Percussion over the __ is performed to assess the resonance of the apices of the lungs.

The missing word in the sentence "Percussion over the __ is performed to assess the resonance of the apices of the lungs." is "chest". So, the complete sentence is "Percussion over the chest is performed to assess the resonance of the apices of the lungs."

Here are the steps to reach this conclusion:

1. Understand the context: The sentence is talking about a medical procedure (percussion) used to assess the condition of the lungs.

2. Identify the missing word: The blank is where a part of the body should be, as that's where the percussion is performed.

3. Fill in the blank: The percussion is performed over the chest to assess the lungs. Therefore, the word "chest" fits perfectly in the blank.