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: RESULTS : The sensory action potential amplitude of the right lateral antebrachial cutaneous nerve ( LACN ) ( 6 . 2 uV ) was lower than that of the left ( 13 . 1 uV ) .
### Output Text:
RESULTS : The sensory action potential amplitude of the right lateral antebrachial cutaneous nerve ( LACN ) ( 6 . 2 uV ) was lower than that of the left ( 13 . 1 uV ) . 