Why did the doctor refuse to treat Coyotito?

Kino tells the doctor's servant that his child was poisoned by a scorpion. The doctor is a fat man who longs for civilized living. Although the doctor is at home, he refuses to treat Coyotito unless he knows that he has money. The servant asks if Kino has money, and when he can only offer small seed pearls, the servant tells Kino that the doctor has gone out.