In this photo taken Wednesday, Sept. 1, 2012, Dr. Davis Mathis, visits with an inmate in the hospital unit at the California Medical Facility in Vacaville, Calif. Mathis, a board certified physician, was the highest paid prison doctor last year, earning a base salary of $239,572 and an additional $169,548 for working overnight shifts, weekends and holidays. Prison doctors say they are worth the higher pay because they face the constant threat of assault from inmates. (AP Photo/Rich Pedroncelli)
