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: The degree of vacuolar degeneration of myocardial cells was analyzed in relation to the duration of adriamycin treatment ( 2 mg / kg , once a week ) .
### Output Text:
The degree of vacuolar degeneration of myocardial cells was analyzed in relation to the duration of <span class="chemical">adriamycin</span> treatment ( 2 mg / kg , once a week ) . 