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: Histological evaluation of hearts from all rats given DOX revealed significant slight degrees of perivascular and interstitial fibrosis .
### Output Text:
Histological evaluation of hearts from all rats given <span class="chemical">DOX</span> revealed significant slight degrees of perivascular and interstitial fibrosis . 