The "doctor's office" represents the place where Benjy is taken to be castrated. Since we experience that event from his extremely partial perspective - all he remembers of that event is that "when I breathed in, I couldn't breathe out again" (53), which presumably refers to being rendered unconscious by inhaling ether before the operation - we can't say whether the surgery took place in a hospital or a doctor's office, and if the latter, which doctor might have performed it.
