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: Male rats that received prenatal dexamethasone on days 15 and 16 , 17 and 18 , and 13 and 14 of gestation had elevated blood pressures at 6 months of age ; the latter group did not have a reduction in glomerular number .
### Output Text:
Male rats that received prenatal <span class="chemical">dexamethasone</span> on days 15 and 16 , 17 and 18 , and 13 and 14 of gestation had elevated blood pressures at 6 months of age ; the latter group did not have a reduction in glomerular number . 