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: Metallothionein induction reduces caspase - 3 activity and TNFalpha levels with preservation of cognitive function and intact hippocampal neurons in carmustine - treated rats .
### Output Text:
<span class="chemical">Metallothionein</span> induction reduces caspase - 3 activity and TNFalpha levels with preservation of cognitive function and intact hippocampal neurons in <span class="chemical">carmustine</span> - treated rats . 