In "The Love Song of J. Alfred Prufrock," the speaker (Prufrock) compares the sunset to a "patient etherised upon a table." Why do you suppose he would compare a sunset to a patient who has been anesthetized and is waiting for a operation?
The speaker does not compare the sunset to "a patient etherised upon a table," but says:
Let us go then, you and I,
When the evening is spread out against the sky
Like a patient etherized upon a table;
Let us go, through certain half-deserted streets. . .
The image seems to be that of a city spread out under the evening sky. It is not the sunset or the evening but the city that interests the speaker. It is like an etherized patient because the speaker is inviting the reader to participate with him in what might be called "exploratory surgery." When the speaker says, "Let us go, through certain half-deserted streets . . ." it is as if we are now inside the patient's body. In fact, it could be construed that we are inside the patient's intestines, winding our way along in darkness. The patient is etherized upon an operating table in preparation for an painless operation. That is the only reason a patient is ever etherized upon an operating table.
The quotation in Italian that forms the epigraph of the poem is from Dante's "Inferno." In that epic poem, Virgil conducts the poet Dante through all the different circles of Hell. T. S. Eliot is making another analogy, comparing the modern city to Hell, a place of suffering for all its wretched inhabitants. The fragments that make up "The Love Song of J. Alfred Prufrock" represent scenes glimpsed in the exploration of the city and also thoughts in the mind of Prufrock as he wanders aimlessly in darkness. He seems to be returning on his own footsteps when he repeats the lines:
In the room the women come and go
Talking of Michelangelo
So we are not only getting depressing glimpses of the city at night but equally depressing glimpses of the mind of the speaker.