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: Additionally , oral galactose administration led to the appearance of galactose in the blood .
### Output Text:
Additionally , oral <span class="chemical">galactose</span> administration led to the appearance of <span class="chemical">galactose</span> in the blood . 