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: Our results suggest that adriamycin is a more potent cardiotoxin in monkeys than in man , and that leukemia may be a consequence of prolonged treatment with this drug .
### Output Text:
Our results suggest that <span class="chemical">adriamycin</span> is a more potent cardiotoxin in monkeys than in man , and that leukemia may be a consequence of prolonged treatment with this drug . 