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: Male Wistar rats were treated by Dex ( 30 u g / kg / day subcutaneously ) or saline for 14 days .
### Output Text:
Male Wistar rats were treated by <span class="chemical">Dex</span> ( 30 u g / kg / day subcutaneously ) or saline for 14 days . 