What actions taken by the doctor in Chapter Three show that he is trying to take advantage of Kino and his family?

The doctor's newfound interest in Kino stems from a manipulative and dangerous greed. His visit to Kino reveals that he not only wishes to secure part of Kino's new fortune through the salary the doctor might receive for treatment but, as shown by the doctor's attempt to locate the pearl in Kino's hut, that he intends to steal the pearl. Steinbeck makes clear that the doctor does not visit Kino to cure his son; in fact, he indicates that the doctor's treatment of Coyotito might even be superfluous.