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: After adrenaline infusion for 30 s , there were large unstained areas in the left brain in right - pawed animals , and vice versa in left - pawed animals .
### Output Text:
After <span class="chemical">adrenaline</span> infusion for 30 s , there were large unstained areas in the left brain in right - pawed animals , and vice versa in left - pawed animals . 