Scan the following lines from William Butler Yeats's poem "Sailing to Byzantium." Indicate the rhyme scheme. Consume my heart away; sick with desire And fastened to a dying animal It knows not what it is; and gather me Into the artifice of eternity.

The lines you refer to appear in the third stanza of Yeats's poem. All of "Sailing to Byzantium" is written in ottava rima, a meter of Italian origin that translates to the "eight-line rhyme" (notice that each of the four stanzas that comprise the poem is eight lines). Each line is written in iambic pentameter, though there are a few small breaks in the measured beats of this form.
The rhyme scheme emerges organically from the ottava rima. Here are the lines you're looking at; I've bolded the words we'll look at to determine the rhyme scheme:

Consume my heart away; sick with desire

And fastened to a dying animal

It knows not what it is; and gather me

Into the artifice of eternity.



"Desire" does not rhyme with any of the following three end-rhymes. We'll assign it the letter "A" to represent its rhyme. "Animal" also does not rhyme with any of the other end-rhymes. We'll assign it the letter "B." However, "me" and "eternity" rhyme with each other; we'll assign them both the letter C to represent that relationship. Thus, we've determined that these four lines follow the rhyme scheme ABCC.

If you look more broadly at the poem, each stanza follows the rhyme pattern ABABABCC. So, there are three alternate rhymes in each stanza, and each stanza ends with one double rhyme in its closing couplet.