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: The pressor response to the intracisternal ( i . c . ) injection of carbachol ( 1 mug ) in anesthetized rats was analyzed .
### Output Text:
The pressor response to the intracisternal ( i . c . ) injection of <span class="chemical">carbachol</span> ( 1 mug ) in anesthetized rats was analyzed . 