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: Marked differences were observed between female and male rats with regard to base line ( control ) hepatic concentration of triglyceride and output of triglyceride .
### Output Text:
Marked differences were observed between female and male rats with regard to base line ( control ) hepatic concentration of <span class="chemical">triglyceride</span> and output of <span class="chemical">triglyceride</span> . 