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: Group 1 had a moderate negative correlation between plasma histamine change and systemic vascular resistance ( r = 0 . 58 ; P less than 0 . 05 ) not present in group 4 .
### Output Text:
Group 1 had a moderate negative correlation between plasma <span class="chemical">histamine</span> change and systemic vascular resistance ( r = 0 . 58 ; P less than 0 . 05 ) not present in group 4 . 