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: Bilateral vagotomy and sympathectomy or prior administration of a ganglion blocker failed to inhibit the occurrence of the ketamine - induced tachycardia , while it was completely abolished in the reserpinized dogs or by a prior injection of a beta - blocking agent into the SA node artery .
### Output Text:
Bilateral vagotomy and sympathectomy or prior administration of a ganglion blocker failed to inhibit the occurrence of the <span class="chemical">ketamine</span> - induced tachycardia , while it was completely abolished in the reserpinized dogs or by a prior injection of a beta - blocking agent into the SA node artery . 