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: Pupillometric changes while on DEP , especially changes in the total power of pupillary oscillation , were dramatically different than those observed in the eight other study subjects who did not become manic .
### Output Text:
Pupillometric changes while on <span class="chemical">DEP</span> , especially changes in the total power of pupillary oscillation , were dramatically different than those observed in the eight other study subjects who did not become manic . 