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: Depressed hepatic secretion of triglyceride accounted only for 30 to 50 % of accumulated hepatic triglyceride , indicating that additional mechanisms must be involved in the production of the triglyceride - rich fatty liver in response to tetracycline .
### Output Text:
Depressed hepatic secretion of <span class="chemical">triglyceride</span> accounted only for 30 to 50 % of accumulated hepatic <span class="chemical">triglyceride</span> , indicating that additional mechanisms must be involved in the production of the <span class="chemical">triglyceride</span> - rich fatty liver in response to <span class="chemical">tetracycline</span> . 