Kino reacts to the scorpion stinging his son with impotent rage, while his wife tries to administer medical attention.
The incident with the scorpion demonstrates Kino’s impotence. He is unable to save his son from the scorpion, even when he sees danger coming. He reacts not just by killing the scorpion, but by smashing it to dust. Still, his revenge is useless. His son is still stung.
Then, snarling, Kino had it, had it in his fingers, rubbing it to a paste in his hands. He threw it down and beat it into the earth floor with his fist, and Coyotito screamed with pain in his box. (ch 1)
His wife Juana, on the other hand, jumps into action. She sucks the poison from the wound while Kino stands helplessly by. He is frozen in inaction, because he knows there is nothing he can do to save his son.
The difference in Kino and Juana’s actions shows their personalities. Kino destroys the scorpion, which makes him feel better but does not help the baby. Juana at least attempts to help the boy by sucking the poison from the wound. The reader feels sorry for and frustrated with Kino.
This incident is only an example of Kino's powerlessness. Even when he has the pearl, he is not able to use it to save his son.