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: It is concluded that with the above mentioned vincristine dose schedule signs and symptoms of vincristine neuropathy are reversible for a great deal and prognosis is fairly good .
### Output Text:
It is concluded that with the above mentioned <span class="chemical">vincristine</span> dose schedule signs and symptoms of <span class="chemical">vincristine</span> neuropathy are reversible for a great deal and prognosis is fairly good . 