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: In four subacute toxicity studies , the intravenous administration of cefonicid or cefazedone to beagle dogs caused a dose - dependent incidence of anemia , neutropenia , and thrombocytopenia after 1 - 3 months of treatment .
### Output Text:
In four subacute toxicity studies , the intravenous administration of <span class="chemical">cefonicid</span> or <span class="chemical">cefazedone</span> to beagle dogs caused a dose - dependent incidence of anemia , neutropenia , and thrombocytopenia after 1 - 3 months of treatment . 