How are the homes of the poor distinguished from the homes of the rich in The Pearl?

Poor indigenous folk like Kino and his family live in brush houses, primitive dwelling places made out of scrub vegetation. The social and racial elite, such as the doctor, never venture out to this neck of the woods. They get to live in an upmarket neighborhood, in palatial houses made of more durable material such as stone and plaster.
Kino and Juana get to see how the other half live when they take their son, Coyotito, who's been bitten by a scorpion, to the doctor for urgent treatment. The houses in the swanky neighborhood where the doctor lives couldn't be any more different from the row of brush houses where the indigenous people are forced to live in squalor. Here, the high walls of houses are adorned with bougainvillea, a genus of bush renowned for its vibrant purple color. Behind these walls lie beautiful gardens, from which can be heard the sound of caged birds singing and the splash of cooling water against burning hot flagstones.
All in all, we are left in no doubt as to the enormous gulf in wealth and opportunity that exists between the rich and the poor in this part of the world.