Dorothy Millicent Horstmann played a significant yet often unacknowledged role in the development of the polio vaccine . In the late 1940s and early 1950s, before polio immunizations were considered feasible, she conducted groundbreaking animal studies which proved that the polio virus reaches the nervous system through the bloodstream. In 1952, while working at the Yale School of Medicine, she set up an experiment to determine whether polio first appeared in the blood before moving on to the brain. She fed monkeys and chimpanzees small quantities of polio virus , then examined the blood for traces of the it. The animals did not immediately develop symptoms of polio, yet small traces of virus were observable in their blood. Many of the animals later developed paralysis, one of polio's debilitating symptoms.

Horstmann was born July 2, 1911, in Spokane, Washington, to Henry and Anna (Humold) Horstmann. She received her B.A. in 1936 and her...