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: This study investigated alleviation of streptomycin - induced vestibulotoxicity by edaravone in guinea pigs .
### Output Text:
This study investigated alleviation of <span class="chemical">streptomycin</span> - induced vestibulotoxicity by <span class="chemical">edaravone</span> in guinea pigs . 