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: Isoproterenol ( 100mg / kg ) was injected subcutaneously on the 13th and 14th days to induce acute myocardial infarction .
### Output Text:
<span class="chemical">Isoproterenol</span> ( 100mg / kg ) was injected subcutaneously on the 13th and 14th days to induce acute myocardial infarction . 