This is one of the first films in which the beating human heart is portrayed during open-heart surgery.
Olivia de Havilland and Robert Mitchum prepared for their roles by attending eight operations. Broderick Crawford attended an autopsy for his autopsy scene and promptly got sick.
There was a such a boisterous atmosphere on this shoot that Robert Mitchum described it as "not so much a cast as a brewery !"
The four operations that are shown are a laminectomy, a subtotal gastrectomy, plastic surgery on a hand, and an aortal aneurysm.