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: Effect of polyethylene glycol 400 on adriamycin toxicity in mice .
### Output Text:
Effect of <span class="chemical">polyethylene glycol 400</span> on <span class="chemical">adriamycin</span> toxicity in mice . 