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: A continuous i . v . infusion of argatroban was initiated , and the patient was managed on the general medical floor .
### Output Text:
A continuous i . v . infusion of <span class="chemical">argatroban</span> was initiated , and the patient was managed on the general medical floor . 