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: Epinephrine dysrhythmogenicity is not enhanced by subtoxic bupivacaine in dogs .
### Output Text:
<span class="chemical">Epinephrine</span> dysrhythmogenicity is not enhanced by subtoxic <span class="chemical">bupivacaine</span> in dogs . 