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: Reserpine injection ( one dose of 1 mg / kg s . c . ) every other day for 3 days caused a significant increase in vacuous chewing , tongue protrusion and duration of facial twitching , compared to the control .
### Output Text:
<span class="chemical">Reserpine</span> injection ( one dose of 1 mg / kg s . c . ) every other day for 3 days caused a significant increase in vacuous chewing , tongue protrusion and duration of facial twitching , compared to the control . 