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: Inbred DBA / 2 and C57BL / 6 female mice were injected with CY , and the effect of the drug on the bladder was assessed during 100 days by light microscopy using different staining procedures , and after 30 days by conventional electron microscopy .
### Output Text:
Inbred DBA / 2 and C57BL / 6 female mice were injected with <span class="chemical">CY</span> , and the effect of the drug on the bladder was assessed during 100 days by light microscopy using different staining procedures , and after 30 days by conventional electron microscopy . 