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: Following administration of these agents , the presence , and degree of fasciculation were assessed visually on a four point scale by one investigator who was blinded to the drug administered .
### Output Text:
Following administration of these agents , the presence , and degree of fasciculation were assessed visually on a four point scale by one investigator who was blinded to the drug administered . 