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: Light microscopy study showed severe glomerulonephritis with crescent formation in 60 % of the glomeruli and infiltration of inflammatory cells in the wall of an arteriole .
### Output Text:
Light microscopy study showed severe glomerulonephritis with crescent formation in 60 % of the glomeruli and infiltration of inflammatory cells in the wall of an arteriole . 