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: Sporadic neoplastic lesions were observed in organs other than the liver of some of the animals , irrespective of the diet fed .
### Output Text:
Sporadic neoplastic lesions were observed in organs other than the liver of some of the animals , irrespective of the diet fed . 