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: Moreover , a positive correlation of histamine to gastric hemorrhage and to ulcer was found in those atherosclerotic rats .
### Output Text:
Moreover , a positive correlation of <span class="chemical">histamine</span> to gastric hemorrhage and to ulcer was found in those atherosclerotic rats . 