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: Forty - five minutes later , the animals were randomly treated with PCC ( 100 U / kg ) or saline i . v . ( n = 12 per group ) .
### Output Text:
Forty - five minutes later , the animals were randomly treated with <span class="chemical">PCC</span> ( 100 U / kg ) or saline i . v . ( n = 12 per group ) . 