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: Transgenic and nontransgenic littermates received kanamycin ( 400 mg / kg body weight / day ) for 10 days beginning on day 10 after birth .
### Output Text:
Transgenic and nontransgenic littermates received <span class="chemical">kanamycin</span> ( 400 mg / kg body weight / day ) for 10 days beginning on day 10 after birth . 