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: Seven days of cocaine administration to rats led to an increased oxygen consumption detected in cardiac fibers , specifically through complex I and complex III .
### Output Text:
Seven days of <span class="chemical">cocaine</span> administration to rats led to an increased <span class="chemical">oxygen</span> consumption detected in cardiac fibers , specifically through complex I and complex III . 