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: Following status epilepticus in the rat , dentate granule cell neurogenesis increases greatly , and many of the new neurons appear to develop ectopically , in the hilar region of the hippocampal formation .
### Output Text:
Following status epilepticus in the rat , dentate granule cell neurogenesis increases greatly , and many of the new neurons appear to develop ectopically , in the hilar region of the hippocampal formation . 