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: Effect of calcium chloride on gross behavioural changes produced by carbachol and eserine in cats .
### Output Text:
Effect of <span class="chemical">calcium chloride</span> on gross behavioural changes produced by <span class="chemical">carbachol</span> and <span class="chemical">eserine</span> in cats . 