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: Dexamethasone ( 10 microg / kg per day , s . c . ) or saline was started after 4 days in Ato - treated and non - treated rats and continued for 11 - 13 days .
### Output Text:
<span class="chemical">Dexamethasone</span> ( 10 microg / kg per day , s . c . ) or saline was started after 4 days in <span class="chemical">Ato</span> - treated and non - treated rats and continued for 11 - 13 days . 