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: Following recovery , the monkeys were selectively deafened for high frequencies using kanamycin and furosemide .
### Output Text:
Following recovery , the monkeys were selectively deafened for high frequencies using <span class="chemical">kanamycin</span> and <span class="chemical">furosemide</span> . 