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: METHODS : CHX was injected before the Pilo injection in adult Wistar rats .
### Output Text:
METHODS : <span class="chemical">CHX</span> was injected before the <span class="chemical">Pilo</span> injection in adult Wistar rats . 