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: Experimental studies in healthy human volunteers indicate aminoglycosides cause proximal tubular damage in most patients , but rarely , if ever , cause glomerular or tubular dysfunction .
### Output Text:
Experimental studies in healthy human volunteers indicate <span class="chemical">aminoglycosides</span> cause proximal tubular damage in most patients , but rarely , if ever , cause glomerular or tubular dysfunction . 