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: Atrial thrombosis involving the heart of F - 344 rats ingesting quinacrine hydrochloride .
### Output Text:
Atrial thrombosis involving the heart of F - 344 rats ingesting <span class="chemical">quinacrine hydrochloride</span> . 