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: In addition to its use as a stabilizer / rigidifier of membranes , cholesteryl hemisuccinate , tris salt ( CS ) administration has also been shown to protect rats from the hepatotoxic effects of carbon tetrachloride ( CCl4 ) .
### Output Text:
In addition to its use as a stabilizer / rigidifier of membranes , <span class="chemical">cholesteryl hemisuccinate</span> , <span class="chemical">tris salt</span> ( <span class="chemical">CS</span> ) administration has also been shown to protect rats from the hepatotoxic effects of <span class="chemical">carbon tetrachloride</span> ( <span class="chemical">CCl4</span> ) . 