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: Of the 15 spinal cords of the animals that received 2 - chloroprocaine - CE , 13 showed subpial necrosis ; the nerve roots and subarachnoid vessels were normal .
### Output Text:
Of the 15 spinal cords of the animals that received <span class="chemical">2 - chloroprocaine - CE</span> , 13 showed subpial necrosis ; the nerve roots and subarachnoid vessels were normal . 