Not a cage but an organ:
if he thought about it, he'd go insane.
Yes, if he thought about it
philosophically,
he was a bubble of bad air
in a closed system.
He sleeps on his feet
until the bosses enter from the paths
of Research and Administration-
the same white classmates
This line can be interpreted literally, but more accurately as a figure of speech to express the countless hours he spends in the elevator, restlessly.
Elevator Man 1949