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: An experimental group of rats was treated with puromycin aminonucleoside ( PAN ; 180 mg / kg iv ) , whereas the control group received only vehicle .
### Output Text:
An experimental group of rats was treated with <span class="chemical">puromycin aminonucleoside</span> ( <span class="chemical">PAN</span> ; 180 mg / kg iv ) , whereas the control group received only vehicle . 