I would say that one particular example of symbolism in the story is the tongue depressor. It is an instrument of good, symbolic of the healing powers of the medical profession. Yet, as it splinters into pieces inside the girl's mouth, it is a tool of destruction, used to inflict power from one over another. The spoon is a symbol of this force, an instrument that is symbolic of nourishment and replenishment is an extension of the doctor's savage need to control. The very image of a spoon prying open the mouth of a child is a symbolic representation of how far the doctor is willing to go to inflict his will on the girl. Money is a symbolic element in the story. The doctor makes it clear that the parents are eager to cure their child because of "the money" that they are willing to spend. In this case, the money symbolizes a sense of power or control that the parents are willing to display in the face of the intense means the doctor employs. In an odd way, I see the girl as symbolic of something more than a girl or even as the patient. The doctor's initial description of her is reflective of this symbolic representation:
...an unusually attractive little thing, and as strong as a heifer in appearance. But her face was flushed, she was breathing rapidly, and I realized that she had a high fever. She had magnificent blonde hair, in profusion. One of those picture children often reproduced in advertising leaflets and the photogravure sections of the Sunday papers.
The girl being symbolic of the media's reflection of what it means to be a girl, as well as the fact that the doctor takes such strong physical note lends the symbolic representation that there is an assault, a type of control based subjugation of the older man over the younger girl. This sexual dynamic seems to be another symbol in the story.