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 finding of cocaine - induced vasoconstriction in segments of ( noninnervated ) human umbilical artery suggests that the presence or absence of intact innervation is not sufficient to explain the discrepant data involving the possibility of alpha - mediated effects .
### Output Text:
The finding of <span class="chemical">cocaine</span> - induced vasoconstriction in segments of ( noninnervated ) human umbilical artery suggests that the presence or absence of intact innervation is not sufficient to explain the discrepant data involving the possibility of alpha - mediated effects . 