The narrator's primary metaphor is to describe society as a machine, and he considers the hospital and war in the same way;
Big Nurse is described as a tractor; her gestures are precise/ automatic; her face is calculated/ precision made.
People are "processed."
Vegetable (a patient) is a “a shower of rust and ashes, and now and again a piece of wire and glass” inside.
The brain is considered an "apparatus," put together by "seams."