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: Preoperative platelet count , postoperative course of platelets , and clinical signs of HIT type II were analyzed .
### Output Text:
Preoperative platelet count , postoperative course of platelets , and clinical signs of HIT type II were analyzed . 