"Pink Dog" Elizabeth Bishop

This poem sort of confused me. I think that there is an interesting rhyme scheme, or lack there of. In the first three stanzas, the last words of each the three lines in the stanza rhyme. Then there is more random rhyiming. In stanza six, the last words in the last two lines rhyme. In stanza seven the last words in the first two lines of the stanza rhyme. There seems to be no more rhyming; this just sort of struck me. Is there a reason why? Aside from that, the speaker's tone for the dog changes throughout the stanza. At first, when speaking about the dog, the speaker just talks about the dog's appearance, "naked and pink." Then the speaker starts talking directly to the dog, making this an apostrophe as well. He says, "You are not mad; you have a case of scabies but look intelligent." I cannot tell why the speaker said that the dog looks intelligent. Then she goes on about it's appearance, "hanging teats" after giving birth. The speaker tells of what "they" do with beggars: "throw them in the tidal river," then asks what they would do to a "sick, four-legged dog," saying the dog couldn't last in the river. In order to take care of this problem, the speaker says to dress up for the Carnival. I think this poem is putting down the people in Rio de Janeiro, saying that a dog is equal to or better than the people.