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: Eight received insulin alone , and eight , including two of the original insulin - only group , were given propranolol and insulin .
### Output Text:
Eight received insulin alone , and eight , including two of the original insulin - only group , were given <span class="chemical">propranolol</span> and insulin . 