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: Rats were treated with the vehicle ( 2 mL / kg of distilled water and 5 % w / v cellulose , 10 days ) , gum Arabic ( 2 mL / kg of a 10 % w / v aqueous suspension of gum Arabic powder , orally for 10 days ) , or gum Arabic concomitantly with GM ( 80mg / kg / day intramuscularly , during the last six days of the treatment period ) .
### Output Text:
Rats were treated with the vehicle ( 2 mL / kg of distilled water and 5 % w / v cellulose , 10 days ) , <span class="chemical">gum Arabic</span> ( 2 mL / kg of a 10 % w / v aqueous suspension of <span class="chemical">gum Arabic</span> powder , orally for 10 days ) , or <span class="chemical">gum Arabic</span> concomitantly with <span class="chemical">GM</span> ( 80mg / kg / day intramuscularly , during the last six days of the treatment period ) . 