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: Modafinil was associated with increased daytime sleep latency , as measured by the Multiple Sleep Latency Test , and a nearly significant decrease in subjective daytime sleepiness .
### Output Text:
<span class="chemical">Modafinil</span> was associated with increased daytime sleep latency , as measured by the Multiple Sleep Latency Test , and a nearly significant decrease in subjective daytime sleepiness . 