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: Protective effect of edaravone against streptomycin - induced vestibulotoxicity in the guinea pig .
### Output Text:
Protective effect of <span class="chemical">edaravone</span> against <span class="chemical">streptomycin</span> - induced vestibulotoxicity in the guinea pig . 