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: By contrast , apomorphine - induced locomotion was more prominent in the novel exploratory box .
### Output Text:
By contrast , <span class="chemical">apomorphine</span> - induced locomotion was more prominent in the novel exploratory box . 