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: Because cibenzoline had only weak hypotensive and sinus node depressive effects and was found to be orally active when given to coronary ligation arrhythmia dogs , its clinical usefulness is expected .
### Output Text:
Because <span class="chemical">cibenzoline</span> had only weak hypotensive and sinus node depressive effects and was found to be orally active when given to coronary ligation arrhythmia dogs , its clinical usefulness is expected . 