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: Total extractable myocardial lipid was compared postmortem between a group of control dogs and doxorubicin - treated dogs .
### Output Text:
Total extractable myocardial lipid was compared postmortem between a group of control dogs and <span class="chemical">doxorubicin</span> - treated dogs . 