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: Adult rats given dexamethasone on days 15 and 16 of gestation had more glomeruli with glomerulosclerosis than control rats .
### Output Text:
Adult rats given <span class="chemical">dexamethasone</span> on days 15 and 16 of gestation had more glomeruli with glomerulosclerosis than control rats . 