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: A small increase ( 1 . 5 - fold ) also occurred in the L1 DRG , but no change was detected in the L2 and L5 DRG .
### Output Text:
A small increase ( 1 . 5 - fold ) also occurred in the L1 DRG , but no change was detected in the L2 and L5 DRG . 