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: In ICH induction using 0 . 014 - unit collagenase , heparin enhanced the hematoma volume 3 . 4 - fold over that seen in control ICH animals and the bleeding 7 . 6 - fold .
### Output Text:
In ICH induction using 0 . 014 - unit collagenase , <span class="chemical">heparin</span> enhanced the hematoma volume 3 . 4 - fold over that seen in control ICH animals and the bleeding 7 . 6 - fold . 