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 majority of anionic sites ( 74 % in diabetic and 81 % in control rats ) were found within the lamina rara externa of the glomerular basement membrane .
### Output Text:
The majority of anionic sites ( 74 % in diabetic and 81 % in control rats ) were found within the lamina rara externa of the glomerular basement membrane . 