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: Other myocardial pathophysiologic and metabolic changes induced by barium were manifest , irrespective of the anesthetic employed .
### Output Text:
Other myocardial pathophysiologic and metabolic changes induced by <span class="chemical">barium</span> were manifest , irrespective of the anesthetic employed . 