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: Rats were treated with seven day intravenous infusion of fucoidan ( 30 micrograms h - 1 ) or vehicle .
### Output Text:
Rats were treated with seven day intravenous infusion of <span class="chemical">fucoidan</span> ( 30 micrograms h - 1 ) or vehicle . 