Consume my heart away; sick with desire And fastened to a dying animal It knows not what it is; (21-23)
The "dying animal" (that is, the man himself) seems unwilling here to recognize himself as human. The body is nothing more than a source of physical decay. It’s the spirit, the soul, which he turns to as the definition of his being.
Once out of nature I shall never take My bodily form from any natural thing, (25-26)
The terrors of nature give way to the pleasures of art in the last stanzas of this poem. The only way to avoid the problems of growing old is to become something that doesn’t age at all.
Or set upon a golden bough to sing (30)
Ironically, as soon as the speaker imagines himself as a piece of art, he animates it. As we know, golden birds can’t really sing. The desire to blend life and art produces a bit of tension in this line. It’s not enough to last forever: our speaker wants to push the boundaries of what art can do, as well.