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 results further support the view that calcium ions in excess have an atropine - like action also in the central nervous system .
### Output Text:
These results further support the view that <span class="chemical">calcium</span> ions in excess have an <span class="chemical">atropine</span> - like action also in the central nervous system . 