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: The remaining 73 patients ( 55 women and 18 men ) , all of whom were examined for more than 3 months , were adopted as the subjects of the investigation .
### Output Text:
The remaining 73 patients ( 55 women and 18 men ) , all of whom were examined for more than 3 months , were adopted as the subjects of the investigation . 