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: In the second experiment , four groups of mice received similar treatment in the first experiment , and 30 min after these injections , all mice received a higher dose of lidocaine ( 80 mg / kg ) .
### Output Text:
In the second experiment , four groups of mice received similar treatment in the first experiment , and 30 min after these injections , all mice received a higher dose of <span class="chemical">lidocaine</span> ( 80 mg / kg ) . 