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: Papillomas of the transitional epithelium of the bladder developed in all paracetamol - treated groups , and three rats bore bladder carcinomas .
### Output Text:
Papillomas of the transitional epithelium of the bladder developed in all <span class="chemical">paracetamol</span> - treated groups , and three rats bore bladder carcinomas . 