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: In addition , 90 minutes after CP injection , that is , at the time of administration of morphine , the bladder was removed in some rats for histological examination .
### Output Text:
In addition , 90 minutes after <span class="chemical">CP</span> injection , that is , at the time of administration of <span class="chemical">morphine</span> , the bladder was removed in some rats for histological examination . 