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: Out of a total of 88 courses of this treatment we observed 10 episodes of asymptomatic microscopic haematuria and no episodes of gross haematuria .
### Output Text:
Out of a total of 88 courses of this treatment we observed 10 episodes of asymptomatic microscopic haematuria and no episodes of gross haematuria . 