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: Dimensions of the bruising on the heparin applied areas were measured using transparent millimetric measuring paper .
### Output Text:
Dimensions of the bruising on the <span class="chemical">heparin</span> applied areas were measured using transparent millimetric measuring paper . 