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: SETTING : Marmara University School of Medicine , Department of Histology and Embryology , Zeynep Kamil Women and Children ' s Hospital .
### Output Text:
SETTING : Marmara University School of Medicine , Department of Histology and Embryology , Zeynep Kamil Women and Children ' s Hospital . 