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: Histamine antagonists and d - tubocurarine - induced hypotension in cardiac surgical patients .
### Output Text:
<span class="chemical">Histamine</span> antagonists and <span class="chemical">d - tubocurarine</span> - induced hypotension in cardiac surgical patients . 