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: Cardiovascular dysfunction and hypersensitivity to sodium pentobarbital induced by chronic barium chloride ingestion .
### Output Text:
Cardiovascular dysfunction and hypersensitivity to <span class="chemical">sodium pentobarbital</span> induced by chronic <span class="chemical">barium chloride</span> ingestion . 