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: After 4 weeks the PAN rats were severely proteinuric ( 190 + / - 80 mg / 24 hr ) , and all rats were given colloidal carbon ( CC ) intravenously .
### Output Text:
After 4 weeks the <span class="chemical">PAN</span> rats were severely proteinuric ( 190 + / - 80 mg / 24 hr ) , and all rats were given colloidal <span class="chemical">carbon</span> ( CC ) intravenously . 