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 : 38 female Wistar rats were injected with gentamicin , 40 mg / kg , twice a day for 9 days , 38 with gentamicin + PDTC , and 28 with 0 . 15 M NaCl solution .
### Output Text:
METHODS : 38 female Wistar rats were injected with <span class="chemical">gentamicin</span> , 40 mg / kg , twice a day for 9 days , 38 with <span class="chemical">gentamicin</span> + <span class="chemical">PDTC</span> , and 28 with 0 . 15 M <span class="chemical">NaCl</span> solution . 