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: Male C57BL / 6 mice were administered with subconvulsive dose of pentylenetetrazole ( 37 mg / kg , i . p . ) every other day for 14 injections .
### Output Text:
Male C57BL / 6 mice were administered with subconvulsive dose of <span class="chemical">pentylenetetrazole</span> ( 37 mg / kg , i . p . ) every other day for 14 injections . 