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: Cystitis was evaluated 24 h after its induction by the changes in bladder wet weight and by macroscopic and microscopic analysis .
### Output Text:
Cystitis was evaluated 24 h after its induction by the changes in bladder wet weight and by macroscopic and microscopic analysis . 