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 small EMG values obtained in the high - dose D - MED group were comparable with those recorded in earlier studies from control animals not given any opiate .
### Output Text:
The small EMG values obtained in the high - dose <span class="chemical">D - MED</span> group were comparable with those recorded in earlier studies from control animals not given any opiate . 