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: Similarly , ganglionic blockade with hexamethonium caused a significantly greater fall in LNNA hypertensive rats ( 76 + / - 9 mm Hg ) compared with control rats ( 35 + / - 10 mm Hg ) .
### Output Text:
Similarly , ganglionic blockade with <span class="chemical">hexamethonium</span> caused a significantly greater fall in <span class="chemical">LNNA</span> hypertensive rats ( 76 + / - 9 mm Hg ) compared with control rats ( 35 + / - 10 mm Hg ) . 