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: METH did not alter the motor function and procedural memory of mice as assessed by swimming speed and escape latency to find the platform in a cued version of the water maze task .
### Output Text:
<span class="chemical">METH</span> did not alter the motor function and procedural memory of mice as assessed by swimming speed and escape latency to find the platform in a cued version of the water maze task . 