For = working for?

Context:

Dr. Cushing, born in Cleveland in 1869, was an undergraduate at Yale and finished his career here as a professor of history of medicine. In between, he went to Harvard for medical school, did his early surgical training at Johns Hopkins and became a surgical professor there, and then spent most of his career as chief of neurosurgery, a new specialty, at Peter Bent Brigham Hospital at Harvard (now Brigham and Women’s).

http://www.nytimes.com/2010/08/24/health/24brain.html?_r=2&ref=health