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 high - dose D - MED animals were flaccid , akinetic , and lacked a startle response during the entire experimental period . ( ABSTRACT TRUNCATED AT 250 WORDS )
### Output Text:
The high - dose <span class="chemical">D - MED</span> animals were flaccid , akinetic , and lacked a startle response during the entire experimental period . ( ABSTRACT TRUNCATED AT 250 WORDS ) 