In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Ten patients who had Parkinson ' s disease with disabling dyskinesia were included in this study to evaluate the role of mental ( mental calculation ) and motor ( flexion / extension of right fingers , flexion / extension of left fingers , flexion / extension of the neck , speaking aloud ) tasks on the worsening of peak - dose dyskinesia following administration of an effective single dose of apomorphine .
### Output Text:
Ten patients who had Parkinson ' s disease with disabling dyskinesia were included in this study to evaluate the role of mental ( mental calculation ) and motor ( flexion / extension of right fingers , flexion / extension of left fingers , flexion / extension of the neck , speaking aloud ) tasks on the worsening of peak - dose dyskinesia following administration of an effective single dose of <span class="chemical">apomorphine</span> . 