Arnold graduated from Northwestern University in 1941 with a B.S. degree in Biology and a minor in Chemistry. She and Mary Dailey, another N.U. grad and close friend, started working together at the Joliet Ammunitions Facility as chemical assistants titrating various chemicals for processing.
Mary left first in 1942. Then without telling her what she was doing, she coaxed Jane into following her to the University of Chicago. They both worked as Research Assistants in the Health Division of the Met Lab. Jane was assigned to a Biology area where experiments included studying the effects of radiation exposure on small animals. The objective was to establish safety guidelines for the entire Manhattan Project. They were on the edge. As they analyzed their results, they modified their own safe handling protocol and the radiation safety guidelines for the entire project.
In the spring of 1945 just prior to the first detonation, the experiments shifted to using very "Hot" material. Feeling unsafe, Jane opted out of the program though keeping her vow of silence. She remained concerned about her exposure levels her entire life, until she passed away in 1987.