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: However , unlike these latter , SSR103800 did not produce catalepsy ( retention on the bar test ) up to 30 mg / kg p . o .
### Output Text:
However , unlike these latter , <span class="chemical">SSR103800</span> did not produce catalepsy ( retention on the bar test ) up to 30 mg / kg p . o . 