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: However , livers from female , and especially pregnant female rats , were strikingly resistant to the effects of tetracycline on depression of output of triglyceride under these experimental conditions .
### Output Text:
However , livers from female , and especially pregnant female rats , were strikingly resistant to the effects of <span class="chemical">tetracycline</span> on depression of output of <span class="chemical">triglyceride</span> under these experimental conditions . 