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 : Adult male Swiss Webster mice ( 25 - 32 g ) were given nicotine ( 0 . 05 - 0 . 25 mg / kg s . c . ) or saline 10 min before caffeine ( 70 mg / kg i . p . ) or pentylenetetrazole ( 15 and 30 mg / kg i . p . ) injections .
### Output Text:
METHODS : Adult male Swiss Webster mice ( 25 - 32 g ) were given <span class="chemical">nicotine</span> ( 0 . 05 - 0 . 25 mg / kg s . c . ) or saline 10 min before <span class="chemical">caffeine</span> ( 70 mg / kg i . p . ) or <span class="chemical">pentylenetetrazole</span> ( 15 and 30 mg / kg i . p . ) injections . 