I've heard of this poet, but not the poem. Her name is Rainer Maria Rilke and the poem is called 'The Panther'.
So worn with passing through the bars,
His gaze holds nothing any more.
A thousand bars before him there might loom
And past the thousand bars no world.
The lissom stride of soundless padded pacing,
Revolving in the tiniest of rings,
Is like a dance of strength around a pivot,
Impaling in a trance of mighty will.
Bur rarely is the curtain of the eyeball
Softly parted. Then an image enters in
Which seeps through the tremulous stillness of the limbs
To reach the heart, where it expires.
The imagery here is certainly strong. The big cat is in a pen and, although it can see the people, it choose not to after some time. Why should it? The panther's entire world is in the circle that it endlessly walks.
By chance, I happened to go to a zoo today and saw the big cats. The lions completely ignored us, but they were kind of far away. The tiger, on the other hand, was laying down next to the glass. It simply lay there, looking into the distance, not paying the slightest bit of attention to any of us. We've become wallpaper.
I'd never thought about that before. Now I'll think it every time.