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 metabolism of the cardioselective beta - blocker metoprolol is under genetic control of the debrisoquine / sparteine type .
### Output Text:
The metabolism of the cardioselective beta - blocker <span class="chemical">metoprolol</span> is under genetic control of the <span class="chemical">debrisoquine</span> / <span class="chemical">sparteine</span> type . 