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: We have studied the effects of oral treatment with eslicarbazepine acetate on a whole - animal model in which partial seizures can be elicited repeatedly on different days without changes in threshold or seizure patterns .
### Output Text:
We have studied the effects of oral treatment with <span class="chemical">eslicarbazepine acetate</span> on a whole - animal model in which partial seizures can be elicited repeatedly on different days without changes in threshold or seizure patterns . 