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: Exclusively parenteral daily injections of galactose induce memory deterioration in rodents and are used to generate animal aging model , but the effects of oral galactose treatment on cognitive functions have never been tested .
### Output Text:
Exclusively parenteral daily injections of <span class="chemical">galactose</span> induce memory deterioration in rodents and are used to generate animal aging model , but the effects of oral <span class="chemical">galactose</span> treatment on cognitive functions have never been tested . 