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: Mice lacking mPGES - 1 are resistant to lithium - induced polyuria .
### Output Text:
Mice lacking mPGES - 1 are resistant to <span class="chemical">lithium</span> - induced polyuria . 