How does Juana treat Coyotito's scorpion sting?

Immediately after Coyotito is stung by the scorpion, Juana attempts to suck the venom out of his wound before she and Kino travel into town to see the European doctor. Unfortunately, the supercilious European doctor refuses to see Coyotito because Kino and Juana are too poor to pay him for his services. When they return to their hut, Juana gathers brown seaweed and makes a flat damp poultice to place on her son's swollen shoulder. Steinbeck writes that Juana's ancient remedy was probably better than anything the doctor could have prescribed to heal the infant, but the remedy lacked his authority and was simple. Towards the end of chapter 2, Juana removes the poultice from Coyotito's shoulder and discovers that the swelling has gone down significantly. Once the European doctor learns that Kino has found the Pearl of the World, he visits his hut and seems to poison Coyotito, who has been recovering. Since Kino lacks education and knowledge, he cannot tell if the doctor has purposely harmed his son in order to cure him of another ailment. It is implied that Juana's ancient remedy healed Coyotito.

Juana and Kino are too poor to afford a doctor so they use an old-fashioned natural remedy to treat Coyotito's wound. Juana makes a poultice out of seaweed, which she then applies to her son's swollen shoulder. The treatment seems to work and the swelling goes down immediately after Kino discovers the valuable pearl. It's almost as if the pearl has brought Kino and his family good luck, at least for now.
The use of an old natural remedy to treat Coyotito's wound illustrates the significant cultural gap that separates Kino's family from the modern world. Natural remedies are an important part of indigenous culture, and Kino and Juana want to maintain the old traditions for as long as possible. Although they are prepared to resort to modern medicine if needs be, they're forced by the doctor's indifference to stick to what's tried and trusted. Besides, the doctor proves himself to be a devious, trustworthy individual, who as well as trying to cheat Kino out of his valuable pearl, cynically prolongs Coyotito's suffering for his own selfish gain.