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: The rats were treated with intraperitoneal reserpine ( 1 mg / kg , ip ) for 3 days every other day .
### Output Text:
The rats were treated with intraperitoneal <span class="chemical">reserpine</span> ( 1 mg / kg , ip ) for 3 days every other day . 