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: Acid protease ( cathepsin D ) activity was increased about tenfold in patients who died and nearly fourfold in those who survived fulminant hepatic failure after paracetamol overdose , whereas activities were increased equally in patients with fulminant hepatic failure due to viral hepatitis whether or not they survived .
### Output Text:
Acid protease ( cathepsin D ) activity was increased about tenfold in patients who died and nearly fourfold in those who survived fulminant hepatic failure after <span class="chemical">paracetamol</span> overdose , whereas activities were increased equally in patients with fulminant hepatic failure due to viral hepatitis whether or not they survived . 