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: METHODS : 24 Rats were divided into 4 groups and received following treatments for 4 weeks ; Corn oil ( control ) , diazinon ( 15mg / kg per day , orally ) and crocin ( 12 . 5 and 25mg / kg per day , intraperitoneally ) in combination with diazinon ( 15 mg / kg ) .
### Output Text:
METHODS : 24 Rats were divided into 4 groups and received following treatments for 4 weeks ; Corn oil ( control ) , <span class="chemical">diazinon</span> ( 15mg / kg per day , orally ) and <span class="chemical">crocin</span> ( 12 . 5 and 25mg / kg per day , intraperitoneally ) in combination with <span class="chemical">diazinon</span> ( 15 mg / kg ) . 