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: Diltiazem was used as a comparison drug and autonomic blockade with atropine and nadolol was applied in some experiments .
### Output Text:
<span class="chemical">Diltiazem</span> was used as a comparison drug and autonomic blockade with <span class="chemical">atropine</span> and <span class="chemical">nadolol</span> was applied in some experiments . 