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: Microinjection of ritanserin into the CA1 region of hippocampus improves scopolamine - induced amnesia in adult male rats .
### Output Text:
Microinjection of <span class="chemical">ritanserin</span> into the CA1 region of hippocampus improves <span class="chemical">scopolamine</span> - induced amnesia in adult male rats . 