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: The increase of galactose concentration in the cerebrospinal fluid was several times lower after oral than after parenteral administration of the same galactose dose .
### Output Text:
The increase of <span class="chemical">galactose</span> concentration in the cerebrospinal fluid was several times lower after oral than after parenteral administration of the same <span class="chemical">galactose</span> dose . 