Justine Johnstone (January 31, 1895 – September 4, 1982) was an American stage and silent screen actress. She was later a pathologist and expert on syphilis. Working under her married name, Justine Wanger, she was part of the team that developed the modern intravenous drip technique. She attended Emma Willard School in Troy, New York. An original performer in the Ziegfeld Follies and a performer in the Folies-Bergere, she appeared in the 1917 Broadway production Over the Top, which starred Fred Astaire. Justine Johnstone married producer Walter Wanger on 13 September 1919; they divorced in 1938. She retained her married name and had borne Wanger no children. Walter Wanger later married the much younger actress Joan Bennett with whom he had a child. After giving up performing, Wanger enrolled in Columbia University, where she studied plant research and served as a research assistant to Samuel Hirshberg and Harold T. Hyman. The team developed the modern I.V. unit; their key breakthrough was to slow down the rate of delivery and avoid what was then known as “speed shock” by introducing the now-ubiquitous drip technique. She later studied and made developments in endocrinology and cancer research and installed a laboratory in her house in Hollywood. Justine Johnstone died in Santa Monica, California from congestive heart failure, aged 87. Her remains are at Chapel of the Pines Crematory.