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: OBJECTIVES : The current study is the first to explore the effects of ecstasy - polydrug use on psychological distress and basal functioning of the HPA axis through assessing the secretion of cortisol across the diurnal period .
### Output Text:
OBJECTIVES : The current study is the first to explore the effects of <span class="chemical">ecstasy</span> - polydrug use on psychological distress and basal functioning of the HPA axis through assessing the secretion of <span class="chemical">cortisol</span> across the diurnal period . 