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: Long - term glutamate supplementation failed to protect against peripheral neurotoxicity of paclitaxel .
### Output Text:
Long - term <span class="chemical">glutamate</span> supplementation failed to protect against peripheral neurotoxicity of <span class="chemical">paclitaxel</span> . 