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: Treatment with antithrombin attenuated the puromycin aminonucleoside - induced hematological abnormalities .
### Output Text:
Treatment with antithrombin attenuated the <span class="chemical">puromycin aminonucleoside</span> - induced hematological abnormalities . 