The Nature of Dysmenorrhea**Read at the annual meeting of the South Atlantic Association of Obstetricians and Gynecologists, Savannah, Ga., Feb. 6 to 8, 1947.††Ciba Pharmaceutical Products, Eli Lilly & Company, and Frederick Stearns & Company have generously supported these investigations. The Pitressin and Pitocin were purchased on the open market. The acetylcholine chloride was supplied by Merck & Company.