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: CONCLUSIONS : The data indicate that pilocarpine - treated animals have an altered ability to react to ( or compensate for ) blood gas changes with changes in ventilation and suggest that it is centrally determined .
### Output Text:
CONCLUSIONS : The data indicate that <span class="chemical">pilocarpine</span> - treated animals have an altered ability to react to ( or compensate for ) blood gas changes with changes in ventilation and suggest that it is centrally determined . 