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: Diazepam - , scopolamine - and ageing - induced amnesia served as the interoceptive behavioral models .
### Output Text:
<span class="chemical">Diazepam</span> - , <span class="chemical">scopolamine</span> - and ageing - induced amnesia served as the interoceptive behavioral models . 