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 dose levels incorporate escalating paclitaxel doses , and intrapatient escalations within a given dose level are permitted if toxicity permits .
### Output Text:
The dose levels incorporate escalating <span class="chemical">paclitaxel</span> doses , and intrapatient escalations within a given dose level are permitted if toxicity permits . 