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: Mature male and female mice from six inbred stains were tested for susceptibility to behavioral seizures induced by a single injection of cocaine .
### Output Text:
Mature male and female mice from six inbred stains were tested for susceptibility to behavioral seizures induced by a single injection of <span class="chemical">cocaine</span> . 