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: Induction by paracetamol of bladder and liver tumours in the rat .
### Output Text:
Induction by <span class="chemical">paracetamol</span> of bladder and liver tumours in the rat . 