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: The ED50 values for morphine when given in combination with CNSB002 ( 5 mg / kg ) were less than the maximum nonsedating dose : 0 . 56 ( 1 . 55 ) in the carrageenan model and 1 . 37 ( 1 . 23 ) in the neuropathy model ( mg / kg ; mean , SEM ) .
### Output Text:
The ED50 values for <span class="chemical">morphine</span> when given in combination with <span class="chemical">CNSB002</span> ( 5 mg / kg ) were less than the maximum nonsedating dose : 0 . 56 ( 1 . 55 ) in the <span class="chemical">carrageenan</span> model and 1 . 37 ( 1 . 23 ) in the neuropathy model ( mg / kg ; mean , SEM ) . 