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: Effects of cromakalim and pinacidil on large epicardial and small coronary arteries in conscious dogs .
### Output Text:
Effects of <span class="chemical">cromakalim</span> and <span class="chemical">pinacidil</span> on large epicardial and small coronary arteries in conscious dogs . 