In 1956, Franklin visited the University of California, Berkeley, where colleagues had suggested her group research the polio virus. In 1957 she applied for a grant from the United States Public Health Service of the National Institutes of Health, which approved £10,000 for three years, the largest fund ever received at Birkbeck. In her grant application, Franklin mentioned her new interest in animal virus research. She obtained Bernal's consent in July 1957, though serious concerns were raised after she disclosed her intentions to research live, instead of killed, polio virus at Birkbeck. Eventually, Bernal arranged for the virus to be safely stored at the London School of Hygiene and Tropical Medicine during the group's research. With her group, Franklin then commenced deciphering the structure of the polio virus while it was in a crystalline state. She attempted to mount the virus crystals in capillary tubes for X-ray studies, but was forced to end her work due to her rapidly failing health.