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: Intracranial injection of an acetylcholine - synthesis inhibitor , hemicholinium , prevented the catalepsy that is usually induced by haloperidol .
### Output Text:
Intracranial injection of an <span class="chemical">acetylcholine</span> - synthesis inhibitor , <span class="chemical">hemicholinium</span> , prevented the catalepsy that is usually induced by <span class="chemical">haloperidol</span> . 