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: These data demonstrate that the hemodynamic changes associated with d - tubocurarine dosing are only partially explained by histamine release .
### Output Text:
These data demonstrate that the hemodynamic changes associated with <span class="chemical">d - tubocurarine</span> dosing are only partially explained by <span class="chemical">histamine</span> release . 