant upbringing or the Hungarian, Szent-Gyorgyi with an equally strong character who combined the will, ambition, intelligence and industry to prove how wrong the elders of their generations were. This reflection on the prevailing and changing attitudes toward laboratory research and the account of the development of major facilities at the Mayo clinic and other medical centers make the book valuable from the scientific historian's point of view. The actual detailing of the analysis of thyroxin and cortisone (the latter meriting a Nobel Prize in 1950) are interesting in revealing the time-consuming but essentially stepwise progress they involved toward the fixed goal. More speculation on the modes of action of hormones and brief asides or footnotes giving a little background information on methods, clinical syndromes, and physiological data would have helped the non-technical reader and enriched the book.