Testosterone and estrogen treatments are common today, but in the late 19th and early 20th centuries the discovery of sex gland secretions led both physicians and the public to believe they had found the secret to bodily rejuvenation. This led to bizarre human experimentation involving injections of glandular fluid, ingestion of glandular tissues and the transplanting of testes and ovaries. Stranger still, the treatments supposedly worked, with both men and women reporting enhanced vitality. Only later would the truth about these placebo-induced results be brought to light. This book explores the early history and practices of "organotherapy" and how it provided important scientific insights despite its pseudoscientific nature.