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: The authors induced myodystrophy in the rat by giving it a diet lacking in vitamin E .
### Output Text:
The authors induced myodystrophy in the rat by giving it a diet lacking in <span class="chemical">vitamin E</span> . 