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Prison doctors get higher pay for dangerous job

All photos by Rich Pedroncelli / AP

Dr. David Mathis waits to be let into the main building of the California Medical Facility in Vacaville, Calif., Sept. 12, 2012.

A whistle hangs from Dr. David Mathis' coat pocket as he does his rounds on Sept. 12. The whistle is worn in case he needs help in an emergency.

Rich Pedroncelli, AP — Dr. David 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 higher pay because they face constant threat of assault from inmates.

EDITOR’S NOTE: These images were made available to NBC News on Oct. 19, 2012.

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Dr. Davis Mathis visits with an inmate in the hospital unit at the California Medical Facility in Vacaville, Calif., Sept. 1.

Dr. David Mathis, center, accompanied by physician's assistant Rob Johnson, left, examines a sore on the foot of an inmate at the California Medical Facility in Vacaville, Calif., Sept. 12.