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: When hippocampal ACh was measured during testing for handling - induced convulsions , extracellular ACh was significantly elevated ( 192 % ) in WSP mice , but was nonsignificantly elevated ( 59 % ) in WSR mice .
### Output Text:
When hippocampal <span class="chemical">ACh</span> was measured during testing for handling - induced convulsions , extracellular <span class="chemical">ACh</span> was significantly elevated ( 192 % ) in WSP mice , but was nonsignificantly elevated ( 59 % ) in WSR mice . 