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: The results indicate that the size of the hilar ectopic granule cell population after status epilepticus is substantial , and stable over time .
### Output Text:
The results indicate that the size of the hilar ectopic granule cell population after status epilepticus is substantial , and stable over time . 