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: High - dose intravenous methotrexate is an effective treatment for the induction of remission after meningeal relapse in acute lymphoblastic leukemia .
### Output Text:
High - dose intravenous <span class="chemical">methotrexate</span> is an effective treatment for the induction of remission after meningeal relapse in acute lymphoblastic leukemia . 