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: Here , we describe a case of severe masseter muscle rigidity ( jaw of steel ) after succinylcholine ( Sch ) administration during general anesthetic management for rigid bronchoscopic removal of a tracheal foreign body .
### Output Text:
Here , we describe a case of severe masseter muscle rigidity ( jaw of steel ) after <span class="chemical">succinylcholine</span> ( <span class="chemical">Sch</span> ) administration during general anesthetic management for rigid bronchoscopic removal of a tracheal foreign body . 