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: These findings suggest the hypothesis that the catalepsy that is produced by neuroleptics such as haloperidol is actually mediated by intrinsic central cholinergic systems .
### Output Text:
These findings suggest the hypothesis that the catalepsy that is produced by <span class="chemical">neuroleptics</span> such as <span class="chemical">haloperidol</span> is actually mediated by intrinsic central cholinergic systems . 