Sentence:  His uncle, a Cardinal, engages a Spanish youth of Moorish descent called Diego, an expert singer and player on the virginal,...to cleanse his <WSD>bosom</WSD> of the perilous stuff, and cure him by the spell of his music. 
Meaning of the word marked with <WSD> tags:  The seat of one's inner thoughts, feelings etc.; one's secret feelings; desire. (from 13thc.)