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: Additionally , 20 to 25 % of paracetamol - treated rats developed hyperplasia of the bladder epithelium , which was not coincident with the presence of bladder calculi .
### Output Text:
Additionally , 20 to 25 % of <span class="chemical">paracetamol</span> - treated rats developed hyperplasia of the bladder epithelium , which was not coincident with the presence of bladder calculi . 