Sentence:  For a moment he thought of going into Crosson 's office to explain that he had to leave , but there was now such a pain in his chest , such a pounding in his <WSD>head</WSD> , that he decided to let it go . 
Meaning of the word marked with <WSD> tags:  the upper part of the human body or the front part of the body in animals; contains the face and brains